The potential for sparing of parotids and escalation of biologically effective dose with intensity-modulated radiation treatments of head and neck cancers: a treatment design study

Geometric factors influencing dosimetric sparing of the parotid glands using IMRT

PURPOSE/OBJECTIVE

To determine the relationship between the parotid volume, parotid-planning target volume (PTV) overlap, and dosimetric sparing of the parotid with intensity-modulated radiation therapy (IMRT).

METHODS AND MATERIALS

Parotid data were collected retrospectively for 51 patients treated with simultaneous boost IMRT. Unresectable patients received 54 or 59.4 Gy to subclinical disease, 70 Gy to gross disease. Patients treated postoperatively received 54, 60, and 66 Gy to low-risk, high-risk, and tumor bed regions. Volume and mean dose of each gland and gland segments outside of and overlapping the PTV were collected. Proximity of each gland to each PTV was recorded.

RESULTS

Dosimetric sparing (mean dose <or =26.5 Gy) was achieved in 66 of 71 glands with < or =21% parotid-PTV overlap and 8 of 23 glands with >21% overlap (p = <0.0001). Among spared glands, the median mean dose in the overlap region was 55.0 Gy in glands with < or =21% overlap, but only 45.4 Gy when overlap >21%. Median mean dose was 25.9 Gy to glands overlapping PTV(54) or PTV(59) alone and 30.0 Gy to those abutting PTV(70) (p < 0.001). Although proximity to PTV(70) was associated with higher parotid dose, satisfactory sparing was achieved in 24 of 43 ipsilateral glands.

CONCLUSIONS

Dosimetric sparing of the parotid is feasible when the parotid-PTV overlap is less than approximately 20%. With more overlap, sparing may result in low doses within the overlap region, possibly leading to inadequate PTV coverage. Gland proximity to the high-dose PTV is associated with higher mean dose but does not always preclude dosimetric sparing.

Three-dimensional conformal radiotherapy for locally advanced (Stage II and worse) head-and-neck cancer: dosimetric and clinical evaluation

PURPOSE

To evaluate the dosimetric parameters of three-dimensional conformal radiotherapy (3D-CRT) in locally advanced head-and-neck tumors (Stage II and above) and the effects on xerostomia.

METHODS AND MATERIALS

A total of 49 patients with histologically proven squamous cell cancer of the head and neck were consecutively treated with 3D-CRT using a one-point setup technique; 17 had larynx cancer, 12 oropharynx, 12 oral cavity, and 6 nasopharynx cancer; 2 had other sites of cancer. Of the 49 patients, 41 received postoperative RT and 8 definitive treatment. Also, 13 were treated with cisplatin-based chemotherapy before and during RT; in 6 cases, 5-fluorouracil was added. The follow-up time was 484-567 days (median, 530 days).

RESULTS

One-point setup can deliver 96% of the prescribed dose to the isocenter, to the whole planning target volume, including all node levels of the neck and without overdosages. The mean dose to the primary planning target volume was 49.54 +/- 4.82 Gy (51.53 +/- 5.47 Gy for larynx cases). The average dose to the contralateral parotid gland was approximately 38 Gy (30 Gy for larynx cases). The maximal dose to the spinal cord was 46 Gy. A Grade 0 Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer xerostomia score corresponded to a mean dose of 30 Gy to one parotid gland. A lower xerostomia score with a lower mean parotid dose and longer follow-up seemed to give rise to a sort of functional recovery phenomenon.

CONCLUSION

Three dimensional-CRT in head-and-neck cancers permits good coverage of the planning target volume with about 10-11 segments and one isocenter. With a mean dose of approximately 30 Gy to the contralateral parotid, we observed no or mild xerostomia.

Preliminary results of a phase I/II study of simultaneous modulated accelerated radiotherapy for nondisseminated nasopharyngeal carcinoma

PURPOSE

To present preliminary results of intensity-modulated radiotherapy (IMRT) with the simultaneous modulated accelerated radiotherapy (SMART) boost technique in patients with nasopharyngeal carcinoma (NPC).

METHODS AND MATERIALS

Twenty patients who underwent IMRT for nondisseminated NPC at the Asan Medical Center between September 2001 and December 2003 were prospectively evaluated. Intensity-modulated radiotherapy was delivered with the "step and shoot" SMART technique at prescribed doses of 72 Gy (2.4 Gy/day) to the gross tumor volume, 60 Gy (2 Gy/day) to the clinical target volume and metastatic nodal station, and 46 Gy (2 Gy/day) to the clinically negative neck region. Eighteen patients also received cisplatin once per week.

RESULTS

The median follow-up period was 27 months. Nineteen patients completed the treatment without interruption; the remaining patient interrupted treatment for 2 weeks owing to severe pharyngitis and malnutrition. Five patients (25%) had Radiation Therapy Oncology Group Grade 3 mucositis, whereas 9 (45%) had Grade 3 pharyngitis. Seven patients (35%) lost more than 10% of their pretreatment weight, whereas 11 (55%) required intravenous fluids and/or tube feeding. There was no Grade 3 or 4 xerostomia. All patients showed complete response. Two patients had distant metastases and locoregional recurrence, respectively.

CONCLUSION

Intensity-modulated radiotherapy with the SMART boost technique allows parotid sparing, as shown clinically and by dosimetry, and might also be more effective biologically. A larger population of patients and a longer follow-up period are needed to evaluate ultimate tumor control and late toxicity.

Monte Carlo–based dosimetry of head-and-neck patients treated with SIB-IMRT

PURPOSE

To evaluate the accuracy of previously reported superposition/convolution (SC) dosimetric results by comparing with Monte Carlo (MC) dose calculations for head-and-neck intensity-modulated radiation therapy (IMRT) patients treated with the simultaneous integrated boost technique.

METHODS AND MATERIALS

Thirty-one plans from 24 patients previously treated on a phase I/II head-and-neck squamous cell carcinoma simultaneous integrated boost IMRT protocol were used. Clinical dose distributions, computed with an SC algorithm, were recomputed using an EGS4-based MC algorithm. Phantom-based dosimetry quantified the fluence prediction accuracy of each algorithm. Dose-volume indices were used to compare patient dose distributions.

RESULTS AND DISCUSSION

The MC algorithm predicts flat-phantom measurements better than the SC algorithm. Average patient dose indices agreed within 2.5% of the local dose for targets; 5.0% for parotids; and 1.9% for cord and brainstem. However, only 1 of 31 plans agreed within 3% for all indices; 4 of 31 agreed within 5%. In terms of the prescription dose, 4 of 31 plans agreed within 3% for all indices, whereas 28 of 31 agreed within 5%.

CONCLUSIONS

Average SC-computed doses agreed with MC results in the patient geometry; however deviations >5% were common. The fluence modulation prediction is likely the major source of the dose discrepancy. The observed dose deviations can impact dose escalation protocols, because they would result in shifting patients to higher dose levels.

Intensity modulated radiotherapy: advantages, limitations and future developments

Intensity modulated radiotherapy (IMRT) is widely used in clinical applications in developed countries, for the treatment of malignant and non-malignant diseases. This technique uses multiple radiation beams of non-uniform intensities. The beams are modulated to the required intensity maps for delivering highly conformal doses of radiation to the treatment targets, while sparing the adjacent normal tissue structures. This treatment technique has superior dosimetric advantages over 2-dimensional (2D) and conventional 3-dimensional conformal radiotherapy (3DCRT) treatments. It can potentially benefit the patient in three ways. First, by improving conformity with target dose it can reduce the probability of in-field recurrence. Second, by reducing irradiation of normal tissue it can minimise the degree of morbidity associated with treatment. Third, by facilitating escalation of dose it can improve local control. Early clinical results are promising, particularly in the treatment of nasopharyngeal carcinoma (NPC). However, as the IMRT is a sophisticated treatment involving high conformity and high precision, it has specific requirements. Therefore, tight tolerance levels for random and systematic errors, compared with conventional 2D and 3D treatments, must be applied in all treatment and pre-treatment procedures. For this reason, a large-scale routine clinical implementation of the treatment modality demands major resources and, in some cases, is impractical. This paper will provide an overview of the potential advantages of the IMRT, methods of treatment delivery, and equipment currently available for facilitating the treatment modality. It will also discuss the limitations of the equipment and the ongoing development work to improve the efficiency of the equipment and the treatment techniques and procedures.

Matched case-control study of quality of life and xerostomia after intensity-modulated radiotherapy or standard radiotherapy for head-and-neck cancer: initial report

PURPOSE

To compare quality of life (QOL) and xerostomia between head-and-neck cancer patients who received standard radiotherapy (RT) and patients matched by factors known to affect QOL who received intensity-modulated RT (IMRT).

METHODS AND MATERIALS

This was a prospective, longitudinal study of patients with head-and-neck cancer requiring bilateral neck irradiation who received IMRT at the University of Michigan and patients who received standard RT at affiliated clinics. Each patient received a validated head-and-neck cancer-related QOL questionnaire (HNQOL) consisting of four multi-item domains--Eating, Communication, Pain, and Emotion--and a validated patient-reported xerostomia questionnaire (XQ). In both questionnaires, the answers were scored 0-100, with higher scores denoting worse QOL or xerostomia. The questionnaires were given before therapy and at 1, 3, 6, 12, 18, and 24 months after the completion of therapy. Each standard RT patient was matched with several IMRT patients according to tumor site, stage, RT status (postoperative or definitive), and age. A linear mixed-effects model was fit to compare outcomes between the two treatment groups and to model trends over time. To account for matching, the differences in scores between the matched sets of patients were fit as a random intercept. Also, matching was taken into account in the model by using the standard error of the within-paired-groups differences.

RESULTS

Between 1997 and 2002, 10 patients who had received standard RT and answered the XQ and HNQOL through at least 1 year were included in the study. Each of these patients was matched with a subgroup of 2-5 patients (median, 3) who had received IMRT, had similar patient and tumor characteristics, and answered the same questionnaires. A total of 30 patients were included in the IMRT group. During the initial months after therapy, the XQ and HNQOL summary scores worsened significantly in both groups compared with the pretherapy scores. Starting at 6 months, improvements of both XQ and HNQOL scores were found over time in the IMRT patients (p = 0.01 and 0.04, respectively), compared with no trend of improvement in the standard RT patients (p = 0.5 and 0.9, respectively). The trend of improvement over time in QOL in the IMRT patients was noted in most of the HNQOL domains (Eating: p = 0.07, Pain: p = 0.05, Emotion: p = 0.04, and Communication: p = 0.13), compared with no trend of improvement in most of the domains in the standard RT patients. As the scores of the IMRT (but not the standard RT) patients improved over time, the differences between the groups in the mean XQ and HNQOL summary scores widened. At 12 months, median XQ and HNQOL scores were lower (better) in the IMRT compared with the standard RT patients by 19 and 20 points, respectively, adjusted for the pretherapy values (p = 0.2). In both groups, the pretherapy XQ and HNQOL summary scores were significantly related to the respective posttherapy scores (p = 0.02 and p < 0.01, respectively).

CONCLUSIONS

After initial posttherapy declines in both groups, xerostomia and QOL improved over time after IMRT but not after standard RT. The potential benefits gained from IMRT in xerostomia or in QOL, compared with standard RT, are best reflected late (> or = 6 months) after therapy.

Comparative dosimetric study of two strategies of intensity-modulated radiotherapy in nasopharyngeal cancer

This study compared the target volume coverage and normal tissues sparing of simultaneous integrated boost (SIB-IMRT, 1-phase) and sequential-IMRT (2-phase) for nasopharyngeal carcinoma (NPC). Fourteen consecutive patients with newly diagnosed primary NPC were enrolled in this study. The CT images were transferred to a commercial planning system for structural delineation. The gross tumor volume (GTV) included gross nasopharyngeal tumor and involved lymph nodes of more than 1-cm diameter. The clinical target volume (CTV) modeled two regions considered to represent different risks. CTV1 encompassed the GTV with 5-10-mm margin of adjacent tissues. CTV2 encompassed ipsilateral or contralateral elective nodal regions at risk of harboring microscopic tumor. A commercial IMRT treatment planning system (Eclipse Version 7.1) was used to provide treatment planning. Seven fixed-gantry (0 degrees, 50 degrees, 100 degrees, 150 degrees, 210 degrees, 260 degrees, 310 degrees ) angles were designated. The 14 patients were treated with sequential-IMRT, and treatment was then replanned with an SIB strategy to compare the dosimetric difference. For the sequential strategy, the dose delivered to CTV1/CTV2 in the first course was 54 Gy (1.8 Gyx30 Fr); while CTV1 was boosted by an additional 16.2 Gy (1.8 Gyx9 Fr) in the second course. For SIB-IMRT, the dose prescribed to CTV1 was 69.7 Gy (2.05 Gyx34 Fr); 56.1 Gy was given to CTV2 (1.65 Gyx34 Fr). A statistical analysis of the dose-volume-histogram of target volumes and critical organs was performed. Paired Student's t-test was used to compare the dosimetric differences between the two techniques. The mean dose to CTV1 was 101.7+/-2.4% and 102.3+/-3.1% of the prescribed dose for SIB-IMRT and sequential-IMRT, respectively. The mean CTV2 dose was 109.8+/-4.7% of the prescribed dose for SIB-IMRT and 112.6+/-6.0% of the prescribed dose for sequential-IMRT. The maximal dose to the spinal cord was 4489+/-495 cGy and 3547+/-767 cGy for SIB and sequential-IMRT (p=0.0001), respectively. The maximal dose to brain stem was significantly higher using SIB technique (5284+/-551 cGy) than sequential-IMRT (4834+/-388 cGy) (p=0.0001). The mean dose to the parotid gland and ear apparatus was significantly lower using SIB-IMRT. The mean dose to the right/left parotids was 2865+/-320 cGy/2903+/-429 cGy and 3567+/-534 cGy/3476+/-489 cGy for SIB and sequential-IMRT, respectively (p=0.0001). Target coverage was the same for both techniques; the dose distribution in the elective nodal area with SIB was superior to that with sequential-IMRT. SIB-IMRT provides better sparing of parotid gland and inner ear structures. Extra caution should be taken when applying SIB-IMRT since critical organs close to the boost volume may receive higher doses.

Comparing 3DCRT and inversely optimized IMRT planning for head and neck cancer: equivalence between step-and-shoot and sliding window techniques

BACKGROUND AND PURPOSE

To investigate the feasibility and the advantages of using Intensity-Modulated Radiotherapy (IMRT) for the treatment of head-and-neck cancer. Comparing different methods to deliver IMRT in this clinical setting.

MATERIALS AND METHODS

Seven patients (four radical; three post-operative), treated on a 6MV Varian Linac (equipped with an 80 leaves MLC) in accordance with a routine 3DCRT plan, were replanned. Original treatment plans were computed to irradiate a primary Planning Target Volume (PTV1, 54 Gy) and then to perform a boost on a PTV2 (radical: 70.2 Gy; post-operative: 64.8 Gy). IMRT dose plans were inversely-optimized using appropriate constraints with the Helios tool on a Varian Eclipse system. Once the optimal fluences were calculated, different modalities to deliver IMRT were considered: Sliding Window (SW) and Step and Shoot (SS) techniques using a different number of intensity levels to approximate the optimal fluences (e.g. 5, 10 and 20). Mean dose, maximum dose and a number of dose-volume parameters regarding CTV1, CTV2, PTV1, PTV2, OARs (spinal and planning spinal cord, parotids, optical structures, brain and temporal mandibular joint) were considered to compare the five modalities (3DCRT, SW, SS5, SS10, SS20); the Conformity Index (CI), the Irradiated Volume (IV) and the Treated Volume (TV) were also considered in the comparison.

RESULTS

A more uniform coverage of the PTV in the IMRT dose plans with respect to the 3DCRT plan was found (for PTV2: V90% = 94.3 for 3DCRT, 97.6 for SS5, 98 for SS10 and 98.1 for SW; V107% = 20.7 for 3DCRT, 5.9 for SS5, 2 for SS10 and 1.3 for SW). Concerning OARs, they all present a significant reduction of mean and/or maximum dose and dose-volume patterns assessed from DVHs: in particular the mean dose of parotids decrease on average of about 13.5Gy passing from 3DCRT to IMRT with an average reduction of NTCP ranging from about 20% to more than 40% for radically treated patients, depending on the chosen end-point. IV and TV are also slightly smaller with IMRT. The results obtained with SS techniques employing 10 or more intensity levels are comparable with those obtained with SW; no differences between SS10 and SW may be appreciated when considering the DVHs of PTV, CTV and OARs. On the other hand, in some cases SS5 may be slightly sub-effective with respect to SS10-SW when considering PTV coverage and Dmax of the spinal cord.

CONCLUSIONS

With the Varian planning and delivery system, Step-and-shoot approximations of inversely optimised fluences in head-neck IMRT compare well with SW delivery, even with only five intensity levels. With a number of intensity level of 10 or more, no differences can be appreciated in PTV coverage/OAR sparing with respect to SW.

Does radiation dose to the salivary glands and oral cavity predict patient-rated xerostomia and sticky saliva in head and neck cancer patients treated with curative radiotherapy?

BACKGROUND AND PURPOSE

To investigate the association between the mean salivary gland and oral cavity dose, with patient-rated moderate and severe xerostomia and sticky saliva.

PATIENTS AND METHODS

One hundred and fifty-seven patients treated with bilateral irradiation for head and neck cancer were included. The parotid and submandibular glands and the oral cavity were delineated on plannings-CT scans. At baseline and 6 and 12 months self-reported xerostomia and sticky saliva were assessed using the EORTC QLQ-H&N35 questionnaire.

RESULTS

At 6 months a significant association between the mean parotid (MD(par)) and mean submandibular dose (MD(subm)) and xerostomia was observed (OR - MD(par): 1.17; P=0.002 and OR - MD(subm): 1.08; P = 0.02). Between MD(par) and MD(subm), a significant interaction term was present. No significant association was found with the oral cavity dose. Xerostomia was reversible depending on MD(par) and MD(subm). Considering Sticky saliva, a significant association was found at 6 and 12 months with MD(subm) (OR: 1.03; P < 0.001). The P50 for sticky saliva increased with elapsing time.

CONCLUSIONS

Both MD(par) and MD(subm) influence the risk of xerostomia in irradiated patients at 6 months. This probability as a function of the mean parotid dose significantly depended on the mean dose in the submandibular glands. Sticky saliva mainly depends on MD(subm).

FDG-PET/CT-guided intensity modulated head and neck radiotherapy: a pilot investigation

BACKGROUND

2-deoxy-2[(18)F]fluoro-D-glucose-positron emission tomography (FDG-PET) imaging can be registered with CT images and can potentially improve neck staging sensitivity and specificity in patients with head and neck squamous cell cancer. The intent of this study was to examine the use of registered FDG-PET/CT imaging to guide head and neck intensity modulated radiotherapy (IMRT) planning.

METHODS

Twenty patients with squamous cell carcinoma of the oral cavity, oropharynx, larynx, or hypopharynx underwent FDG-PET and contrast-enhanced CT imaging of the head and neck before neck dissection surgery. Combined FDG-PET/CT images were created by use of a nonrigid image registration algorithm. All IMRT plans were theoretical and were not used for treatment. We prescribed 66 Gy in 30 fractions to FDG-avid CT abnormalities and nodal zones directly involved with disease, without prophylactic coverage of uninvolved neck levels. Matched CT-guided IMRT plans designed according to the specifications of Radiation Therapy Oncology Group (RTOG) H-0022 were available for comparison. We investigated the feasibility of FDG-PET/CT-directed IMRT dose escalation in five patients with FDG-avid disease located away from critical normal structures. After 66 Gy, FDG-avid disease with 0.5-cm margins was boosted in 220 cGy increments until dose-limiting criteria were reached.

RESULTS

Elimination of prophylactic coverage to FDG-PET/CT-negative neck levels markedly reduced mean dose (Dmean) to the contralateral parotid gland (p < .001) and Dmean to the laryngeal cartilage (p = .001). No FDG-PET/CT-directed plan missed pathologically verified nodal disease. During the dose escalation exercise, we successfully increased the dose to 95% of the planning target volume (PTV95%) to a mean of 7490 cGy (range, 7153-8098 cGy).

CONCLUSIONS

We demonstrate early proof of the principle that FDG-PET/CT-guided IMRT planning can selectively target and intensify treatment of head and neck disease while reducing critical normal tissue doses. Routine clinical use of such planning should not be engaged until the accuracy of FDG-PET/CT is fully validated. Future directions, including refinement of treatment to gross disease and radiologically uninvolved neck nodal levels, are discussed.

Effect of patient setup errors on simultaneously integrated boost head and neck IMRT treatment plans

PURPOSE

The purpose of this study is to determine dose delivery errors that could result from random and systematic setup errors for head-and-neck patients treated using the simultaneous integrated boost (SIB)-intensity-modulated radiation therapy (IMRT) technique.

METHODS AND MATERIALS

Twenty-four patients who participated in an intramural Phase I/II parotid-sparing IMRT dose-escalation protocol using the SIB treatment technique had their dose distributions reevaluated to assess the impact of random and systematic setup errors. The dosimetric effect of random setup error was simulated by convolving the two-dimensional fluence distribution of each beam with the random setup error probability density distribution. Random setup errors of sigma = 1, 3, and 5 mm were simulated. Systematic setup errors were simulated by randomly shifting the patient isocenter along each of the three Cartesian axes, with each shift selected from a normal distribution. Systematic setup error distributions with Sigma = 1.5 and 3.0 mm along each axis were simulated. Combined systematic and random setup errors were simulated for sigma = Sigma = 1.5 and 3.0 mm along each axis. For each dose calculation, the gross tumor volume (GTV) received by 98% of the volume (D(98)), clinical target volume (CTV) D(90), nodes D(90), cord D(2), and parotid D(50) and parotid mean dose were evaluated with respect to the plan used for treatment for the structure dose and for an effective planning target volume (PTV) with a 3-mm margin.

RESULTS

Simultaneous integrated boost-IMRT head-and-neck treatment plans were found to be less sensitive to random setup errors than to systematic setup errors. For random-only errors, errors exceeded 3% only when the random setup error sigma exceeded 3 mm. Simulated systematic setup errors with Sigma = 1.5 mm resulted in approximately 10% of plan having more than a 3% dose error, whereas a Sigma = 3.0 mm resulted in half of the plans having more than a 3% dose error and 28% with a 5% dose error. Combined random and systematic dose errors with sigma = Sigma = 3.0 mm resulted in more than 50% of plans having at least a 3% dose error and 38% of the plans having at least a 5% dose error. Evaluation with respect to a 3-mm expanded PTV reduced the observed dose deviations greater than 5% for the sigma = Sigma = 3.0 mm simulations to 5.4% of the plans simulated.

CONCLUSIONS

Head-and-neck SIB-IMRT dosimetric accuracy would benefit from methods to reduce patient systematic setup errors. When GTV, CTV, or nodal volumes are used for dose evaluation, plans simulated including the effects of random and systematic errors deviate substantially from the nominal plan. The use of PTVs for dose evaluation in the nominal plan improves agreement with evaluated GTV, CTV, and nodal dose values under simulated setup errors. PTV concepts should be used for SIB-IMRT head-and-neck squamous cell carcinoma patients, although the size of the margins may be less than those used with three-dimensional conformal radiation therapy.

Predictive factors of local-regional recurrences following parotid sparing intensity modulated or 3D conformal radiotherapy for head and neck cancer

BACKGROUND AND PURPOSE

Predictive factors for local-regional (LR) failures after parotid-sparing, Intensity modulated (IMRT) or 3D conformal radiotherapy for head and neck (HN) cancers were assessed.

PATIENTS AND METHODS

One hundred and fifty-eight patients with mostly stages III-IV HN squamous cell carcinoma underwent curative bilateral neck irradiation aimed at sparing the parotid glands. Patient, tumor, and treatment factors were analyzed as predictive factors for LR failure.

RESULTS

Twenty-three patients had LR recurrence (19 in-field and four marginal). No differences were found in the doses delivered to the PTVs of patients with or without in-field recurrences. In univariate analysis, tumor site was highly predictive for LR failure in both postoperative and definitive RT patients. In postoperative RT patients, pathologic tumor size, margin status, extracapsular extension (ECE) and number of lymph node metastases, were also significantly predictive. Multivariate analysis showed tumor site (oropharynx vs. other sites) to be a significant predictor in all patients, and involved margins and number of involved lymph nodes in postoperative patients.

CONCLUSIONS

Clinical rather than dosimetric factors predicted for LR failures in this series, and were similar to those reported following standard RT. These factors may aid in the selection of patients for studies of treatment intensification using IMRT.

Comparing step-and-shoot IMRT with dynamic helical tomotherapy IMRT plans for head-and-neck cancer

PURPOSE

The goal of this planning study was to compare step-and-shoot intensity-modulated radiotherapy (IMRT) plans with helical dynamic IMRT plans for oropharynx patients on the basis of dose distribution.

METHODS AND MATERIALS

Five patients with oropharynx cancer had been previously treated by step-and-shoot IMRT at the University Medical Centre Utrecht, The Netherlands, applying five fields and approximately 60-90 segments. Inverse planning was carried out using Plato, version 2.6.2. For each patient, an inverse IMRT plan was also made using Tomotherapy Hi-Art System, version 2.0, and using the same targets and optimization goals. Statistical analysis was performed by a paired t test.

RESULTS

All tomotherapy plans compared favorably with the step-and-shoot plans regarding sparing of the organs at risk and keeping an equivalent target dose homogeneity. Tomotherapy plans in particular realized sharper dose gradients compared with the step-and-shoot plans. The mean dose to all parotid glands (n = 10) decreased on average 6.5 Gy (range, -4 to 14; p = 0.002). The theoretical reduction in normal tissue complication probabilities in favor of the tomotherapy plans depended on the parotid normal tissue complication probability model used (range, -3% to 32%).

CONCLUSION

Helical tomotherapy IMRT plans realized sharper dose gradients compared with the clinically applied step-and shoot plans. They are expected to be able to reduce the parotid normal tissue complication probability further, keeping a similar target dose homogeneity.

The sensitivity of dose distributions for organ motion and set-up uncertainties in prostate IMRT

BACKGROUND AND PURPOSE

To determine the effect of organ motion and set-up uncertainties on IMRT dose distributions for prostate.

METHODS

For five patients, IMRT techniques were designed to irradiate the CTV (prostate plus seminal vesicles). Technique I delivered 78 Gy to PTV1 (CTV+10 mm margin). Technique II delivered 68 Gy to PTV1, and a 10 Gy boost to PTV2 (CTV+an anisotropic margin of 0 to 5 mm). Technique III delivered 68 Gy to PTV1 and simultaneously 78 Gy to PTV2. Uncertainties were simulated using population statistics of organ motion and set-up accuracy. The average TCP (TCPpop) of the CTV and average NTCP (NTCPpop) of the rectal wall were calculated.

RESULTS

The planning TCP was a good predictor for TCPpop for Techniques I and II. Technique III was sensitive for geometrical uncertainties, reducing TCPpop by 0.8 to 2.4% compared to planning. NTCPpop was reduced for Technique III by a factor 2.6 compared to Technique I. For all plans, the planning NTCP was strongly correlated with NTCPpop.

CONCLUSIONS

Dose distributions created with Techniques I and II are insensitive for geometrical uncertainties, while Technique III resulted in a reduction of TCPpop. This reduction can be compensated by a small dose escalation, while still resulting in an NTCPpop of the rectal wall that is lower or comparable to Technique I.

A comparison of mean parotid gland dose with measures of parotid gland function after radiotherapy for head-and-neck cancer: implications for future trials

PURPOSE

To determine the most adequate parameter to measure the consequences of reducing the parotid gland dose.

METHODS AND MATERIALS

One hundred eight patients treated with radiotherapy for various malignancies of the head and neck were prospectively evaluated using three methods. Parotid gland function was objectively determined by measuring stimulated parotid flow using Lashley cups and scintigraphy. To assess xerostomia-related quality of life, the head-and-neck cancer module European Organization for Research and Treatment of Cancer QLQ (Quality of Life Questionnaire) H&N35 was used. Measurements took place before radiotherapy and 6 weeks and 12 months after the completion of radiotherapy. Complication was defined for each method using cutoff values. The correlation between these complications and the mean parotid gland dose was investigated to find the best measure for parotid gland function.

RESULTS

For both flow and scintigraphy data, the best definition for objective parotid gland toxicity seemed to be reduction of stimulated parotid flow to < or =25% of the preradiotherapy flow. Of all the subjective variables, only the single item dry mouth 6 weeks after radiotherapy was found to be significant. The best correlation with the mean parotid gland dose was found for the stimulated flow measurements. The predictive ability was the highest for the time point 1 year after radiotherapy. Subjective findings did not correlate with the mean parotid dose.

CONCLUSIONS

Stimulated flow measurements using Lashley cups, with a complication defined as flow < or =25% of the preradiotherapy output, correlated best with the mean parotid gland dose. When reduction of the mean dose to the parotid gland is intended, the stimulated flow measurement is the best method for evaluating parotid gland function.

Review of current treatment practices for carcinoma of the head and neck

The past two decades have witnessed a paradigm shift in the treatment of squamous cell carcinoma of the head and neck. Innovation in chemotherapy, radiotherapy and surgery has led to the assimilation of these modalities into our treatment algorithms. This modern multipart treatment plan has led to improved survival; however, this has come at the cost of increased toxicity. New and future therapies will be more tumour specific and, ideally, less toxic. Current research centres on these tumour-specific therapies with the anticipation of improved survival with decreased toxicity. This article will review the standard of care, recent advances and unfulfilled needs in the treatment of squamous cell carcinoma of the head and neck.

Dose sculpting with generalized equivalent uniform dose

With intensity-modulated radiotherapy (IMRT), a variety of user-defined dose distribution can be produced using inverse planning. The generalized equivalent uniform dose (gEUD) has been used in IMRT optimization as an alternative objective function to the conventional dose-volume-based criteria. The purpose of this study was to investigate the effectiveness of gEUD optimization to fine tune the dose distributions of IMRT plans. We analyzed the effect of gEUD-based optimization parameters on plan quality. The objective was to determine whether dose distribution to selected structures could be improved using gEUD optimization without adversely altering the doses delivered to other structures, as in sculpting. We hypothesized that by carefully defining gEUD parameters (EUD0 and n) based on the current dose distributions, the optimization system could be instructed to search for alternative solutions in the neighborhood, and we could maintain the dose distributions for structures already satisfactory and improve dose for structures that need enhancement. We started with an already acceptable IMRT plan optimized with any objective function. The dose distribution was analyzed first. For structures that dose should not be changed, a higher value of n was used and EUD0 was set slightly higher/lower than the EUD value at the current dose distribution for critical structures/targets. For structures that needed improvement in dose, a higher to medium value of n was used, and EUD0 was set to the EUD value or slightly lower/higher for the critical structure/target at the current dose distribution. We evaluated this method in one clinical case each of head and neck, lung and prostate cancer. Dose volume histograms, isodose distributions, and relevant tolerance doses for critical structures were used for the assessment. We found that by adjusting gEUD optimization parameters, the dose distribution could be improved with only a few iterations. A larger value of n could lead to faster convergence and a medium value of n could result in a search in a broader area. Such improvement could also be achieved by optimization based on other criteria, but the gEUD-based method has the advantage of efficiency and flexibility. Therefore, gEUD-based optimization can be used as a tool to improve IMRT plans by adjusting the planning parameters, thereby making dose sculpting feasible.

Application of intensity-modulated radiation therapy for pediatric malignancies

Novel radiation therapy delivery techniques have moved very slowly in the field of pediatric oncology. Some collaborative groups allow new radiation therapy delivery techniques in their trials. In many instances, the option of using these techniques is not addressed. These newer techniques of radiation delivery have the potential to reduce the probability of the common late effects of radiation and at the same time, potentially improve upon control and survival. The purpose of this study is to show the feasibility of IMRT in pediatric patients. No treatment results or toxicities will be presented. Five patients with a variety of pediatric malignancies received intensity-modulated radiation therapy (IMRT) at our institution as part of their disease management. A rigid immobilization device was developed for each patient and a computed tomography (CT) simulation was performed in the treatment position. In 3 of the patients, magnetic resonance imaging (MRI) scans were coregistered with the planning CT to facilitate target and critical structure delineation. In all but 1 patient, coplanar beam arrangements were used in the IMRT planning process. All IMRT plans exhibited a high degree of conformality. Dose homogeneity inside the tumor and rapid dose falloff outside the target volume is characteristic of IMRT plans, which allows for improved normal tissue sparing. Dose distributions were obtained for all plans, as well as dose and volume relationship histograms, to evaluate the fitness of the plans. IMRT is a viable alternative to conventional treatment techniques for pediatric cancer patients. The improved dose distributions coupled with the ease of delivery of the IMRT fields make this technique very attractive, especially in view of the potential to increase local control and possibly improve on survival.

Dosimetric advantages of IMRT simultaneous integrated boost for high-risk prostate cancer

PURPOSE

A sequential two-phase process, initial and boost irradiation, is the common practice for the radiotherapy management of high-risk prostate cancer. In this work, we explore the feasibility of using intensity modulated radiation therapy (IMRT) simultaneous integrated boost (SIB), a single-phase process, to simultaneously deliver high dose to the prostate and lower dose to the pelvic nodes. In addition, we introduce the concept of voxel-equivalent dose for the comparison of treatment plans.

METHODS AND MATERIALS

The SIB is designed to deliver the same dose (e.g., 45 Gy, 25 x 1.8 Gy) as the conventional method to the pelvic nodes and to deliver higher doses to prostate in the same 25 fractions (i.e., hypofractionation). The equivalent uniform dose (EUD) was used to determine suitable SIB fractionations that deliver the biologically equivalent doses to prostate. For tumor, the EUD was estimated based on the linear quadratic (LQ) model. The most recent LQ parameters derived from clinical data for prostate cancer were used. The sensitivity of LQ parameters was evaluated. The EUD for normal tissue was computed based on the widely used Lyman model. To be able to consider biologic effectiveness spatially (e.g., voxel by voxel), we propose a new concept, termed the voxel-equivalent dose (VED). The calculation of VED was similar to that for EUD, except that it was done within a voxel. To demonstrate dosimetric feasibility and advantages of the proposed IMRT SIB, we have performed a retrospective planning study on selected patient cases using commercial IMRT and three-dimensional (3D) planning systems. Four treatment scenarios were considered: (1) the conventional 3D plan for initial whole-pelvic irradiation and subsequent conventional 3D boost plan for prostate gland, (2) the conventional 3D plan for initial whole-pelvic irradiation and subsequent IMRT boost plan for prostate, (3) IMRT plan for initial whole-pelvic irradiation and subsequent IMRT boost plan for prostate, and (4) IMRT SIB. EUDs and VED-based dose-volume histograms for prostate, pelvic nodes, small bowel, rectum, bladder, and other tissue for all 4 scenarios were compared.

RESULTS

A series of equivalent hypofractionation regimens suitable for the IMRT SIB were obtained for high-risk prostate cancer. For example, the conventional treatment regimen of 42 x 1.8 Gy (EUD = 75.4 Gy) would be equivalent to a SIB regimen of 25 x 2.54 Gy. From the comparison of 3D VED dose distributions and dose-volume histograms between the SIB and the conventional two-phase irradiation, we found that the SIB offers better or equivalent dose conformity to prostate and pelvic nodes and better sparing to the critical structures. For example, for the 4 treatment scenarios with a prostate EUD of 75.4 Gy, the corresponding rectal EUDs are 67.1 (3D + 3D), 65.6 Gy (3D + IMRT), 63.7 Gy (IMRT + IMRT), and 62.0 Gy (SIB).

CONCLUSIONS

A new IMRT simultaneous integrated boost strategy that irradiates prostate via hypofractionation while irradiating pelvic nodes with the conventional fractionation is proposed for high-risk prostate cancer. Compared to the conventional two-phase treatment, the proposed SIB technique offers potential advantages, including better sparing of critical structures, more efficient delivery, shorter treatment duration, and better biologic effectiveness.

Les carcinomes du nasopharynx : de la biologie à la clinique

Nasopharyngeal carcinomas (NPC) are very different from other head and neck cancers because of their specific multifactorial etiology and their geographic distribution. Epstein-Barr Virus (EBV) is implicated in oncogenesis of NPC in association with genetic alterations such as inactivation of the p16/Ink4, p19/ARF, RASSF1 or Blu genes. Tumoral tissues include a very abundant characteristic lymphoid infiltrate. Inflammatory cytokines are produced by both malignant and infiltrating cells. There is no efficient immune response against the tumor. On the opposite, infiltrating lymphocytes might play a role in tumor development. Serological methods and detection of circulating viral DNA are expected to become useful for early detection of relapse and on a longer term for primary screening. NPC are often diagnosed at a late stage because patients may remain asymptomatic for a long time. Computed tomography (CT scan) and magnetic resonance imaging (MRI) are complementary for the initial evaluation. Positron emission tomography (PET) is efficient for the evaluation of treatment efficiency and detection of relapses. Treatment is based on radiotherapy and chemotherapy. Their optimal use needs to be evaluated by phase III trials but positive results have been obtained by concomitant association of radiotherapy and chemotherapy. Targeted therapies are being studied with strategies based on disruption of viral latency, use of replicative adenoviruses or anti-tumor vaccination.

Intensity-modulated radiation therapy in the treatment of head and neck cancer

Intensity-modulated radiation therapy (IMRT) is a new technical improvement of radiotherapy, in which computer-controlled treatment machines produce multiple beams of radiotherapy whose intensity is optimized to deliver a high dose of radiation to specified volumes, while reducing the dose to adjacent non-target organs. The potential benefits include the ability to deliver higher doses to the target with an improved safety than has previously been possible, and to reduce side effects and complications. Using IMRT to treat some head and neck cancers is especially attractive due to the close vicinity of the targets and many critical, dose-limiting and non-involved structures, and because of the lack of breathing-related motion. The main clinical uncertainties in the use of IMRT for head and neck cancer relate to uncertainties in the extent of radiation to the target areas. In addition, large volumes of adjacent, non-target tissue receive moderate to low radiation doses, raising concerns of increased risk of radiation-related carcinogenesis in young patients. Initial promising clinical data have emerged from IMRT treatment of several head and neck tumor sites.

Simultaneous integrated boost intensity-modulated radiotherapy for locally advanced head-and-neck squamous cell carcinomas: II—clinical results

PURPOSE

To perform a Phase I radiation dose-escalation trial to determine the maximal tolerable dose (MTD) deliverable to the gross tumor volume (GTV) using an accelerated fractionation with simultaneous integrated boost intensity-modulated radiotherapy regimen with parotid gland sparing as the sole therapy in the treatment of locally advanced head-and-neck squamous cell carcinoma. The primary objective was the definition of the MTD using established criteria of quantifying acute dose-limiting toxicity (DLT). Secondary objectives included analysis of failure patterns, tumor control rates, and toxicity.

METHODS AND MATERIALS

Between July 1999 and June 2002, eligible patients with bulky Stage II to Stage IVB head-and-neck squamous cell carcinoma, excluding laryngeal primaries, were enrolled. Intensity-modulated radiotherapy was delivered with 6-MV photons using a "sliding-window" technique. Enrollment of 6 patients for each dose level was planned; if DLTs were seen in >2 of 6 patients, the previous dose was to be expanded by an additional 6 patients to confirm that dose level as the MTD. All schedules administered a total of 30 fractions, but with escalating doses per fraction (2.27, 2.36, and 2.46 Gy) to achieve a total dose to the GTV of 68.1, 70.8, and 73.8 Gy, respectively. The remaining target tissues were constrained to receive the same dose in all patients regardless of the GTV dose level. The clinical target volume, defined as tissue within 1 cm around the GTV (at high risk of subclinical disease), received 60 Gy in 30 fractions of 2.0 Gy. The electively irradiated target volume, defined as the clinically uninvolved lymph node-bearing tissues, received 54 Gy in 30 fractions of 1.8 Gy. The parotid glands were spared to the degree possible without compromising target coverage. Acute toxicity was scored weekly using National Cancer Institute Common Toxicity Criteria. DLT was defined as any Grade 4 acute toxicity or any acute toxicity requiring either a dose reduction or a treatment break of >5 treatment days.

RESULTS

Of 18 men and 2 women (average age, 57 years; range, 37-80 years), 17 presented with oropharyngeal primary tumors, and 1 each with squamous cell carcinoma of the oral cavity, nasopharynx, and hypopharynx. None of the 6 patients at dose level 1, and 2 of the 6 patients initially enrolled at dose level 2, developed DLT. Both patients treated at dose level 3 required a 3-day treatment break and dose reduction after rapid development of Grade 3 toxicity (by Day 15). Six additional confirmatory patients subsequently enrolled at dose level 2 completed treatment without DLT. At least 50% of the total parotid gland volume received <30 Gy in 14 patients (average, 54% of volume), with an average mean dose of 32 Gy. In contrast, >/=50% of the distal parotid gland volume received <25 Gy in 15 patients (average, 63% of volume), with an average mean dose of 24 Gy. With a median follow-up of 20 months from the date of enrollment and 28 months for surviving patients, the actuarial 2-year local control (primary site), regional control (nodal sites), and distant control rate was 76.3%, 66.7%, and 71.8%, respectively.

CONCLUSION

Dose level 2, 70.8 Gy in 30 fractions of 2.36 Gy, was defined as the MTD deliverable to the GTV using this accelerated fractionation with simultaneous integrated boost intensity-modulated radiotherapy regimen with parotid gland sparing as the sole treatment for locally advanced head-and-neck squamous cell carcinoma. Adequate parotid sparing was achievable in most cases. Early toxicity, tumor control, and survival rates compared favorably with the outcomes after other accelerated regimens.

Planning quality and delivery efficiency of sMLC delivered IMRT treatment of oropharyngeal cancers evaluated by RTOG H-0022 dosimetric criteria

The time required to deliver intensity‐modulated radiation therapy (IMRT) treatments can be significantly longer than conventional treatments, especially for the segmented multileaf collimator (sMLC) delivery system with a large record and verification (R&V) overhead. In this work, we evaluate the impact of the number of intensity‐modulated beams (IMBs) and the number of intensity levels (ILs) on the quality and delivery efficiency of IMRT plans, generated by the Corvus planning system for sMLC delivery on a Siemens LINAC with the Lantis R&V system. Detailed studies were performed for three image data sets of previously treated oropharyngeal patients. Treatment plans for patient 1 were developed using 5, 7, 9, or 15 evenly spaced axial IMBs as well as one with 7 axial IMBs whose directions were user‐selected, each using ILs of 3, 5, 10, or 20. For patients 2 and 3, plans with 15 IMBs and 20 ILs were not attempted. A total of 42 plans were developed using three oropharyngeal cancer CT image data sets. Plan quality was evaluated by assessing compliance with the Radiation Therapy Oncology Group (RTOG) H‐0022 protocol criteria and the physician's clinical judgment. Plan efficiency was accessed by the number of segments of each plan. We found that for our treatment‐planning and delivery system, an IMRT plan that uses a moderate number of IMBs and ILs, such as 7 or 9 IMBs with 3 or 5 ILs, would appear to be the optimal approach when both quality of the plan and delivery efficiency are considered. Based on this study, we have routinely used 9 IMBs with 3 ILs or 7 IMBs with 5 ILs for head and neck patients. A retrospective comparison indicates that delivery efficiency is improved on the order of 30% compared to plans generated with 9 IMBs with 5 ILs.

PACS number: 87.53.Tf

Simultaneous integrated boost for breast cancer using imrt: a radiobiological and treatment planning study

PURPOSE

The purpose of this work is to explore the possibility of using intensity-modulated radiation therapy (IMRT) to deliver the boost dose to the tumor bed simultaneously with the whole-breast IMRT to reduce the radiation treatment time by 1-2 weeks.

METHODS AND MATERIALS

The biologically effective dose (BED) for different treatments was calculated using the linear-quadratic (LQ) model with parameters previously derived for breast cancer from clinical data (alpha/beta = 10Gy, alpha = 0.3Gy(-1)). A potential doubling time of 15 days (from in vitro measurements) for breast cancer and a generic alpha/beta ratio of 3 Gy for normal tissues were used. A series of regimens that use IMRT as initial treatment and an IMRT simultaneous integrated boost (SIB) were derived using biologic equivalence to conventional schedules. Possible treatment plans with IMRT SIB to the tumor bed were generated for 2 selected breast patients, 1 with a shallow tumor and 1 with a deep-seated tumor. Plans with a simultaneous integrated electron boost were also generated for comparison. Dosimetric merits of these plans were evaluated based on dose volume histograms.

RESULTS

A commonly used conventional treatment of 45 Gy (1.8 Gy x 25) to the whole breast and then a boost of 20 Gy (2 Gy x 10) is biologically equivalent to an alternative plan of 1.8 Gy x 25 to the whole breast with a 2.4 Gy x 25 SIB to the tumor bed. The new regime reduces treatment time from 7 to 5 weeks. For the patient with a deep-seated tumor, the IMRT plans reduce the volume of the breast that receives high doses (compared with the conventional photon boost plan) and provides good coverage of the target volumes.

CONCLUSION

It is biologically and dosimetrically feasible to reduce the overall treatment time for breast radiotherapy by using an IMRT simultaneous integrated boost. For selected patient groups, IMRT plans with a new regimen can be equal to or better than conventional plans.

Potential outcomes of modalities and techniques in radiotherapy for patients with hypopharyngeal carcinoma

BACKGROUND AND PURPOSE

To determine potential improvements in treatment outcome for patients with hypopharyngeal carcinoma, T4N0M0, using proton and intensity modulated photon radiotherapy (IMRT) compared to a standard 3D conformal radiotherapy treatment (3D-CRT) in terms of local tumour control probability, TCP, and normal tissue complication probability (NTCP) for the spinal cord and the parotid glands using.

PATIENTS AND METHODS

Using the three-dimensional treatment-planning system, Helax-TMS, 5 patients were planned with protons, IMRT, and 3D-CRT plans. The prescribed dose used was 30 fractions x 2.39 Gy for the protons and IMRT and 35 fractions x 2.00 Gy for 3D-CRT. The treatment plans were evaluated using dose volume data and dose response models were used to calculate TCP and NTCP. The target volumes were delineated to spare the parotid glands. A dose escalation was made for protons and IMRT using NTCP constraints to the spinal cord.

RESULTS

On average, protons and IMRT increase TCP by 17% compared to 3D-CRT. For the spinal cord NTCP values are zero for all methods and patients. Average NTCP values for the parotid glands were >90% for 3D-CRT and significantly lower for protons and IMRT varying from 43-65%. The average parotid gland dose was 33 Gy for the protons, 38 Gy for IMRT and 48 Gy for 3D-CRT.

CONCLUSIONS

Protons and IMRT gave a significant TCP increase compared to 3D-CRT while no significant difference between protons and IMRT was found. Protons generally show lower non-target tissue doses, which indicates a possibility for further dose escalation. Large individual dose differences between protons and IMRT for parotid glands indicate that some patients may benefit more from protons and others from IMRT.

Les contraintes aux organes à risque en radiothérapie par modulation d'intensité des cancers ORL

Constraint definitions in intensity modulated radiation therapy is a key point factor during the treatment planning process. In literature some data are available about dose constraints and volumes according to the tissue architectures. Following ICRU recommendations, organs at risk organized in a parallel structure could receive an acceptably small proportion of high dose component. Mean dose and dose volume histogram is a most convenient tool for incorporating such constraints. Organs described as a serial structure are supposed to receive less than the given maximum dose, directly linked to the occurrence of complications. Dmax is the best way to describe such events. These constraints are new tools in radiation therapy, available for optimizing the dose distribution in target volume, sparing the organs at risk to protect the organ function or at least decreasing the late functional damages like xerostomia. It is necessary to define with accuracy gross target volumes and clinical target volume with available radio-anatomical guidelines before introducing current constraints on each volume in the inverse dosimetry. The management of these constraints remains under the responsibility of the clinicians. A permanent compromise has to be chosen between homogeneity of the dose distribution in the target volume and the probability of preserving functions of organs at risk.

Intensity-modulated radiation therapy: overlapping co-axial modulated fields

The Varian multi-leaf collimator has a 14.5 cm leaf extension limit from each carriage. This means the target volumes in the head and neck region are sometimes too wide for standard width-modulated fields to provide adequate dose coverage. A solution is to set up asymmetric co-axial overlapping fields. This protects the MLC carriage while in return the MLC provides modulated dose blending in the field overlap region. Planar dose maps for coincident fields from the Pinnacle radiotherapy treatment planning system are compared with planar dose maps reconstructed from radiographic film and electronic portal images. The film and portal images show small leaf-jaw matchlines at each field overlap border. Linear profiles taken across each image show that the observed leaf-jaw matchlines from the accelerator images are not accounted for by the treatment planning system. Dose difference between film reconstructed electronic portal images and planning system are about 2.5 cGy in a modulated field at d(max). While the magnitude of the dose differences are small improved round end leaf modelling combined with a finer dose calculation grid may minimize the discrepancy between calculated and delivered dose.

Independent dosimetric calculation with inclusion of head scatter and MLC transmission for IMRT

Independent verification of the MU settings and dose calculation of IMRT treatment plans is an important step in the IMRT quality assurance (QA) procedure. At present, the verification is mainly based on experimental measurements, which are time consuming and labor intensive. Although a few simplified algorithms have recently been proposed for the independent dose (or MU) calculation, head scatter has not been precisely taken into account in all these investigations and the dose validation has mainly been limited to the central axis. In this work we developed an effective computer algorithm for IMRT MU and dose validation. The technique is superior to the currently available computer-based MU check systems in that (1) it takes full consideration of the head scatter and leaf transmission effects; and (2) it allows a precise dose calculation at an arbitrary spatial point instead of merely a point on the central axis. In the algorithm the dose at an arbitrary spatial point is expressed as a summation of the contributions of primary and scatter radiation from all beamlets. Each beamlet is modulated by a dynamic modulation factor (DMF), which is determined by the MLC leaf trajectories, the head scatter, the jaw positions, and the MLC leaf transmission. A three-source model was used to calculate the head scatter distribution for irregular segments shaped by MLC and the scatter dose contributions were computed using a modified Clarkson method. The system reads in MLC leaf sequence files (or RTP files) generated by the Corvus (NOMOS Corporation, Sewickley, PA) inverse planning system and then computes the doses at the desired points. The algorithm was applied to study the dose distributions of several testing intensity modulated fields and two multifield Corvus plans and the results were compared with Corvus plans and experimental measurements. The final dose calculations at most spatial points agreed with the experimental measurements to within 3% for both the specially designed testing fields and the clinical intensity modulated field. Furthermore, excellent agreement (mostly within +/- 3.0%) was also found between our independent calculation and the ion chamber measurements at both central axis and off-axis positions for the multifield Corvus IMRT plans. These results indicate that the approach is robust and valuable for routine clinical IMRT plan validation.

A study of planning dose constraints for treatment of nasopharyngeal carcinoma using a commercial inverse treatment planning system

PURPOSE

The purpose of this study was to develop and test planning dose constraint templates for tumor and normal structures in the treatment of nasopharyngeal carcinoma (NPC) using a specific commercial inverse treatment planning system.

METHODS AND MATERIALS

Planning dose constraint templates were developed based on the analyses of dose-volume histograms (DVHs) of tumor targets and adjacent sensitive structures by clinically approved treatment plans of 9 T1-2 and 16 T3-4 NPC patients treated with inverse planned intensity-modulated radiation therapy (IP-IMRT). DVHs of sensitive structures were analyzed by examining multiple defined endpoints, based on the characteristics of each sensitive structure. For each subgroup of patients with T1-2 and T3-4 NPC, the resulting mean values of these defined endpoint doses were considered as templates for planning dose constraints and subsequently applied to a second group of patients, 5 with T1-2 NPC and 5 with T3-4 NPC. The 10 regenerated plans (called new plans) were compared to the original clinical plans that were used to treat the second group of patients, based on plan conformity index and DVHs.

RESULTS

The conformity indices of the new plans were comparable to the original plans with no statistical difference (p = 0.85). Among the serial sensitive structures evaluated, there was a significant decrease with the new plans in the dose to the spinal cord when analyzed by the maximum dose (p = 0.001), doses encompassing 1 cc of the spinal cord volume (p = 0.001) and 3 cc of the spinal cord volume (p = 0.001). There was no significant difference in the mean maximum dose to the brainstem between the new plans and the original plans (p = 0.36). However, a significant difference in the mean maximum dose to the brainstem was seen among the different T-stages (p = 0.04). A decrease with the new plan to the brainstem in the doses encompassing 5% and 10% of the volume was of borderline statistical significance (p = 0.08 and p = 0.06, respectively). There were no statistical differences between the new plans and the original plans in the mean doses to the chiasm, optic nerve, or eye for each of the endpoints considered. For parallel sensitive structures in the new plans, there was a significant increase in the average mean dose to the parotid glands (p = 0.01), a decrease that was of borderline significance in the average mean dose to the temporomandibular joint (p = 0.07), but no difference in the average mean dose to the ear.

CONCLUSIONS

The statistical analysis showed that new plans are comparable to the original plans for most of the sensitive structures except for a trade-off between a dose reduction to the spinal cord in the new plans and an increase in the mean dose to the parotid glands. These tested planning dose constraint templates can serve as good "starting points" for an inverse plan of NPC using a specific commercial inverse treatment planning system.

Four Decades of Continuing Innovation With Fluorouracil: Current and Future Approaches to Fluorouracil Chemoradiation Therapy

Purpose

Chemoradiotherapy, the combination of external radiation therapy and concurrent chemotherapy, has been the basis for the oncologic management of many patients since its development in the 1960s. Fluorouracil (FU) chemoradiotherapy has demonstrated success in several organ sites with multiple dosing schedules that now guide the selection of oral analogs of FU to provide new chemoradiotherapy options.

Methods

This article reviews the metabolism and pharmacology of FU and the advantages of administration of FU by continuous infusion or bolus. The potential role and impact of the oral fluorouracil prodrugs UFT, S-1, BOF-A2, and capecitabine as replacements for intravenous administration are discussed. The results of recent chemoradiotherapy studies with FU from 2000 to 2003 are summarized in rectal, head and neck, esophageal, gastric, pancreatic, biliary, anal, and cervical cancers.

Results

Chemoradiotherapy with FU has the potential to widen the therapeutic window by minimizing normal tissue toxicity while maintaining effective tumor toxicity. Overall, FU chemoradiotherapy maximizes local control and, for some tumor sites (such as head and neck, pancreatic, biliary, cervical, esophageal, and gastric cancers), improves survival rates. Moreover, FU chemoradiotherapy results in improved organ preservation with excellent functional outcome in several anatomic sites including head and neck cancer, anal, and rectal cancer, with improved sphincter preservation.

Conclusion

FU chemoradiotherapy continues to play an important role in the management of many cancer sites. During the last four decades, optimal dosing schedules have produced a therapeutic gain. The introduction of oral prodrug analogs will likely further improve the results of FU therapy in several organ systems, such as the rectum, head and neck, and esophagus.

Radiothérapie conformationnelle avec modulation d'intensité des cancers des voies aérodigestives supérieures avec irradiation bilatérale du cou : résultats préliminaires

PURPOSE

To report preliminary results of a prospective study of intensity-modulated radiotherapy (IMRT) for head and neck squamous cell carcinoma (HNC) with bilateral irradiation of the neck.

PATIENTS AND METHODS

At the Alexis Vautrin Cancer Center, 23 patients have been treated with IMRT for HNC since January 2002-August 2003. The first 10 patients with a minimum follow-up of 3 months were analyzed. All tumors were oropharyngeal. There were four females and six males, with a mean age of 50 years (range 39-66). Stages were I-II in eight and III-IV in two. CTV1 was microscopic disease and N0 neck (prescribed dose : 50 Gy) and CTV2 was macroscopic disease and the volume at risk (prescribed dose: 66-70 Gy). PTV were CTV + 5 mm. Patient's immobilization consisted of a five-point head neck shoulder thermoplastic mask. Set-up verifications were done by semi-automatically matching portal images and digitized reconstructed radiographs. IMRT used dynamic multileaf collimation. Five patients (group A) received 50 Gy IMRT (two post-operative and three with a brachytherapy boost with a mean dose: 27.5 Gy), and five patients (group B) received 66-70 Gy IMRT (four post-operative). Acute and late normal tissue effects were graded according to the RTOG-EORTC radiation morbidity scoring criteria.

RESULTS

With a median follow-up of 7.4 months (range 3-18.5), no patient died or had loco-regional relapse. The displacements were <4 mm in 98% cases. CTV1 and 2 received 95% of the prescribed dose in 100% of the volume. On average the mean dose to the contralateral parotid was 25.5 Gy for group A vs. 31 Gy for group B (P = 0.09). Mean doses <26 Gy were obtained in three of five patients in group A vs. zero of five patients in group B (P = 0.04). Acute skin toxicities were grade 1 in five patients, grade 2 in four and grade 3 in one. Acute mucositis cases were grade 1 in three patients, grade 2 in five and localized grade 3 in two. At 3 months, 50% of the patients had a grade 0-1 late xerostomia.

CONCLUSION

The 26 Gy dose limit constraint to the contralateral parotid was easier to satisfy when IMRT was prescribed at a maximum dose of 50 Gy. Acute toxicity is low. The displacements in the mask indicate that it is possible to define the PTV as CTV + 4 mm. This reduction should decrease the mean dose to the parotids. At 3 months, a 50% rate of grade 0-1 late xerostomia encourages the hope of a very low rate at 2 years.

Recurrences near base of skull after IMRT for head-and-neck cancer: implications for target delineation in high neck and for parotid gland sparing

PURPOSE

Locoregional (LR) failures near the base of the skull, and their relationships to the targets in the high neck, were examined in a series of patients who underwent intensity-modulated radiotherapy (IMRT) for head-and-neck cancer.

METHODS AND MATERIALS

Between 1994 and 2002, 133 patients with non-nasopharyngeal head-and-neck squamous cell carcinoma completed a course of curative, parotid-sparing RT. Treatment was delivered until 1996 with conformal three-dimensional techniques and thereafter with multisegmental static IMRT. Of the 133 patients, 80 had oropharyngeal, 27 oral cavity, 12 hypopharyngeal, 11 laryngeal, and 3 unknown primary cancer. The AJCC stage was I in 1, II in 6, III in 26, IVA in 83, and IVB in 12; cancer was recurrent in 5. Sixty patients received primary and 73 postoperative IMRT. 86% of patients (n = 115) had ipsilateral neck metastasis. In all patients, the contralateral neck was clinically node negative but was judged to be at high risk of subclinical disease. Delineation of the superior-most extent of the nodal targets was consistent and corresponded with Rouviere's observations. In the contralateral clinically node-negative neck, the uppermost Level II nodal target was the subdigastric (SD) nodes. To ensure coverage, the uppermost clinical target volume was delineated at the axial CT image in which the posterior belly of the digastric muscle crossed the jugular vein. In the ipsilateral neck, which was node positive in most patients, the uppermost Level II clinical target volume was delineated through the base of the skull. The uppermost retropharyngeal (RP) nodal target was delineated at the level of the top of the C1 vertebral body, accommodating Rouviere's description of the location of the lateral RP nodes. The dose prescription was 70 Gy for the primary planning target volumes (PTVs); 64 Gy and 60 Gy for PTV of the postoperative beds with and without extracapsular extension, respectively; and 50-54 Gy for PTVs of nonoperated subclinical disease, at 1.8-2.0 Gy fractions. In-field or marginal recurrences were defined as those occurring when >95% or 20-95% of the recurrence volume, respectively, had received >95% of the prescribed dose.

RESULTS

At a median follow-up of 32 months (range, 6-107 months), 21 patients (16%) had locoregional recurrence. Seventeen recurrences were in-field and four were marginal. The most prevalent nodal recurrence was in Level II bilaterally, where all failures were in-field. In-field failures were observed in the ipsilateral high neck cranial to the SD nodes (all in initially node-positive neck). No recurrences occurred in the contralateral high neck, cranial to the SD nodes, which was not included in the targets. The 95% confidence interval for the risk of recurrence in that region was 0-2.7%. Three RP nodal failures were observed; two were marginal, occurring ipsilateral and contralateral to the primary tumors, and centered cranial to the top of C1. After these recurrences, the RP nodal clinical target volumes were delineated bilaterally through the base of skull, without subsequent RP recurrence. These target delineation guidelines allowed the achievement of a mean contralateral parotid dose of < or =26 Gy (found previously to preserve salivary output significantly) in 82% of the patients. The 3-year actuarial LR recurrence-free survival rate of primary and postoperative IMRT patients was similar (81% and 84%, respectively). Oropharyngeal cancer patients had the greatest LR recurrence-free survival rate (94%, p <0.001). No statistically significant differences were found in the dose delivered to the PTVs or the in-field recurrence volume between patients who had or did not have LR failure.

CONCLUSION

These results suggest that when the contralateral node-negative side of the neck has a high risk of subclinical metastasis, it is adequate to include the SD nodes as the cranial-most Level II nodal target in non-nasopharyngeal head-and-neck cancer. In the node-positive side of the neck, this nodal level should be delineated more cranially. The RP nodal targets should be delineated more cranially. The RP nodal targets should be delineated bilaterally and should extend to the base of the skull, rather than to the top of C1. These guidelines allowed substantial sparing of the contralateral parotid gland. The results of this series validate a consensus for target delineation adopted recently by cooperative radiotherapy groups.

Dosimetric study of optimal beam number and arrangement for treatment of nasopharyngeal carcinoma with intensity-modulated radiation therapy

The purpose of this dosimetric study was to evaluate the effect of beam number and arrangement on the dose distribution with intensity-modulated radiation therapy in patients with nasopharyngeal cancer. Computed tomography data sets of seven patients who were treated for nasopharyngeal carcinoma at the Peter MacCallum Cancer Centre were used for the present dosimetric study. The dose planned was 70 Gy in 7 weeks for the gross nasopharyngeal and nodal disease and the biological equivalents of 60 Gy in 6 weeks for the high-risk and 50 Gy in 5 weeks for the low-risk nodal disease. A plan using seven fields was compared to that using nine fields in all patients. Plans were assessed on the dose to the planning target volume (PTV) and the degree of parotid sparing achieved by evaluating both dose-volume histograms (DVH) and axial slices. Seven fields (three anterior and four posterior) provide good PTV coverage and satisfactory parotid sparing in patients with localized nasopharyngeal lesions. Nine fields appear to be better for tumours with significant posterolateral parapharyngeal extension. Parotid sparing is consistently better with nine fields. Both DVH and axial slices need to be evaluated before accepting any plan.

Comparative dosimetric evaluation of the simultaneous integrated boost with photon intensity modulation in head and neck cancer patients

BACKGROUND AND PURPOSE

The objective of this study is to evaluate, at planning and dosimetric level, the potential benefits of the simultaneous integrated boost (SIB) concept with intensity-modulated radiation therapy (IMRT), using a comparative analysis on physical dose distributions corrected for radiobiological models. The concept of SIB at the end of the treatment has been analysed as an alternative acceleration scheme.

PATIENTS AND METHODS

Physical dose distributions were computed on a commercial planning system (Varian Cadplan-Helios) for five patients presenting with advanced head and neck carcinomas. Treatment plans were designed using five IMRT beams. Three fractionation strategies were compared in the study: the standard sequential irradiation SEQ of elective and boost volumes, the pure SIB, and a modified SIB (SEQ/SIB), where the actual SIB follows a first phase of conventional fractionation to the elective volume. All physical dose distributions were corrected using a linear quadratic biological model, taking into account also repopulation and time at repopulation onset. Objective quantities, derived from biological dose volume histograms, were used for the analysis.

RESULTS

Physical doses equivalent to 50 and 80 Gy (in fractions of 2 Gy) to elective volume and boost were calculated for the SIB and SEQ/SIB regimes. With SIB 54 and 72 Gy dose levels have to be delivered in 30 fractions, while in the SEQ/SIB scheme 36 Gy are delivered in 20 sessions to the elective volume, and further 18 and 35.5 Gy during the last 10 fractions are delivered to elective volume and boost, respectively (for a total physical dose of 71.5 Gy). The comparison showed: (1) the boost target homogeneity resulted in generally acceptable and comparable among sequential and modified SIB schemes, while it was statistically worse for the pure SIB approach; (2) the fraction of elective target volume not included in the boost volume was characterised by a higher level of dose heterogeneity; (3) the spinal cord never reached tolerance levels and maximum point dose was on average below 38 Gy (biologically corrected to 2 Gy/fraction); and (4) sparing of parotid glands strongly depends on their eventual inclusion in the target volumes: for glands not included or only partially included, it was possible on average to keep the dose to 2/3 of the volume below 29 Gy for all regimes (32 Gy as physical dose).

CONCLUSIONS

Feasibility of SIB techniques and in particular of the modified SIB appears to be dosimetrically proven and the results reported here justify the activation of a phase I protocol to verify clinically their impact using IMRT photon-based techniques.

A comparison of forward and inverse treatment planning for intensity-modulated radiotherapy of head and neck cancer

BACKGROUND AND PURPOSE

To compare intensity-modulated treatment plans of patients with head and neck cancer generated by forward and inverse planning.

MATERIALS AND METHODS

Ten intensity-modulated treatment plans, planned and treated with a step&shoot technique using a forward planning approach, were retrospectively re-planned with an inverse planning algorithm. For this purpose, two strategies were applied. First, inverse planning was performed with the same beam directions as forward planning. In addition, nine equidistant, coplanar incidences were used. The main objective of the optimisation process was the sparing of the parotid glands beside an adequate treatment of the planning target volume (PTV). Inverse planning was performed both with pencil beam and Monte Carlo dose computation to investigate the influence of dose computation on the result of the optimisation.

RESULTS

In most cases, both inverse planning strategies managed to improve the treatment plans distinctly due to a better target coverage, a better sparing of the parotid glands or both. A reduction of the mean dose by 3-11Gy for at least one of the parotid glands could be achieved for most of the patients. For three patients, inverse planning allowed to spare a parotid gland that had to be sacrificed by forward planning. Inverse planning increased the number of segments compared to forward planning by a factor of about 3; from 9-15 to 27-46. No significant differences for PTV and parotid glands between both inverse planning approaches were found. Also, the use of Monte Carlo instead of pencil beam dose computation did not influence the results significantly.

CONCLUSION

The results demonstrate the potential of inverse planning to improve intensity-modulated treatment plans for head and neck cases compared to forward planning while retaining clinical utility in terms of treatment time and quality assurance.

Comparison of conformal and intensity-modulated techniques for simultaneous integrated boost radiotherapy of upper esophageal carcinoma

AIM: To compare intensity-modulated radiotherapy (IMRT) with conformal radiotherapy (CRT) by investigating the dose profiles of primary tumors, electively treated regions, and the doses to organs at risk.

METHODS: CRT and IMRT plans were designed for five patients with upper esophageal carcinoma. For each patient, target volumes for primary lesions (67.2 Gy) and electively treated regions (50.4 Gy) were predefined. An experienced planner manually designed one CRT plan. Four IMRT plans were generated with the same dose-volume constraints, but with different beam arrangements. Indices including dose distributions, dose volume histograms (DVHs) and conformity index were compared.

RESULTS: The plans with three intensity-modulated beams were discarded because the doses to spinal cord were lager than the tolerable dose 45Gy, and the dose on areas near the skin was up to 50Gy. When the number of intensity beams increased to five, IMRT plans were better than CRT plans in terms of the dose conformity and homogeneity of targets and the dose to OARs. The dose distributions changed little when the beam number increased from five to seven and nine.

CONCLUSION: IMRT is superior to CRT for the treatment of upper esophageal carcinoma with simultaneous integrated boost (SIB). Five equispaced coplanar intensity-modulated beams can produce desirable dose distributions. The primary tumor can get higher equivalent dose by SIB technique. The SIB-IMRT technique shortens the total treatment time, and is an easier, more efficient, and perhaps a less error-prone way in delivering IMRT.

Application of influence diagrams to prostate intensity-modulated radiation therapy plan selection

The purpose is to incorporate clinically relevant factors such as patient-specific and dosimetric information as well as data from clinical trials in the decision-making process for the selection of prostate intensity-modulated radiation therapy (IMRT) plans. The approach is to incorporate the decision theoretic concept of an influence diagram into the solution of the multiobjective optimization inverse planning problem. A set of candidate IMRT plans was obtained by varying the importance factors for the planning target volume (PTV) and the organ-at-risk (OAR) in combination with simulated annealing to explore a large part of the solution space. The Pareto set for the PTV and OAR was analysed to demonstrate how the selection of the weighting factors influenced which part of the solution space was explored. An influence diagram based on a Bayesian network with 18 nodes was designed to model the decision process for plan selection. The model possessed nodes for clinical laboratory results, tumour grading, staging information, patient-specific information, dosimetric information, complications and survival statistics from clinical studies. A utility node was utilized for the decision-making process. The influence diagram successfully ranked the plans based on the available information. Sensitivity analyses were used to judge the reasonableness of the diagram and the results. In conclusion, influence diagrams lend themselves well to modelling the decision processes for IMRT plan selection. They provide an excellent means to incorporate the probabilistic nature of data and beliefs into one model. They also provide a means for introducing evidence-based medicine, in the form of results of clinical trials, into the decision-making process.

Clinical use of intensity-modulated radiotherapy: part I

Intensity-modulated radiotherapy (IMRT) is a novel conformal radiotherapy technique which is gaining increasing clinical use worldwide. This article aims to summarize the published data pertaining to clinical indications of this therapy for head and neck, central nervous system, and lung tumours. The main indications in head and neck cancer are parotid gland sparing and dose escalation to tumours close to organs at risk. For central nervous system tumours, IMRT has been used to reduce normal tissue radiation by more conformal dose distributions. To date, the majority of reports concern patients treated in the context of clinical trials, and for most tumour types longer term follow up of treated patients will be required to confirm the clinical benefits of IMRT.

Intensity-modulated radiation therapy: Not a dry eye in the house

Inverse planned intensity-modulated radiation therapy (IMRT) has been applied to patients in a conformal fashion in order to avoid the lacrimal gland. In the present study, we report a patient in which a potential planned dose of 63 Gy to the lacrimal gland for a conventional plan was reduced to 12 Gy to the lacrimal gland for the IMRT plan. Dose objective inverse planning was provided using a Pinnacle treatment planning computer and treatment was delivered using a Varian dynamic multileaf collimator (MLC) on a Varian linear accelerator. Because multiple MLC segments are used to deliver the modulated treatment, conventional dose checks by manual calculation are not practical. To aid in an alternative dosimetric verification process, the Pinnacle planning computer has two unique dose tools, which provide axial and beams eye view doses on user-specified check phantoms. The combined field axial dose tool matched our ion chamber dose checks within +/- 2.4% at the isocentre. The individual beams eye view dose tool matched film dose maps within +/- 3% in the umbra.

Level II lymph nodes and radiation-induced xerostomia

PURPOSE

To investigate the influence of the cranial border of electively irradiated Level II lymph nodes on xerostomia in patients with oropharyngeal cancer using three-dimensional conformal and intensity-modulated radiotherapy (3D-CRT and IMRT).

METHODS AND MATERIALS

The target volumes and organs at risk were delineated on the planning CT scans of 12 patients. Two elective target volumes were delineated. The first had the transverse process of the C1 atlas and the second had the transverse process of the C2 axis as cranial border of the Level II lymph nodes. 3D-CRT and IMRT planning were performed for both elective volumes, resulting in two plans per patient and technique, called the C1 and C2 plans, respectively. Irradiation of the ipsilateral elective volume up to C1 and the contralateral up to C2 was also performed for IMRT. The normal tissue complication probability (NTCP) for xerostomia 1 year after RT was calculated using the parotid mean dose.

RESULTS

The average mean dose +/- standard deviation (SD) to the contralateral parotid gland was reduced from 33 +/- 5 Gy for the IMRT C1 plans to 26 +/- 4 Gy for the IMRT C2 plans and from 51 +/- 6 Gy to 49 +/- 7 Gy for the 3D-CRT C1 and C2 plans, respectively. The associated NTCP +/- SD for xerostomia was 38% +/- 10% for IMRT C1 plans and 24% +/- 6% for IMRT up to C2 on the contralateral side, regardless of which cranial border was irradiated on the ipsilateral side. For the 3D-CRT C1 and C2 plans, an NTCP value of 74% +/- 12% and 71% +/- 15% was obtained, respectively. The NTCP for xerostomia of the ipsilateral parotid gland was 53% +/- 17% and 45% +/- 20% for the IMRT C1 and C2 plans and 89% +/- 11% and 87% +/- 12% for the 3D-CRT C1 and C2 plans, respectively.

CONCLUSION

Lowering the cranial border of the Level II lymph nodes from C1 to C2, in the case of bilateral elective neck irradiation, could be considered on the contralateral side when the risk of metastasis on that side is very low. This is especially true when IMRT is used, because the relative reduction of NTCP for xerostomia 1 year after RT could be up to 68% compared with conventional conformal RT up to C1.

Assessment of different IMRT boost delivery methods on target coverage and normal-tissue sparing

PURPOSE

Because of biologic, medical, and sometimes logistic reasons, patients may be treated with 3D conformal therapy or intensity-modulated radiation therapy (IMRT) for the initial treatment volume (PTV(1)) followed by a sequential IMRT boost dose delivered to the boost volume (PTV(2)). In some patients, both PTV(1) and PTV(2) may be simultaneously treated by IMRT (simultaneous integrated boost technique). The purpose of this work was to assess the sequential and simultaneous integrated boost IMRT delivery techniques on target coverage and normal-tissue sparing.

MATERIALS AND METHODS

Fifteen patients with head-and-neck (H&N), lung, and prostate cancer were selected for this comparative study. Each site included 5 patients. In all patients, the target consisted of PTV(1) and PTV(2). The prescription doses to PTV(1) and PTV(2) were 46 Gy and 66 Gy (H&N cases), 45 Gy and 66.6 Gy (lung cases), 50 Gy and 78 Gy (prostate cases), respectively. The critical structures included the following: spinal cord, parotid glands, and brainstem (H&N structures); spinal cord, esophagus, lungs, and heart (lung structures); and bladder, rectum, femurs (prostate structures). For all cases, three IMRT plans were created: (1) 3D conformal therapy to PTV(1) followed by sequential IMRT boost to PTV(2) (sequential-IMRT(1)), (2) IMRT to PTV(1) followed by sequential IMRT boost to PTV(2) (sequential-IMRT(2)), and (3) Simultaneous integrated IMRT boost to both PTV(1) and PTV(2) (SIB-IMRT). The treatment plans were compared in terms of their dose-volume histograms, target volume covered by 100% of the prescription dose (D(100%)), and maximum and mean structure doses (D(max) and D(mean)).

RESULTS

H&N cases: SIB-IMRT produced better sparing of both parotids than sequential-IMRT(1), although sequential-IMRT(2) also provided adequate parotid sparing. On average, the mean cord dose for sequential-IMRT(1) was 29 Gy. The mean cord dose was reduced to approximately 20 Gy with both sequential-IMRT(2) and SIB-IMRT. Prostate cases: The volume of rectum receiving 70 Gy or more (V(>70 Gy)) was reduced to 18.6 Gy with SIB-IMRT from 22.2 Gy with sequential-IMRT(2). SIB-IMRT reduced the mean doses to both bladder and rectum by approximately 10% and approximately 7%, respectively, as compared to sequential-IMRT(2). The mean left and right femur doses with SIB-IMRT were approximately 32% lower than obtained with sequential-IMRT(1). Lung cases: The mean heart dose was reduced by approximately 33% with SIB-IMRT as compared to sequential-IMRT(1). The mean esophagus dose was also reduced by approximately 10% using SIB-IMRT as compared to sequential-IMRT(1). The percentage of the lung volume receiving 20 Gy (V(20 Gy)) was reduced to 26% by SIB-IMRT from 30.6% with sequential-IMRT(1).

CONCLUSIONS

For equal PTV coverage, both sequential-IMRT techniques demonstrated moderately improved sparing of the critical structures. SIB-IMRT, however, markedly reduced doses to the critical structures for most of the cases considered in this study. The conformality of the SIB-IMRT plans was also much superior to that obtained with both sequential-IMRT techniques. The improved conformality gained with SIB-IMRT may suggest that the dose to nontarget tissues will be lower.

Segmental IMRT for oropharyngeal cancer in a clinical setting

BACKGROUND AND PURPOSE

To develop a segmental intensity-modulated radiotherapy (IMRT) technique for the treatment of oropharyngeal cancer.

PATIENTS AND METHODS

Eight patients previously treated for oropharyngeal cancer were replanned with segmental IMRT. The dose distribution was optimized using beam geometries consisting of 3, 5, 7 and 9 equiangular beams. The optimization procedure resulted in a theoretical fluence for each beam. In order to vary the number of segments, the optimized fluence was divided into four different equidistant levels. The final dose distribution was calculated using clinically deliverable segments obtained from optimized fluence.

RESULTS

For our segmental IMRT technique the dose homogeneity within the target volumes improved when the total number of segments increased and reached a saturation level at approximately 150 segments. Seven beams were sufficient to achieve the saturation level for dose homogeneity. The mean dose to the parotid glands depended on the beam geometry and tumor location and did not depend on the number of segments. On average the mean dose to the contralateral parotid gland was 35.7 Gy (27.1-39.9 Gy) for all seven beam plans.

CONCLUSIONS

Seven beams are sufficient to achieve an acceptable dose homogeneity within the target volumes and significant parotid sparing. These results will be used to introduce IMRT in routine clinical practice.

Potential of intensity-modulated radiotherapy to escalate doses to head-and-neck cancers: What is the maximal dose?

PURPOSE

To investigate the potential of intensity-modulated radiotherapy (IMRT) to escalate doses to head-and-neck cancer and find the maximal dose that could be prescribed to the target volume with IMRT while doses to critical organs were maintained at their currently acceptable levels. The secondary goal was to search for limits in current IMRT technology.

METHODS AND MATERIALS

For a group of 12 head-and-neck cancer patients with different tumor locations and shapes, we performed IMRT planning using a simultaneous integrated boost strategy, that is, the gross tumor volume (GTV), clinical target volume (CTV), and electively treated nodes were treated simultaneously at different dose levels. The critical structures involved in the treatment field that needed to be spared included the brainstem, spinal cord, and parotid glands, depending on the disease site. Nine coplanar 6-MV photon beams were used for planning with the IMRT system developed at our institution, and dose-volume criteria were used for optimization. By varying the optimization parameters, we gradually increased the dose to the GTV while keeping the dose to the critical structures at less than the acceptable tolerance level. The criteria for accepting the plan included the following: (1) the prescription dose to the GTV had to cover 99% of the volume, and the dose homogeneity of the GTV needed to be <10%; (2) the prescription to the CTV (which was set either at 60 Gy or 10 Gy less than that of the GTV) had to cover 95% of the volume, and the same amount of normal tissue outside the CTV received the CTV prescription dose as in the current acceptable plan; (3) the prescription to the electively treated lymph nodes needed to cover 90% of the volume; and (4) the maximal dose to the brainstem and spinal cord had to be <55 Gy and 45 Gy, respectively. For parotid glands, the dose needed to be as low as possible without compromising the target doses. The deliverable plans as determined by the actual multileaf collimator leaf sequences were used for the final evaluation. To verify that the acceptable plans were deliverable, the experimental measurements of planar dose distribution were performed in phantom with film.

RESULTS

The maximal dose to the GTV varied from 86 to 176 Gy if the CTV dose increased with the GTV dose. It was reduced to 76-82 Gy if the CTV dose was kept at 60 Gy. The competing criteria usually are the requirements of the tolerance doses to the critical organs and target dose homogeneity, not the target prescription dose. Using more beams only increased the dose marginally. The results could change significantly if a different set of criteria for the plan evaluation were used. Dosimetric measurements confirmed that such a high dose and dose gradient could be delivered accurately with dynamic multileaf collimators. Statistical analyses showed no significant correlations between the maximal doses and the number of GTVs and volume of GTVs and CTVs.

CONCLUSION

Doses to head-and-neck cancers with simultaneous integrated boost IMRT can be escalated to a greater level than currently prescribed clinically. The limit of IMRT in head-and-neck cancer has not been reached at the current prescription level of 70 Gy. Such high total and fractionated doses should be carefully evaluated before being prescribed clinically.

Quality of life after parotid-sparing IMRT for head-and-neck cancer: a prospective longitudinal study

PURPOSE

Parotid-sparing intensity-modulated radiotherapy (IMRT) for head-and-neck cancer reduces xerostomia compared with standard RT. To assess potential improvements in broader aspects of quality of life (QOL), we initiated a study of patient-reported QOL and its predictors after IMRT.

MATERIALS AND METHODS

This was a prospective longitudinal study of head-and-neck cancer patients receiving multisegmental static IMRT. Patients were given a validated xerostomia questionnaire (XQ), and a validated head-and-neck cancer-related QOL questionnaire consisting of four multi-item domains: Eating, Communication, Pain, and Emotion. The Eating domain contains one question (total of six) asking directly about xerostomia. In both questionnaires, higher scores denote worse symptoms or QOL. The questionnaires and measurements of salivary output from the major glands were completed before RT started (pre-RT) and at 3, 6, and 12 months after RT. The association between the QOL scores and patient-, tumor-, and therapy-related factors was assessed using the random effects model.

RESULTS

Thirty-six patients participating in the study completed the questionnaires through 12 months. The XQ scores worsened significantly at 3 months compared with the pre-RT scores, but later they improved gradually through 12 months (p = 0.003), in parallel with an increase in the salivary output from the spared salivary glands. The QOL summary scores were stable between the baseline (pre-RT) and 3 months after RT scores. Patients receiving postoperative RT (whose pre-RT questionnaires were taken a few weeks after surgery) tended to have improved scores after RT, reflecting the subsidence of acute postoperative sequelae, compared with a tendency toward worsened scores in patients receiving definitive RT. After 3 months, statistically significant improvement was noted in the summary QOL scores for all patients, through 12 months after RT (p = 0.01). The salivary flow rates, tumor doses, mean oral cavity dose, age, gender, sites or stages of tumor, surgery, and use of chemotherapy were not associated with the QOL scores at any point. The mean dose to the parotid glands correlated with the QOL scores at 3 months (p = 0.05) but not at other post-RT periods. The XQ and QOL summary scores did not correlate before RT but were significantly correlated at each post-RT point (p < 0.01), with a linear correlation coefficient (r) of 0.59, 0.72, and 0.67 at 3, 6, and 12 months, respectively. At these points, the XQ scores also correlated significantly with the scores of each of the individual QOL domains (p < or = 0.01), including the domains Pain and Emotion, which did not contain any xerostomia-related question.

CONCLUSION

After parotid-sparing IMRT, a statistically significant correlation was noted between patient-reported xerostomia and each of the domains of QOL: Eating, Communication, Pain, and Emotion. Both xerostomia and QOL scores improved significantly over time during the first year after therapy. These results suggest that the efforts to improve xerostomia using IMRT may yield improvements in broad aspects of QOL.

Set-up improvement in head and neck radiotherapy using a 3D off-line EPID-based correction protocol and a customised head and neck support

PURPOSE

First, to investigate the set-up improvement resulting from the introduction of a customised head and neck (HN) support system in combination with a technologist-driven off-line correction protocol in HN radiotherapy. Second, to define margins for planning target volume definition, accounting for systematic and random set-up uncertainties.

METHODS AND MATERIALS

In 63 patients 498 treatment fractions were evaluated to develop and implement a 3D shrinking action level correction protocol. In the comparative study two different HN-supports were compared: a flexible 'standard HN-support' and a 'customised HN-support". For all three directions (x, y and z) random and systematic set-up deviations (1 S.D.) were measured.

RESULTS

The customised HN-support improves the patient positioning compared to the standard HN-support. The 1D systematic errors in the x, y and z directions were reduced from 2.2-2.3 mm to 1.2-2.0 mm (1 S.D.). The 1D random errors for the y and z directions were reduced from 1.6 and 1.6 mm to 1.1 and 1.0 mm (1S.D.). The correction protocol reduced the 1D systematic errors further to 0.8-1.1 mm (1 S.D.) and all deviations in any direction were within 5 mm. Treatment time per measured fraction was increased from 10 to 13 min. The total time required per patient, for the complete correction procedure, was approximately 40 min.

CONCLUSIONS

Portal imaging is a powerful tool in the evaluation of the department specific patient positioning procedures. The introduction of a comfortable customised HN-support, in combination with an electronic portal imaging device-based correction protocol, executed by technologists, led to an improvement of overall patient set-up. As a result, application of proposed recipes for CTV-PTV margins indicates that these can be reduced to 3-4 mm.

Prevention and treatment of the consequences of head and neck radiotherapy

The location of the primary tumor or lymph node metastases dictates the inclusion of the oral cavity, salivary glands, and jaws in the radiation treatment portals for patients who have head and neck cancer. The clinical sequelae of the radiation treatment include mucositis, hyposalivation, loss of taste, osteoradionecrosis, radiation caries, and trismus. These sequelae may be dose-limiting and have a tremendous effect on the patient's quality of life. Most treatment protocols to prevent these sequelae are still based on clinical experience, but alternatives based on fundamental basic and clinical research are becoming more and more available. Many of these alternatives either need further study before they can be incorporated into the protocols commonly used to prevent and treat the radiation-related oral sequelae or await implementation of these protocols. In this review, the various possibilities for prevention and/or treatment of radiation-induced changes in healthy oral tissues and their consequences are discussed.

Oral sequelae of head and neck radiotherapy

In addition to anti-tumor effects, ionizing radiation causes damage in normal tissues located in the radiation portals. Oral complications of radiotherapy in the head and neck region are the result of the deleterious effects of radiation on, e.g., salivary glands, oral mucosa, bone, dentition, masticatory musculature, and temporomandibular joints. The clinical consequences of radiotherapy include mucositis, hyposalivation, taste loss, osteoradionecrosis, radiation caries, and trismus. Mucositis and taste loss are reversible consequences that usually subside early post-irradiation, while hyposalivation is normally irreversible. Furthermore, the risk of developing radiation caries and osteoradionecrosis is a life-long threat. All these consequences form a heavy burden for the patients and have a tremendous impact on their quality of life during and after radiotherapy. In this review, the radiation-induced changes in healthy oral tissues and the resulting clinical consequences are discussed.

Simultaneous integrated boost intensity-modulated radiotherapy for locally advanced head-and-neck squamous cell carcinomas. I: dosimetric results

PURPOSE

This report describes the dosimetric analyses of a Phase I/II protocol, designed to examine the capabilities of an institutionally developed intensity-modulated radiotherapy (IMRT) system with respect to dose escalation. The protocol employed stringent dosimetric guidelines in the treatment of locally advanced head-and-neck squamous cell carcinomas (HNSCC) with radiotherapy alone using IMRT and the simultaneous integrated boost (SIB) technique.

METHODS AND MATERIALS

The first 14 patients enrolled on the protocol were included in this analysis. Escalating doses of 68.1 Gy (6 patients), 70.8 Gy (6 patients), and 73.8 Gy (2 patients) were delivered to the gross tumor volume (GTV) in 30 fractions. Simultaneously, constant dose coverage was given to the subclinical disease and the electively treated nodal regions, which received 60 Gy and 54 Gy, respectively, in all three cohorts. Parotid glands were spared to the degree possible without compromising target coverage. The following indices are reported for the GTV: (1) dose to specified percent volumes (e.g., D(98) and D(2)); (2) homogeneity index defined as the ratio (D(2) - D(98))/D(prescription); (3) biologically equivalent uniform dose (EUD); and (4) an index of conformality, PITV, defined as the ratio of volume enclosed within the prescribed isodose surface to the target volume. Treatments were planned and delivered with nine 6-MV photon beams using the multileaf collimator (MLC) "sliding window" technique.

RESULTS

Mean doses to 98% of GTV were 68.4 Gy, 70.5 Gy, and 70.8 Gy, and average GTV dose homogeneity was 6.7%, 7.6%, and 8.8% for the three cohorts. The average doses to the parotid gland proximal to and distant from GTV were 41.3 Gy and 25.7 Gy, respectively. Dose distributions measured in phantom showed good agreement with calculations.

CONCLUSIONS

Treatment of locally advanced HNSCC using SIB-IMRT as described is feasible. Treatment planning and delivery are safer and more efficient than with conventional three-dimensional processes. Predicted dose distributions can be accurately delivered with excellent conformality using dynamic MLC. At least one of the parotid glands can be adequately spared. Patient follow-up continues and will allow eventual quantitative correlation of delivered dose distributions with clinical outcomes.