The dose to the parotid glands with IMRT for oropharyngeal tumors: the effect of reduction of positioning margins

Reducing Salivary Toxicity with Adaptive Radiotherapy (ReSTART): A Randomized Controlled Trial Comparing Conventional IMRT to Adaptive IMRT in Head and Neck Squamous Cell Carcinomas

BACKGROUND

The utility of Adaptive Radiotherapy (ART) in Head and Neck Squamous Cell Carcinoma (HNSCC) remains to be ascertained. While multiple retrospective and single-arm prospective studies have demonstrated its efficacy in decreasing parotid doses and reducing xerostomia, adequate randomized evidence is lacking.

METHODS AND ANALYSIS

ReSTART (Reducing Salivary Toxicity with Adaptive Radiotherapy) is an ongoing phase III randomized trial of patients with previously untreated, locally advanced HNSCC of the oropharynx, larynx, and hypopharynx. Patients are randomized in a 1:1 ratio to the standard Intensity Modulated Radiotherapy (IMRT) arm {Planning Target Volume (PTV) margin 5 mm} vs. Adaptive Radiotherapy arm (standard IMRT with a PTV margin 3 mm, two planned adaptive planning at 10th and 20th fractions). The stratification factors include the primary site and nodal stage. The RT dose prescribed is 66Gy in 30 fractions for high-risk PTV and 54Gy in 30 fractions for low-risk PTV over six weeks, along with concurrent chemotherapy. The primary endpoint is to compare salivary toxicity between arms using salivary scintigraphy 12 months' post-radiation. To detect a 25% improvement in the primary endpoint at 12 months in the ART arm with a two-sided 5% alpha value and a power of 80% (and 10% attrition ratio), a sample size of 130 patients is required (65 patients in each arm). The secondary endpoints include acute and late toxicities, locoregional control, disease-free survival, overall survival, quality of life, and xerostomia scores between the two arms.

DISCUSSION

The ReSTART trial aims to answer an important question in Radiation Therapy for HNSCC, particularly in a resource-limited setting. The uniqueness of this trial, compared to other ongoing randomized trials, includes the PTV margins and the xerostomia assessment by scintigraphy at 12 months as the primary endpoint.

Impact of hypofractionated schemes in radiotherapy for locally advanced head and neck cancer patients

OBJECTIVE

To analyze two cohorts of locally advanced head and neck cancer (LAHNC) patients treated with two schedules of hypofractionated radiotherapy and 5 versus 3 mm clinical target volume-planning target volume (CTV-PTV) margins.

METHODS

145 patients were included. The patient cohort was divided into two groups. Group A included 97 patients treated with 69.96/54.45 grays (Gy) to the high-risk and low-risk volumes, respectively, in 33 fractions, with 5 mm margins. Group B included 48 patients treated with 66/54 Gy in 30 fractions using 3 mm margins. Toxicity was recorded according to the Common Toxicity Criteria version 3. Patient outcomes for locoregional control (LRC), disease-free survival (DFS), and overall survival (OS) were determined.

RESULTS

Median follow-up was 26 months. In terms of toxicity, acute dysphagia worsened significantly (P = 0.003) in group B, whereas acute salivary toxicity tended to significance (P = 0.071). No significant late toxicity differences were recorded. Rates of LRC at 1 and 2 years were 90.1% ± 2.6% and 84.2% ± 3.4%, respectively, with superiority for group A (P = 0.045). The statistical significance remained for the low-dose level (P = 0.007) but not for high dose (P = 0.110). Rates of DFS at 1 and 2 years were 84.9% ± 3.1% and 76.5% ± 3.9%, respectively, whereas rates of OS were 95.9% ± 1.8% and 91.6% ± 2.7%, respectively. No differences were observed between the two groups in terms of DFS (P = 0.270) and OS (P = 0.152).

CONCLUSION

The use of reduced CTV to PTV margins and dose reduction with hypofractionation schedule can improve the pattern of toxicity in LAHNC patients. This approach resulted in an increased rate of locoregional progression, particularly in low-risk regions.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:E163-E170, 2020.

Optimization of the margin expanded from the clinical to the planned target volume during intensity-modulated radiotherapy for nasopharyngeal carcinoma

During the radiotherapy process, the emergence of set-up errors is nearly inevitable. Because set-up errors were not detected and corrected daily, planned target volumes were formed by expanding the clinical target volume according to each unit's experience. We optimized the margins of clinical and planned target volumes during administration of intensity-modulated radiotherapy for nasopharyngeal carcinoma. A total of 72 patients newly diagnosed with non-metastatic nasopharyngeal carcinoma and treated with Tomotherapy were prospectively enrolled in the study. For each patient, one megavoltage computed tomography scan was obtained after conventional positioning, online correction, and daily tomotherapy delivery. The interfraction set-up errors were determined using a planning CT based on the registered scan. The mean interfraction errors were -2.437±2.0529 mm, 0.0652±2.3844 mm, 0.318±1.8314 mm, and 0.197±1.8721° for the medial-lateral, superior-inferior, and anterior-posterior directions, and the direction of rotation, respectively. The total M_PTV in the three directions was 7.53 mm, 1.83 mm, and 2.08 mm, respectively. The 3-mm margins in the superior-inferior and anterior-posterior directions uniformly expanded from the clinical target volume should be sufficient, and the marging in the medial-lateral direction was up to 7.5 mm. These results suggest that personalized M_PTV may be adopted for intensity-modulated radiotherapy planning.

Analysis of setup error based on CTVision for nasopharyngeal carcinoma during IGRT

The aim of the present study was to investigate the role of CTVision in interfractional setup errors during intensity‐modulated radiation therapy (IMRT) in 12 nasopharyngeal carcinoma (NPC) patients. The trend of setup errors as a function of time during a fractionated radiotherapy course was investigated, and the influence of reconstructive thickness on image reconstruction for setup errors was analyzed. The appropriate planning target volume (PTV) margin and planning risk volume (PRV) margin were defined to provide a reference for the design of IMRT for NPC. Based on CTVision, online CT was performed weekly for each patient. Setup errors were measured by registration between the CT reconstructed image and reference image. Mean of setup errors, estimated population systematic (:), and population random (σ) errors were calculated using SPSS (v15.0). Optimum PTV and PRV margins were calculated. In the clinical data, for the LR (left–right), SI (superior–inferior), and AP (anterior–posterior) directions, : was 0.8, 0.8, and 1.0 mm, respectively, and σ was 1.0, 1.3, and 0.8 mm, respectively. In the LR, SI, and AP directions, PTV margins were at least 2.7, 2.9, and 3.0 mm, respectively, and PRV margins were at least 1.5, 1.7, and 1.7 mm, respectively. No significant differences in setup errors were observed during the fractionated radiotherapy course (p>0.05). However, CT image reconstruction with different thicknesses affected the accuracy of measurements for setup errors, particularly in the SI direction. The application of CTVision to correct setup errors is important and can provide reasonable margins to guarantee the coverage of PTVs and spare organs at risk. A thickness of 3 mm in the reconstructed image is appropriate for the measurement of setup errors by image registration.

PACS number(s): 87.55.Qr

Measuring radiotherapy setup errors at multiple neck levels in nasopharyngeal cancer (NPC): A case for differential PTV expansion

BACKGROUND AND PURPOSE

We aim to quantify the magnitude of the systematic and random setup errors at three different anatomical levels of the neck in Nasopharyngeal Carcinoma (NPC) when clivus matching is used, and recommend appropriate PTV margins for each level.

MATERIAL AND METHODS

Thirty-six patients undergoing image-guided radiotherapy (IGRT) each with 9 scheduled CBCTs were reviewed. The magnitude of setup errors were measured at the level of the clivus, C4 and C7 vertebrae, before and after CBCT correction. The 3D displacements, systematic and random errors were calculated for each level. The appropriate PTV expansion was determined using Van Herk's formula.

RESULTS

Mean 3D displacement was 1.88, 2.66 and 3.35 mm at the clivus, C4 and C7 before correction. The differences were statistically significant (p<0.05). The PTV margin required without correction was 2.33, 4.33 and 6.52 mm respectively. These were reduced to 1.20, 3.72 and 6.08 mm after CBCT corrections.

CONCLUSIONS

Variability is seen in setup errors at the clivus, C4 and C7 vertebral levels. A variable planning margin approach with reduced margin at the clivus is recommended. Use of daily CBCT allows the PTV expansion to be reduced to 1.2 mm.

Radiation dose response simulation for biomechanical-based deformable image registration of head and neck cancer treatment

Biomechanical-based deformable image registration is conducted on the head and neck region. Patient specific 3D finite element models consisting of parotid glands (PG), submandibular glands (SG), tumor, vertebrae (VB), mandible, and external body are used to register pre-treatment MRI to post-treatment MR images to model the dose response using image data of five patients. The images are registered using combinations of vertebrae and mandible alignments, and surface projection of the external body as boundary conditions. In addition, the dose response is simulated by applying a new loading technique in the form of a dose-induced shrinkage using the dose-volume relationship. The dose-induced load is applied as dose-induced shrinkage of the tumor and four salivary glands. The Dice Similarity Coefficient (DSC) is calculated for the four salivary glands, and tumor to calculate the volume overlap of the structures after deformable registration. A substantial improvement in the registration is found by including the dose-induced shrinkage. The greatest registration improvement is found in the four glands where the average DSC increases from 0.53, 0.55, 0.32, and 0.37 to 0.68, 0.68, 0.51, and 0.49 in the left PG, right PG, left SG, and right SG, respectively by using bony alignment of vertebrae and mandible (M), body (B) surface projection and dose (D) (VB+M+B+D).

Treatment of T3 laryngeal cancer in the Netherlands: a national survey

Background

Treatment strategies for T3 laryngeal carcinoma include radiotherapy (RT) with or without chemotherapy (CT) and sometimes surgery. We conducted a national survey to determine how T3 laryngeal carcinoma is currently being managed in the Netherlands.

Methods

A questionnaire on general treatment policy, also inquiring details on RT and CT, was sent to all 13 radiotherapy departments accredited for treatment of head and neck cancer (HNC) in the Netherlands.

Results

Twelve centers completed the questionnaire. All centers reported using RT with or without CT. Upfront laryngectomy is rarely performed.

At 9/12 centers, CT is added to RT in cases with large tumors in T3N0 disease. Three centers use a volume criterion (3–6 cc); 6 centers don’t specify “large” with such criteria. CT consists of cisplatin 3-weekly (7 centers) or weekly (2 centers), unless contra-indicated or age; 6 centers use an age limit of 70 years. RT is given concomitantly with CT 5×/week except at the 2 centers where cisplatin weekly is combined with 6 fractions/week. In case of RT only, treatment is accelerated. Lymph node levels II-IV are treated electively.

In T3N+ disease, 11/12 centers treat non-bulky T3N1 with RT only. Volume criteria for combined CT-RT are the same as above. Two centers perform an upfront neck dissection in case of (resectable) N3 disease; 10 centers treat T3N2-3 cancer with primary CT-RT, 2 centers don’t use the N-stage criterion.

Total RT dose is 68–70 Gy, the elective dose varies between 46 and 57.75 Gy. Eight centers use a simultaneous integrated boost technique.

Conclusions

Treatment of T3 laryngeal cancer in the Netherlands is generally comparable, with CT-RT for voluminous T3N0 and most T3N+ tumors, but there are some differences between the centers in the use of chemotherapy and the dose-fractionation schemes. Therefore, the aim of the National Platform RT HNC is further standardization of RT dose, fractionation and delivery techniques.

Dosimetric benefit to organs at risk following margin reductions in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy

Introduction

It is important to decrease the radiation exposure of normal tissue in intensity-modulated radiation therapy (IMRT). Minimizing planning target volume (PTV) margins with more precise target localization techniques can achieve this goal. This study aimed to quantify the extent to which organs at risk (OARs) are spared when using reduced margins in the treatment of nasopharyngeal carcinoma (NPC).

Methods

Two IMRT plans were regenerated for 40 patients with NPC based on two PTV margins, which were reduced or unchanged following cone beam computed tomography online correction. The reduced-margin plan was optimized based on maximal dose reduction to OARs without compromising target coverage. Dosimetric comparisons were evaluated in terms of target coverage and OAR sparing.

Results

Improvements in target coverage occurred with margin reduction, and significant improvements in dosimetric parameters were observed for all OARs (P < 0.05) except for the right optic nerve, chiasm, and lens. Doses to OARs decreased at a rate of 1.5% to 7.7%. Sparing of the left parotid and right parotid, where the mean dose (D_mean) decreased at a rate of 7.1% and 7.7%, respectively, was greater than the sparing of other OARs.

Conclusions

Significant improvements in OAR sparing were observed with margin reduction, in addition to improvement in target coverage. The parotids benefited most from the online imaging-guided approach.

Potential advantages of volumetric arc therapy in head and neck cancer

BACKGROUND

Intensity-modulated radiation therapy (IMRT) uses solid compensators or multileaf collimators to modulate the intensity of radiation in each field, delivering highly conformal dose distributions. This technique allows treating volumes with concave shapes when the target is close to a critical structure. The movement of multileaf collimator under computer control can modulate the dose in 3 main ways: IMRT with static field with segments, IMRT with dynamic delivery, and IMRT rotational therapy. Volumetric modulated arc therapy (VMAT) is a novel radiation technique that creates conformal distributions with variable gantry speed, dynamic movements of multileaf collimator, and variations in dose rate. The purpose of this study was to review the basis of VMAT, highlighting the differences with other IMRT techniques.

Incorporating single-side sparing in models for predicting parotid dose sparing in head and neck IMRT

PURPOSE

Sparing of single-side parotid gland is a common practice in head-and-neck (HN) intensity modulated radiation therapy (IMRT) planning. It is a special case of dose sparing tradeoff between different organs-at-risk. The authors describe an improved mathematical model for predicting achievable dose sparing in parotid glands in HN IMRT planning that incorporates single-side sparing considerations based on patient anatomy and learning from prior plan data.

METHODS

Among 68 HN cases analyzed retrospectively, 35 cases had physician prescribed single-side parotid sparing preferences. The single-side sparing model was trained with cases which had single-side sparing preferences, while the standard model was trained with the remainder of cases. A receiver operating characteristics (ROC) analysis was performed to determine the best criterion that separates the two case groups using the physician's single-side sparing prescription as ground truth. The final predictive model (combined model) takes into account the single-side sparing by switching between the standard and single-side sparing models according to the single-side sparing criterion. The models were tested with 20 additional cases. The significance of the improvement of prediction accuracy by the combined model over the standard model was evaluated using the Wilcoxon rank-sum test.

RESULTS

Using the ROC analysis, the best single-side sparing criterion is (1) the predicted median dose of one parotid is higher than 24 Gy; and (2) that of the other is higher than 7 Gy. This criterion gives a true positive rate of 0.82 and a false positive rate of 0.19, respectively. For the bilateral sparing cases, the combined and the standard models performed equally well, with the median of the prediction errors for parotid median dose being 0.34 Gy by both models (p = 0.81). For the single-side sparing cases, the standard model overestimates the median dose by 7.8 Gy on average, while the predictions by the combined model differ from actual values by only 2.2 Gy (p = 0.005). Similarly, the sum of residues between the modeled and the actual plan DVHs is the same for the bilateral sparing cases by both models (p = 0.67), while the standard model predicts significantly higher DVHs than the combined model for the single-side sparing cases (p = 0.01).

CONCLUSIONS

The combined model for predicting parotid sparing that takes into account single-side sparing improves the prediction accuracy over the previous model.

The potential of helical tomotherapy in the treatment of head and neck cancer

A decade after its first introduction into the clinic, little is known about the clinical impact of helical tomotherapy (HT) on head and neck cancer (HNC) treatment. Therefore, we analyzed the basics of this technique and reviewed the literature regarding HT's potential benefit in HNC. The past two decades have been characterized by a huge technological evolution in photon beam radiotherapy (RT). In HNC, static beam intensity-modulated radiotherapy (IMRT) has shown superiority over three-dimensional conformal RT in terms of xerostomia and is considered the standard of care. However, the next-generation IMRT, the rotational IMRT, has been introduced into the clinic without any evidence of superiority over static beam IMRT other than being substantially faster. Of these rotational techniques, HT is the first system especially developed for IMRT in combination with image-guided RT. HT is particularly promising for the treatment of HNC because its sharp dose gradients maximally spare the many radiosensitive organs at risk nearby. In addition, HT's integrated computed tomography scan assures a very precise dose administration and allows for some adaptive RT. Because HT is specifically developed for IMRT in combination with (integrated) image-guidance, it allows for precise dose distribution ("dose painting"), patient setup, and dose delivery. As such, it is an excellent tool for difficult HNC irradiation. The literature on the clinical results of HT in HNC all show excellent short-term (≤2 years) results with acceptable toxicity profiles. However, properly designed trials are still warranted to further substantiate these results.

Evaluation of inter-fraction and intra-fraction errors during volumetric modulated arc therapy in nasopharyngeal carcinoma patients

Background

This prospective study was conducted to evaluate inter- and intra-fraction errors in nasopharyngeal carcinoma (NPC) patients undergoing volumetric modulated arc therapy (VMAT) using cone-beam computed tomography (CBCT) and to thus obtain planning target volume (PTV) margins to effectively guide treatment in the future.

Methods

Fifteen NPC patients scheduled to undergo VMAT were prospectively enrolled in the study. For each patient, three CBCT scans were obtained; one after daily conventional positioning, one after online correction with 2 mm tolerance and one after 1 week of VMAT delivery. The scans were registered to the planning CT to determine the inter- and intra-fraction errors. Patient positioning errors were analyzed for time trends over the course of radiotherapy. PTV margins were calculated from the systematic (Σ) and random (σ) errors.

Results

The average absolute values of the pre-correction, post-correction and intra-fraction errors (in order) were 1.1, 0.6 and 0.4 mm in the medial–lateral (ML) direction, 1.2, 0.7 and 0.5 mm in the superior–inferior (SI) direction and 1.1, 0.7 and 0.5 mm in the anterior–posterior (AP) direction. The corresponding Σ were 1.0–1.4 mm, 0.4–0.5 mm and 0.2–0.4 mm, while the corresponding σ were 0.7–0.8 mm, 0.6–0.7 mm and 0.5–0.6 mm. With time, gradual increases in both the inter- and intra-fraction three-dimensional displacements were observed (P = 0.019 and P = 0.044, respectively). The total PTV margins accounting for pre-correction and intra-fraction errors were 3.4–4.1 mm and those accounting for post-correction and intra-fraction errors were 1.7–2.2 mm.

Conclusions

CBCT is an effective modality to evaluate and improve the accuracy of VMAT in NPC patients. Inter- and intra-fraction three-dimensional displacements increased as a function of time during the course of radiotherapy. In our institution, we recommend a PTV margin of 5 mm for NPC patients undergoing VMAT without CBCT and 3 mm for those treated with rigorous daily CBCT scans.

The residual setup errors of different IGRT alignment procedures for head and neck IMRT and the resulting dosimetric impact

PURPOSE

To assess residual setup errors during head and neck radiation therapy and the resulting consequences for the delivered dose for various patient alignment procedures.

METHODS AND MATERIALS

Megavoltage cone beam computed tomography (MVCBCT) scans from 11 head and neck patients who underwent intensity modulated radiation therapy were used to assess setup errors. Each MVCBCT scan was registered to its reference planning kVCT, with seven different alignment procedures: automatic alignment and manual registration to 6 separate bony landmarks (sphenoid, left/right maxillary sinuses, mandible, cervical 1 [C1]-C2, and C7-thoracic 1 [T1] vertebrae). Shifts in the different alignments were compared with each other to determine whether there were any statistically significant differences. Then, the dose distribution was recalculated on 3 MVCBCT images per patient for every alignment procedure. The resulting dose-volume histograms for targets and organs at risk (OARs) were compared to those from the planning kVCTs.

RESULTS

The registration procedures produced statistically significant global differences in patient alignment and actual dose distribution, calling for a need for standardization of patient positioning. Vertically, the automatic, sphenoid, and maxillary sinuses alignments mainly generated posterior shifts and resulted in mean increases in maximal dose to OARs of >3% of the planned dose. The suggested choice of C1-C2 as a reference landmark appears valid, combining both OAR sparing and target coverage. Assuming this choice, relevant margins to apply around volumes of interest at the time of planning to take into account for the relative mobility of other regions are discussed.

CONCLUSIONS

Use of different alignment procedures for treating head and neck patients produced variations in patient setup and dose distribution. With concern for standardizing practice, C1-C2 reference alignment with relevant margins around planning volumes seems to be a valid option.

Interfractional and intrafractional errors assessed by daily cone-beam computed tomography in nasopharyngeal carcinoma treated with intensity-modulated radiation therapy: a prospective study

This prospective study was to assess interfractional and intrafractional errors and to estimate appropriate margins for planning target volume (PTV) by using daily cone-beam computed tomography (CBCT) guidance in nasopharyngeal carcinoma (NPC). Daily pretreatment and post-treatment CBCT scans were acquired separately after initial patient setup and after the completion of each treatment fraction in 10 patients treated with IMRT. Online corrections were made before treatment if any translational setup error was found. Interfractional and intrafractional errors were recorded in the right-left (RL), superior-inferior (SI) and anterior-posterior (AP) directions. For the translational shifts, interfractional errors >2 mm occurred in 21.7% of measurements in the RL direction, 12.7% in the SI direction and 34.1% in the AP direction, respectively. Online correction resulted in 100% of residual errors ≤2 mm in the RL and SI directions, and 95.5% of residual errors ≤2 mm in the AP direction. No residual errors >3 mm occurred in the three directions. For the rotational shifts, a significant reduction was found in the magnitudes of residual errors compared with those of interfractional errors. A margin of 4.9 mm, 4.0 mm and 6.3 mm was required in the RL, SI and AP directions, respectively, when daily CBCT scans were not performed. With daily CBCT, the margins were reduced to 1.2 mm in all directions. In conclusion, daily CBCT guidance is an effective modality to improve the accuracy of IMRT for NPC. The online correction could result in a 70-81% reduction in margin size.

Xerostomia: a day and night difference

PURPOSE

To compare patient-reported xerostomia during daytime and during nighttime with objectively measured parotid and submandibular gland function in a cohort of head-and-neck cancer (HNC) patients treated with RT.

MATERIALS AND METHODS

A cohort of 138 HNC patients underwent objective measurements of parotid (PF) and submandibular (SMF) gland function and completed a xerostomia questionnaire (XQ) before RT, at 6 weeks, 6 months and 1 year after RT. No attempt was made to spare the submandibular gland(s). The XQ contained specific questions concerning the sensation of dry mouth during day- (XD) and nighttime (XN), scored on a 5-point Likert scale. Patients with no or mild (grade 1-3) xerostomia and patients with more severe (grade 4-5) complaints were grouped together.

RESULTS

Before RT, no association existed between dry mouth complaints and PF or SMF. At 6 weeks, 6 months and 1 year after RT; 37%, 51% and 36% had grade 4-5 XD and 65%, 64% and 56% had grade 4-5 XN, respectively. Patients with grade 4-5 XD and XN had significantly worse SMF at all time points after RT compared to patients with grade 1-3 XD and XN, while PF was significantly worse only at 6 weeks after RT. In multivariate analyses, SMF was consistently the most important factor related to XN after treatment. PF significantly influenced XD at 6 weeks and 1 year after RT.

CONCLUSIONS

Differentiating between complaints during day- and nighttime in xerostomia research is necessary. Dry mouth at night is a frequent problem after (parotid-sparing) RT for HNC and is explained by submandibular gland dysfunction. Sparing of the contralateral submandibular gland, in addition to parotid gland sparing, may result in improved patient-reported xerostomia.

Technical advances and pitfalls in head and neck radiotherapy

Intensity Modulated Radiotherapy (IMRT) is the standard of care in the treatment of head and neck squamous cell carcinomas (HNSCC) based on level 1 evidence. Technical advances in radiotherapy have revolutionized the treatment of HNSCC, with the most tangible gain being a reduction in long term morbidity. However, these benefits come with a serious and sobering price. Today, there is a greater chance of missing the target/tumor due to uncertainties in target volume definition by the clinician that is demanded by the highly conformal planning process involved with IMRT. Unless this is urgently addressed, our patients would be better served with the historically practiced non conformal radiotherapy, than IMRT which promises lesser morbidity. Image guided radiotherapy (IGRT) ensures the level of set up accuracy warranted to deliver a highly conformal treatment plan and should be utilized with IMRT, where feasible. Proton therapy has a theoretical physical advantage over photon therapy due to a lack of "exit dose". However, clinical data supporting the routine use of this technology for HNSCC are currently sparse. The purpose of this article is to review the literature, discuss the salient issues and make recommendations that address the gaps in knowledge.

Variation of neck position with image-guided radiotherapy for head and neck cancer

PURPOSE

An understanding of the setup variation of the low neck in relation to the upper neck is necessary to define appropriate planning margins, while treating the full neck with intensity-modulated radiotherapy (IMRT) technique.

MATERIALS AND METHODS

The setup of 20 sequential head and neck cancer patients was studied. Daily position verification was performed with a computed tomography (CT) on rails. An upper neck point was defined as the anterior-most portion of the cervical spine on the lowest CT cut on which both styloid processes are visible. A low neck point was defined as the anterior-most portion of the cervical spine on the lowest CT cut on which the thyroid gland was visible bilaterally. This procedure was carried out on the planning CT and on each daily treatment CT. The variation of the low neck was analyzed, assuming perfect alignment of the upper neck anatomy.

RESULTS

Daily treatment CT of upper neck anterior cervical spine points were normalized to the planning CT. Relative to this coordinate system, the low neck cervical spine point was displaced an average of 3.08 mm anteriorly, ±0.17 mm. There was no systematic lateral or craniocaudal displacement. Random setup errors resulted in low neck standard deviations of 3.9 mm (anteroposterior), 3.3 mm (lateral), and 2.6 mm (craniocaudal).

CONCLUSIONS

Position variation in the low neck varied in excess of the planning margins. There was a systematic anterior displacement. Random setup error was greater than expected. The results suggest that the neck volumes located distant from the region of fusion should be drawn with larger planning margins.

Dosimetric variations of target volumes and organs at risk in nasopharyngeal carcinoma intensity-modulated radiotherapy

OBJECTIVE

The aim of this study was to evaluate the actual dose variability to the targets and organs at risk (OARs) during nasopharyngeal carcinoma (NPC) intensity-modulated radiotherapy (IMRT) and to investigate the significance of replanning.

METHODS

11 NPC patients were included in this study. Each patient had both a planning CT and weekly repeated CT. Simulated plans that were generated by using the same beam configurations mapped to the repeated CT represented the actual delivered doses to the target volumes and OARs. An IMRT replanning was performed with the fifth week CT scan. Doses among the initial plan, the simulated plans and replanning were compared.

RESULTS

There were no significant dosimetric differences in the gross tumour volume, clinical target volume (CTV) 1 or CTV2 for either the simulated plans or the replanning compared with the initial plan. Dosimetric variability of both parotid glands and the brain stem were unique to each individual, and doses to the spinal cord were always maintained within the limit. Replanning in the fifth week had significantly decreased the doses delivered to both parotids (p-values of the mean dose were 0.015 and 0.026 for the left and right parotid, respectively), whereas it did not reduce the doses to the brain stem and spinal cord. There was no relationship between dose variability and weight loss.

CONCLUSIONS

There are no significant dose changes for target volumes and spinal cord, and doses to the brain stem and both parotid glands changed individually during NPC IMRT. Replanning helps to spare bilateral parotids.

New advances in high-technology radiotherapy for head and neck cancer

Radiotherapy has an integral role in the treatment of head and neck cancer. Although radiotherapy has the potential to cure patients with advanced disease it also carries the potential for significant long-term morbidity. New technologies in the setting of head and neck radiotherapy are emerging, which have the potential to increase the cure rate and decrease toxicity. These new technologies include improved radiotherapy treatment design (intensity modulated radiation therapy) and improved planning and implementation (image-guided radiation therapy). Some of these advances are discussed in this article.

MRI/linac integration

PURPOSE/OBJECTIVES

In radiotherapy the healthy tissue involvement still poses serious dose limitations. This results in sub-optimal tumour dose and complications. Daily image guided radiotherapy (IGRT) is the key development in radiation oncology to solve this problem. MRI yields superb soft-tissue visualization and provides several imaging modalities for identification of movements, function and physiology. Integrating MRI functionality with an accelerator can make these capacities available for high precision, real time IGRT.

DESIGN AND RESULTS

The system being built at the University Medical Center Utrecht is a 1.5T MRI scanner, with diagnostic imaging functionality and quality, integrated with a 6MV radiotherapy accelerator. The realization of a prototype of this hybrid system is a joint effort between the Radiotherapy Department of the University of Utrecht, the Netherlands, Elekta, Crawley, U.K., and Philips Research, Hamburg, Germany. Basically, the design is a 1.5 T Philips Achieva MRI scanner with a Magnex closed bore magnet surrounded by a single energy (6 MV) Elekta accelerator. Monte Carlo simulations are used to investigate the radiation beam properties of the hybrid system, dosimetry equipment and for the construction of patient specific dose deposition kernels in the presence of a magnetic field. The latter are used to evaluate the IMRT capability of the integrated MRI linac.

CONCLUSIONS

A prototype hybrid MRI/linac for on-line MRI guidance of radiotherapy (MRIgRT) is under construction. The aim of the system is to deliver the radiation dose with mm precision based on diagnostic quality MR images.

Unilateral versus bilateral irradiation in squamous cell head and neck cancer in relation to patient-rated xerostomia and sticky saliva

BACKGROUND AND PURPOSE

To investigate the association between radiation technique with patient-rated moderate and severe xerostomia and sticky saliva.

MATERIALS AND METHODS

One hundred and fifty patients treated with bilateral or unilateral irradiation for head and neck cancer were included. The salivary glands and the oral cavity were delineated on plannings-CT scans. Xerostomia and sticky saliva were assessed using the EORTC QLQ-H&N35 questionnaire at baseline and 6 and 12 months.

RESULTS

At 6 months a significant association between radiation technique and the mean parotid dose (MD(parb)) and xerostomia was observed (Odds ratio (OR)-technique: 2.55; p=0.04 and OR-MD(parb): 1.04; p=0.009). Considering the individual salivary glands, only the mean dose in the contralateral parotid gland (MD(parcl)) is associated with xerostomia (OR: 1.04; p<0.0001). Moreover, the threshold dose for a 50% probability (P50) on xerostomia increased from 21 Gy with bilateral to 44 Gy for unilateral irradiation.

CONCLUSIONS

Both technique and MD(parb) influence the risk of xerostomia in irradiated patients. Of all individual salivary glands, only MD(parcl) is of utmost importance for xerostomia. The shift in the P50 observed for xerostomia suggests that sparing of the contralateral parotid gland is compensated by hyperfunction of the contralateral parotid gland.

Quantification of Trade-Off Between Parotid Gland Sparing and Planning Target Volume Underdosages in Clinically Node-Negative Head-and-Neck Intensity-Modulated Radiotherapy

PURPOSE

To quantify the trade-off between parotid gland sparing and planning target volume (PTV) underdosages for head-and-neck intensity-modulated radiotherapy.

METHODS AND MATERIALS

A planning study was performed for 4 patients with either soft palate or tonsil tumors treated with external radiotherapy up to 46 Gy. The trade-off between underdosages in the PTV and sparing of the parotid glands was investigated by systematically varying the optimization objectives for the inverse planning. A new way of presenting dose-volume information allows easy detection of small PTV subvolumes with underdosages that cannot be assessed in conventional cumulative dose-volume histograms. A simple radiobiological model to estimate the control probability for an electively irradiated neck level was developed.

RESULTS

The average dose to the parotid glands can decrease by >10 Gy by allowing the PTV to be underdosed in such a way that the radiobiological model predicts a decrease in subclinical disease control probability of (typically) 1% to a few percent.

CONCLUSION

The trade-off between parotid gland sparing and underdosages in the PTV has been quantified by the use of an alternative method to present dose-volume information and by the use of a radiobiological model to predict subclinical disease control probability.

Future Issues in Highly Conformal Radiotherapy for Head and Neck Cancer

Improving the conformity of the radiation dose to targets in the head and neck promises reduced toxicity and, in some cases, potentially improved local-regional tumor control. Intensity-modulated radiotherapy (IMRT) is a method that allows highly conformal delivery of radiotherapy. In recent years, its use has spread rapidly in both academic and community radiation oncology facilities. The use of IMRT has raised multiple issues related to target definition, optimal treatment delivery methods, and the need to account for anatomic changes occurring during therapy. Some of these issues are reviewed in this article.

Intensity-modulated radiotherapy significantly reduces xerostomia compared with conventional radiotherapy

PURPOSE

Xerostomia is a severe complication after radiotherapy for oropharyngeal cancer, as the salivary glands are in close proximity with the primary tumor. Intensity-modulated radiotherapy (IMRT) offers theoretical advantages for normal tissue sparing. A Phase II study was conducted to determine the value of IMRT for salivary output preservation compared with conventional radiotherapy (CRT).

METHODS AND MATERIALS

A total of 56 patients with oropharyngeal cancer were prospectively evaluated. Of these, 30 patients were treated with IMRT and 26 with CRT. Stimulated parotid salivary flow was measured before, 6 weeks, and 6 months after treatment. A complication was defined as a stimulated parotid flow rate <25% of the preradiotherapy flow rate.

RESULTS

The mean dose to the parotid glands was 48.1 Gy (SD 14 Gy) for CRT and 33.7 Gy (SD 10 Gy) for IMRT (p < 0.005). The mean parotid flow ratio 6 weeks and 6 months after treatment was respectively 41% and 64% for IMRT and respectively 11% and 18% for CRT. As a result, 6 weeks after treatment, the number of parotid flow complications was significantly lower after IMRT (55%) than after CRT (87%) (p = 0.002). The number of complications 6 months after treatment was 56% for IMRT and 81% for CRT (p = 0.04).

CONCLUSIONS

IMRT significantly reduces the number of parotid flow complications for patients with oropharyngeal cancer.

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.

IMRT using simultaneously integrated boost (SIB) in head and neck cancer patients

Background

Preliminary very encouraging clinical results of intensity modulated radiation therapy (IMRT) in Head Neck Cancer (HNC) are available from several large centers. Tumor control rates seem to be kept at least at the level of conventional three-dimensional radiation therapy; the benefit of normal tissue preservation with IMRT is proven for salivary function. There is still only limited experience with IMRT using simultaneously integrated boost (SIB-IMRT) in the head and neck region in terms of normal tissue response.

The aim of this work was (1) to establish tumor response in HNC patients treated with SIB-IMRT, and (2) to assess tissue tolerance following different SIB-IMRT schedules.

Results

Between 1/2002 and 12/2004, 115 HNC patients have been curatively treated with IMRT. 70% received definitive IMRT (dIMRT), 30% were postoperatively irradiated. In 78% concomitant chemotherapy was given.

SIB radiation schedules with 5–6 × 2 Gy/week to 60–70 Gy, 5 × 2.2 Gy/week to 66–68.2 Gy (according to the RTOG protocol H-0022), or 5 × 2.11 Gy/week to 69.6 Gy were used.

After mean 18 months (10–44), 77% of patients were alive with no disease. Actuarial 2-year local, nodal, and distant disease free survival was 77%, 87%, and 78%, respectively. 10% were alive with disease, 10% died of disease. 20/21 locoregional failures occurred inside the high dose area. Mean tumor volume was significantly larger in locally failed (63 cc) vs controlled tumors (32 cc, p <0.01), and in definitive (43 cc) vs postoperative IMRT (25 cc, p <0.05); the locoregional failure rate was twofold higher in definitively irradiated patients.

Acute reactions were mild to moderate and limited to the boost area, the persisting grade 3/4 late toxicity rate was low with 6%. The two grade 4 reactions (dysphagia, laryngeal fibrosis) were observed following the SIB schedule with 2.2 Gy per session.

Conclusion

SIB-IMRT in HNC using 2.0, 2.11 or 2.2 Gy per session is highly effective and safe with respect to tumor response and tolerance. SIB with 2.2 Gy is not recommended for large tumors involving laryngeal structures.

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.

Adequate margins for random setup uncertainties in head-and-neck IMRT

PURPOSE

To investigate the effect of random setup uncertainties on the highly conformal dose distributions produced by intensity-modulated radiotherapy (IMRT) for clinical head-and-neck cancer patients and to determine adequate margins to account for those uncertainties.

METHODS AND MATERIALS

We have implemented in our clinical treatment planning system the possibility of simulating normally distributed patient setup displacements, translations, and rotations. The planning CT data of 8 patients with Stage T1-T3N0M0 oropharyngeal cancer were used. The clinical target volumes of the primary tumor (CTV(primary)) and of the lymph nodes (CTV(elective)) were expanded by 0.0, 1.5, 3.0, and 5.0 mm in all directions, creating the planning target volumes (PTVs). We performed IMRT dose calculation using our class solution for each PTV margin, resulting in the conventional static plans. Then, the system recalculated the plan for each positioning displacement derived from a normal distribution with sigma = 2 mm and sigma = 4 mm (standard deviation) for translational deviations and sigma = 1 degrees for rotational deviations. The dose distributions of the 30 fractions were summed, resulting in the actual plan. The CTV dose coverage of the actual plans was compared with that of the static plans.

RESULTS

Random translational deviations of sigma = 2 mm and rotational deviations of sigma = 1 degrees did not affect the CTV(primary) volume receiving 95% of the prescribed dose (V(95)) regardless of the PTV margin used. A V(95) reduction of 3% and 1% for a 0.0-mm and 1.5-mm PTV margin, respectively, was observed for sigma = 4 mm. The V(95) of the CTV(elective) contralateral was approximately 1% and 5% lower than that of the static plan for sigma = 2 mm and sigma = 4 mm, respectively, and for PTV margins <5.0 mm. An additional reduction of 1% was observed when rotational deviations were included. The same effect was observed for the CTV(elective) ipsilateral but with smaller dose differences than those for the contralateral side. The effect of the random uncertainties on the mean dose to the parotid glands was not significant. The maximal dose to the spinal cord increased by a maximum of 3 Gy.

CONCLUSIONS

The margins to account for random setup uncertainties, in our clinical IMRT solution, should be 1.5 mm and 3.0 mm in the case of sigma = 2 mm and sigma = 4 mm, respectively, for the CTV(primary). Larger margins (5.0 mm), however, should be applied to the CTV(elective), if the goal of treatment is a V(95) value of at least 99%.

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.

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.

Scintigraphic assessment of early and late parotid gland function after radiotherapy for head-and-neck cancer: a prospective study of dose-volume response relationships

PURPOSE

To investigate the value of scintigraphy as an indirect measurement of parotid function after radiotherapy (RT).

METHODS AND MATERIALS

Ninety-six patients with primary or postoperative RT for various malignancies in the head-and-neck region were prospectively evaluated. Parotid gland scintigraphy was performed before RT and 6 weeks and 1 year after RT. The uptake, excretion fraction of the saliva from the parotid gland to the oral cavity (SEF), and the ratios of uptake and SEF after and before treatment were calculated. CT-based treatment planning was used to derive dose-volume histograms of the parotid glands. To establish the effects of both the radiation dose and the volume of the parotid gland irradiated, the normal tissue complication probability model proposed by Lyman was fit to the data.

RESULTS

The mean maximal uptake of 192 parotid glands decreased significantly from 3329 counts (ct)-/s before RT to 3084 ct/s and 3005 ct/s at 6 weeks and 1 year after RT. The SEF before treatment was 44.7%. The SEF decreased to 18.7% at 6 weeks after RT, but recovered to a SEF of 32.4% at 1 year after RT. A significant correlation was found between the uptake 1 year after RT and the mean parotid dose. The reduction in post-RT SEF correlated significantly with the mean parotid gland dose. The normal tissue complication probability model parameter TD50 was found to be 29 and 43 Gy at 6 weeks and 1 year after RT, respectively, when a complication was defined as a posttreatment SEF parotid ratio of <45%.

CONCLUSIONS

The effects of radiation on parotid gland function using scintigraphy could be well established. A statistically significant correlation between the SEF ratio and the mean parotid dose was shown, with some recovery of function at 1 year after RT, comparable with the flow results. When direct flow measurements are not feasible, parotid scintigraphy appears to be a good indicator of gland function.

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.

Serious adverse effects of amifostine during radiotherapy in head and neck cancer patients

BACKGROUND AND PURPOSE

Amifostine has been shown to protect against xerostomia induced by radiotherapy for head and neck cancer, but its impact on the therapeutic index is unknown. This is the first report focusing on amifostine related adverse effects leading to discontinuation of amifostine treatment.

PATIENTS AND METHODS

Thirty-nine patients from two centers irradiated for head and neck cancer received i.v.-infusions of amifostine prior to each radiation fraction. In a phase III study, two daily amifostine doses, 200 mg/m(2) (n = 21) and 340 mg/m(2) (n = 18), were compared for protection against radiation induced toxicity. Total radiation dose was 60-70Gy (2Gy per fraction), nine patients received concurrent chemotherapy with cisplatin/5-FU. amifostine was usually discontinued after >1 episode of serious toxicity during subsequent treatment sessions.

RESULTS

In 16/39 patients (41%) amifostine was discontinued due to severe adverse effects, which led to discontinuation of the phase III study. In four of 16 patients radiotherapy was delayed due to amifostine related adverse effects for 1-3 days. Discontinuation occurred more often in patients receiving chemotherapy. The results led to a literature review for amifostine treatment during radiotherapy in head and neck cancer patients. Regarding our series and published series using an amifostine schedule comparable to ours, total discontinuation rate was 27% (57/214). Discontinuation was significantly influenced by chemotherapy (P = 0.007) but not by amifostine dose (P = 0.156).

CONCLUSION

Daily i.v. administration of amifostine during radiotherapy in head and neck cancer is associated with a high rate of serious adverse effects leading to discontinuation of amifostine treatment and sometimes delay of radiotherapy.

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.

Location of cervical lymph node metastases in oropharyngeal and hypopharyngeal carcinoma: implications for cranial border of elective nodal target volumes

PURPOSE

To analyze the exact location of the most cranial metastatic cervical lymph node in patients with oropharyngeal or hypopharyngeal carcinoma. This was done to specify the cranial border of the elective nodal target volume for improvement of parotid-sparing irradiation.

METHODS AND MATERIALS

The most cranial metastatic lymph node, ipsilateral and, when present, contralateral, was delineated on 58 diagnostic CT scans of patients with node-positive oropharyngeal or hypopharyngeal carcinoma. The distances from the delineated lymph node to the base of the skull were measured in all planes.

RESULTS

The mean ipsilateral and contralateral distance to the base of the skull in the coronal plane was 25.6 mm (range 2.6-73.8; SD 14.7) and 34.7 mm (range 10.4-78.9; SD 14.0), respectively (p = 0.002). Ipsilateral and contralateral metastatic lymph nodes were located within 20 mm below the base of the skull in 24 patients (41%) and 3 patients (5%), respectively.

CONCLUSION

Contralateral metastatic lymph nodes are more caudally located than are ipsilateral metastatic lymph nodes. In elective irradiation, lowering the cranial border of the contralateral nodal target volume with 20 mm below the base of the skull should be considered.

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.