Dose-volume specification: new challenges with intensity-modulated radiation therapy

Quantification of gross tumour volume changes between simulation and first day of radiotherapy for patients with locally advanced malignancies of the lung and head/neck

INTRODUCTION

To quantify changes in gross tumour volume (GTV) between simulation and initiation of radiotherapy in patients with locally advanced malignancies of the lung and head/neck.

METHODS

Initial cone beam computed tomography (CT) scans from 12 patients with lung cancer and 12 with head/neck cancer (head and neck squamous cell carcinoma (HNSCC)) treated with intensity-modulated radiotherapy with image guidance were rigidly registered to the simulation CT scans. The GTV was demarcated on both scans. The relationship between percent GTV change and variables including time interval between simulation and start, tumour (T) stage, and absolute weight change was assessed.

RESULTS

For lung cancer patients, the GTV increased a median of 35.06% (range, -16.63% to 229.97%) over a median interval of 13 days (range, 7-43), while for HNSCC patients, the median GTV increase was 16.04% (range, -8.03% to 47.41%) over 13 days (range, 7-40). These observed changes are statistically significant. The magnitude of this change was inversely associated with the size of the tumour on the simulation scan for lung cancer patients (P < 0.05). However, the observed changes in GTV did not correlate with the duration of the interval for either disease site. Similarly, T stage, absolute weight change and histologic type (the latter for lung cancer cases) did not correlate with degree of GTV change (P > 0.1).

CONCLUSION

While the observed changes in GTV were moderate from the time of simulation to start of radiotherapy, these findings underscore the importance of image guidance for target localisation and verification, particularly for smaller tumours. Minimising the delay between simulation and treatment initiation may also be beneficial.

Dosimetric impact of daily setup variations during treatment of canine nasal tumors using intensity-modulated radiation therapy

Intensity-modulated radiation therapy (IMRT) can be employed to yield precise dose distributions that tightly conform to targets and reduce high doses to normal structures by generating steep dose gradients. Because of these sharp gradients, daily setup variations may have an adverse effect on clinical outcome such that an adjacent normal structure may be overdosed and/or the target may be underdosed. This study provides a detailed analysis of the impact of daily setup variations on optimized IMRT canine nasal tumor treatment plans when variations are not accounted for due to the lack of image guidance. Setup histories of ten patients with nasal tumors previously treated using helical tomotherapy were replanned retrospectively to study the impact of daily setup variations on IMRT dose distributions. Daily setup shifts were applied to IMRT plans on a fraction-by-fraction basis. Using mattress immobilization and laser alignment, mean setup error magnitude in any single dimension was at least 2.5 mm (0-10.0 mm). With inclusions of all three translational coordinates, mean composite offset vector was 5.9 +/- 3.3 mm. Due to variations, a loss of equivalent uniform dose for target volumes of up to 5.6% was noted which corresponded to a potential loss in tumor control probability of 39.5%. Overdosing of eyes and brain was noted by increases in mean normalized total dose and highest normalized dose given to 2% of the volume. Findings suggest that successful implementation of canine nasal IMRT requires daily image guidance to ensure accurate delivery of precise IMRT distributions when non-rigid immobilization techniques are utilized. Unrecognized geographical misses may result in tumor recurrence and/or radiation toxicities to the eyes and brain.

ICRU reference dose in an era of intensity-modulated radiation therapy clinical trials: correlation with planning target volume mean dose and suitability for intensity-modulated radiation therapy dose prescription

BACKGROUND AND PURPOSE

IMRT clinical trials lack dose prescription and specification standards similar to ICRU standards for two- and three-dimensional external beam planning. In this study, we analyzed dose distributions for patients whose treatment plans incorporated IMRT, and compared the dose determined at the ICRU reference point to the PTV doses determined from dose-volume histograms. Additionally, we evaluated if ICRU reference type single-point dose prescriptions are suitable for IMRT dose prescriptions.

MATERIALS AND METHODS

For this study, IMRT plans of 117 patients treated at our institution were randomly selected and analyzed. The treatment plans were clinically applied to the following disease sites: abdominal (11), anal (10), brain (11), gynecological (15), head and neck (25), lung (15), male pelvis (10) and prostate (20). The ICRU reference point was located in each treatment plan following ICRU Report 50 guidelines. The reference point was placed in the central part of the PTV and at or near the isocenter. In each case, the dose was calculated and recorded to this point. For each patient--volume and dose (PTV, PTV mean, median and modal) information was extracted from the planned dose-volume histogram.

RESULTS

The ICRU reference dose vs PTV mean dose relationship in IMRT exhibited a weak positive association (Pearson correlation coefficient 0.63). In approximately 65% of the cases studied, dose at the ICRU reference point was greater than the corresponding PTV mean dose. The dose difference between ICRU reference and PTV mean doses was 2% in approximately 79% of the cases studied (average 1.21% (+/-1.55), range -4% to +4%). Paired t-test analyses showed that the ICRU reference doses and PTV median doses were statistically similar (p=0.42). The magnitude of PTV did not influence the difference between ICRU reference and PTV mean doses.

CONCLUSIONS

The general relationship between ICRU reference and PTV mean doses in IMRT is similar to that in 3D CRT distributions. Point doses in IMRT are influenced by the degree of intensity modulation as well as calculation grid size utilized. Although the ICRU reference point type prescriptions conceptually may be extended for IMRT dose prescriptions and used as a representative of tumor dose, new universally acceptable dose prescription and specification standards for IMRT based on RTOG IMRT prescription model incorporating dose-volume specification would likely lead to greater consistency among treatment centers.

Quantification of incidental dose to potential clinical target volume (CTV) under different stereotactic body radiation therapy (SBRT) techniques for non-small cell lung cancer – Tumor motion and using internal target volume (ITV) could improve dose distribution in CTV

PURPOSE

Clinical target volume (CTV), although present, is usually not considered during stereotactic body radiation therapy (SBRT) for non-small cell lung cancer. This study aimed to quantify the incidental dose to the potential CTV under different SBRT techniques.

MATERIALS AND METHODS

Ten patients with various tumor motions were included in the study. Gated-4DCT was performed for all patients. Three treatment plans were generated. Plan A was based on free breathing gross tumor volume (GTV) from a regular CT. Plan B was based on internal target volume (ITV) from gated 4DCT. Plan C was a perfect gated treatment at the exhale phase. The hypothetical CTV was represented by three CTV shells (5, 10, and 15 mm). Time-averaged dose for different respiratory phases was calculated for 18 representative points in each shell.

RESULTS

The minimum doses for plans A, B, and C were 84+/-20%, 94+/-3%, and 80+/-17% of the isocenter dose to the 5mm shell, 72+/-27%, 64+/-7%, and 20+/-11% to the 10mm shell, and 38+/-27%, 27+/-17%, and 6+/-7% to the 15 mm shell, respectively. The caudal and cranial ends of each shell usually had lower dose compared to the other points on the shell. Plan B had the most uniform and reasonable doses to the CTV shells, and patients with large respiratory motion had significantly higher minimum dose than patients with less motion.

CONCLUSION

The potential CTV may incidentally receive adequate and relatively homogeneous doses when ITV is used and the patients have large respiratory motion. However, it could be underdosed for gated treatment or for patients with little motion.

Comparison of inverse-planned three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for non–small-cell lung cancer

PURPOSE

Lungs are the major dose-limiting organ during radiotherapy (RT) for non-small-cell lung cancer owing to the development of pneumonitis. This study compared intensity-modulated RT (IMRT) with three-dimensional conformal RT (3D-CRT) in reducing the dose to the lungs.

METHODS

Ten patients with localized non-small-cell lung cancer underwent computed tomography (CT). The planning target volume (PTV) was defined and the organs at risk were outlined. An inverse-planning program, AutoPlan, was used to design the beam angle-optimized six-field noncoplanar 3D-CRT plans. Each 3D-CRT plan was compared with a series of five IMRT plans per patient. The IMRT plans were created using a commercial algorithm and consisted of a series of three, five, seven, and nine equidistant coplanar field arrangements and one six-field noncoplanar plan. The planning objectives were to minimize the lung dose while maintaining the dose to the PTV. The percentage of lung volume receiving >20 Gy (V20) and the percentage of the PTV covered by the 90% isodose (PTV90) were the primary endpoints. The PTV90/V20 ratio was used as the parameter accounting for both the reduction in lung volume treated and the PTV coverage.

RESULTS

All IMRT plans, except for the three-field coplanar plans, improved the PTV90/V20 ratio significantly compared with the optimized 3D-CRT plan. Nine coplanar IMRT beams were significantly better than five or seven coplanar IMRT beams, with an improved PTV90/V20 ratio.

CONCLUSION

The results of our study have shown that IMRT can reduce the dose to the lungs compared with 3D-CRT by improving the conformity of the plan.

Method comparison of ultrasound and kilovoltage x-ray fiducial marker imaging for prostate radiotherapy targeting

Several measurement techniques have been developed to address the capability for target volume reduction via target localization in image-guided radiotherapy; among these have been ultrasound (US) and fiducial marker (FM) software-assisted localization. In order to assess interchangeability between methods, US and FM localization were compared using established techniques for determination of agreement between measurement methods when a 'gold-standard' comparator does not exist, after performing both techniques daily on a sequential series of patients. At least 3 days prior to CT simulation, four gold seeds were placed within the prostate. FM software-assisted localization utilized the ExacTrac X-Ray 6D (BrainLab AG, Germany) kVp x-ray image acquisition system to determine prostate position; US prostate targeting was performed on each patient using the SonArray (Varian, Palo Alto, CA). Patients were aligned daily using laser alignment of skin marks. Directional shifts were then calculated by each respective system in the X, Y and Z dimensions before each daily treatment fraction, previous to any treatment or couch adjustment, as well as a composite vector of displacement. Directional shift agreement in each axis was compared using Altman-Bland limits of agreement, Lin's concordance coefficient with Partik's grading schema, and Deming orthogonal bias-weighted correlation methodology. 1,019 software-assisted shifts were suggested by US and FM in 39 patients. The 95% limits of agreement in X, Y and Z axes were +/-9.4 mm, +/-11.3 mm and +/-13.4, respectively. Three-dimensionally, measurements agreed within 13.4 mm in 95% of all paired measures. In all axes, concordance was graded as 'poor' or 'unacceptable'. Deming regression detected proportional bias in both directional axes and three-dimensional vectors. Our data suggest substantial differences between US and FM image-guided measures and subsequent suggested directional shifts. Analysis reveals that the vast majority of all individual US and FM directional measures may be expected to agree with each other within a range of 1-1.5 cm. Since neither system represents a gold standard, clinical judgment must dictate whether such a difference is of import. As IMRT protocols seek dose escalation and PTV reduction predicated on US- and FM-guided imaging, future studies are needed to address these potential clinically relevant issues regarding the interchangeability and accuracy of novel positional verification techniques. Comparison series with multiple image-guidance systems are needed to refine comparisons between targeting methods. However, we do not advocate interchangeability of US and FM localization methods.

Fractionated Radiotherapy Techniques

A convergence of advances in patient immobilization and localization, patient imaging, beam shaping and delivery, and treatment planning has led to considerable improvement in the ability to deliver highly conformal radiation treatments by radiosurgical or fractionated radiotherapy techniques. The selection of the "best" treatment technique for any given patient needs to consider the morphology of the target and regional organs at risk as well as available technology and institutional expertise.

Cone-beam-CT guided radiation therapy: technical implementation

BACKGROUND AND PURPOSE

X-ray volumetric imaging system (XVI) mounted on a linear accelerator is available for image guidance applications. In preparation for clinical implementation, phantom and patient imaging studies were conducted to determine the irradiation parameters that would trade-off image quality, patient dose and scanning time.

PATIENTS AND METHODS

The XVI image quality and imaging dose were benchmarked against those obtained with a helical CT scanner for a head and body phantom. The irradiation parameters were varied including the total imaging dose, number of projections, field of view, reconstruction resolution and use of a scatter rejection grid. We characterized the image quality based on relative contrast, noise, contrast to noise ratio (CNR) and point spread function (PSF). XVI scans of pelvis, head and neck and lung patients were acquired and submitted to a range of observers to identify the favorable reconstruction parameters.

RESULTS

Phantom studies have demonstrated that a scatter rejection grid reduces photon scattering and improves the image uniformity. For the body phantom, the helical CT and the wide field XVI technique produce similar image quality, with surface doses of 0.025 and 0.044 Gy respectively. We have demonstrated that the local tomography technique improves the image contrast and the CNR while reducing the skin dose by 40-50% compared to the wide field technique. Clinical scans of head and neck, lung and prostate patients present good soft tissue contrast and excellent bone definition.

CONCLUSIONS

With adjustment of irradiation parameters and an imaging surface dose of less than 0.05 Gy, high quality XVI images can be obtained for a phantom simulating the body thickness. XVI is currently feasible for image-guided treatments of head and neck, torso and pelvic areas using soft tissue and bony structures.

Method to account for dose fractionation in analysis of IMRT plans: Modified equivalent uniform dose

PURPOSE

To propose a modified equivalent uniform dose (mEUD) to account for dose fractionation using the biologically effective dose without losing the advantages of the generalized equivalent uniform dose (gEUD) and to report the calculated mEUD and gEUD in clinically used intensity-modulated radiotherapy (IMRT) plans.

METHODS AND MATERIALS

The proposed mEUD replaces the dose to each voxel in the gEUD formulation by a biologically effective dose with a normalization factor. We propose to use the term mEUD(D(o))(/n(o)) that includes the total dose (D(o)) and number of fractions (n(o)) and to use the term mEUD(o) that includes the same total dose but a standard fraction size of 2 Gy. A total of 41 IMRT plans for patients with nasopharyngeal cancer treated at our institution between October 1997 and March 2002 were selected for the study. The gEUD and mEUD were calculated for the planning gross tumor volume (pGTV), planning clinical tumor volume (pCTV), parotid glands, and spinal cord. The prescription dose for these patients was 70 Gy to >95% of the pGTV and 59.4 Gy to >95% of the pCTV in 33 fractions.

RESULTS

The calculated average gEUD was 72.2 +/- 2.4 Gy for the pGTV, 54.2 +/- 7.1 Gy for the pCTV, 26.7 +/- 4.2 Gy for the parotid glands, and 34.1 +/- 6.8 Gy for the spinal cord. The calculated average mEUD(D(o))(/n(o)) using 33 fractions was 71.7 +/- 3.5 Gy for mEUD(70/33) of the pGTV, 49.9 +/- 7.9 Gy for mEUD(59.5/33) of the pCTV, 27.6 +/- 4.8 Gy for mEUD(26/33) of the parotid glands, and 32.7 +/- 7.8 Gy for mEUD(45/33) of the spinal cord.

CONCLUSION

The proposed mEUD, combining the gEUD with the biologically effective dose, preserves all advantages of the gEUD while reflecting the fractionation effects and linear and quadratic survival characteristics.

Impact of geometric uncertainties on evaluation of treatment techniques for prostate cancer

PURPOSE

To assess the impact of patient repositioning and internal organ motion on prostate treatment plans using three-dimensional conformal and intensity-modulated radiotherapy.

METHODS AND MATERIALS

Four-field, six-field, and simplified intensity-modulated arc therapy plans were generated for 5 prostate cancer patients. The planning target volume was created by adding a 1-cm margin to the clinical target volume. A convolution model was used to estimate the effect of random geometric uncertainties during treatment. Dose statistics, tumor control probabilities, and normal tissue complication probabilities were compared with and without the presence of uncertainty. The impact of systematic uncertainties was also investigated.

RESULTS

Compared with the planned treatments, the delivered dose distribution with random geometric uncertainties displayed an increase in the apparent minimal dose to the prostate and seminal vesicles and a decrease in the rectal volume receiving a high dose. This increased the tumor control probabilities and decreased the normal tissue complication probabilities. Changes were seen in the percentage of prostate volume receiving 100% and 95% of the prescribed dose, and the minimal dose and tumor control probabilities for the target volume. In addition, the volume receiving at least 65 Gy, the minimal dose, and normal tissue complication probabilities changed considerably for the rectum. The simplified intensity-modulated arc therapy technique was the most sensitive to systematic errors, especially in the anterior-posterior and superior-inferior directions.

CONCLUSION

Geometric uncertainties should be considered when evaluating treatment plans. Contrary to the widely held belief, increased conformation of the dose distribution is not always associated with increased sensitivity to random geometric uncertainties if a sufficient planning target volume margin is used. Systematic errors may have a variable effect, depending on the treatment technique used.

Combined inhibition of extracellular signal-regulated kinases and HSP90 sensitizes human colon carcinoma cells to ionizing radiation

Indomethacin, a common nonsteroidal anti-inflammatory drug, has been shown to enhance radiation-mediated cell-killing effect through the activation of p38 mitogen-activated protein kinase (MAPK). We found that indomethacin strongly reduced the basal level of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in HT-29 human colon carcinoma cells. The inhibition of ERK1/2 by indomethacin was only observed in cells with high basal activities of ERK1/2 such as HT-29 cells, but not in cells with low basal activities, such as HeLa. Cell cycle analysis of HT-29 cells exposed with indomethacin showed a partial G1/S arrest and slow DNA synthesis. However, the treatment with NS398, a specific COX-1/2 inhibitor, failed to show any effect on cell cycle, indicating that the inhibition of COX-1/2 is not responsible for cell cycle arrest. Since U0126, a specific inhibitor for MEK1/2, also induced a partial G1/S arrest, the G1/S arrest induced by indomethacin is, at least in part, caused by the inhibition of ERK1/2. Cell proliferation of HT-29 was inhibited by the treatment of U0126 but not in HeLa cells, and the treatment of HT-29 cells with U0126 enhanced radiation sensitivity possibly due to the accumulation of cells in G1 phase. We found that 17-allylamino-17-demethoxygeldanamycin, a geldanamycin delivative, radiosensitized HT-29 cells at a relatively low dose of irradiation, and indomethacin and U0126 further enhanced this effect. Therefore, tumor cells with elevated ERK1/2 activity can be effectively sensitized to radiation treatment by a combinational inhibition of HSP90 and MAPK activity.

The impact of daily setup variations on head-and-neck intensity-modulated radiation therapy

PURPOSE

Intensity-modulated radiation therapy (IMRT) in the treatment of head-and-neck (H&N) cancer provides the opportunity to diminish normal tissue toxicity profiles and thereby enhance patient quality of life. However, highly conformal treatment techniques commonly establish steep dose gradients between tumor and avoidance structures. Daily setup variations can therefore significantly compromise the ultimate precision of idealized H&N IMRT delivery. This study provides a detailed analysis regarding the potential impact of daily setup variations on the overall integrity of H&N IMRT.

METHODS AND MATERIALS

A series of 10 patients with advanced H&N cancer were prospectively enrolled in a clinical trial to examine daily H&N radiation setup accuracy. These patients were treated with conventional shrinking field design using three-dimensional treatment planning techniques (not IMRT). Immobilization and alignment were performed using modern H&N practice techniques including conventional thermoplastic masking, baseplate fixation to the treatment couch, three-point laser alignment, and weekly portal film evaluation. After traditional laser alignment, setup accuracy was assessed daily for each patient by measuring 3 Cartesian and 3 angular deviations from the specified isocenter using a high-precision, optically guided patient localization system, which affords submillimeter setup accuracy. These positional errors were then applied to a distinct series of 10 H&N IMRT plans for detailed analysis regarding the impact of daily setup variation (without optical guidance) on the ultimate integrity of IMRT plans over a 30-day treatment course. Dose-volume histogram (DVH), equivalent uniform dose (EUD), mean total dose (mTd), and maximal total dose (MTD) for normal structures were analyzed for IMRT plans with and without incorporation of daily setup variation.

RESULTS

Using conventional H&N masking and laser alignment for daily positioning, the mean setup error in any single dimension averaged 3.33 mm. However, when all six degrees of freedom were accounted for, using the optically guided patient localization system, the mean composite vector offset was 6.97 mm with a standard deviation of 3.63 mm. Superimposition of mean offset vectors on idealized H&N IMRT treatment plans enabled evaluation of resultant shifts in DVH, EUD, mTd, and MTD calculations. Partial geographic tumor miss (GTV underdosing) and normal tissue overdosing was common when these mean positional offsets were incorporated. The decrease in EUD for defined tumor volumes ranged up to 21% when the largest offset histories were applied, and 3-14% for plans when the least and median offset histories were applied.

CONCLUSION

The successful implementation of H&N IMRT requires accurate and reproducible treatment delivery over a 6- to 7-week treatment course. The adverse impact of daily setup variation, which occurs routinely with conventional H&N masking techniques, may be considerably greater than recognized. Isocenter verification checks on two-dimensional orthogonal films may not sufficiently alert the clinician to the magnitude of three-dimensional offset vectors and the resultant impact on the quality of overall IMRT delivery. Unrecognized geographic miss and resultant target underdose may occur. Similarly, selected normal structures such as parotid glands may receive higher doses than intended. The results of this study suggest that more rigorous immobilization techniques than conventional masking and routine patient setup tracking methodologies are important for the accurate monitoring and successful delivery of high-quality IMRT for H&N cancer.

Radiotherapy for nasopharyngeal carcinoma--transition from two-dimensional to three-dimensional methods

This review describes the clinical background that underlies the transition from two-dimensional to three-dimensional (3D) planning techniques in the treatment of nasopharyngeal cancer (NPC). A systematic search of the Medline was performed using 'nasopharyngeal carcinoma', 'radiotherapy', '3-dimensional conformal radiotherapy', 'stereotactic radiosurgery/radiotherapy' and 'intensity-modulated radiotherapy' as keywords. Citing evidence from the published literature and their own institutional experience, the authors critically examined the positive impact of 3D methods--with emphasis on intensity-modulated radiotherapy (IMRT)--on target coverage and geometric accuracy, sparing of normal organs, and dosimetric homogeneity. Potential problems related to the widespread practice of IMRT such as quality assurance, utilization of medical resources and the risk of developing radiation-induced secondary cancers were highlighted. Application of IMRT within the context of altered fractionation, dose escalation and concurrent chemotherapy were discussed. The article concluded with a suggested treatment approach and research direction for different stages of NPC.

Dysphagia and aspiration after chemoradiotherapy for head-and-neck cancer: which anatomic structures are affected and can they be spared by IMRT?

PURPOSE

To identify the anatomic structures whose damage or malfunction cause late dysphagia and aspiration after intensive chemotherapy and radiotherapy (RT) for head-and-neck cancer, and to explore whether they can be spared by intensity-modulated RT (IMRT) without compromising target RT.

METHODS AND MATERIALS

A total of 26 patients receiving RT concurrent with gemcitabine, a regimen associated with a high rate of late dysphagia and aspiration, underwent prospective evaluation of swallowing with videofluoroscopy (VF), direct endoscopy, and CT. To assess whether the VF abnormalities were regimen specific, they were compared with the VF findings of 6 patients presenting with dysphagia after RT concurrent with high-dose intra-arterial cisplatin. The anatomic structures whose malfunction was likely to cause each of the VF abnormalities common to both regimens were determined by literature review. Pre- and posttherapy CT scans were reviewed for evidence of posttherapy damage to each of these structures, and those demonstrating posttherapy changes were deemed dysphagia/aspiration-related structures (DARS). Standard three-dimensional (3D) RT, standard IMRT (stIMRT), and dysphagia-optimized IMRT (doIMRT) plans in which sparing of the DARS was included in the optimization cost function, were produced for each of 20 consecutive patients with advanced head-and-neck cancer.

RESULTS

The posttherapy VF abnormalities common to both regimens included weakness of the posterior motion of the base of tongue, prolonged pharyngeal transit time, lack of coordination between the swallowing phases, reduced elevation of the larynx, and reduced laryngeal closure and epiglottic inversion, contributing to a high rate of aspiration. The anatomic structures whose malfunction was the likely cause of each of these abnormalities, and that also demonstrated anatomic changes after RT concurrent with gemcitabine doses associated with dysphagia and aspiration, were the pharyngeal constrictor muscles (median thickness near midline 2.5 mm before therapy vs. 7 mm after therapy; p = 0.001), the supraglottic larynx (median thickness, 2 mm before therapy vs. 4 mm after therapy; p < 0.001), and, similarly, the glottic larynx. The constrictors and the glottic and supraglottic larynx were, therefore, deemed the DARS. The lowest maximal dose delivered to a stricture volume was 50 Gy. Reducing the volumes of the DARS receiving > or =50 Gy (V(50)) was, therefore, a planning and evaluation goal. Compared with the 3D plans, stIMRT reduced the V(50) of the pharyngeal constrictors by 10% on average (range, 0-36%, p < 0.001), and doIMRT reduced these volumes further, by an additional 10% on average (range, 0-38%; p <0.001). The V(50) of the larynx (glottic + supraglottic) was reduced marginally by stIMRT compared with 3D (by 7% on average, range, 0-56%; p = 0.054), and doIMRT reduced these volumes by an additional 11%, on average (range, 0-41%; p = 0.002). doIMRT reduced laryngeal V(50) compared with 3D, by 18% on average (range 0-61%; p = 0.001). Certain target delineation rules facilitated sparing of the DARS by IMRT. The maximal DARS doses were not reduced by IMRT because of their partial overlap with the targets. stIMRT and doIMRT did not differ in target doses, parotid gland mean dose, spinal cord, or nonspecified tissue maximal dose.

CONCLUSIONS

The structures whose damage may cause dysphagia and aspiration after intensive chemotherapy and RT are the pharyngeal constrictors and the glottic and supraglottic larynx. Compared with 3D-RT, moderate sparing of these structures was achieved by stIMRT, and an additional benefit, whose extent varied among the patients, was gained by doIMRT, without compromising target doses. Clinical validation is required to determine whether the dosimetric gains are translated into clinical ones.

International Conference on Translational Research ICTR 2003 Conference Summary: marshalling resources in a complex time

The knowledge, tools, and environment for the practice of radiation oncology are changing rapidly. The National Cancer Institute has articulated the need for a balanced portfolio, including the interrelated components of discovery, development, and delivery. Underpinning practice is the emerging knowledge from molecular, cellular, and tumor biology that is the engine of discovery. The use of high-throughput technologies to analyze biochemical and molecular profiles will ultimately enable the individualization of cancer treatment requiring the appropriate integration of radiation with a range of systemic therapies, including chemotherapy, biologic therapy, and immunotherapy. Technological advances in treatment delivery using photons, brachytherapy, particle therapy, radioisotopes, and other forms of energy require an improved ability to localize the tumor and critical subregions and to ensure necessary tissue immobilization and/or real-time target adjustment. Functional imaging is helping to define tumor characteristics and response to treatment. The development of appropriate radiation oncology treatment requires a wide range of expertise, a multimodality approach, and multi-institutional collaboration to provide improved and cost-effective outcome. The delivery of appropriate cancer care to those who need it requires biology and technology but also reaching the underserved populations worldwide. ICTR 2003 demonstrated substantial progress in translational radiation oncology. Faced with financial constraints for research and patient care, the broad field of radiation oncology must continually examine and balance its research and development portfolio and invest in its future leaders to enable it be an important contributor to the future of cancer care.

Techniques to modulate radiotherapy toxicity and outcome in soft tissue sarcoma

Radiotherapy (RT) targeting of soft tissue sarcoma presents considerable opportunity and challenges in realizing the dual goals of tissue and function preservation and maintaining high local control. Traditional RT target volumes used for soft tissue sarcoma have largely been constrained by available technology and are not ideal in some situations. The advent of very precise treatment planning and delivery systems, including three-dimensional conformal radiotherapy and intensity-modulated radiotherapy, means it is possible to select target volumes that more closely approach the optimum. Consequently, these new approaches provide great opportunity for treatment enhancement in the future. It can be expected that newer techniques for RT planning and delivery will challenge the existing dogma concerning target delineation for optimal radiotherapy outcome. It can be foreseen that the precise knowledge of appropriate targets will continue to evolve for different clinical scenarios and likely be greatly influenced by enhanced imaging capability. Advancement of three-dimensional conformal radiotherapy and intensity-modulated radiotherapy over the next decade must rely on the consistent reporting and sharing of results concerning outcome of normal tissue from volumetric treatment planning.

Intensity-Modulated Radiation Therapy for Prostate Cancer

Prostate cancer is among the most common solid malignancies. A number of treatment alternatives exist for localized prostate cancer, including observation, prostatectomy, brachytherapy, and external-beam radiation therapy (EBRT). External-beam radiation therapy has changed dramatically during the past several years. Older techniques paved the way for 3-dimensional conformal radiation therapy (CRT), which in turn facilitated the introduction of intensity-modulated radiation therapy (IMRT). The prostate has served as a model disease site for the implementation of IMRT. As indicated by a growing body of experience, IMRT for prostate cancer represents a major technologic and clinical advance for radiation therapy. In this article, a review is provided of the evolution of EBRT leading to IMRT, the unique features making the prostate an ideal disease site for employing IMRT, the details of the clinical implementation of prostate IMRT and supporting technologic advancements, and the currently reported clinical outcomes of IMRT in prostate cancer. In addition, future directions of prostate IMRT, both technologic and clinical, are discussed.

Role of radiation therapy and radiosurgery in glioblastoma multiforme

Randomized trials have supported a role for radiation therapy in the initial management of Glioblastoma Multiforme (GBM) for over twenty-five years. Although technological advances in imaging and three-dimensional treatment planning have reduced the toxicity for patients and have allowed safe radiation dose escalation, unfortunately they have not produced a correspondingly dramatic improvement in overall survival. The dose of 60 Gy partial brain RT remains the standard of care for patients with newly diagnosed GBM. Recently completed randomized trials of brachytherapy and radiosurgery do not support these modalities in the initial management of GBM, but these and other focal RT techniques such as intensity modulated radiation therapy enable safe retreatment in selected patients. Future studies will need to explore radiation biologic response modification and radiosensitization through targeted therapies.

Radiotherapy quality assurance: time for everyone to take it seriously

Like high-risk industries, radiotherapy requires intense attention to detail, alertness, precision, and adequate human and material resources to minimise the risk of irreversible consequences. Clinical trials data such as that generated by the Quality Assurance programme of the Radiotherapy Group of the European Organization for Research and Treatment of Cancer (EORTC) in this issue of the Journal have been instrumental in identifying problems with technical quality, the understanding of which can have a direct impact on improving the quality of care in the community. Consistency in absolute dosimetry, dose delivery, volume definition and reproducibility are paramount in radiotherapy quality assurance and have become even more important with the advent of conformal therapy. Extension of these principles to other oncological disciplines has added an additional dimension of improvement. Waiting times and measures of access must also be monitored if overall quality at the population level is to be assessed and enhanced. Lessons should be learned from clinical trials methodology in the use of intervention-specific guidelines, physician education and real time audit of treatment planning decisions. In the future, novel approaches, such as web based systems may further improve education and audit. Wider application and audit of evidence-based management guidelines about the use radiotherapy will bring to standard clinical practice the quality benefits that are considered a basic minimum standard for clinical trials.