Dosimetric intercomparison for two Australasian clinical trials using an anthropomorphic phantom

Measuring the dose in bone for spine stereotactic body radiotherapy

PURPOSE

Current quality assurance of radiotherapy involving bony regions generally utilises homogeneous phantoms and dose calculations, ignoring the challenges of heterogeneities with dosimetry problems likely occurring around bone. Anthropomorphic phantoms with synthetic bony materials enable realistic end-to-end testing in clinical scenarios. This work reports on measurements and calculated corrections required to directly report dose in bony materials in the context of comprehensive end-to-end dosimetry audit measurements (63 plans, 6 planning systems).

MATERIALS AND METHODS

Radiochromic film and microDiamond measurements were performed in an anthropomorphic spine phantom containing bone equivalent materials. Medium dependent correction factors, k_med, were established using 6 MV and 10 MV Linear Accelerator Monte Carlo simulations to account for the detectors being calibrated in water, but measuring in regions of bony material. Both cortical and trabecular bony material were investigated for verification of dose calculations in dose-to-medium (D_m,m) and dose-to-water (D_w,w) scenarios.

RESULTS

For D_m,m calculations, modelled correction factors for cortical and trabecular bone in film measurements, and for trabecular bone in microDiamond measurements were 0.875(±0.1%), 0.953(±0.3%) and 0.962(±0.4%), respectively. For D_w,w calculations, the corrections were 0.920(±0.1%), 0.982(±0.3%) and 0.993(±0.4%), respectively. In the audit, application of the correction factors improves the mean agreement between treatment plans and measured microDiamond dose from -2.4%(±3.9%) to 0.4%(±3.7%).

CONCLUSION

Monte Carlo simulations provide a method for correcting the dose measured in bony materials allowing more accurate comparison with treatment planning system doses. In verification measurements, algorithm specific correction factors should be applied to account for variations in bony material for calculations based on D_m,m and D_w,w.

THERMOLUMINESCENCE DOSIMETRY (TLD) IN MEDICINE: FIVE 'W'S AND ONE HOW

Thermoluminescence dosimetry (TLD) has a long history of applications in medicine. However, despite its versatility and sensitivity its use is anecdotally diminishing, at least in part due to the complexity and work intensity of a quality TLD service. The present paper explores the role of TLD in medicine using a common inquiry methodology (5W1H) which systematically asks 'Who, What, When, Where, Why and How' to identify what role TLD could and should play in medical applications.

Development of a novel and low-cost anthropomorphic pelvis phantom for 3D dosimetry in radiotherapy

Purpose

The aim of this study was to construct a low-cost, anthropomorphic, and 3D-printed pelvis phantom and evaluate the feasibility of its use to perform 3D dosimetry with commercially available bead thermoluminescent dosimeters (TLDs).

Material and methods

A novel anthropomorphic female phantom was developed with all relevant pelvic organs to position the bead TLDs. Organs were 3D-printed using acrylonitrile butadiene styrene. Phantom components were confirmed to have mass density and computed tomography (CT) numbers similar to relevant tissues. To find out clinically required spatial resolution of beads to cause no perturbation effect, TLDs were positioned with 2.5, 5, and 7.5 mm spacing on the surface of syringe. After taking a CT scan and creating a 4-field conformal radiotherapy plan, 3 dose planes were extracted from the treatment planning system (TPS) at different depths. By using a 2D-gamma analysis, the TPS reports were compared with and without the presence of beads. Moreover, the bead TLDs were placed on the organs’ surfaces of the pelvis phantom and exposed to high-dose-rate (HDR) ⁶⁰Co source. TLDs’ readouts were compared with the TPS calculated doses, and dose surface histograms (DSHs) of organs were plotted.

Results

3D-printed phantom organs agreed well with body tissues regarding both their design and radiation properties. Furthermore, the 2D-gamma analysis on the syringe showed more than 99% points passed 3%- and 3-mm criteria at different depths. By calculating the integral dose of DSHs, the percentage differences were –1.5%, 2%, 5%, and 10% for uterus, rectum, bladder, and sigmoid, respectively. Also, combined standard uncertainty was estimated as 3.5% (k = 1).

Conclusions

A customized pelvis phantom was successfully built and assessed to confirm properties similar to body tissues. Additionally, no significant perturbation effect with different bead resolutions was presented by the external TPS, with 0.1 mm dose grid resolution.

END-TO-END AUDIT: COMPARISON OF TLD AND LITHIUM FORMATE EPR DOSIMETRY

The aim of this study was to test two different solid state dosimetry systems for the purpose of end-to-end audits of radiotherapy volumetric modulated arc therapy (VMAT) technique; a lithium formate electron paramagnetic resonance system and a lithium fluoride thermoluminescent dosimetry system. As a complement to the solid state systems, ion chamber measurements were performed. A polystyrene phantom with a planning target volume (PTV) and an organ at risk (OAR) structure was scanned using CT. A VMAT dose plan was optimized to deliver 2 Gy to the target volume and to minimize the dose to the OAR. The different detectors were inserted into the phantom and the planned dose distribution was delivered. The measured doses were compared to the treatment planning system (TPS) calculated doses. Good agreement was found between the TPS calculated and the measured doses, well accepted for the dose determinations in remote dosimetry audits of VMAT treatment technique.

A comparison of IROC and ACDS on-site audits of reference and non-reference dosimetry

PURPOSE

Consistency between different international quality assurance groups is important in the progress toward similar standards and expectations in radiotherapy dosimetry around the world, and in the context of consistent clinical trial data from international trial participants. This study compares the dosimetry audit methodology and results of two international quality assurance groups performing a side-by-side comparison at the same radiotherapy department, and interrogates the ability of the audits to detect deliberately introduced errors.

METHODS

A comparison of the core dosimetry components of reference and non-reference audits was conducted by the Imaging and Radiation Oncology Core (IROC, Houston, USA) and the Australian Clinical Dosimetry Service (ACDS, Melbourne, Australia). A set of measurements were conducted over 2 days at an Australian radiation therapy facility in Melbourne. Each group evaluated the reference dosimetry, output factors, small field output factors, percentage depth dose (PDD), wedge, and off-axis factors according to their standard protocols. IROC additionally investigated the Electron PDD and the ACDS investigated the effect of heterogeneities. In order to evaluate and compare the performance of these audits under suboptimal conditions, artificial errors in percentage depth dose (PDD), EDW, and small field output factors were introduced into the 6 MV beam model to simulate potential commissioning/modeling errors and both audits were tested for their sensitivity in detecting these errors.

RESULTS

With the plans from the clinical beam model, almost all results were within tolerance and at an optimal pass level. Good consistency was found between the two audits as almost all findings were consistent between them. Only two results were different between the results of IROC and the ACDS. The measurements of reference FFF photons showed a discrepancy of 0.7% between ACDS and IROC due to the inclusion of a 0.5% nonuniformity correction by the ACDS. The second difference between IROC and the ACDS was seen with the lung phantom. The asymmetric field behind lung measured by the ACDS was slightly (0.3%) above the ACDS's pass (optimal) level of 3.3%. IROC did not detect this issue because their measurements were all assessed in a homogeneous phantom. When errors were deliberately introduced neither audit was sensitive enough to pick up a 2% change to the small field output factors. The introduced PDD change was flagged by both audits. Similarly, the introduced error of using 25° wedge instead of 30° wedge was detectible in both audits as out of tolerance.

CONCLUSIONS

Despite different equipment, approach, and scope of measurements in on-site audits, there were clear similarities between the results from the two groups. This finding is encouraging in the context of a global harmonized approach to radiotherapy quality assurance and dosimetry audit.

Credentialing of radiotherapy centres in Australasia for TROG 09.02 (Chisel), a Phase III clinical trial on stereotactic ablative body radiotherapy of early stage lung cancer

OBJECTIVE

A randomised clinical trial comparing stereotactic ablative body radiotherapy (SABR) with conventional radiotherapy for early stage lung cancer has been conducted in Australia and New Zealand under the auspices of the TransTasman Radiation Oncology Group (NCT01014130). We report on the technical credentialing program as prerequisite for centres joining the trial.

METHODS

Participating centres were asked to develop treatment plans for two test cases to assess their ability to create plans according to protocol. Dose delivery in the presence of inhomogeneity and motion was assessed during a site visit using a phantom with moving inserts.

RESULTS

Site visits for the trial were conducted in 16 Australian and 3 New Zealand radiotherapy facilities. The tests with low density inhomogeneities confirmed shortcomings of the AAA algorithm for dose calculation. Dose was assessed for a typical treatment delivery including at least one non-coplanar beam in a stationary and moving phantom. This end-to-end test confirmed that all participating centres were able to deliver stereotactic ablative body radiotherapy with the required accuracy while the planning study demonstrated that they were able to produce acceptable plans for both test cases.

CONCLUSION

The credentialing process documented that participating centres were able to deliver dose as required in the trial protocol. It also gave an opportunity to provide education about the trial and discuss technical issues such as four-dimensional CT, small field dosimetry and patient immobilisation with staff in participating centres. Advances in knowledge: Credentialing is an important quality assurance tool for radiotherapy trials using advanced technology. In addition to confirming technical competence, it provides an opportunity for education and discussion about the trial.

A 2D ion chamber array audit of wedged and asymmetric fields in an inhomogeneous lung phantom

PURPOSE

The Australian Clinical Dosimetry Service (ACDS) has implemented a new method of a nonreference condition Level II type dosimetric audit of radiotherapy services to increase measurement accuracy and patient safety within Australia. The aim of this work is to describe the methodology, tolerances, and outcomes from the new audit.

METHODS

The ACDS Level II audit measures the dose delivered in 2D planes using an ionization chamber based array positioned at multiple depths. Measurements are made in rectilinear homogeneous and inhomogeneous phantoms composed of slabs of solid water and lung. Computer generated computed tomography data sets of the rectilinear phantoms are supplied to the facility prior to audit for planning of a range of cases including reference fields, asymmetric fields, and wedged fields. The audit assesses 3D planning with 6 MV photons with a static (zero degree) gantry. Scoring is performed using local dose differences between the planned and measured dose within 80% of the field width. The overall audit result is determined by the maximum dose difference over all scoring points, cases, and planes. Pass (Optimal Level) is defined as maximum dose difference ≤3.3%, Pass (Action Level) is ≤5.0%, and Fail (Out of Tolerance) is >5.0%.

RESULTS

At close of 2013, the ACDS had performed 24 Level II audits. 63% of the audits passed, 33% failed, and the remaining audit was not assessable. Of the 15 audits that passed, 3 were at Pass (Action Level). The high fail rate is largely due to a systemic issue with modeling asymmetric 60° wedges which caused a delivered overdose of 5%-8%.

CONCLUSIONS

The ACDS has implemented a nonreference condition Level II type audit, based on ion chamber 2D array measurements in an inhomogeneous slab phantom. The powerful diagnostic ability of this audit has allowed the ACDS to rigorously test the treatment planning systems implemented in Australian radiotherapy facilities. Recommendations from audits have led to facilities modifying clinical practice and changing planning protocols.

The development of practice standards for radiation oncology in Australia: a tripartite approach

In many areas of health care, practice standards have become an accepted method for professions to assess and improve the quality of care delivery. The aim of this work is to present the development of practice standards for radiation oncology in Australia, highlighting critical points and lessons learned. Following a review of radiotherapy services in Australia, a multidisciplinary group with support from the Australian Government developed practice standards for radiation oncology in Australia. The standards were produced in a multistep process including a nationwide survey of radiotherapy centres and piloting of the standards in a representative subset of all Australian radiotherapy centres. The standards are grouped into three sections: Facility management (covering staffing, data management, equipment and processes); Treatment planning and delivery (providing more detailed guidance on prescription, planning and delivery); Safety and quality management (including radiation safety, incident monitoring and clinical trials participation). Each of the 16 standards contains specific criteria, a commentary and suggestions for the evidence required to demonstrate compliance. The development of the standards was challenging and time consuming, but the collaborative efforts of the professions resulted in standards applicable throughout Australia and possibly further afield.

Results from a multicenter prostate IMRT dosimetry intercomparison for an OCOG-TROG clinical trial

PURPOSE

A multi-institution dosimetry intercomparison has been undertaken of prostate intensity modulated radiation therapy (IMRT) delivery. The dosimetry intercomparison was incorporated into the quality assurance for site credentialing for the Trans-Tasman Radiation Oncology Group Prostate Fractionated Irradiation Trial 08.01 clinical trial.

METHODS

An anthropomorphic pelvic phantom with realistic anatomy was used along with multiplanar dosimetry tools for the assessment. Nineteen centers across Australia and New Zealand participated in the study.

RESULTS

In comparing planned versus measured dose to the target at the isocenter within the phantom, all centers were able to achieve a total delivered dose within 3% of planned dose. In multiplanar analysis with radiochromic film using the gamma analysis method to compare delivered and planned dose, pass rates for a 5%/3 mm criterion were better than 90% for a coronal slice through the isocenter. Pass rates for an off-axis coronal slice were also better than 90% except for one instance with 84% pass rate.

CONCLUSIONS

Strengths of the dosimetry assessment procedure included the true anthropomorphic nature of the phantom used, the involvement of an expert from the reference center in carrying out the assessment at every site, and the ability of the assessment to detect and resolve dosimetry discrepancies.

Quality assurance for clinical trials

Cooperative groups, of which the Radiation Therapy Oncology Group is one example, conduct national clinical trials that often involve the use of radiation therapy. In preparation for such a trial, the cooperative group prepares a protocol to define the goals of the trial, the rationale for its design, and the details of the treatment procedure to be followed. The Radiological Physics Center (RPC) is one of several quality assurance (QA) offices that is charged with assuring that participating institutions deliver doses that are clinically consistent and comparable. The RPC does this by conducting a variety of independent audits and credentialing processes. The RPC has compiled data showing that credentialing can help institutions comply with the requirements of a cooperative group clinical protocol. Phantom irradiations have been demonstrated to exercise an institution's procedures for planning and delivering advanced external beam techniques (1-3). Similarly, RPC data indicate that a rapid review of patient treatment records or planning procedures can improve compliance with clinical trials (4). The experiences of the RPC are presented as examples of the contributions that a national clinical trials QA center can make to cooperative group trials. These experiences illustrate the critical need for comprehensive QA to assure that clinical trials are successful and cost-effective. The RPC is supported by grants CA 10953 and CA 81647 from the National Cancer Institute, NIH, DHHS.

Short-term neoadjuvant androgen deprivation and radiotherapy for locally advanced prostate cancer: 10-year data from the TROG 96.01 randomised trial

BACKGROUND

The TROG 96.01 trial assessed whether 3-month and 6-month short-term neoadjuvant androgen deprivation therapy (NADT) decreases clinical progression and mortality after radiotherapy for locally advanced prostate cancer. Here we report the 10-year results.

METHODS

Between June, 1996, and February, 2000, 818 men with T2b, T2c, T3, and T4 N0 M0 prostate cancers were randomly assigned to receive radiotherapy alone, 3 months of NADT plus radiotherapy, or 6 months of NADT plus radiotherapy. The radiotherapy dose for all groups was 66 Gy, delivered to the prostate and seminal vesicles (excluding pelvic nodes) in 33 fractions of 2 Gy per day (excluding weekends) over 6·5-7·0 weeks. NADT consisted of 3·6 mg goserelin given subcutaneously every month and 250 mg flutamide given orally three times a day. NADT began 2 months before radiotherapy for the 3-month NADT group and 5 months before radiotherapy for the 6-month NADT group. Primary endpoints were prostate-cancer-specific mortality and all-cause mortality. Treatment allocation was open label and randomisation was done with a minimisation technique according to age, clinical stage, tumour grade, and initial prostate-specific antigen concentration (PSA). Analysis was by intention-to-treat. The trial has been closed to follow-up and all main endpoint analyses are completed. The trial is registered with the Australian New Zealand Clinical Trials Registry, number ACTRN12607000237482.

FINDINGS

802 men were eligible for analysis (270 in the radiotherapy alone group, 265 in the 3-month NADT group, and 267 in the 6-month NADT group) after a median follow-up of 10·6 years (IQR 6·9-11·6). Compared with radiotherapy alone, 3 months of NADT decreased the cumulative incidence of PSA progression (adjusted hazard ratio 0·72, 95% CI 0·57-0·90; p=0·003) and local progression (0·49, 0·33-0·73; p=0·0005), and improved event-free survival (0·63, 0·52-0·77; p<0·0001). 6 months of NADT further reduced PSA progression (0·57, 0·46-0·72; p<0·0001) and local progression (0·45, 0·30-0·66; p=0·0001), and led to a greater improvement in event-free survival (0·51, 0·42-0·61, p<0·0001), compared with radiotherapy alone. 3-month NADT had no effect on distant progression (0·89, 0·60-1·31; p=0·550), prostate cancer-specific mortality (0·86, 0·60-1·23; p=0·398), or all-cause mortality (0·84, 0·65-1·08; p=0·180), compared with radiotherapy alone. By contrast, 6-month NADT decreased distant progression (0·49, 0·31-0·76; p=0·001), prostate cancer-specific mortality (0·49, 0·32-0·74; p=0·0008), and all-cause mortality (0·63, 0·48-0·83; p=0·0008), compared with radiotherapy alone. Treatment-related morbidity was not increased with NADT within the first 5 years after randomisation.

INTERPRETATION

6 months of neoadjuvant androgen deprivation combined radiotherapy is an effective treatment option for locally advanced prostate cancer, particularly in men without nodal metastases or pre-existing metabolic comorbidities that could be exacerbated by prolonged androgen deprivation.

FUNDING

Australian Government National Health and Medical Research Council, Hunter Medical Research Institute, AstraZeneca, and Schering-Plough.

A methodology for TLD postal dosimetry audit of high-energy radiotherapy photon beams in non-reference conditions

BACKGROUND AND PURPOSE

A strategy for national TLD audit programmes has been developed by the International Atomic Energy Agency (IAEA). It involves progression through three sequential dosimetry audit steps. The first step audits are for the beam output in reference conditions for high-energy photon beams. The second step audits are for the dose in reference and non-reference conditions on the beam axis for photon and electron beams. The third step audits involve measurements of the dose in reference, and non-reference conditions off-axis for open and wedged symmetric and asymmetric fields for photon beams. Through a co-ordinated research project the IAEA developed the methodology to extend the scope of national TLD auditing activities to more complex audit measurements for regular fields.

MATERIALS AND METHODS

Based on the IAEA standard TLD holder for high-energy photon beams, a TLD holder was developed with horizontal arm to enable measurements 5cm off the central axis. Basic correction factors were determined for the holder in the energy range between Co-60 and 25MV photon beams.

RESULTS

New procedures were developed for the TLD irradiation in hospitals. The off-axis measurement methodology for photon beams was tested in a multi-national pilot study. The statistical distribution of dosimetric parameters (off-axis ratios for open and wedge beam profiles, output factors, wedge transmission factors) checked in 146 measurements was 0.999+/-0.012.

CONCLUSIONS

The methodology of TLD audits in non-reference conditions with a modified IAEA TLD holder has been shown to be feasible.

Quality in radiation oncology

A modern approach to quality was developed in the United States at Bell Telephone Laboratories during the first part of the 20th century. Over the years, those quality techniques have been adopted and extended by almost every industry. Medicine in general and radiation oncology in particular have been slow to adopt modern quality techniques. This work contains a brief description of the history of research on quality that led to the development of organization-wide quality programs such as Six Sigma. The aim is to discuss the current approach to quality in radiation oncology as well as where quality should be in the future. A strategy is suggested with the goal to provide a threshold improvement in quality over the next 10 years.

Short-term androgen deprivation and radiotherapy for locally advanced prostate cancer: results from the Trans-Tasman Radiation Oncology Group 96.01 randomised controlled trial

BACKGROUND

Androgen deprivation is an established treatment regimen for disseminated prostate cancer; however, its role in patients with localised cancer is less clear. We did a large randomised controlled trial to determine whether 3 months or 6 months of androgen deprivation given before and during radiotherapy improves outcomes for patients with locally advanced prostate cancer.

METHODS

818 men with locally advanced prostate cancer were randomly assigned to: no androgen deprivation (ie, radiotherapy alone: 66 Gy in 33 fractions of 2 Gy per day over 6.5-7.0 weeks to the prostate and seminal vesicles); 3 months' androgen deprivation with 3.6 mg goserelin given subcutaneously every month and 250 mg flutamide given orally three times a day starting 2 months before radiotherapy (same regimen as control group); or 6 months' androgen deprivation, with the same regimen, starting 5 months before radiotherapy (same regimen as control group). Primary endpoints were time to local failure and prostate-cancer-specific survival; secondary endpoints were distant failure, disease-free survival, and freedom from salvage treatment. Analyses were done by intention to treat.

FINDINGS

802 (98%) patients were eligible for analysis. Median follow-up was 5.9 years (range 0.1-8.5). Compared with patients assigned no androgen deprivation, those assigned 3 months' treatment had significantly improved local failure (hazard ratio [HR] 0.56 [95% CI 0.39-0.79], p=0.001), biochemical failure-free survival (0.70 [0.56-0.88], p=0.002), disease-free survival (0.65 [0.52-0.80], p=0.0001), and freedom from salvage treatment (0.73 [0.56-0.96], p=0.025). 6 months' androgen deprivation significantly improved local failure (0.42 [0.28-0.62], p<0.0001), biochemical failure-free survival (0.58 [0.46-0.74], p<0.0001), disease-free survival (0.56 [0.45-0.69], p<0.0001), freedom from salvage treatment (0.53 [0.40-0.71], p<0.0001), distant failure (0.67 [0.45-0.99], p=0.046) and prostate-cancer-specific survival (0.56 [0.32-0.98], p=0.04) compared with no androgen deprivation.

INTERPRETATION

6 months' androgen deprivation given before and during radiotherapy improves the outlook of patients with locally advanced prostate cancer. Further follow-up is needed to estimate precisely the size of survival benefits. Increased radiation doses and additional periods of androgen deprivation might lead to further benefit.

Use of alanine for dosimetry intercomparisons among Italian radiotherapy centers

A pilot program of postal dosimetry intercomparison among 16 Italian Radiotherapy Centers was performed using the ISS Alanine/EPR dosimetry as a transfer system. Dosimeters were irradiated at 10 Gy with high-energy photon beams, both in reference condition in a water phantom and in an anthropomorphic phantom during the simulated treatment of rectum cancer. Intercomparison design along with alanine performances analyzing the different contributions to the combined uncertainty in dose assessment are reported. Main results of the pilot intercomparison, terminated in 2002, are also presented.

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.

Current calibration, treatment, and treatment planning techniques among institutions participating in the Children's Oncology Group

PURPOSE

To report current technology implementation, radiation therapy physics and treatment planning practices, and results of treatment planning exercises among 261 institutions belonging to the Children's Oncology Group (COG).

METHODS AND MATERIALS

The Radiation Therapy Committee of the newly formed COG mandated that each institution demonstrate basic physics and treatment planning abilities by satisfactorily completing a questionnaire and four treatment planning exercises designed by the Quality Assurance Review Center. The planning cases are (1) a maxillary sinus target volume (for two-dimensional planning), (2) a Hodgkin's disease mantle field (for irregular-field and off-axis dose calculations), (3) a central axis blocked case, and (4) a craniospinal irradiation case. The questionnaire and treatment plans were submitted (as of 1/30/02) by 243 institutions and completed satisfactorily by 233. Data from this questionnaire and analyses of the treatment plans with monitor unit calculations are presented.

RESULTS

Of the 243 clinics responding, 54% use multileaf collimators routinely, 94% use asymmetric jaws routinely, and 13% use dynamic wedges. Nearly all institutions calibrate their linear accelerators following American Association of Physicists in Medicine protocols, currently 16% with TG-51 and 81% with TG-21 protocol. Treatment planning systems are relied on very heavily for all calculations, including monitor units. Techniques and results of each of the treatment planning exercises are presented.

CONCLUSIONS

Together, these data provide a unique compilation of current (2001) radiation therapy practices in institutions treating pediatric patients. Overall, the COG facilities have the equipment and the personnel to perform high-quality radiation therapy. With ongoing quality assurance review, radiation therapy compliance with COG protocols should be high.