Clinical Investigation
Quality Control of Involved Field Radiotherapy in Patients With Early-Favorable (HD10) and Early-Unfavorable (HD11) Hodgkin's Lymphoma: An Analysis of the German Hodgkin Study Group

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Purpose

The German Hodgkin Study Group (GHSG) set up a radiotherapy (RT) reference center within the Department of Radiation Oncology at the University of Cologne to undertake quality assurance of the group's clinical studies. In the HD10 trial (early-favorable stages) and HD11 trial (early-unfavorable stages) all patients received involved field (IF)-RT (30 Gy vs. 20 Gy) within a combined-modality approach. For these patients a central prospective review of all diagnostic imaging was performed by expert radiation oncologists to control disease extension and to define IF treatment volume.

Methods and Materials

On the basis of simulation films, verification films, and radiotherapy case report form (CRF) an expert panel evaluated retrospectively the adequacy of irradiated IF treatment portals according to the RT prescription, applied radiation doses, treatment time, and technical parameters.

Results

Between 1999 and 2006 a total of 825 of 1370 randomized patients of the HD10 trial (60%) and 954 of 1422 patients of the HD11 trial (67%) were evaluated by the panel. Radiotherapy was rated as suboptimal in 47% of all reviewed cases. Although the participating RT centers received a precise RT prescription, most difficulties occurred in the adequate coverage of the IF (40%), followed by technical faults (12%). Deviations from the prescribed single daily dose (1.8–2 Gy), weekly dose, and total reference dose were rare (1%).

Conclusions

As a consequence of these findings, radiation oncologists were trained on the definition of IF-RT at GHSG meetings and at the annual meetings of the German Society for Therapeutic Radiation Oncology. Possible correlations between RT quality and relapse rate will be investigated.

Introduction

Treatment strategies in Hodgkin's lymphoma (HL) have changed dramatically during recent years. For many decades the optimal and standard treatment for early-stage favorable HL was extended-field radiotherapy. Today major study groups have changed from extended-field radiotherapy to involved-field (IF) radiotherapy preceded by short-term chemotherapy to reduce the extent of late toxicities without the risk of lowering the overall survival rates (1). Since its beginning, more than 13,000 patients with HL have been enrolled into the multicenter randomized trials of the German Hodgkin Study Group (GHSG). Within four completed study generations the treatment of HL has developed in a stepwise manner by using the results of the completed protocols. With respect to radiotherapy, the study group successfully evaluated different dose–effect relationships and could also prove the efficacy of IF radiotherapy in early stages in combination with effective chemotherapy (2). The GHSG, with 460 participating study institutions, set up a radiotherapy reference center within the Department of Radiation Oncology at the University of Cologne to undertake quality assurance of the group's clinical studies (3). The HD4 study (early-favorable stages) demonstrated that major protocol violations, especially the design of the EF radiotherapy fields, were associated with a statistically significant reduction in freedom from treatment failure (4). In the HD10 trial (early-favorable stages) and HD11 trial (early-unfavorable stages) all patients received IF radiotherapy (30 Gy vs. 20 Gy) within a combined-modality approach. To guarantee the treatment quality of IF radiotherapy for these patients, an extensive quality control program was conducted. It was based on a central prospective radiation oncologic review of all patients' entire diagnostic imaging and clinical findings. An individual radiotherapy prescription was provided for every study patient. The results of this review were reported recently (5). The prospective review had a significant impact on the correctness of stage definition, allocation to treatment groups, and on the extension of the IF treatment volume.

By checking the simulation films, verification films, and radiation treatment protocols of the patients in the HD10 and HD11 trials, an expert radiotherapy panel evaluated the adequacy of irradiated IF treatment portals, applied radiation doses, treatment time, and technical parameters according to the radiotherapy prescription retrospectively. We initiated this evaluation of the quality control program before the final results of our randomized trials will be available. In the present analysis of this quality control program we report on 1779 patients analyzed by the panel.

Section snippets

Study design

Between 1998 and 2003, 1370 patients were enrolled into the GHSG trial HD10 (early-favorable stages) and 1422 patients into the HD11 trial (early-unfavorable stages). The HD10 trial was a multicenter, four-arm, randomized study and tested 4 × ABVD (Adriamycin, bleomycin, vinblastine, dacarbazine) against 2 × ABVD followed by 20 Gy IF radiotherapy vs. 30 Gy IF radiotherapy (Fig. 1). This study was designed to find the optimal radiation dose and number of cycles of ABVD chemotherapy combined with

Results

Between 1999 and 2006 a total of 825 of 1370 randomized patients in HD10 (60%) and 954 of 1422 patients in HD11 (67%) were evaluated by the panel.

Discussion

The quality of radiotherapy in HL depends on the successful completion of each of the following steps. (1) Correct identification of sites of involvement and sites at significant risk for microscopic disease. This requires an ability to perform an accurate and complete physical examination, to interpret the diagnostic images used for staging, and to know about the region at risk and patterns of spread of HL. (2) Selection and design of treatment field that will adequately cover the volume at

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Supported by the “Competence Network Malignant Lymphoma” Federal German Ministry of Education and Research and the “Deutsche Krebshilfe.”

Presented at the 49th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO), October 28–November 1, 2007, Los Angeles, CA.

Conflict of interest: none.

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