AN UPDATED DOSE-RESPONSE ANALYSIS IN HODGKINS-DISEASE

Although radiotherapy cures a very high percentage of early stage patients with Hodgkin's disease (HD), there is a controversial dichotomy in the dose recommendations believed necessary to achieve > 95% local control: Whereas one school of thought is to administer 40-44 Gy, other reports claim equal results with about 36 Gy. It is also not clear what doses are required for various tumor cell burdens. The original recommendation of 40-44 Gy was derived from a retrospective analysis of in-field control of disease from mostly kilovoltage data three decades ago. However, there have been many advances in the evaluation of the extent of the disease and in the practice of radiotherapy since the 1960s. Many more dose-control studies have been published in recent years, necessitating a revisit to the dose-response question in HD. Here we have compiled the dose-control data from the 60s to the 90s and analyzed the original and the updated data with the same statistical method to see any differences. We also have performed similar analysis of dose-control information for subclinical disease, < 6 cm and > 6 cm disease. Whereas original analysis (1040 sites at risk) suggested 98% in-field control with 44 Gy, our re-analysis including modern megavoltage data (4117 sites at risk) shows that similar in-field control rates could be achieved with 37.5 Gy. With megavoltage radiotherapy, the doses required for 98% in-field control for subclinical disease and disease of < 6 cm and > 6 cm are, 32.4 Gy (1426 sites at risk), 36.9 Gy (1005 sites at risk) and 37.4 Gy (98 sites at risk), respectively. The results of current updated analysis will provide in-field disease control probabilities for different disease burdens and can serve as a guide in deciding dose prescriptions for practicing radiation oncologists.