The optimal dose of radiation in Hodgkin's disease: An analysis of clinical and treatment factors affecting in-field disease control

Purpose: The purpose of this study is to analyze the effect of radiation do se, as well as other clinical and therapeutic factors, on in-field disease control. Patients and Materials: The study population comprised 232 patients with St age I and II Hodgkin's disease (HD) treated with curative intent at the Uni versity of Florida with radiotherapy (RT) alone (169 patients) or chemother apy and radiotherapy (CMT) (63 patients). Sites of involvement and radiatio n doses were prospectively recorded and correlated with sites of disease re currence. Results: Freedom from relapse and absolute survival rates at 10 years were as follows: 76% and 77%, entire group; 76% and 80%, RT group; 79% and 70%, CMT group; 85% and 78%, Stage I; and 71% and 77%, Stage II. Treatment failu re occurred in 50 patients (22%) including in-field failure in 22 patients (9%). In-field failure was rare in electively treated sites. Multivariate a nalysis of clinical factors (tumor size, number of sites involved, B-sympto ms, gender, histology, age, and site of involvement) and treatment factors (use of chemotherapy, number of cycles of chemotherapy, radiation dose, rad iation treatment volume, and radiation treatment time) showed only tumor si ze (p = 0.0001) to be significantly correlated with in-field disease contro l. In RT patients, the in-field failure rate according to tumor size was as follows: 0% for less than or equal to 3 cm; 4% for > 3 cm and less than or equal to 6 cm; 23% for > 6 cm and less than or equal to 9 cm; and 36% for > 9 cm. In CMT patients, the in-field failure rate was as follows: 0% for l ess than or equal to 3 cm; 0% for > 3 and less than or equal to 6 cm; 5% fo r > 6 cm and less than or equal to 9 cm; and 26% for > 9 cm. In-field recur rence was not a predominant pattern of failure in RT patients,vith small tu mors (less than or equal to 6 cm); thus, the difference in in-field control in tumors less than or equal to 6 cm between doses less than or equal to 3 5 Gy (6%) and doses greater than or equal to 36 Gy (0%) was not statistical ly significant. In larger tumors (> 6 cm), in-field recurrence was a predom inant pattern of failure; the in-held failure rate in RT patients with tumo rs > 6 cm of 30% for doses less than or equal to 35 Gy was not significantl y different from 25% for doses > 35 Gy. In moderately bulky tumors (> 6 cm and less than or equal to 9 cm), the addition of chemotherapy did appear to increase in-field disease control; the in-field failure rate was 23% with RT and 5% with CMT (p = 0.07). Conclusion: Our data do not demonstrate statistically significant evidence of increasing tumor control in HD with doses > 30 Gy. The data do show that increasing tumor size is associated with increased rates of in-field failu re, and the addition of chemotherapy may improve in-field disease control i n tumors > 6 cm. In-held recurrence in large tumors remains a predominant p attern of failure, however, and the role of radiation doses higher than 30- 35 Gy in this high-risk subset warrants further study. (C) 1999 Elsevier Sc ience Inc.