Involved-nodal radiation therapy as a component of combination therapy for limited-stage Hodgkin's lymphoma: a question of field size.

Abstract

Combined-modality therapy is the standard of care for limited-stage Hodgkin's lymphoma (HL). Radiation therapy has evolved from extended-field radiation therapy (EFRT) to involved-field radiation therapy (IFRT), reducing toxicity while maintaining high cure rates. Recent publications recommend a further reduction to involved-nodal radiation therapy (INRT), however, this has not been clinically validated. We identified 325 patients with limited-stage HL, diagnosed between May 1, 1989 and April 1, 2005, and treated with chemotherapy and radiation therapy following era-specific guidelines: EFRT until 1996; IFRT from 1996 to 2001; INRT < or = 5 cm from 2001 to the present. INRT < or = 5 cm was defined as the prechemotherapy nodal volume with margins < or = 5 cm to account for physiological movement, set-up variation, and the limitations of conventional simulation and radiation therapy techniques. Exclusion criteria were age younger than 16, fluorine-18 fluorodeoxyglucose positron emission tomography, non-doxorubicin, bleomycin, vinblastine, and dacarbazine-like chemotherapy, and/or more than four chemotherapy cycles. At diagnosis, median age was 35 years; 52% male; stage IA 29%; stage IIA 71%. Ninety-five percent of patients received two chemotherapy cycles. The three radiation therapy groups were: EFRT, 39%; IFRT, 30%; and INRT < or = 5 cm, 31%. Median follow-up of living patients was 80 months. Median time to relapse was 37 months. Twelve relapses occurred: four after EFRT (3%); five after IFRT (5%); and three after INRT < or = 5 cm (3%; P = .9). No marginal recurrences occurred after INRT < or = 5 cm. Locoregional relapse (LRR) occurred in five patients: three after EFRT; two with IFRT; and none with INRT < or = 5 cm. At 5 years, progression-free survival (PFS) was 97%, and overall survival (OS) was 95%. At 10 years, PFS and OS were 95% and 90%, respectively. Reduction in field size appears to be safe, without an increased risk of LRR in patients receiving INRT < or = 5 cm.