Purpose: To determine the efficacy of small doses of radiation in patients with recurrent or refractory low-grade lymphoma masses.
Methods and materials: Patients with refractory or relapsing low-grade lymphoma masses. The two largest diameters of the tumor mass were measured, whenever possible, before and after treatment. A dose of 4 Gy of radiotherapy was delivered to tumor sites in 2 fractions. Patients were evaluated for response 1-4 months later and at regular follow-up visits.
Results: Forty-eight patients with low-grade lymphomas according to the working formulation received low-dose radiotherapy between March 1987 and November 1998. Most patients had advanced disease at the time of radiation treatment, and 80% had received at least two chemotherapy regimens before treatment. The median interval between the initial diagnosis and radiotherapy was 2.7 years (range 0-22 years). Low-dose radiation was delivered to 135 tumor sites. Nodal and extranodal tumor sites represented 80% and 20% of masses, respectively. An objective response was obtained in 81% of the sites, with 57% attaining a complete remission. The 2-year actuarial freedom from local progression (FFLP) rate was 56% (95% CI, 46-66%). Tumor masses </=5 cm in diameter had a significantly higher 2-year FFLP rate than larger masses (51% vs. 27%). It is noteworthy that the 2-year FFLP rate for patients treated with less than 2 chemotherapy regimens before radiotherapy was significantly higher than the 2-year FFLP rate for more heavily treated patients (96% vs. 48%). The 2-year FFLP rates for extranodal tumor sites and nodal sites were not significantly different. The tumor size (< or =5 cm vs. > 5 cm), the number of chemotherapy regimens (0-1 vs. more), and age at time of radiation treatment (< or =65 years or > 65 years) were significant predictive parameters of response to treatment.
Conclusions: In this retrospective study, low-dose radiation proved efficient, with long-lasting effects in the majority of patients with recurrent or refractory low-grade lymphomas. This simple and nontoxic treatment should be investigated prospectively in patients with advanced disease and a low tumor burden not immediately warranting chemotherapy.