Potential role for low dose limited-field radiation therapy (2 x 2 grays) in advanced low-grade non-Hodgkin's lymphomas

The purpose of this retrospective study was to evaluate the efficacy of low-dose limited field radiation therapy (LDLRT) in low-grade non-Hodgkin's lymphoma (NHL) patients, in order to outline its possible role. The rationale of the analysis was as follows: (1) there is no clear dose-response relationship for radiation therapy (RT) in localized low-grade non-Hodgkin's lymphomas (LGNHL); (2) long-term disease-free survival can be achieved in advanced LGNHL with low-dose (1.5-2 Gy) fractionated total body irradiation; (3) moreover, some of our previous LGNHL patients stopped their conventional planned RT course for convenience after 5 to 7.5 Gy and remained free from local progression in irradiated volumes for a long period of time. Patient selection criteria were the following: (1) patients with low-grade NHL (LGNHL); (2) patients who received no other form of therapy concomitantly with LDLRT until evaluation of the response; (3) patients who received a planned dose of 4 Gy in two fractions and over 3 days in a limited field. Out of 37 patients, 27 patients were fully evaluable. Twenty-two patients had stage III or IV disease. The median longevity of the disease was 73 months. Twenty-five patients had previously received chemotherapy (18 with anthracyclines). Nineteen patients had received one LDLRT course only. Eight patients responding to the first LDLRT had received at least one subsequent LDLRT course. After the first LDLRT course, an objective response in irradiated sites was observed in 24 of the 27 patients (89 per cent). Ten and 14 patients respectively demonstrated a complete response (CR) (37 per cent) and partial response (PR) (52 per cent). Freedom from progression in irradiated volumes for evaluable patients ranged from 4 to 35 months. Among the eight patients who received at least two LDLRT courses, a total of 20 different areas were irradiated, and 15 areas (75 per cent) showed a CR. Toxicity due to LDLRT was minimal. In conclusion, low-dose limited-field RT resulted in a high proportion of responses in LGNHL. The mechanisms explaining this radioresponsiveness are poorly understood. However, the efficacy of LDLRT could have several clinical applications in the general management of patients with advanced LGNHL.