Analyses of dose-response in radiotherapy for patients with mature T/NK-cell lymphomas according to the WHO classification.

Background and Purpose: This study was conducted to analyze the influence of radiotherapy doses and chemotherapy doses and clinical parameters on in-field disease control in order to assess the optimal radiation doses for treatment of mature T/NK-cell lymphomas according to the newly proposed WHO classification.
Patients and Methods: Subjects consisted of 62 patients with mature T/NK-cell lymphomas treated with radiotherapy at four Japanese institutions between 1983 and 2002. We reevaluated all histopathological specimens of non-Hodgkin's lymphomas (NHL), using the WHO classification. Radiation therapy was usually delivered to the involved field. The majority of patients also received adriamycin-based chemotherapy such as CHOP, modified CHOP, or more intensive chemotherapy.
Results: There were no significant differences in radiosensitivity among subtypes of mature T/NK-cell lymphomas, at least between extranodal NK/T-cell lymphomas, nasal type and peripheral T-cell lymphomas, unspecified. There was a radiation dose-response in non-bulky mature T/NK-cell lymphomas, indicating that radiation doses of more than 52 Gy may be required to obtain in-field control. However, it was difficult to obtain local control of bulky T-cell lymphomas, even with high doses of irradiation.
Conclusions: Mature T/NK-cell lymphomas were more radioresistant than B-cell lymphomas such as diffuse large B-cell lymphomas (DLBCL). The chemotherapy including adriamycin did not improve the in-field control of mature T/NK-cell lymphomas. These results were obtained by using non-randomized data and the significance of these results is limited by bias in data. However, our results suggest that the treatment strategy which is usually used for DLBCL, that is, a combined modality of CHOP and around 40 Gy of radiotherapy, may not be sufficiently effective for mature T/NK-cell lymphomas.