[Radiation therapy of localized diffuse large B-cell lymphoma]

Diffuse large B-cell lymphoma is most frequently encountered non-Hodgkin's lymphoma in Japan, and about half of the cases present as Ann-Arbor stage I or II localized disease. Randomized clinical trials have revealed that chemotherapy combined with radiation therapy of the involved field yields superior outcome compared with chemotherapy alone. However, optimal chemotherapy cycles remain to be studied. Short-course chemotherapy, such as 3 cycles of CHOP, seems to be adequate for low bulk tumors, and full-course chemotherapy, such as 6-8 cycles of CHOP, seems to be required for larger tumors. Involved field radiation is a regional radiation that includes involved lymph nodes or extranodal sites, although the details vary between institutes. The precise definition of involved field radiation must be examined and clarified. The dose of involved field radiation after chemotherapy is also controversial. Most researchers apply at least 30 Gy to sites in complete remission, whereas a larger dose seems to be necessary for sites in partial remission. Stratification according to various prognostic factors is mandatory to tailor the management of localized diffuse large B-cell lymphoma.