Is Radiation Therapy Effective for DLBCL As a Salvage after Chemotherapy?: A Study of 180 Diffuse Large B Cell Lymphoma (DLBCL) Cases at a Single Institution

Introduction: Radiation therapy (RT) for localized- refractory or relapsed diffuse large B cell lymphoma (DLBCL) after chemotherapy is a standard therapy. Though some cases achieve complete remission (CR) after RT for local residual disease, others reveal disease progression after RT.

Methods: We analyzed DLBCL receiving RT on the purpose of achieving remission after chemotherapy at Cancer Institute Hospital from October 2005 to January 2014. All patients (pts.)’ histopathology samples were reviewed by expert hematopathologists, according to the WHO classification. All RT regimens were planned by expert lymphoma radiotherapists.

Results: A total of 180 pts. were included in this study. Baseline pts.’ characteristics were a median age of 65.2 years (range, 17.3-88.1 years), 105 male and 75 female, 87 pts. (48.3%) receiving radiation therapy as an adjuvant therapy after 3 cycles of R-CHOP therapy, 43 pts. (23.9%) receiving RT for low SUV max (1.2-7.94) residual disease at positron emission tomography-computed tomography (PET-CT) evaluation after chemotherapy, 38 pts. (21.1%) receiving for primary refractory, and 12 pts. (6.7%) for localized relapsed DLBCL after previous chemotherapy. A median total dose of RT was 30.6Gy (range, 16.0Gy-50.4Gy). After RT, 5 pts. (5.7%) of adjuvant therapy were progressive, 5 pts. (11.6%) of the pts. with low SUVmax at PET-CT, 25 pts. (65.8%) of primary refractory, and 11 pts. (91.7%) of relapsed DLBCL. Disease progressions outside of the radiation fields were recognized at 5 pts. (100.0%) of adjuvant therapy, 5 pts. (100.0%) of low SUV max cases, 12 pts. (48.0%) of primary refractory, and 10 pts. (90.9%) of localized relapsed DLBCL. There was no treatment related mortality during RT. At a median follow-up time of 33.3 months (range, 6.5-74.0), the 2 year progression free survival (PFS) after RT and overall survival (OS) rates are 74.4%, 76.7%, respectively. In Adjuvant group, PFS and OS were 94.5%, 93.1%, respectively. In low SUV max group, 70.1%, 83.7%, primary refractory group, 34.2%, 39.5%, and relapsed group, 8.3%, 50.0%, respectively.

Conclusions: RT as adjuvant therapy and for low SUV max residual disease after chemotherapy resulted in a good prognosis. High rates of disease progression outside the RT field were outstanding and they might indicate the limitation of local treatment for DLBCL. Because RT triggers few severe adverse events, it is tolerable even for elderly people and patients with long history of chemotherapy. However, it may be desirable for primary refractory and relapsed DLBCL as localized disease after chemotherapy to treat with chemotherapy as a systematic therapy.