Bi-Institutional Analysis of Stage III/IV Diffuse Large B Cell Lymphomas (DLBCL) Patients Undergoing Consolidative Radiotherapy: Potential for Improved Overall Survival (OS) and Progression Free Survival (PFS)

Abstract

Diffuse large B-cell lymphoma (DLBCL) is the most common of the aggressive non-Hodgkin’s lymphomas. Systemic therapy is considered essential, with the established regimen in the modern age consisting of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) for three to six cycles. The use of consolidative radiation therapy after chemotherapy is a topic of debate, especially for stage III/IV patients. Some institutions have treated select stage III/IV DLBCL patients, if patients presented with bulky disease, had a partial response to chemotherapy, or had skeletal involvement at initial site of presentation. The exact role of consolidative radiotherapy in stage III/IV cohort is not known. A de-identified database consisting of 287 patients across two institutions, Emory Winship Cancer Institute (Atlanta, GA) and Duke Cancer Institute (Durham, NC), treated for DLBCL was compiled. Patients were selected from this database if found to have histologically confirmed stage III-IV DLBCL at diagnosis, and determined to have achieved complete response after systemic therapy. Those that were observed were then compared with those that additionally received consolidative radiotherapy. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method, and survival distributions were compared using log-rank tests for patients receiving systemic therapy alone versus systemic therapy combined with consolidative radiotherapy. Statistical significance was assessed at the 0.05 level, and the statistical analysis was performed using a data and decision management product. Of the 287 patients included in the database, 188 met our selection criteria. Of note, the majority of these patients were treated with R-CHOP, with a minority receiving a modified rituximab-containing regimen or no rituximab at all. Additionally, this subgroup included patients with or without bulky disease at diagnosis. Of the selected patients, 53 received consolidative radiotherapy and the remaining 135 received chemotherapy therapy alone. At the 5-year time point, consolidative radiotherapy was associated with significantly improved OS (87.4% vs. 72.9%, p=0.0134) and PFS (85.9% vs. 49.2%, p<0.0001). The addition of consolidative radiotherapy for advanced stage DLBCL patients who demonstrate complete response after chemotherapy is associated with a 14.5% absolute benefit in 5 yr OS and a 36.7% absolute benefit in 5 yr PFS, when pooling data together from two different institutions. This work provides a basis for the use of consolidative radiation therapy in patients treated for DLBCL who demonstrate complete response after systemic therapy.