Leukemia/Lymphoma/Hematologic

SS 25 - Hematologic 2 - Translating Better Technology to Reduced Toxicity

181 - Are Higher Doses of Consolidation Radiation Therapy Necessary for Diffuse Large B-Cell Lymphoma With Osseous Involvement

Tuesday, October 23
2:10 PM - 2:20 PM
Location: Room 004

Are Higher Doses of Consolidation Radiation Therapy Necessary for Diffuse Large B-Cell Lymphoma Eith Osseous Involvement
J. W. C. Lee1, B. Pitcher2, and C. R. Kelsey1; 1Department of Radiation Oncology, Duke University, Durham, NC, 2Department of Biostatistics and Bioinformatics, Duke Cancer Institute, Durham, NC

Purpose/Objective(s): Up to 10% of patients with diffuse large B-cell lymphoma (DLBCL) present with skeletal involvement. Higher doses of consolidation radiation therapy (RT) have traditionally been recommended for osseous sites (~40 Gy). For example, a recent large retrospective study reported a median dose of 44 Gy for primary bone DLBCL (IJROBP 2015;92:122). Our institution has consistently utilized lower doses of RT (20-30 Gy), providing a unique cohort to study dose and outcomes in osseous DLBCL. We hypothesized that more conventional doses of radiation therapy (~30 Gy) would be associated with high rates of local control (≥95%).

Materials/Methods: We retrospectively identified all patients with DLBCL with osseous involvement who received first-line chemotherapy and consolidation RT at our institution from 1995 – 2016. We extracted clinical and treatment characteristics from the medical record including IPI parameters, sites of osseous disease, chemotherapy regimen, radiation dose and fractionation, patterns of failure, and clinical outcomes. Time-to-event endpoints were estimated using the Kaplan-Meier method.

Results: 51 patients received combined modality therapy for DLBCL with osseous involvement during the time interval. Median follow-up was 73 months. The median age at diagnosis was 58; 31/51 (60%) of patients had early stage disease, 24/51 (47%) had IPI scores 0-1, 48/51 (94%) received at least four cycles of combination chemotherapy, 47/51 (92%) received CHOP, and 44/51 (86%) received rituximab. Following chemotherapy, a complete response (CR) by PET was achieved in 41/51 (80%) and a partial response (PR) in 9/51 (18%); one patient had a post-chemotherapy CT that showed a CR but did not undergo metabolic imaging. Consolidation RT was given to all sites of osseous involvement in 46/51 (90%); the remaining received consolidation RT to 1-2 dominant osseous lesions only. The median RT dose was 30 Gy (range 20-40 Gy), which included 25 patients receiving 20-29 Gy, 15 patients receiving 30-36 Gy, and 11 patients receiving >36 Gy. The median RT dose was 24 Gy for patients in CR and 36 Gy for patients in PR. Eight patients had relapse of their DLBCL, two of which were within the RT field. Of these two in-field relapses, one patient had a CR to chemotherapy and received 30 Gy while the other patient had a PR and received 39.6 Gy. These two patients simultaneously failed at multiple distant sites also. The 5-year freedom from local recurrence was 98% (95% CI 93-100%) for those in CR and 89% (95% CI 71-100%) for those in PR. For all patients, the 5-year freedom from local recurrence was 96% (95% CI 91-100%), progression-free survival was 79% (95% CI 68-92%), and overall survival was 89% (95% CI 80-99%).

Conclusion: In patients with DLBCL with osseous involvement who achieve a CR following first-line immunochemotherapy, a standard dose of consolidation RT (e.g., 30 Gy for early-stage disease) is recommended and leads to high rates of local control (98% in this series). A higher dose of RT in the setting of a PR is appropriate.

Author Disclosure: J.W. Lee: None. B. Pitcher: None. C.R. Kelsey: None.

Jessica Lee, MD

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Employment
Duke University Medical Center: Resident: Employee

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