Clinical Retrospective Analysis of 42 Patients with Primary Bone Lymphoma Treated at Maisonneuve-Rosemont Hospital
Authors: Guo Katie , Boileau Melissa , Fortin Bernard , Aubin Francine , Petrella Tony , Isler Marc , Mottard Sophie , Cohen Sandra , Mollica Luigina , Beaudet Julie , Fleury Isabelle 
Published: October 2019

Abstract
Introduction
Primary bone lymphoma (PBL) is an uncommon form of lymphoma. Diffuse large B-cell lymphoma (DLBCL) represents the main histology associated with PBL. Clinicopathological understanding and management of PBL rely only on retrospective series.
Methods
Cases of DLBCL diagnosed by bone biopsy treated in one referring center between 1993 and 2014 were retrospectively reviewed (Montreal, Canada). Bone biopsies done as part of the bone marrow analysis were excluded. Patients files were analyzed to determine if patient had primary bone lymphoma or systemic lymphoma with bony involvement. We excluded patient with distant lymph node or other extranodal involvement. Data on clinical presentation, staging procedures and treatment management including use of radiotherapy was collected. Staging was performed according to WHO classification of soft tissue tumors (2002). Survival time and time to recurrence were calculated from the date of the first documented treatment until recurrence or death with the Kaplan-Meier method. Prognostic factors of recurrence or death were explored with log-rank tests and Cox proportional hazards models. Competing risks analysis was attempted to isolate deaths from lymphoma and death from other causes. Our study was approved by local research and ethic committees.
Results
We retrieved 42 cases of PBL with a median age of 63 years (23-83) treated between October 1995 and April 2014. We identified 3/14 (21%) GCB and 11/14 (79%) non-GCB subtypes based on the modified Hans algorithm (Meyer et al., JCO 2011). The most common presenting symptom was pain (88%). 12/42 (33%) patients had an IPI score ≥ 3. We identified 18 (43%) stage I, 11 (26%) stage II and 13 (31%) stage IV. 20/42 (48%) had bulky disease (≥ 10cm). Among the 37 patients treated with curative intent, 36 (97%) received CHOP-based regimen and 23 (62%) received rituximab. 30 of these 37 (81%) patients received additional radiotherapy of which 67% received a dose of radiotherapy between 36-50 Gy. Overall response rate for patients treated with curative intent was 86%. With a median follow up of 64.8 months for the whole cohort, the 5- and 10-year overall survival was 73% and 54%, respectively. The 5- and 10-year progression-free survival was 70% and 49% respectively. Age, LDH, stage (I-II vs IV), ECOG (0-1 vs 2-4), IPI (0-2 vs 3-5), use of radiotherapy or addition of rituximab were associated with differences in survival and progression rates that did not reach statistical significance given the limited number of patients in our cohort and the fact that half of the deaths were attributed to other causes. A larger cohort would be required to demonstrate a benefit with rituximab. Response was based on positron emission tomography-computed tomography (TEP-CT) imaging in 12 patients. There was an insufficient number of patients to evaluate the role of adding radiotherapy in patient complete remission defined by PET-CT.
Conclusion
Our survival rates reproduce published data from series of PBL (Ramadan et al., Ann Oncol 2007; Bruno Ventre et al., Oncologist 2014), although the benefit of adding rituximab did not reach statistical significance in our cohort. The role of radiotherapy in the era of response defined by PET-CT remains to be defined.

Disclosures
Fleury: Gilead: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Roche: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Lundbeck: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Speakers Bureau.