Hematologic Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_43_2789 - Low-Dose (4 Gy) Radiation Therapy as an Effective Treatment Modality for Relapsed Refractory Mantle Cell Lymphoma

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Low-Dose (4 Gy) Radiation Therapy as an Effective Treatment Modality for Relapsed Refractory Mantle Cell Lymphoma
M. S. Ning1, S. A. Milgrom2, J. R. Gunther2, C. C. Pinnix2, K. M. Christopherson3, E. D. Brooks4, J. Khoury1, M. L. Wang5, and B. Dabaja2; 1University of Texas MD Anderson Cancer Center, Houston, TX, 2The University of Texas MD Anderson Cancer Center, Division of Radiation Oncology, Houston, TX, 3University of Texas at MD Anderson Cancer Center, Houston, TX, 4The University of Texas MD Anderson Cancer Center, Houston, TX, 5UT MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s): Mantle cell lymphoma (MCL) has an aggressive clinical course with a continuous relapse pattern resulting in poor survival. While MCL is radiosensitive, radiation therapy (RT) is underutilized, deferring to multiple chemotherapy regimens as the basis of treatment. This study assesses the role of low-dose RT in the management of MCL.

Materials/Methods: From 2014 to 2017, a total of 19 patients with relapsed/refractory MCL were treated for 65 lesions with involved-site RT to a dose of 4 Gy in one (n=6) or two (n=59) daily fractions. Primary endpoint was in-field response for each site. Associations with clinical variables were examined via Cox proportional hazards modeling.

Results: Median follow-up of all 65 sites following RT was 10.4 months (range: 1.7-39.7). Treated sites included: 38 subcutaneous,15 nodal, 7 gastrointestinal, 3 orbital, and 2 mucosal. Median tumor size at time of RT was 2.8 cm (range: 0.9-11.5). The 19 patients had previously received a median 4 courses (range: 1-8) of systemic therapy since initial diagnosis. Eight patients (42%) had received stem cell transplant, and 11 (58%) had received higher dose RT (>4 Gy) for MCL. Each patient received low-dose ISRT (4 Gy) to a median of 2 sites (range: 1-16), with the first course delivered a median 3.5 years (range: 0.6-19.2) following initial diagnosis. For 11 patients (58%), the initially treated lesions were the only sites of measurable disease at the time of RT. Blastoid histology was documented in 4 patients (21%). Of the 65 sites, 45 (69%) were treated with concurrent systemic therapy. Complete response (CR) was achieved for 53 sites (82%), assessed at a median 75 days (range: 5-192) post-RT by imaging and/or clinical exam, while partial response (PR) occurred for 5 sites (8%) assessed at a median 20 days (range: 16-86) post-RT. On multivariable analysis for all 65 lesions, concurrent chemotherapy was associated with CR (HR 4.9 [95% CI 1.9-12.8], p<.001); whereas blastoid histology (HR .11 [95% CI .02-.6], p=.010), photon (versus electron) modality (HR .20 [95% CI .07-.5], p=.002), and longer interval (>2 years) from initial diagnosis (HR .28, p=.04 [95% CI .08-.9]) were associated with decreased likelihood of CR. Local relapse (LR) occurred at 9 sites (14%) at a median 49 days (range: 13-648); one site was successfully re-treated to an additional 4 Gy with CR. On multivariable analysis, soft tissue site was associated with decreased likelihood of LR (HR .09, p=.03 [95% CI .01–.8]). There were no grade ≥2 toxicities from RT. Five patients remained without evidence of disease at last follow-up (median 6.4 months [range: 1.8-21.2]).

Conclusion: MCL is a radiosensitive disease with excellent response to even low-dose RT. Given the absence of significant acute toxicity, low-dose ISRT (4 Gy) should be considered as a viable treatment modality for MCL, even in the setting of relapsed or chemo-refractory disease.

Author Disclosure: M.S. Ning: None. S.A. Milgrom: None. C.C. Pinnix: None. K.M. Christopherson: None.

Matthew Ning, MD

MD Anderson Cancer Center

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