1098 - Optimizing Palliative Radiation Therapy for Primary Cutaneous B-Cell Lymphoma: Is Ultra-Low Dose (4 Gy) Enough?
Presenter(s)
G. Gard1, M. Kozak1, A. M. Patel2, N. B. Desai1, E. Yilmaz3, H. Wolfe3, F. Awan3, P. Ramakrishnan Geethakumari3, H. W. Goff4, and K. A. Kumar1; 1Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 2Department of Radiation Oncology, Harvard, Boston, MA, 3Department of Hematology and Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 4Department of Dermatology, University of Texas Southwestern Medical Center, Dallas, TX
Purpose/Objective(s): Primary cutaneous B-cell lymphoma (PCBCL) is a radiosensitive indolent lymphoma, and while current NCCN guidelines suggest 24-30 Gy for curative doses, lower doses (4-12 Gy) are often used in both curative and palliative settings due to excellent response rates and ability to retreat if needed. ILROG recommends 4 Gy for palliation of PCBCL, as opposed to 8-12 Gy for mycosis fungoides (MF), but data is limited on the optimal dose for PCBCL. This study assesses the clinical outcomes of PCBCL lesions treated with focal low-dose radiation treatment (RT), with a hypothesis that 4 Gy results in less durable local control and more retreatments compared to 8-12 Gy.
Materials/Methods: An IRB-approved retrospective study identified 174 PCBCL (follicle center or marginal zone) lesions from 49 patients diagnosed by pathology and clinical picture who were treated at a single institution with low-dose focal RT from 2016-2024. Patient, tumor, and treatment characteristics were reviewed. The primary outcome was freedom from treatment failure (FFTF), defined as receiving retreatment of any kind (radiation or medical therapy) to the same lesion that received previous RT. Response rates were recorded based on follow up notes from the radiation oncologist or dermatologist as complete response [CR] (no lesion visible), partial response [PR] (improvement with remaining visible lesion), stable disease [SD] (similar appearance as prior to radiation), and progressive disease [PD] (lesion progressed).
Results: 49% of lesions were follicle center, and 51% were marginal zone. 135 lesions received 4Gy (including previously irradiated lesions) and had 1-year FFTF of 77.1% and 2-year FFTF of 69.3%. Lesions that received no prior radiation were noted as “de novo” and outcomes were compared among those treated with 4Gy, 8Gy, or 12Gy. 114 de novo 4Gy lesions had 1- and 2-year FFTF of 74.8%. 13 de novo 8-12Gy lesions had 1- and 2-year FFTF of 100%, which was statistically significantly higher than the 4 Gy de novo group (p=0.043). At first follow up (~3 months), the 4 Gy group had CR of 62% and PR of 29%; meanwhile, the 8-12Gy group had CR of 61% and PR of 39%. Toxicity was minimal in both groups with no grade 3+ toxicities. The most common adverse reaction was hyperpigmentation and grade 1-2 dermatitis.
Conclusion: In the largest study to date of PCBCL treated with focal low-dose RT, we demonstrate that initial treatment with 4 Gy results in 25% of lesions requiring retreatment within 1 year. In comparison, initial treatment with 8-12 Gy results in statistically significantly higher 1- and 2-year FFTF with similar toxicity, as has been previously shown in MF. While 4 Gy may still be appropriate for pure palliation, 8-12 Gy should be considered for PCBCL for more durable local control with similar minimal toxicities.