Low-Dose Radiotherapy for Primary Cutaneous Indolent B-Cell Lymphomas: a Multicenter Retrospective Study.

Abstract

Primary indolent cutaneous B-cell lymphomas (PCBCL) account for approximately 20% of all primary cutaneous lymphomas. Radiotherapy (RT) has a well-established therapeutic role in treating PCBCL, and recent evidence suggests that low-dose schedules may be effective as frontline treatment. In this multicenter retrospective observational study, we aimed to evaluate the efficacy and safety of low-dose RT (LDRT) in patients affected with PCBCL. We retrospectively reviewed 75 patients with 137 cutaneous lesions treated across three Italian Radiation Oncology Centers between 2010 and 2023. The lesions included 77 Marginal Zone Lymphomas (PCMZL), 55 Follicle Center Lymphomas (PCFCL), and 5 other low-grade lymphomas. All lesions were treated with LDRT. Fifteen lesions (11%) were treated with orthovoltage, 117 lesions (85%) with electrons, and 5 lesions (4%) with photons (3D-CRT). The median age was 60 years (range 25-89), with a median follow-up of 44.35 months (range 8.88-144.3). The overall progression free survival (PFS) at 12, 24, 36 and 48 months after LDRT was 83 % (95 % CI: 0.74-0.92), 59 % (95 % CI: 0.48-0.72), 49 % (95 % CI: 0.38-0.63), and 42 % (95 % CI: 0.31-0.57), respectively. The overall local control (LC) rate at 12, 24, 36 and 48 months was 87 % (95 % CI: 0.81-0.93), 80 % (95 % CI: 0.73-0.88), 79 % (95 % CI: 0.72-0.87), and 77 % (95 % CI: 0.70-0.86), respectively. Additionally, 64 recurrences (19 %) in 29 patients were documented at sites distant from the initially irradiated lesion. Larger lesions (>2.5 cm) and multifocal presentation were associated with worse progression-free survival (PFS) and LC. Histologic subtype, lesion site, and prior treatments did not significantly influence outcomes. LDRT was very well tolerated and no grade 3 + toxicity events were detected. Our analysis reinforces the role of LDRT in the management of PCBCL, demonstrating excellent local control rates and a favorable toxicity profile. Further prospective studies are warranted to confirm these results and to optimize treatment protocols.