De-escalated radiotherapy for indolent primary cutaneous B-cell lymphoma.

Abstract

Radiotherapy (RT) has an established role in the curative treatment of indolent primary cutaneous B‑cell lymphoma (PCBCL). With the role of low-dose regimens such as 2 × 2 Gy being uncertain, we compared conventional-dose RT to alow-dose approach and investigated outcome and toxicities. We retrospectively reviewed the medical records of 26patients with 44cutaneous lesions treated at our institution between 2007 and 2017, comprising 22marginal zone lymphoma (PCMZL) lesions and 22follicle center lymphoma (PCFCL) lesions. Seven lesions (16%) were treated with low-dose RT (LDRT) (4 Gy) and 37 (84%) with conventional-dose RT (≥24 Gy, median 40 Gy). Median follow-up duration was 76months. The overall response rate (ORR) was 91% (complete response rate [CRR]: 75%). The 5‑year local control rate (LCR) was 88% and the 10-year LCR was 84%. The response rates were significantly higher following conventional-dose RT (ORR: 92% vs. 86%; CRR: 84% vs. 29%; P = 0.007). In terms of radiation dose, the rate of infield relapses (14% vs. 11%, P = 0.4) and the 5‑year LCR (86% vs. 90%, P = 0.4) were comparable in the LDRT and conventional-dose RT groups. During RT courses, about two-thirds of patients experienced mild toxicities, with gradeI andII acute toxicity rates of 61% and 9%, respectively, with lower incidences of gradeI (14% vs. 70%) and gradeII (0% vs. 8%, P = 0.004) toxicities following LDRT. This long-term analysis confirms the excellent outcome of RT in the management of PCBCL. The LDRT concept with 4 Gy was associated with acomparable LCR and reduced rates of acute toxicity. However, the response rates were significantly lower for this group and LDRT may therefore not be recommended as standard treatment.