Radiotherapy for indolent primary cutaneous B-cell lymphoma: an international multicenter ILROG analysis

Area of Science:

• Oncology
• Dermatology
• Radiation Oncology

Background:

• Low-grade primary cutaneous B-cell lymphoma is typically treated with radiotherapy.
• International recommendations for radiotherapy use vary.
• An international collaborative study was initiated to analyze treatment outcomes.

Purpose of the Study:

• To evaluate the efficacy and toxicity of radiotherapy for low-grade primary cutaneous B-cell lymphoma.
• To compare outcomes between different radiotherapy dose fractionation schedules.
• To identify prognostic factors influencing treatment response and survival.

Main Methods:

• Retrospective analysis of 535 patients with limited (T1/T2) primary cutaneous marginal zone or follicle center lymphoma.
• Data collected from 22 institutions internationally between 1995 and 2023.
• Patients treated with radiotherapy, with analysis of dose, fractionation, response, local control, and toxicity.

Main Results:

• Complete response rates were high (91%) at a median of 3.6 months post-radiotherapy.
• No significant difference in complete or overall response rates between treatments ≤4 Gy and >4 Gy.
• Lower doses (≤4 Gy) were associated with inferior 5-year local control (73% vs. 96%) but a favorable toxicity profile.
• Radiation dose was a significant prognostic factor, but higher doses did not improve overall survival.

Conclusions:

• Radiotherapy is an effective treatment for indolent skin lymphoma with low toxicity.
• High response rates are achievable with lower radiotherapy doses (≤4 Gy).
• While lower doses offer a toxicity benefit, they result in reduced local control compared to conventional doses.