Optimizing Palliative Focal Radiation Therapy Dose in Cutaneous T-Cell Lymphoma: How Low Can You Go?

Purpose: Primary cutaneous T-cell lymphomas (CTCLs) are radiosensitive tumors with variable and often relapsing courses. Local dis-ease can be treated with low-dose focal palliative radiation therapy (RT), though little data supports the use of a specific dose. This study assesses clinical outcomes after focal RT to a total dose of 4 Gy, 8 Gy, or 12 Gy.Methods and Materials: An International Review Board-approved, retrospective, single-institution study was performed of 225 lesions in 41 patients with primary CTCL treated with low-dose focal RT from 2015 to 2020. Patient, tumor, and treatment characteris-tics were reviewed. The primary outcome was freedom from treatment failure (FFTF), defined as time to requiring local retreatment, and secondary outcomes included response rates and toxicities.Results: Of the 225 lesions, 90 received 4 Gy, 106 received 8 Gy, and 29 received 12 Gy. Lesions treated with 12 Gy (96%) or 8 Gy (92%) had a significantly higher 1-year FFTF compared with 4 Gy (77%) (P = .034). Overall response rate and complete response rate were not sig-nificantly different between different doses (P = .117), though there was a trend toward higher overall response rate at initial assessment with 8 Gy versus 4 Gy (91.5% vs 82.2%, P = .057). Toxicity was low, with 7.1% of lesions having grade 2 or higher radiation dermatitis.Conclusions: In primary CTCL lesions treated with focal palliative RT, a dose response was noted favoring 8 to 12 Gy, with 1-year FFTF rates over 90%. However, 4 Gy resulted in substantially better outcomes than previously reported, with 77% requiring no further treatment at 1 year and comparable response rates to higher doses. While our data substantiates 8 to 12 Gy as the standard of care, it also suggests that 4 Gy should be considered an acceptable alternative in situations with concern for radiation toxicities, such as with fragile or heavily pretreated skin.(c) 2022 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

Automated summary

This study assessed the clinical outcomes of low-dose focal radiation therapy (RT) with total doses of 4 Gy, 8 Gy, or 12 Gy in primary cutaneous T-cell lymphomas (CTCLs). The results showed significantly higher 1-year freedom from treatment failure (FFTF) rates in the 8 Gy and 12 Gy groups compared to the 4 Gy group. Overall response rates and toxicities were comparable among different dose groups. The study suggests that 8 Gy and 12 Gy are the standard of care, but 4 Gy can be considered as an acceptable alternative.