Recommendations for the Optimal Radiation Dose in Patients With Primary Cutaneous Anaplastic Large Cell Lymphoma: A Report of the Dutch Cutaneous Lymphoma Group.

Purpose: To determine the optimal radiation dose for treatment of primary cutaneous anaplastic large cell lymphoma (C-ALCL) with solitary or localized, multifocal or recurrent skin lesions.

Methods And Materials: In this multicenter study, patients with C-ALCL who had been treated with radiation therapy (RT) between 1984 and 2016 were retrieved from the Dutch registry of cutaneous lymphomas. Distinction was made between patients first presenting with solitary or localized lesions (n=63), with multifocal skin lesions (n=6), and patients with a skin relapse (n=22). Radiation doses, treatment response, and follow-up were evaluated. Radiation doses were categorized as low-dose (≤20 Gy), intermediate-dose (21-39 Gy), and high-dose (≥40 Gy) RT.

Results: Of 63 patients presenting with solitary or localized skin lesions, 61 (97%) showed a complete response (CR). There were no differences in CR between low-dose (16 of 17), intermediate-dose (15 of 15), and high-dose RT (30 of 31). After a median follow-up of 46 months, 30 of 63 patients (48%) had a relapse, but in-field relapses were never observed. Six of 6 patients (100%) initially presenting with multifocal skin lesions showed a CR (3 of 3 low-dose, 2 of 2 intermediate-dose, 1 of 1 high-dose RT). After a median follow-up of 27 months, 3 of 6 patients had a relapse. Treatment of 33 skin relapses in 22 patients showed no differences in CR between low-dose (18 of 19), intermediate-dose (6 of 6), and high-dose RT (8 of 8). In the last 10 years there has been a decrease in radiation dose used in the treatment of C-ALCL. Treatment of multifocal and recurrent lesions with a dose of 8 Gy (2 × 4 Gy) resulted in CR of 17 of 18 lesions.

Conclusions: Our results show that a radiation dose of 20 Gy (8 × 2.5 Gy) is effective in patients presenting with solitary or localized skin lesions. For patients with multifocal skin lesions and patients with a skin relapse, a dose of 8 Gy (2 × 4 Gy) may be sufficient.