MARs correlate with mogamulizumab efficacy and increased survival in CTCL. (A) Clinical pictures of a patient with MAR before mogamulizumab (far left), at the time of MAR 7 months later (center-left), and in complete remission without treatment after rash (center-right) with close-up on hypopigmented macules consistent with vitiligo minor 18 months after onset of the treatment (far right). (B) Histogram of the top ten T-cell clone frequencies in skin in this patient before mogamulizumab (dominant T-cell clone, left), at the time of MAR 7 months later (middle, polyclonal pattern), and in complete remission without treatment after rash (right, polyclonal pattern) by high-throughput sequencing data of T-cell receptor gene β in skin. (C) Flow cytometry of peripheral blood T cells in this patient showing complete blood remission at the time of rash and 18 months later (<250 CD4⁺CD26^– T cells/mm³). (D) Flow cytometry of peripheral blood CD158k⁺ (left) and CD4⁺CD26^– T cells (right) in patients treated with mogamulizumab with and without rash showing a sharp decrease in the blood tumor burden (as measured by the absolute number of CD158k⁺ and CD4⁺CD26^– T cells) at the time of rash (if any) and 3 months after onset of the treatment in both groups. (E) Tumor clone frequencies in patients with rash (upper panel) and no rash (lower panel) at baseline, at the time of first and second rashes, and at baseline and during follow-up, respectively, by high-throughput sequencing of T-cell receptor gene β in skin showing a significant decrease in the skin tumor burden at the time of the first rash; further decrease at the time of the second rash is noted in patients with rash. (F) Kaplan-Meier curves of overall survival in mogamulizumab-treated CTCL patients with (red) and without(blue) rash (upper panel) and in the subgroup of patients with SS (lower panel). ***P < .001. HR, hazard ratio; M3, month 3.