Monitoring the decrease of circulating malignant T cells in cutaneous T-Cell lymphoma during photopheresis and interferon therapy

Background: The prognosis of patients with stage IV cutaneous T-cell lymphoma (CTCL) is grim and therapeutic options are limited. Treatment of advanced-stage CTCL is aimed at suppressing the dominant T-cell clone, which is typically present in the skin, peripheral blood, and lymph nodes. Observations: We detected the expansion of 1 T-cell clone expressing the T-cell receptor Vbeta14 in the peripheral blood of a patient with stage IVA CTCL. Before initiation of combination therapy with photopheresis and low-dose interferon alpha, the dominant T-cell clone represented 84% of the total T-cell population. After successful therapy, this clone showed a dramatic decrease to 6% of the T-cell population after 6 months of treatment. This reduction in the percentage of the malignant T-cell population in response to therapy was paralleled by clinical skin improvement from initial generalized erythroderma to undetectable skin disease. Conclusions: This case demonstrates that response to combination treatment with photopheresis and low-dose interferon alpha in patients with advanced CTCL may be accurately and quantitatively followed up by monitoring the percentage of the malignant T-cell clone (when identifiable) within the total circulating T-cell population by flow cytometry.