Low-Dose Total Skin Electron Beam Therapy as Part of a Multimodality Regimen for Treatment of Sézary Syndrome: Clinical, Immunologic, and Molecular Analysis

Abstract

Importance: Sézary syndrome (SS) is an advanced form of cutaneous T-cell lymphoma with few long-term remissions observed.

Objective: To profile 3 patients with SS who have experienced long-term remission following the addition of low-dose total skin electron beam therapy (TSEBT) to systemic regimens of extracorporeal photopheresis, bexarotene, and interferon-γ.

Design, setting, and participants: This is a retrospective case series with additional investigations of patient-donated samples to assess therapeutic response. The study was conducted at the University of Pennsylvania Cutaneous Lymphoma Clinic and follows 3 patients with stage IVA1 CD4+ SS who presented to the clinic between November 1, 2009, and November 1, 2017, and who had a history of SS that was refractory to multimodality systemic therapy prior to receiving low-dose TSEBT.

Interventions: Patients were treated in a multimodality fashion with combined extracorporeal photopheresis, bexarotene, interferon-γ, and low-dose TSEBT.

Main outcomes and measures: To characterize treatment responses in these patients, the extent of skin disease was measured with the modified severity weighted assessment tool. Blood disease was measured with flow cytometric assessments of Sézary cell count, CD4:CD8 ratio, and high throughput sequencing of the T-cell receptors. To assess for restoration of immune function, we measured markers of immune exhaustion, including PD-1 (programmed cell death 1), TIGIT (T-cell immunoreceptor with immunoglobulin and ITIM domains), CTLA4 (cytotoxic T-lymphocyte-associated protein 4), TOX (thymocyte selection-associated high mobility group box protein), and Foxp3 (forkhead box P3) on circulating CD4 and CD8 T cells, along with production capacity of interferon-γ by lymphocytes following activation stimuli.

Results: Following administration of low-dose TSEBT and maintenance of the other therapies, remissions ranged from 24 to 30 months, with complete responses in 2 patients ongoing. Markers of immune exhaustion including PD-1, TIGIT, CTLA4, TOX, and Foxp3 were significantly reduced from baseline following TSEBT, along with enhanced production capacity of interferon-γ by lymphocytes following activation stimuli. High throughput sequencing demonstrated near-complete eradication of the circulating clone among 2 of 3 patients with stable levels in 1.

Conclusions and relevance: We describe 3 patients who achieved long-term clinical and molecular remissions following low-dose TSEBT as part of a multimodality regimen for treatment of SS. As long-term remissions in SS are uncommon, this approach demonstrates promise, and clinical trials should be considered.

Figure 1.. Normalization of Modified Severity Weighted Assessment Tool (mSWAT), Sézary Cells, Lactate Dehydrogenase, and Immune Biomarkers After Total Skin Electron Beam Therapy (TSEBT)

A, The mSWAT was used to quantify the extent and severity of skin lesions over time. B, Peripheral blood mononuclear cells were extracted from patient blood samples and stained with CD3, CD4, CD8, CD45, CD7, and CD26. Data were acquired by gating on cells with the side scatter and CD45⁺ characteristics of lymphocytes. The number of CD4⁺/CD7^- Sézary cells are presented as a fraction of total lymphocytes. C, Peripheral blood mononuclear cells were collected and stained as in panel B. The ratio of CD4 to CD8 cells is presented as an indicator of the prevalence of Sézary cells in the peripheral blood. D, The lactate dehydrogenase activity in peripheral blood samples before and after TSEBT. E, Blood samples were collected from patients before and approximately 6 months after TSEBT. Peripheral blood mononuclear cells were isolated and stained with antibodies against CD26, FCRL3, VB2 clonality, TIGIT, Helios, and Tox. The figure shows the percentage of lymphocytes positive for each marker. F, Peripheral blood mononuclear cells were cultured in the presence of resiquimod for 72 hours and interferon (IFN)- γ secretion was determined by enzyme-linked immunosorbent assay.

Figure 2.. High Throughput Sequencing (HTS) of T-Cell Receptors (TCRs) Before and After Total Skin Electron Beam Therapy (TSEBT)

Total reads of TCR clones in samples from patients as determined by HTS of the V and J regions of the TCRβ gene. Blood samples were collected before TSEBT and approximately 6 months after TSEBT. Restoration of clonal diversity can be appreciated post-TSEBT among patients 1 and 2.