Low-Dose Total Skin Electron Beam Therapy as Part of a Multimodality Regimen for Treatment of Sézary Syndrome

Key Points

Question

What treatment options are available for patients with Sézary syndrome (SS) that is resistant to multiple treatments?

Findings

This case series describes 3 patients with treatment-refractory SS who received low-dose total skin electron beam therapy (TSEBT) as part of a multimodality systemic regimen for treatment of SS and who experienced long-term clinical remissions; additional investigations demonstrated reversal of the immune dysfunction characteristic of SS.

Meaning

The combination regimen of low-dose TSEBT with immunotherapy should be considered for further use and study in patients with refractory SS; given the good tolerability of low-dose TSEBT, it would be a valuable addition to SS management if proven to be effective.

This case series discusses 3 patients with Sézary syndrome who were treated with low-dose total skin electron beam therapy as part of a multimodality systemic regimen.

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.

Introduction

Cutaneous T-cell lymphomas (CTCLs) are malignant neoplasms of skin-trafficking T cells. The most common subtypes are mycosis fungoides (MF) and Sézary syndrome (SS). The latter is a CTCL variant in which patients typically present with erythroderma and significant blood disease, and it manifests distinct genomic alterations and molecular pathogenesis from MF.¹ While patients with early-stage MF have a normal life expectancy, patients with advanced-stage MF and SS have a median survival of only 3.9 to 6.0 years.^2,3

Management of advanced-stage MF and SS remains extremely challenging. Approved systemic therapies include oral retinoids, chemotherapy, interferons (IFNs), monoclonal antibodies, extracorporeal photopheresis (ECP), histone deacetylase inhibitors, and allogeneic hematopoietic stem cell transplant. Most of these therapies rarely produce prolonged responses, with median progression-free survivals ranging from 3.9 to 9.2 months for common single agents.⁴ To achieve more durable responses, patients are frequently offered combination therapies.^5,6 However, few studies have examined specific multimodality regimens, and treatment choices are often based on institutional experience and availability.^5,6,7

In this report, we describe a series of patients with previously refractory SS who experienced long-term clinical and molecular responses after adding low-dose total skin electron beam therapy (TSEBT) to stable systemic immunotherapy regimens. We assess disease biomarkers and perform assays of immune function before and after TSEBT. Overall, the novel use of low-dose TSEBT with systemic immunomodulating therapy shows promise in the treatment of refractory SS.

Methods

Patients

After obtaining approval from the University of Pennsylvania Institutional Review Board and written informed patient consent, we conducted a retrospective case series of patients with a history of SS, presenting between 2009 and 2017, who had refractory disease on multimodality systemic therapy prior to receiving low-dose TSEBT. Staging was based on the revised International Society for Cutaneous Lymphomas/European Organization for Research and Treatment of Cancer guidelines.⁸

Treatment Protocol

All patients were on stable systemic regimens, including ECP, bexarotene, and IFN-α or IFN-γ prior to and during TSEBT (Table). Patient 1 received 1200 cGy, with 100 cGy per fraction, over 3 weeks. Patient 2 received 800 cGy, with 200 cGy per fraction, over 2 weeks. Patient 3 received 1200 cGy, with 200 cGy per fraction, over 2 weeks.

Table. Patient Characteristics, Systemic Therapies, and Adverse Effects Following Total Skin Electron Beam Therapy (TSEBT).

Patient/sex/agea (decade)	Disease duration, y	Therapy prior to TSEBT	Duration of therapy before TSEBT, mo	Therapy during remission	Remission duration, mo	Adverse effects
1/M/80s	2	IFN-αb	24	IFN-γ	30	Fatigue
		IFN-γ	1	Bexarotene
		Bexarotene	5	ECP
		ECP	23
		PUVA	22
2/M/70s	5.5	IFN-γ	58	IFN-γ	25	Temporary fever, chills, AMS
		Bexarotene	68	Bexarotene
		ECP	68	ECP
3/M/50s	1	IFN-αb	6	IFN-γ	24	Fatigue
		IFN-γ	1	Bexarotene
		Bexarotene	6	ECP
		ECP	6

Abbreviations: AMS, altered mental state; ECP, extracorporeal photopheresis; IFN, interferon; PUVA, combination of psoralen and long-wave ultraviolet radiation.

^aAge at presentation.

^bTherapies discontinued prior to TSEBT. All other therapies were used concomitantly with TSEBT.

Response Evaluation

The primary end point was global response based on clinical examination of skin and lymph nodes and laboratory evaluation of peripheral blood. Complete clinical response was defined as full resolution of skin lesions, as well as regression of nodal and blood disease if present. After 2015, skin disease was scored using the modified severity weighted assessment tool (mSWAT).⁹

Flow Cytometry

To detect antigen expression on T cells, 1 million peripheral blood mononuclear cells (PBMCs) per sample were stained with fluorochrome-conjugated antibodies against cluster of differentiation (CD)26, Fc receptor-like protein 3 (FCRL3), VB2 clonality, T-cell immunoreceptor with immunoglobulin and ITIM domains (TIGIT), Helios, and thymocyte selection-associated high mobility group box protein (Tox) for 30 minutes on ice. Cells were analyzed with an LSRII flow cytometer (Becton Dickinson).

Enzyme-Linked Immunosorbent Assay

From each patient, we isolated 2 million PBMCs from blood collected before and approximately 6 months after TSEBT. These cells were cultured for 72 hours with 10 μg/mL resiquimod or beads coated with anti-CD3/CD28 antibodies. Levels of IFN-γ in supernatants were assessed using the Duoset Enzyme-Linked Immunosorbent Assay kit (R&D Systems).

T-Cell Receptor Sequencing

For each sample, DNA was extracted from PBMCs, then T-cell receptor (TCR)β CDR3 and TCRγ CDR3 regions were amplified and sequenced using ImmunoSEQ (Adaptive Biotechnologies) from 100 to 400 ng of DNA template. Bias-controlled V and J gene primers were used to amplify rearranged V(D)J segments for high throughput sequencing at approximately 20 times coverage. After correcting sequencing errors via a clustering algorithm, CDR3 segments were annotated according to the International ImMunoGeneTics collaboration, identifying which V, D, and J genes contributed to each rearrangement.^10,11

Results

Patient Characteristics

A total of 3 patients were identified who had a history of SS that was refractory to systemic therapy prior to low-dose TSEBT (Table). All 3 had presented with erythroderma and were diagnosed with stage IVA1 CD4+ SS. All patients were men, and mean age was 65 years at presentation. None had clinically detectable lymphadenopathy. Each patient had refractory severe skin and blood disease on the systemic regimens noted in the Table. Apart from these systemic treatments, patients 2 and 3 had also received topical carmustine and/or meclorethamine prior to TSEBT.

Response to Therapy

After receiving TSEBT, all 3 patients experienced complete remission of skin disease. Patients 2 and 3 had significant reductions in mSWAT at early time points following TSEBT, and complete resolution occurred over 6 to 20 months (Figure 1A). Patient 1 did not have baseline mSWAT scores, as he presented prior to our implementation of that metric. However, his documented clinical examinations record the resolution of skin lesions within 3 months.

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.

The lengths of remission are noted in the Table. After 30 months, having missed 4 weeks of IFN-γ treatment, patient 1 developed pruritic red patches and recurrent blood disease (Figure 1B). After resuming IFN-γ treatment, his lesions completely resolved, and he has been in remission for 48 additional months. Patients 2 and 3 have been in continued clinical and molecular remission.

Certain disease-associated biomarkers normalized following TSEBT. The CD4⁺/CD7⁻ lymphocyte fraction, CD4:CD8 ratio, and lactate dehydrogenase became normal in all patients (Figure 1, B-D). The markers of immune exhaustion FCRL3, TIGIT, Helios, and Tox declined, as well as the Vb2 marker expressed on the malignant clone in 1 patient, while the CD4+/CD26+ population recovered (Figure 1E). As a surrogate measure of T helper class 1 immunity, quantitation of IFN-γ secretion by PBMCs demonstrated restoration of a more normal immune response after TSEBT (Figure 1F). High throughput sequencing of the TCR detected a dominant clone in the blood in all pre-TSEBT samples that was replaced by a more normal polyclonal distribution in 2 patients following TSEBT (Figure 2).

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.

Discussion

To our knowledge, low-dose TSEBT at 800 cGy to 1200 cGy has not been previously described as an addition to combination ECP, bexarotene, and IFN-γ. The use of conventional-dose TSEBT at 3600 Gy with this regimen was previously described as significantly debulking skin and blood disease in the treatment of SS.¹² However, conventional-dose TSEBT is poorly tolerated, producing pain, blistering, or alopecia in the majority of patients, and repeated treatments are not recommended.¹³ This study’s description of long-term clinical remissions and immune recovery following low-dose TSEBT in 3 patients suggests that this treatment deserves further study as an addition to multimodality systemic therapy.

Limitations

While these long-term remissions are encouraging, only limited conclusions can be drawn from a small case series, and more extensive studies including clinical trials should be considered. As SS is an uncommon disease, large trials can be challenging, but this report adds to the evidence that low-dose TSEBT may merit further evaluation for treatment of patients with refractory SS.

Conclusions

When TSEBT is used alone, responses are common but usually short lived. In a previous large retrospective study,¹⁴ conventional-dose TSEBT produced a median progression-free survival of only 3.7 months in patients with SS. The long-term remissions we describe in this report suggest that the concurrent systemic therapies, ECP, bexarotene, and IFN-γ, may be important in potentiating the effects of TSEBT. In particular, we hypothesize that IFN-γ may play a critical role in sustaining the remissions following TSEBT. This cytokine is known to restore T helper class 1 function, activate and potentiate cytotoxic effector cells, and activate antigen-presenting cells.¹⁵ Indeed, 1 patient in our study experienced a relapse in skin and blood after missing several weeks of IFN-γ treatment but regained his remission after its reintroduction. The multimodality regimen of ECP, bexarotene, and IFN-γ may help maintain the tumor burden at a lower level after TSEBT produces apoptosis and debulking of the malignant SS cells. As SS cells express surface and soluble factors that inhibit immunity,¹⁵ the reduction in malignant burden likely explains the normalization of immune function that we observed in these patients.