Systemic therapy for metastatic melanoma (MM) has dramatically changed in the past decades. Specific BRAF/MEK inhibitors for BRAF-mutant MM induced response rates of 70-80%, with a progression-free survival (PFS) of 11-15 months and a median overall survival (OS) of more than 2 years (1). Furthermore, immunotherapy using monoclonal antibodies directed against the checkpoint molecules CTLA-4 (cytotoxic T lymphocyte antigen-4) and PD-1 (programmed death antigen 1) or its ligand PD-L-1 induced response rates of about 15% and 40%, respectively, regardless of the presence of BRAF mutations and with usually durable responses (2, 3). Despite these important results, over half of patients do not respond to modern immunotherapy or relapse after a temporary response to either targeted or immunological treatments. For wild-type BRAF melanomas, anti-PD-1 agents are the first choice of treatment, and for patients with primary resistance or progressing to anti-PD-1 the prognosis is very poor with a second/further line including the anti-CTLA-4 ipilimumab, cytotoxic chemotherapy, or drugs in experimental trials.

As known, tumor associated antigens (TAA) are neoantigens produced by tumor cells capable to elicit an immune response, mainly mediated by cytotoxic-T lymphocytes (4). Many attempts are being made to increase tumor immunogenicity and to induce a more powerful immune response including systemic or intratumoral co-adjuvant molecules, radiations, cytotoxic drugs (5, 6). Moreover, the abscopal effect has been reported in some patients, consisting in a response to a local therapy, most often radiation, not only at the treated lesion site but also systemically, leading to a shrinkage of untreated, distant lesions (7). Trials using concurrent or sequential radiotherapy and immunotherapy are ongoing with the aim of exploiting their synergistic effects and identifying the best timing for the two treatments (8). Electrochemotherapy (ECT) is a strategy associating the electroporation of tumor cells with the simultaneous administration of antineoplastic drugs, generally bleomycin. The phenomenon of reversible electroporation increases cell permeability when a pulsed electrical current is applied to tissues. This enhances the cytotoxicity of bleomycin with minimal systemic side effects. Small tumor size predicts better response, durable tumor control, and fewer side-effects (9, 10). It has been reported that in addition to direct cell death, ECT is able to induce a local and systemic immune response thanks to its capability to release TAA from electroporated tumor cells (11–13). Thus, it has been hypothesized that the combination of ECT with systemic immunotherapy could constitute an effective strategy to induce an immunological durable and strong response against the tumor (14–17). So far, apart from anecdotal cases reported in literature (18–21), there are no studies that have verified this association on a large patient population, nor has the possibility of reverting resistance to immunotherapy been explored with the use of local treatments such as ECT.

Here, we report the case of an elderly patient with a locally advanced melanoma of the scalp presenting primary resistance to the anti-PD-1 nivolumab that was reverted after two ECT procedures.

We report the case of an elderly patient with melanoma of the scalp relapsed after surgical resection and then successfully treated with ECT and systemic immunotherapy. The patient showed a primary resistance to the anti-PD-1 nivolumab that was reverted after the second ECT procedure. ECT is an established local ablative treatment for primary or metastatic tumoral lesions with different histologies able to induce a response rate of 80% regardless of the histological type, particularly in superficial lesions that are more easily approached with this technique (9, 10, 22). Moreover, in selected patients with metastatic disease, ECT represents a useful tool to control oligoprogression allowing the continuation of systemic treatment and prolongation of overall survival (23). ECT has also been shown to induce a local and systemic immune response. ECT followed by CpG oligodeoxynucleotide injection is able to trigger both potent local synergistic antitumor effects and a systemic antitumor response at untreated tumor lesions (11). Moreover, ECT induces a massive recruitment of macrophages and CD3+ CD8+ T cells with a decrease of CD4+ FOXP3+ T regulatory cells in melanoma metastases (12). Finally, ECT promotes Langerhans cells migration from the tumor to the draining lymph nodes and plasmacytoid and dermal dendritic cells recruitment at the site of the lesion (13).

In our patient, a response to systemic immunotherapy was noted after the second ECT procedure. We hypothesized that the response of the patient’s disease was induced by the release of TAA and their presentation by the antigen presenting cells to T-lymphocytes, turning a non-T cell inflamed into T-cell inflamed tumor with consequent strong antitumoral effects. Unfortunately, the complete absence of cancer cells observed at the second biopsy of the lesions did not allow to perform any further immunohistochemical and molecular investigations to confirm our hypothesis. Interestingly, after 6 cycles of anti-PD1 treatment, the patient developed a vitiligo-like skin depigmentation that is the known expression of CD8⁺ activation against antigens shared by melanoma and melanocytes, and has been strongly associated with better outcomes in melanoma patients treated with immunotherapy (24). Moreover, the onset of grade 4 hypothyroidism at the initial response also demonstrated the synergistic antineoplastic activity induced by ECT and anti-PD-1. Also the pemphigoid that the patient recently developed is an immune-mediated condition, and its onset is to be attributed to the anti-PD-1 treatment. Of interest, at the analysis of peripheral blood parameters we found a progressive increase of the neutrophils/lymphocytes ratio (NLR) and platelets/lymphocytes ratio (PLR) during the non-response phase; then, at the initial tumor shrinkage, both of these parameters fell to a minimum value while maintaining a constant plateau level. It has been recently reported that NLR and PLR are prognostic biomarkers in different types of cancers including melanoma (25). These findings derive from the demonstration that neutrophils and platelets contribute to cancer cell growth and migration and from the evidence of the inter-relationship between thrombosis, inflammation and cancer immune surveillance (26). Moreover, they seem predictive of a worse efficacy of both chemotherapy and immunotherapy (27, 28). Finally, an early increase of NLR during treatment with PD-1 inhibitor monotherapy seems able to identify patients with a shorter survival and correlate with time to treatment failure (27). In our patient, NLR and PLR presented an increase over the latest months of treatment while maintaining complete response, as a consequence of a neutrophilic leukocytosis which is referrable to the purulent superinfection of the pemphigoid lesions that he developed.

In our case, ECT changed the quality of life of our patient, but it also actually changed his response to checkpoint inhibitor immunotherapy with a positive impact on his PFS and OS. Thus, it could represent a potential innovative potential innovative strategy in combination with systemic immunotherapy in order to generate a strong systemic long-lasting antitumoral immunity against melanoma. These results might contribute to design novel trials to verify this combination in a large patients’ population.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Ethical review and approval was not required for the study on human participants in accordance with the local legislation and institutional requirements. The patients/participants provided their written informed consent to participate in this study. Written informed consent was obtained from the individual(s) for the publication of any potentially identifiable images or data included in this article.

Conceptualization, MG, SS, and DQ. Data collection, IR, DQ, SS, and MG. Methodology, DQ, LF, and AL. Analysis, writing, and editing, DQ, AL, LF, SS, IR, AS, AA, GA, MM, SS, SR, GT, and MG. Supervision, MG and DQ. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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