Nodal Merkel Cell Carcinoma with Unknown Primary Site and No Distant Metastasis: A Single-Center Series.

Merkel cell carcinoma (MCC) is a very rare and aggressive neuroendocrine carcinoma originating from Merkel cells, typically with a skin nodule; however, it exceptionally presents with only a basin lymph node localization, with neither a cutaneous primary site nor distant metastases. From 1996 to 2020, among patients with histologically confirmed MCC managed at a neuroendocrine neoplasm-referral center, we selected those with an exclusive nodal basin, no distant metastasis, and an unknown primary site defined by cross-sectional and physical examination. A total of 55 out of 310 patients fulfilled the selection criteria. The median age was 64 years and the majority were males. Inguinal lymph-nodes were the most common anatomic site. With a median follow-up of 4.3 years, the 5-year relapse-free survival (RFS) rate was 56.6 (95% CI 42.0-68.8%) and the 5-year cancer specific survival (CSS) rate was 68.5 (95% CI 52.8-79.9%) for the whole population. The 36 patients (65.5%) undergoing lymphadenectomy (LND) + radiotherapy (RT) ± chemotherapy had a 5-year RFS rate of 87.2% (95% CI 65.5-95.7%) and a 5-year CSS rate of 90.5% (95% CI 67.0-97.5), which were better than those receiving LND alone. In a multivariable analysis, the survival benefit for LND + RT remained significant. Results from one of the largest single-center series of nMCC-UP suggest that a curative approach including RT can be effective, similar to what is observed for stage IIIB MCC. Multicentric studies with homogenous populations should be carried out in this controversial clinical entity, to minimize the risk of biases and provide robust data.

Different Response to Immunotherapy According to Melanoma Histologic Subtype.

Superficial spreading melanoma (SSM) and nodular melanoma (NM) are the most common melanoma histologic subtypes and are characterized by different biological features. We retrospectively analyzed all consecutive patients with advanced melanoma, treated with anti-PD-1 and/or anti-CTLA-4 at our center, with data available on primary tumor subtype. The primary objective was to assess the association between histologic subtype and patients' outcomes. In addition, we analyzed whole-exome and whole-transcriptome sequencing data of a cohort of advanced melanoma to identify genes and related pathways, characterized by significant differences between NMs and SSMs. Twenty-one patients with NM and 39 with SSM, treated with anti-PD-1(53/60) as monotherapy or combined with anti-CTLA-4 (7/60), were analyzed. All known clinical-pathologic prognostic factors were well balanced between NM and SSM groups, except for the ECOG-PS score. The overall response rate was 52.4% (95% confidence interval, 29.8-74.3) in the NMs group versus 20.5% (9.3-36.5) in the SSMs group (P-value=0.02). The median progression-free survival and overall survival were, respectively, 13.9 and 44.5 months in the NMs group versus only 3.2 and 12 months in SSMs group (progression-free survival P-value=0.032; overall survival P-value=0.002). Multivariable analysis adjusting for the ECOG-PS, confirmed similar results. Whole-exome and whole-transcriptome data of 28 NMs and 21 SSMs were analyzed. No significant differences were observed in terms of both TMB and frequency of mutation in any gene. A total of 266 genes were overexpressed in NMs as compared with SSMs, and enrichment-analysis revealed a significant enrichment (false discovery rate<0.05) of genes belonging to immune-related pathways involved in antigens presentation mechanisms, response to interferon gamma and neutrophil activation. We provided clinical evidences suggesting a relevant association between melanoma histologic subtype and response to immunotherapy.

Sex-Based Dimorphism of Anticancer Immune Response and Molecular Mechanisms of Immune Evasion.

PURPOSE: We previously demonstrated that sex influences response to immune checkpoint inhibitors. In this article, we investigate sex-based differences in the molecular mechanisms of anticancer immune response and immune evasion in patients with NSCLC. EXPERIMENTAL DESIGN: We analyzed (i) transcriptome data of 2,575 early-stage NSCLCs from seven different datasets; (ii) 327 tumor samples extensively characterized at the molecular level from the TRACERx lung study; (iii) two independent cohorts of 329 and 391 patients, respectively, with advanced NSCLC treated with anti-PD-1/anti-PD-L1 drugs. RESULTS: As compared with men, the tumor microenvironment (TME) of women was significantly enriched for a number of innate and adaptive immune cell types, including specific T-cell subpopulations. NSCLCs of men and women exploited different mechanisms of immune evasion. The TME of females was characterized by significantly greater T-cell dysfunction status, higher expression of inhibitory immune checkpoint molecules, and higher abundance of immune-suppressive cells, including cancer-associated fibroblasts, MDSCs, and regulatory T cells. In contrast, the TME of males was significantly enriched for a T-cell-excluded phenotype. We reported data supporting impaired neoantigens presentation to immune system in tumors of men, as molecular mechanism explaining the findings observed. Finally, in line with our results, we showed significant sex-based differences in the association between TMB and outcome of patients with advanced NSCLC treated with anti-PD-1/PD-L1 drugs. CONCLUSIONS: We demonstrated meaningful sex-based differences of anticancer immune response and immune evasion mechanisms, that may be exploited to improve immunotherapy efficacy for both women and men.