Immune Status in Merkel Cell Carcinoma: Relationships With Clinical Factors and Independent Prognostic Value

Immunosuppression (IS) currently is not considered in staging for Merkel cell carcinoma (MCC). An analysis of the National Cancer Database (NCDB) was performed to investigate immune status as an independent predictor of overall survival (OS) for patients with MCC and to describe the relationship between immune status and other prognostic factors.

The NCDB was queried for patients with a diagnosis of MCC from 2010 to 2016 who had known immune status. Multivariable Cox proportional hazards models were used to define factors associated with OS. Secondary models were constructed to assess the association between IS etiology and OS. Multivariable logistic regression models were used to characterize relationships between immune status and other factors.

The 3-year OS was lower for the patients with IS (44.6%) than for the immunocompetent (IC) patients (68.7%; p < 0.0001). Immunosuppression was associated with increased adjusted mortality hazard (hazard ratio [HR], 2.36, 95% confidence interval [CI], 2.03-2.75). The etiology of IS was associated with OS (p = 0.0015), and patients with solid-organ transplantation had the lowest 3-year OS (32.7%). Immunosuppression was associated with increased odds of greater nodal burden (odds ratio [OR], 1.70; 95% CI, 1.37-2.11) and lymphovascular invasion (OR, 1.58; 95% CI, 1.23-2.03).

Immune status was independently prognostic for the OS of patients with localized MCC. The etiology of IS may be associated with differential survival outcomes. Multiple adverse prognostic factors were associated with increased likelihood of IS. Immune status, and potentially the etiology of IS, may be useful prognostic factors to consider for future MCC staging systems.