Systemic immune suppression predicts diminished Merkel cell carcinoma-specific survival independent of stage

Abstract

Merkel cell carcinoma (MCC) is an aggressive cutaneous malignancy linked to a contributory virus (Merkel cell polyomavirus). Multiple epidemiologic studies have established an increased incidence of MCC among persons with systemic immune suppression. Several forms of immune suppression are associated with increased MCC incidence, including hematologic malignancies, HIV/AIDS, and immunosuppressive medications for autoimmune disease or transplant. Indeed, immune-suppressed individuals represent ∼10% of MCC patients, a significant overrepresentation relative to the general population. We hypothesized that immune-suppressed patients may have a poorer MCC-specific prognosis and examined a cohort of 471 patients with a combined follow-up of 1,427 years (median 2.1 years). Immune-suppressed patients (n=41) demonstrated reduced MCC-specific survival (40% at 3 years) compared with patients with no known systemic immune suppression (n=430; 74% MCC-specific survival at 3 years). By competing risk regression analysis, immune suppression was a stage-independent predictor of worsened MCC-specific survival (hazard ratio 3.8, P<0.01). Thus, immune-suppressed individuals have both an increased chance of developing MCC and poorer MCC-specific survival. It may be appropriate to follow these higher-risk individuals more closely, and, when clinically feasible, there may be a benefit of diminishing iatrogenic systemic immune suppression.

Figure 1. Merkel cell carcinoma survival and immune suppression

Large graph: Persons with immune suppression (n=41) had significantly worsened Merkel cell carcinoma (MCC) specific survival as compared to those without systemic immune suppression (n=430) on univariate (hazard ratio 3.0; p < 0.01) and multivariate (hazard ratio 3.8; p < 0.01) competing risk regression analyses (Table 2). Numbers at risk at one, three, five, and seven years indicated below. Small graphs: Effects of immune suppression persisted across stage at presentation.