Second neoplasms in patients with Merkel cell carcinoma

BACKGROUND. Merkel cell carcinoma (MCC) has been associated with a high incidence of other skin tumors and hematological malignancies. The purpose of this study was to analyze data from the Israel Cancer Registry regarding the incidence of second neoplasms in patients with MCC and their impact on survival. METHODS. Sixty-seven patients in whom MCC was diagnosed between 1983 and 1999 were included. Data were collected on age, gender and ethnic origin, dates of diagnosis of MCC and any other neoplasm, and date and cause of death, if applicable. Comparison of MCC-specific survival, estimated by the Kaplan-Meier product limit method, between patients with no other neoplasm and those with second primary tumors was performed by log rank test. Age-specific standardized incidence ratio (SIR) was calculated using 5751 age- and ethnic-matched malignant melanoma patients as a control group. RESULTS. Seventeen patients (25%) had a second neoplasm before, concomitant with, or after the diagnosis of MCC; 2 of them also had a third primary tumor. The SIR was 2.8 (95% CI; range, 1.38-4.22), significantly higher than the control group. Almost half the tumors were squamous cell carcinomas, either skin or head and neck, and most of the remainder were hematological malignancies or breast and ovarian adenocarcinomas. On univariate analysis, the presence of another neoplasm, regardless of its chronology, was associated with higher MCC-specific mortality (65% vs. 40% for patients with MCC only; P = 0.022). Analysis of only those patients in whom a second neoplasm developed during follow-up after treatment for MCC yielded an estimated actuarial risk of developing a second primary of 2.1% for each year of observation. CONCLUSIONS. There is a high incidence of second neoplasms, including noncutaneous solid tumors, in patients with MCC. The presence of these neoplasms, whether they appear before, after, or simultaneously with MCC, is associated with a higher MCC-specific mortality.