DP05 (P53) Incidence of Merkel cell carcinoma in the Republic of Ireland (1994–2019)

Abstract

Abstract Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine cutaneous malignancy most commonly observed in those aged over 65 years. Merkel cell carcinoma is twice as common in males as in females and is 25 times more common in those with fair skin than in those with darker skin types. Solid organ transplant recipients have a 24-fold increased risk of developing MCC. There was a 95% increase in the incidence of MCC in the USA from 2000 to 2013, with further increases predicted. The aim of this study was to investigate the trends of incidence of MCC in the Republic of Ireland. Age-standardized rates were calculated using the 2013 European standard population. There were 447 histologically confirmed MCCs diagnosed between 1994 and 2019. Forty-nine per cent of cases (n = 220) were in males. Median age was 80 years (range 15–19 to 95+). The median age for males was 78 years and the median age for females was 82 years. On average, there were seven cases of MCC diagnosed annually between 1994 and 1998 vs. 27 cases of MCC annually diagnosed between 2015 and 2019—almost a quadrupling of case numbers. The age-adjusted incidence rate of MCC for both male and females is detailed in Table 1. Previous literature has indicated that MCC is twice as common in males than in females. Our cohort differed in that there was a slight female predominance in patients diagnosed with MCC. This is in keeping with published literature from Northern European groups, which have also demonstrated a female predominance in MCC. While the absolute number of MCC diagnosed in Ireland has increased in both males and females, the age-adjusted incidence rate is increasing in males, but there has not been a significant change in females. Other Northern European groups have also demonstrated an increase in the incidence of MCC in males that was not observed in females. This study adds to the body of epidemiological data on MCC. Table 1Age-adjusted incidence rates of Merkel cell carcinoma (MCC)Cases of MCCAge-standardized rate (per 100 000 person-years)SE95% confidence intervalMales 1994–1999230.520.130.27–0.77 2000–2004210.370.080.21–0.53 2005–2009350.790.150.50–1.08 2010–2014661.190.160.88–1.50 2015–2019751.050.120.81–1.29Females 1994–1999260.360.070.22–0.50 2000–2004440.670.100.47–0.87 2005–2009540.790.110.57–1.01 2010–2014450.570.090.39–0.75 2015–2019580.650.090.47–0.83