OBJECTIVES: MRCLS is a rare cancer with high unmet medical needs. Estimating the potential patient volume helps inform medicine development; however, epidemiologic data for MRCLS in Europe is scarce due to limited European data sources. This analysis estimated the incidence and prevalence of MRCLS patients in EU27 by extrapolating data from the US.

METHODS: The US SEER 18 registries were used to produce the 5-year (2014–2018) average annual incidence rates and 10-year (2009–2018) limited duration prevalence (LDP) rates of MRCLS by 10-year age groups and sex. Ten-year LDP of MRCLS represents the number of people alive on a certain day who were diagnosed with MRCLS within the past 10 years, not indicating all patients who have lived for the entire duration. All rates were age-standardized and applied to the July 2020 EU27 age- and sex-stratified population (estimated from the Eurostat database) to obtain counts of MRCLS patients in EU27. The inability to account for factors other than age/sex distribution is a limitation. For validation, the current study output was compared to limited publicly available epidemiology data in EU (eg, that from French registries).

RESULTS: Out of ~450 million people in EU27 in July 2020, there were estimated 792 new MRCLS cases within the last year (incidence) and 6259 prevalent cases (10-year LDP). Over 99% of cases were adults; around 58% were male. Among 10-year age groups, those aged 50–59 years constituted the largest proportion (>20%). Approximately one-third of the cases were patients aged 60+ years. Sensitivity analyses produced similar findings when extrapolating from the 10-year average incidence rates.

CONCLUSIONS: Despite being rare, MRCLS impacted hundreds of patients in Europe in 2020. Future studies using European datasets, when available, are needed to confirm our findings, as well as to further estimate patient segments by tumor characteristics, biomarkers, and treatment settings of interest.