Beyond the pleura: National trends in mesothelioma mortality by anatomical site in Spain, 1999–2024

Objectives Mesothelioma mortality continues to reflect asbestos exposure because of its long latency. While previous Spanish studies focused primarily on pleural disease, this study assessed mesothelioma mortality across the ICD-10 C45 category in Spain from 1999 to 2024. Materials and methods: A population-based time-trend study was conducted using mortality data (ICD-10 C45) from the Spanish National Statistics Institute. Age-standardised mortality rates (ASMRs) were calculated using the 2013 European Standard Population. Temporal trends and sex-specific parallelism were evaluated using Joinpoint regression. Results Among 9733 recorded mesothelioma deaths (7311 men, 2422 women), ASMRs were consistently higher in men, although temporal trends were parallel by sex. Overall mortality increased until 2016 (annual percentage change [APC] 2.3%, 95% CI 1.5–3.0) and subsequently declined non-significantly, yielding an average annual percentage change (AAPC) of 1.0% (95% CI 0.2–1.7) for 1999–2024. Pleural mortality increased until 2011 before declining non-significantly, whereas recorded peritoneal mortality increased throughout the study period (AAPC 2.0%, 95% CI 0.7–3.2). Deaths coded as unspecified site (C45.9) showed the largest increase in ASMR (AAPC 2.1%, 95% CI 1.1–3.1) and accounted for 43.5% of male and 31.8% of female mesothelioma deaths in 2024. Conclusions Absolute mesothelioma deaths increased in Spain while age-standardised rates attenuated after 2016. The continued increase in recorded peritoneal mortality and the substantial contribution of unspecified-site deaths indicate that surveillance should not rely solely on pleural mesothelioma, highlighting the need for comprehensive monitoring of the complete ICD-10 C45 category and improved anatomical classification.