Abstract
Background: Malignant mesothelioma is a rare cancer primarily associated with occupational asbestos exposure impacting mesothelial cells. Despite regulations against asbestos use, this cancer continues to be a public health concern given its long latency and shifting age cohorts – older populations with higher risk historical exposures and younger cohorts with lower rates, potentially distorting the true picture of population incidence risk and trends. The objective of this study was to assess the current role of age, period, and cohort (APC) effects on malignant mesothelioma incidence. This study extends previous work which examined cases reported up until 2013 through 2022.
Methods: Incident mesothelioma cases (pleural and total) were identified using SEER-8 cancer registry data (1975-2022). Effects of mesothelioma incidence trends were described utilizing the US National Cancer Institute’s APC analysis web tool, estimating 5-year age intervals, calendar periods, and birth cohorts, stratified by age and gender groups (male and female; age 0-74 and 75+ years old).
Results: Annual incidence of mesothelioma among younger males (aged 0-74 years) has significantly decreased: -1.8%/year for all mesothelioma (95% CI: -3.3, -0.3) and -2.2%/year for pleural mesothelioma (95% CI: -4.0, -0.4). Comparatively, net drifts for mesothelioma incidence among older adults (75+ years) increased. Birth-cohort-adjusted incidence among younger males declined following a peak during the period of 1980-1984. Meanwhile, rates have continued to increase among older adults but remained mostly unchanged among younger females. Temporal patterns in mesothelioma incidence varied across age groups, suggesting birth cohort effects. The peak birth cohort for pleural and total mesothelioma incidence among younger males was 1917-1921, while flatter patterns of change among females and older males made the identification of peaks less definitive.
Conclusions: Results support an association between 1970’s asbestos regulations with declining occupational asbestos exposures post-World War II, and declining mesothelioma incidence among younger males, suggesting disappearing occupational asbestos causal risk for malignant mesothelioma. Increasing rates in the older age group may be attributable to longevity-related factors influencing later onset risk, including disease latency, aging and its associated decline in immune function, radiotherapy and chemotherapy from prior cancer treatments, and genetic susceptibility.