Background: The presence of a second primary cancer (SPC) in patients with pleural mesothelioma (PM) may impact overall survival and suggest a common mechanism of carcinogenesis or an underlying germline genetic alteration.
Methods: We evaluated the occurrence of SPCs within PM cases collected from 2000 to 2018 by the Lombardy Mesothelioma Registry and their prognostic implications. Kaplan-Meier analysis was performed to estimate median survival times, together with univariate and multivariate Cox regression models to estimate hazard ratios (HR) and 95% confidence intervals (CI) of death.
Results: The median overall survival (OS) of the entire study population (N = 6646) was 10.9 months (95% CI: 10.4-11.2); patient age and histotype were the strongest prognostic factors. No substantial survival difference was observed by the presence of an SPC (10.5 months in 1000 patients with an SPC vs. 10.9 months in 5646 patients in the non-SPC group, HR 1.03, p = 0.40). Shorter OS in the SPC group was only observed in 150 patients with the non-epithelioid subtype (median OS of 5.4 vs. 7.1 months, HR 1.21, p = 0.03).
Conclusions: The diagnosis of an SPC did not influence the outcome of PM patients in the overall study population but was associated with shorter OS in non-epithelioid cases. Further studies are needed to clarify the role of SPCs as markers of genetic susceptibility in mesothelioma.
Keywords: asbestos; cancer registry; genetic susceptibility; pleural mesothelioma; second primary cancer; survival.