Ambient air pollution and survival in SCLC/LCNEC: Analysis of a single centre retrospective cohort

Small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma of the lung (LCNEC) are the deadliest forms of lung cancer with dismal prognosis. Recent evidence suggests that, beyond cigarette smoke, air pollution can have a role in the pathogenesis of non-small cell lung cancer (NSCLC) and is associated with poorer survival. However, whether air pollutants exposure could affect survival outcomes in SCLC/LCNEC is unknown.

We retrospectively analysed data from SCLC/LCNEC cases observed in the province of Brescia province Brescia between 2017 and 2021. Air pollutants mean concentrations were calculated during the same timeframe and the Brescia province was divided in six subareas dichotomized into lightly and heavily polluted areas based on the mean PM_2.5 concentrations. Primary endpoint was to determine the impact of air pollutants exposure on SCLC/LCNEC overall survival (OS). Additionally, we explored the distribution of SCLC/LCNEC across the subareas classified for different air pollutants concentrations.

We observed 221 cases of SCLC/LCNEC, accounting for about 18 % of new lung cancer cases. Residency in heavily polluted areas (HR 1.51, p = 0.03) and extensive stage disease at diagnosis (HR 2.47, p = 0.0001) emerged as independent factors for poorer survival. Exploratory analyses showed an association between the distribution of SCLC/LCNEC cases and higher PM₁₀ and NO₂ concentrations (OR 1.16, p < 0.001 and OR 1.46, p < 0.001, respectively).

These results indicate that long-term exposure to high levels of PM_2.5 represent an independent unfavourable prognostic factor for SCLC/LCNEC. Our data suggest that air pollution may also favour the onset of these malignant diseases. Case-control studies are warranted to confirm these preliminary results.