O-135 Exploring the etiology of rare cancers using a large multi-ore mining cohort

Introduction

Cohort studies may be limited in their ability to investigate rare cancers because of their size, length of follow-up, or access to cancer registry data. This study examines exposure patterns for nasal, nasopharyngeal, laryngeal, salivary gland, and bone cancer using a large multi-ore mining cohort.

Materials & Methods

From 1928–1988 underground miners in Ontario, a region where gold, uranium, nickel, and other ores are mined, were required to undergo an annual medical exam, and record their mining work history to receive certification. These data were used to create the Mining Master File (MMF) cohort. Cancers were identified through linkage with the Ontario Cancer Registry (1964–2017). Cancer risk among miners was compared to the general population using Standardized Incidence Ratios (SIR) and between groups of miners in the cohort using Poisson regression.

Results

The cohort consisted of 61,397 male miners. Nasal cancer was somewhat elevated (48 cases, SIR=1.44, 95% confidence Interval (CI)=1.06–1.91) but the observed excess was largely localized to miners who had the majority of employment in nickel mines (SIR=2.09, CI=1.37–3.06). Nasopharyngeal cancer was similarly elevated (44 cases, SIR=1.42, CI=1.03–1.91) but in contrast the excess risk was limited to gold mining (SIR=2.70, CI=1.57–4.33). A small elevation was observed for larynx cancer (307 cases, SIR=1.26, CI=1.12–1.40), but was not limited to one ore type. Bone cancer was clearly elevated (58 cases, SIR=1.91, CI=1.45–2.47), with ore-specific elevations seen among uranium (SIR=2.46, CI=1.22–4.40) followed by nickel mining (SIR=2.04, CI=1.29–3.06). Salivary gland was only slightly elevated (54 cases, SIR=1.09, CI=0.82–1.42), but the risk among uranium miners exposed to radon was high (SIR=2.97, CI=1.81–4.59) and increased monotonically with employment duration.

Conclusion

This analysis demonstrated the power of this cohort to identify associations for rare cancers. Although the association of nickel with nasal cancer was expected, some other associations were surprising and warrant further investigation.