Changing patterns of second primary malignancies and cause-specific mortality among patients with major salivary glands cancers in the United States: A population-based study.

Abstract

e18081 Background: Salivary gland neoplasms are rare entities that comprise approximately 5% of all head and neck malignancies. The incidence of major salivary gland (MSG) cancers has increased about 54% from 1970 to 2000 in the United States (US). We undertook this study to investigate the risk of second primary malignancies (SPMs) and cause-specific mortality (CSM) in patients with MSG cancers using a national registry from the US. Methods: We estimated the incidence of SPMs among two-month survivors of MSG cancers using the Surveillance, Epidemiology, and End Results (SEER)-18 registries between 2008 to 2018. The risk of SPMs were calculated using standardized incidence ratios (SIRs) and the CSM by standardized mortality ratios (SMRs) and absolute excess risk (AER)/10,000 population. Results: We included 845 patients with MSG cancers in this study. The median age of diagnosis was 67 yrs (range 0 - 85 yrs). The median follow-up duration was 24 months (range 0 - 130 months). The median latency period for SPM development was 30 months (range 4 - 117 months). A total of 38 (4.5%) patients developed 41 SPMs at last follow-up. The SPM risk for cohort was significantly elevated (SIR = 1.81, 95% confidence interval [CI] = 1.30 - 2.46) compared with general population. The SPM risk was statistically higher among males (SIR = 2.42, 95% CI = 1.66 - 3.42) but not significant in females (SIR = 0.95, 95% CI = 0.44 - 1.81). Specific sites with highest SPMs risk included tonsil (SIR = 52.45, 95% CI = 1.33 - 292.22) followed by oral cavity (SIR = 15.55, 95% CI = 7.11 - 29.52). The risk for tonsil cancers were high from 5 to 10 years of initial diagnosis. While risk for oral cavity cancers, remained high throughout follow-up period. At the last follow-up, 214 (25%) patients had died. There was statistically significant risk of mortality due to MSG cancers (SMR = 5,453.61, 95% CI = 4,385.34 - 6,703.41, AER = 517.87) and oral cavity cancers (SMR = 663.40, 95% CI = 537.97 - 809.29, AER = 557.41) (Table). Conclusions: Our study concludes that men with MSG cancers are at an increased risk for SPMs compared to women. The risk of specific SPMs (tonsil and oral cavity cancers) was high even after a long period from the initial diagnosis of MSG cancers. This highlights the need for long-term surveillance in these patients for SPMs development.[Table: see text]