Temporal trends and racial disparities in anal squamous cell carcinoma outcomes: A population-based study.

Abstract

e15504 Background: Anal squamous cell carcinoma (SCC) is a relatively uncommon malignancy, accounting for approximately 2% of gastrointestinal tract cancers. Human papillomavirus (HPV) infection is implicated in 80% of cases, and thus key risk factors include immunosuppression and sexual behaviors associated with HPV exposure. This study aimed to characterize current incidence and survival trends in anal SCC using the Surveillance, Epidemiology, and End Results (SEER) Database. Methods: SEER Research Plus Data (17 Registries, 2000-2022) was used to identify cases of primary anal squamous cell carcinoma using ICD-O-3 histology codes 8050-8084 and Primary Site ICD-O-3 C21.0-C21.8 in individuals aged 15 or older. Data were then categorized by era, age group, sex, and race/ethnicity. Multivariable Cox proportional hazards models were used to evaluate associations between overall survival and diagnosis era, age group, sex, race/ethnicity, and stage at diagnosis. Results: A total of 29,584 patients were identified with anal SCC, with registry incidence estimated 2.44 per 100,000 persons. The mean age at diagnosis was 62.0; 64% were female and 36% were male. Non-Hispanic White patients accounted for 78.5% of cases, followed by Black (9.8%), Hispanic (9.2%), Asian/Pacific Islander (A/PI) (1.9%), and American Indian/Alaska Native (AI/AN) patients (0.6%). Over the 23-year study period, incidence increased across all racial and ethnic groups (IRR per year 1.04; p < 0.001). In multivariable Cox proportional hazards model adjusted for age and sex, diagnosis era was independently associated with overall survival (p < 0.001). Compared with patients diagnosed between 2000-2004, those diagnosed between 2010-2014 (HR 0.93, 95% CI 0.88-0.98), 2015–2019 (HR 0.86, 95% CI 0.81-0.91), and 2020–2022 (HR 0.81, 95% CI 0.74-0.88) experienced progressively lower hazards of death. When stratified by race/ethnicity, median overall survival was longest among Hispanic (142 months; 95% CI 128-154) and A/PI patients (140; 95% CI 117-166), followed by White (125; 95% CI 121-130). Median overall survival was poorest in Black (94 months; 95% CI 86-105) and AI/AN patients (90; 95% CI 58-152). Conclusions: In this analysis, the incidence of anal SCC increased substantially over time, while overall survival has improved across successive eras. Despite these survival improvements, significant racial and ethnic disparities remain, with worse outcomes observed among Black and American Indian/Alaska Native patients. Rising incidence and persistent racial disparities suggest ongoing gaps in prevention, early detection, and equitable cancer care. One-year overall survival for anal SCC by race/ethnicity, 2000–2022. Race 2000-2004 2005-2009 2010-2014 2015-2019 2020-2022 White 85.6 86.3 88.3 88.2 88.3 Black 79.3 79.2 85.7 86.6 86 Hispanic 89.3 86.7 90 89.6 89.1 A/PI 90.4 87.3 88.4 91.3 85.6 AI/AN 90.9 90 92.5 84.2 85.9