20-year incidence trends of anal squamous cell carcinoma.

Abstract

e15503 Background: Anal Squamous Cell Carcinoma (SCCA) accounts for 90% of cases of anal cancer. ~95% of SCCAs are driven by Human Papilloma Virus (HPV). We did a follow-up population-based analysis to assess incidence trends of SCCA over 20 years (2000-2019) in era of HPV vaccination (available since 2006). Methods: Data was extracted from Surveillance, Epidemiology, and End Results (SEER) database for years 2000-2019. Joinpoint regression models were fitted to identify a discrete joints (year) that represented a statistically significant change in direction of the trend of overall SCCA incidence. The average annual percentage change (AAPC) in age-adjusted incidence rate in all subgroups pre- and post-2009 (statistically significant joinpoint year) was measured. (Table 1). Results: 30,294 new cases of SCCA were identified from 2000-2019, with majority in females (61.6%), white population (86.5%), and ages 40-79 years (84.1%). A significant joinpoint for SCCA incidence was observed in 2009, wherein APC of 2.8% (95% CI 2.0-3.6) in 2000-2009 was reduced to 0.5% (95% CI -0.1-1.2) in 2009-2019 (82% relative reduction [RR]). In subgroup analysis, evaluating the trends after identifying a discrete joint (2009), we found that APC for White population reduced from 3.1% (P < 0.0001) to 1.1% (P = 0.022) (65% RR), and for Black population, APC of 3.2% (P = 0.0015) seem to flatten out at 0.3% (P = 0.768) in post-2009 years (91% RR). Ages 20-39 had a -4.2% (P = 0.028) APC pre-2009 that showed increase to 1.3% (P = 0.214) post-2009, however, small sample size noted. In ages 40-59, APC of 4.7% (P < 0.0001) seem to flatten out at -0.5% (P = 0.393) (111% RR). Ages 60-79 had a similar APC (2.4% [P = 0.0011] and 2.5% [P = 0.0001], respectively). In males, APC of 2.8% (P = 0.002) flattened out to 0.5% (P = 0.249) and females reduced from 3.2% (P < 0.001) to 1.2% (P = 0.009). Conclusions: In this study, we found a trend of decrease in the rate of growth of SCCA incidence pre- and post-2009, overall and among various subgroups. Furthermore, our results suggest that widespread education and scaling up access to HPV vaccination can decrease and potentially reverse the SCCA incidence. [Table: see text]