Anal Cancers in Previously Screened Versus Unscreened Patients: Tumor Stage and Treatment Outcomes.

Abstract

Targeted screening programs for patients at high risk for anal squamous cell carcinoma have been proposed; however, the evidence in support of screening remains unclear. This study aimed to determine whether screening high-risk patients (predominantly those living with HIV) detected squamous cell carcinoma at an earlier stage compared to the routine practice of not screening. This is a cohort study. This study was conducted at a quaternary care center in Canada. Included patients were at least 18 years old with a pathologic diagnosis of invasive anal squamous cell carcinoma between 2002 and 2022. Patients diagnosed through a high-risk screening program were compared to those who did not undergo screening. The primary outcome was clinical stage at presentation, categorized as T1N0M0 vs. other. Secondary outcomes included treatments received, treatment failure, and overall survival. A total of 612 anal squamous cell carcinoma patients were included, with 26 of those patients diagnosed through a screening program. Patients with screen-detected cancers had greater odds of presenting with T1N0M0 tumors compared to unscreened patients (18 [69.2%] vs. 84 [14.3%]; adjusted odds ratio 9.95; 95% confidence interval 3.95-25.08). A propensity score matched sensitivity analysis found similar results (odds ratio 11.13; 95% confidence interval 4.67-26.52; p < 0.001). Screened patients had greater odds of treatment with wide local excision alone, as opposed to any combination of chemotherapy, radiation, and surgery (3 [12.5%] vs. 18 [3.2%]; odds ratio 4.38; 95% confidence interval 1.20-16.04). There were no statistically significant differences in treatment failure or overall survival between groups. The small number of screened patients limits the power of the analysis. Screening for anal squamous cell carcinoma amongst high-risk populations detects cancers at an earlier stage. Patients with screen-detected cancers also had a greater likelihood of being candidates for wide local excision alone, which may have spared them the morbidity associated with chemoradiotherapy or abdominoperineal resection.