537PTiming to achieve complete response (CR) after definitive chemoradiotherapy (ChRT) in patients with squamous cell carcinoma of the anal (SCCAC) with and without HIV infection: A multicenter retrospective study

Abstract Background The definitive treatment for localized SCCA is ChRT in combination with infusional 5-FU. A meta-analysis of published studies conducted by our group showed that HIV-positive patients (pts) are less cured by ChRT. However, short follow up times may have underestimated the true response rate of HIV-positive pts. We aimed to compare the timing to achieve CR between HIV-negative and positive pts and outcomes according to chemotherapy regimen (Nigro vs ACT2). Methods Retrospective multicenter comparative cohort of consecutive pts with histological diagnosis of SCCA and localized disease who received definitive ChRT. Pts’ characteristics and outcomes were compared according to HIV status. The primary endpoint was CR rate defined by absence of clinical and radiological evidence of disease. Results A total of 179 patients with SCCA were included: 43 (24%) were HIV-positive and 136 (76%) were HIV-negative. HIV-positive pts were more commonly men: 28 (65%) vs 24 (17.6%) (p