537P - Timing 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

BackgroundThe 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). MethodsRetrospective 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. ResultsA 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<0.001) and had clinical stage III: 22 (51%) vs 60 (44%). The overall CR rate was 74.4% vs 83.1% for HIV-positive and negative pts, respectively (P=0.206). Among pts who achieved a CR (N=145), the rates of CR for HIV-positive vs negative pts were, respectively: 32.5% vs 67% at 6 months evaluation and 41.8% vs 16.1% after 6 months (6 to 18 months) post ChRT (p<0.001). More HIV-positive pts underwent salvage surgery: 14 (35.2%) vs 21 (15.4%) (p<0.01). The overall CR rates of HIV-positive pts were 71.4% (10 out of 14) with ACT2 and 63% (14 out of 22) with Nigro. For HIV-negative, the CR rates were: 90.3% (28 out of 31) for ACT2 and 80.2 % (73 out of 91) for Nigro. ConclusionsDelayed CR was more frequently observed among HIV-positive pts. This finding has clinical implications because waiting longer to define CR among these pts may prevent unnecessary anorectal amputations. Legal entity responsible for the studyThe authors. FundingHas not received any funding. DisclosureAll authors have declared no conflicts of interest.