HIV Status and Anal Cancer Treatment Outcomes

Abstract

Nearly 30% of men with anal cancer have a concurrent diagnosis of HIV. Despite the clear link between HIV and developing anal cancer, the influence of HIV on treatment toxicity and oncologic outcomes remains a subject of debate. Furthermore, among HIV positive patients we lack a clear understanding of whether pre-treatment CD4 counts influence outcomes. The purpose of this study was to evaluate the impact of HIV and CD4 counts on toxicity and outcomes among a large national cohort of veterans with anal cancer. We conducted a nationwide retrospective cohort study of 1074 veterans with clinical stage I-III anal squamous cell carcinoma with HIV (n=209; 19%) or without HIV (n=865) diagnosed between 2000 and 2015. We compared HIV+ and HIV- patients with respect to the following endpoints: treatment completion, treatment breaks, acute toxicity, late toxicity, cancer-specific survival, and overall survival. Among the HIV+ subset of patients we determined the influence of pre-treatment CD4 counts on acute and long-term outcomes. We used multivariable logistic, Fine-Gray, and Cox regression models to determine the impact of HIV on different outcomes while controlling for potentially confounding factors. Both HIV+ and HIV- patients were similarly likely to receive standard of care treatment (82% vs 85%, p=0.3), and both received similar total radiation doses (median dose of 54 Gy for both groups, p=0.8). Compared to the HIV- cohort, the HIV+ patients were less likely to receive a second dose of mitomycin C (p=0.006) and more likely to have a radiation treatment break > 5 days (p=0.04), grade 3-4 hematologic toxicity (p<0.001), or be hospitalized within 90 days of radiation (p=0.003). There was no difference between the HIV+ and HIV- groups with respect to tumor- or treatment-related colostomy rates or overall survival (p>0.05), though there was a trend toward increased cancer mortality in the HIV+ group (p=0.05). In the HIV+ cohort, a pre-treatment CD4 count <200 was associated with an increased risk of hospital admission for hematologic toxicity (p=0.01) and grade 3-4 thrombocytopenia (p=0.02), but no differences were seen in other acute toxicity endpoints, long-term colostomy rates, cancer-specific survival, or overall survival. In this large cohort of veterans with anal cancer we found that the presence of HIV was associated with an increased risk of acute treatment-related toxicity, though no significant differences were seen in late toxicity, cancer-specific survival, or overall survival. Further research should seek strategies to better support HIV+ patients through treatment to minimize treatment related toxicity.