Management of anal cancer in the HIV-positive population

Abstract

Squamous cell anal cancer remains an uncommon entity; however, the incidence appears to be increasing in at-risk populations, especially those infected with human papillomavirus (HPV) and human immunodeficiency virus (HIV). Given the ability to cure this cancer using synchronous chemoradiotherapy, management practices of this disease are critical. This article considers treatment strategies for HIV-positive patients with anal cancer, including the impact on chemoradiation-induced toxicities and the role of highly active antiretroviral therapy in the treatment of this patient population. The standard treatment has been fluorouracil (5-FU) and mitomycin (or cisplatin) as chemotherapy agents plus radiation. Consideration to modifying the standard treatment regime is based on the fact that patients with HIV tend to experience greater toxicity, especially when CD4 counts are below 200; these patients also require longer treatment breaks. Additional changes to the chemotherapy dosing, such as giving 5-FU continuously and decreasing mitomycin dose, are evaluated and considered in relation to radiation field sizes in an effort to reduce toxicity, maintain local tumor control, and limit need for colostomy. The opportunity for decreasing the radiation field size and using intensity-modulated radiation therapy (IMRT) is also considered, particularly in light of the fact that IMRT provides dose-sparing while maximizing target volume dose to involved areas. The impact of the immune system in patients with HIV and squamous cell carcinoma of the anus and the associated response to therapy remains unknown. Continued studies and phase III trials will be needed to test new treatment strategies in HIV-infected patients with squamous cell cancer of the anus to determine which treatment protocols provide the greatest benefits.