Charles R. Thomas, Jr, MD

Primary surgery with an abdominoperineal resection (APR) was historically the standard of care for localized anal squamous cell carcinoma. APR achieved 40%-70% survival rates at five years, with local failures from 27%-47%.[1,2] With modern technology and radiation dose escalation, external beam radiation therapy (EBRT) studies have improved complete response rates, decreased morbidity, and improved sphincter preservation rates. Nigro et al added 5-fluorouracil (5FU) and mitomycin C (MMC) to concurrent EBRT [3,4] and impressive complete response rates inspired other groups to investigate the role of chemotherapy as a component of sphincter-preserving therapy. The European Organization for Research and Treatment of Cancer (EORTC) and United Kingdom Coordinating Committee on Cancer Research (UKCCCR) studies reported improved local control and colostomy-free survival when chemotherapy (5FU/MMC) was administered in conjunction with radiation.[5,6] The five-year survival rate for patients receiving standard chemoradiation approaches 70%; however, 20%-40% experience grade 3-4 toxicity, and administration with MMC causes profound hematologic toxicity.

Squamous cell anal cancer remains an uncommon entity; however,the incidence appears to be increasing in at-risk populations, especiallythose infected with human papillomavirus (HPV) and human immunodeficiencyvirus (HIV). Given the ability to cure this cancer using synchronouschemoradiotherapy, management practices of this disease arecritical. This article considers treatment strategies for HIV-positive patientswith anal cancer, including the impact on chemoradiation-inducedtoxicities and the role of highly active antiretroviral therapy in the treatmentof this patient population. The standard treatment has beenfluorouracil (5-FU) and mitomycin (or cisplatin) as chemotherapy agentsplus radiation. Consideration to modifying the standard treatment regimeis based on the fact that patients with HIV tend to experience greatertoxicity, especially when CD4 counts are below 200; these patients alsorequire longer treatment breaks. Additional changes to the chemotherapydosing, such as giving 5-FU continuously and decreasing mitomycin dose,are evaluated and considered in relation to radiation field sizes in an effortto reduce toxicity, maintain local tumor control, and limit need forcolostomy. The opportunity for decreasing the radiation field size andusing intensity-modulated radiation therapy (IMRT) is also considered,particularly in light of the fact that IMRT provides dose-sparing whilemaximizing target volume dose to involved areas. The impact of the immunesystem in patients with HIV and squamous cell carcinoma of theanus and the associated response to therapy remains unknown. Continuedstudies and phase III trials will be needed to test new treatment strategiesin HIV-infected patients with squamous cell cancer of the anus todetermine which treatment protocols provide the greatest benefits.