SCREENING FOR ANAL CANCER

IE Salit¹, J Tinmouth², A Lytwyn³, W Chapman⁴, J Mahony⁵, J Raboud⁶, M Sano^1
1Immunodeficiency Clinic, Toronto General Hospital; ²Division of Gastroenterology, St. Michael's Hospital; ³Departments of Pathology, Sunnybrook and Women's College Health Sciences Centre; ⁴University Health Network; ⁵Department of Pathology and Molecular Medicine, McMaster University; ⁶Public Health, University of Toronto

Among HIV+ males, the relative risk for anal cancer is 163-fold and may not be decreasing despite antiretroviral therapy.
Objectives: 1. To establish an anal cancer screening program using anal Pap smears, Human Papillomavirus (HPV) detection and high resolution anoscopy. 2. To determine the sensitivity, specificity, and predictive values of anal Pap smear cytology, HPV DNA, and oncogenic HPV E6 and E7 mRNA transcripts for detection of high-grade anal squamous intraepithelial lesions (HSIL). 3. To determine the agreement between pathologists. 4. To determine the agreement between anoscopists for site of biopsy.
Methods: Subjects will comprise 680 HIV+ men with a history of anal receptive intercourse. All patients will have anal canal specimens for: (a) (Thin Prep) Pap smears (b) HPV detection (Hybrid Capture) (c) oncogenic HPV E6 and E7 mRNA transcripts and (d) anal canal examination by high resolution anoscopy reviewed independently by 2 anoscopists.
Results: The screening program was initiated in July 2002. Anoscopy images are captured by digital photography. The anoscopists and pathologists initially conferred on the anoscopy images and the histopathology and cytopathology to reach a consensus on diagnostic criteria. To date, 75 patients have undergone screening and partial results are available. High-risk (oncogenic) types of HPV were found in 89% of subjects. Pap smears were abnormal in 33/47(70%) of subjects: high-grade changes (HSIL) in 8/47 (17%) and low-grade changes (LSIL) in 18/47 (38%). Anal biopsies were abnormal in 33/59 (56%): LSIL in 15/59 (25%), HSIL in 17/59 (28%) and anal cancer 1/59 (1.7%). Observation by anoscopy was abnormal in 78%: warts, 56 %; LSIL, 46%; HSIL, 26%; Cancer 1%.
Conclusions: Significant abnormalities have been detected during anal cancer screening. These will require close follow-up and/or therapy.
Anal cancer screening should be implemented for gay men once adequate experience has been gained from studies such as this.

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