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Winter 2006 |
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ANAL CANCER, ANAL DYSPLASIA AND ANAL CONDYLOMA The incidence of anal squamous cell cancer (SCC) has increased 2.7 times in men and 1.7 times in women from 1973 to 2000. The current incidence in men and women is 1.6 and 1.5 per 100,000. This translates to 4-5 anal SCC cancers per year in the Westsound area. The greatest risk factor for anal SCC is infection with the human papilloma virus (HPV). HPV is a robust virus that can survive up to 6 hours outside the body and enter through any break in the skin or mucosa. Direct anal intercourse is not needed for anal warts to develop. Over 100 serotypes of HPV have been identified, though types 6 and 11 are the most common in anal warts. Serotypes 16 and 18 are associated with SCC in both the anal area and the cervix. Virus particles attach to native DNA and readily escape any host immune response. In 1997 over 24 million Americans were infected with HPV. While most anal warts are from non-oncogenic strains genital and anal lesions from oncogenic and non-oncogenic strains are identical to inspection and microscopic evaluation. HIV positive patients have a much higher rate of carcinoma in situ or anal intraepithelial neoplasm III (AIN III), reaching 30% in some series. Cervical intraepithelial neoplasm is also linked to HPV and the progression from CIN III to invasive carcinoma is clearly documented. Unfortunately, there has not been a clear like of AIN III to anal carcinoma. This has lead to controversies in management. Some advocate frequent anal Pap smear and anal colposcopy but this has not been shown to decrease the rate of anal cancer. In fact, anal Pap smear is much less reliable than cervical Pap smear. Cervical pap is obtained from the cervical transition zone under direct vision and yields 8,000 to 12,000 cells and 83-89% accuracy rate. In contrast, anal Pap smear is obtained blindly and yields only 200-300 cells. This achieves a 31-84% false negative rate and a 40-50% false positive rate. In contrast direct biopsy of visible lesions documents dysplasia in over 90% of cases. Treatment of anal condyloma and AIN III is problematic due to a high recurrence rate. Treatment of all visible lesions with excision, laser ablation of electrodessication all result in over a 30% recurrence rate for condyloma. Treatment with imiquimod (Aldara) for 6 weeks prior to surgical intervention has a lower recurrence rate, but the pain of treatment interferes with compliance. At surgery excisional biopsy of the largest lesions allows histologic confirmation of dysplasia, if |
present. Frequent re-inspections and re-treatments are needed for successful irradication. AIN III lesions should have re-inspection every 3 months. If invasive SCC is found, these are excised with negative margins at the anal margin or perineum. Anal canal lesions achieve excellent results with primary chemoradiation, preserving radical surgery for residual cancer or recurrence after chemoradiation. NORTH COUNTY CLINIC PELVIC FLOOR FORUM
RELAY FOR LIFE REMEMBER: COLORECTAL CANCER IS PREVENTABLE!!! |
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Kitsap ColoRectal Surgery, Johnny B. Green, MD, FACS, FASCRS |
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