353 Background: In the U.K., the annual incidence of anal cancer is up to 1.5 per 100,000 per year. Anal intra-epithelial neoplasia (AIN) is believed to be a precursor to squamous cell carcinoma whose incidence is still undetermined. This cell transformation has been associated with human papillomavirus (HPV) infections, in particular HPV 16 and 18. Our aim was to determine the frequency of progression to squamous cell carcinoma (SCC) of the anus in patients with known AIN. Methods: Study subjects with diagnosis of AIN from January 1st 1997 to January 1st 2009 were identified from a prospective database in a single hospital trust. The incidence of a subsequent diagnosis of anal SCC was determined from the local pathology and anal cancer database and cross referenced with the regional cancer database, Thames Cancer Registry. Results: We identified 397 patients (303 males) diagnosed with AIN in the database and HPV infection was identified in n= 395 patients. 15 (4%) patients were diagnosed with anal SCC a median of 5 months, Interquartile range 27 (2- 29 months) after their initial diagnosis. The distribution of AIN 1, 2 and 3 at presentation was 2, 1 and 12 respectively. Of interest, number of patients developed other HPV related cancers during the study period, such as vulva (n=8), cervical (n=3) and penile cancers (n=1). Conclusions: The incidence of anal cancer is higher in patients with known AIN compared to the general population. This justifies surveillance of these patients for anal and other HPV related intraepithelial neoplasia, however the nature of this, anoscopy or clinical examination alone, has yet to be determined.
Human papillomavirus and p16 in squamous cell carcinoma and intraepithelial neoplasia of the vagina
