(HealthDay News) — Available screening and identification of human papillomavirus likely contributed to the increased incidences of squamous cell carcinoma of the anal canal (SCCA) and anal carcinoma in situ (CIS) after 1997, according to research published online March 18 in Journal of Clinical Oncology.

Rebecca A. Nelson, of the City of Hope National Medical Center in Duarte, Calif., and colleagues analyzed data from the Surveillance, Epidemiology, and End Results Program to determine the incidence trends from 1973 to 2009.

According to the researchers, the slope of the incidence rates increased significantly in 1997 with a risk ratio (RR) of 2.2, when they compared the incidences between 1997 to 2009 and 1973 to 1996. Annual percent changes increased significantly for all stages of SCCA and was the greatest for anal carcinoma in situ (CIS). After 1997, RR was significantly higher in women than in men for localized (1.2) and regional stages of SCCA (1.5), but significantly lower for CIS (0.3). Adenocarcinoma annual percent changes remained stable during this time period.

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“This study is the first to demonstrate the dramatic rise in incidence of CIS and SCCA in the context of the stable rates of adenocarcinoma in situ and anal adenocarcinoma,” the authors write. “We suggest that high-risk men as well as women with high-grade anogenital HPV-related epithelial changes be considered for anal cancer screening.”

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