The Natural History of Anal Squamous Dysplasia – An 8 Year Follow Up Study
Suzan Kavusi, Michael R Peterson. University of California, San Diego, CA
Background: The natural history of HPV associated anal squamous dysplasia/anal intraepithelial neoplasia (AIN) has not been well studied, in contrast to cervical squamous dysplasia. A prior study was performed at our institution using a cross section of anal biopsies performed in 2004 that compared the morphologic grade of AIN to p16INK4A status and the results of HPV in situ hybridization. Using this prior data, we attempted to determine the outcome of the patients with AIN and correlate this with their prior AIN grade, p16INK4a status, and HPV in situ hybridization results.
Design: Data from the prior study was obtained, including the morphologic diagnosis, p16INK4a status, and the results of in situ hybridization for high-risk HPV subtypes. Follow up data, including both anal cytology preparations and anal biopsies, were collected from our pathology information system. Patients with less than 4 years of follow up were excluded. For the purposes of this study, ASCUS was considered synonymous with LSIL, and ASC-H with HSIL. The data from the prior study and the follow up material were compared.
Results: A total of 51 patients with an original biopsy diagnosis of LSIL (AIN1) or HSIL (AIN2&3) were included. The follow up period was between four to eight years from the time of initial diagnosis in 2004 (mean= 6.81 years). None of the patients in this cohort developed invasive squamous carcinoma. The follow up by both biopsy and cytology was notably variable. 5 of 13 (38%) patients with LSIL at the index biopsy were found to have HSIL at some point in their follow-up, while 6 of 38 (16%) of patients with HSIL at the index biopsy showed no evidence of HSIL in any of the follow up material. 24 of the total of 51 (47%) patients had at least one benign sampling (and many with multiple). The best predictor of subsequent HSIL on follow up was histological HSIL in the index biopsy (RR 2.189, p=0.0030). P16INK4a status was also significantly associated with HSIL on follow up (RR 1.768, p=0.0273). Interestingly, the presence of high-risk types of HPV was not significantly associated with finding HSIL on follow up (RR 1.441, p=0.0578).
Conclusions: In the time frame of this study, with a mean follow up of almost 7 year and a total of 339 patient-years, none of the patients developed squamous carcinoma. This suggests that AIN typically follows a variable but generally indolent course. The single best predictor of a diagnosis of HSIL in subsequent sampling is a morphologic diagnosis of HSIL, with p16INK4A positivity also being significantly associated with subsequent HSIL.
Wednesday, March 6, 2013 9:30 AM
Poster Session V # 105, Wednesday Morning