The role of PET-CT in the management of anal cancer

Background Anal cancer is an uncommon malignancy of the gastrointestinal tract. Pre- and post-treatment staging of disease is often 230 Tech Coloproctol (2011) 15:215–253 123 inaccurate, however. An emerging tool in non-invasive tumor staging is PET/CT, whose role in the clinical management of anal cancer is yet to be defined. Methods At our Department, 53 consecutive patients diagnosed with anal cancer underwent PET/CT and computed tomography (CT) at pre-treatment workup, and then PET/CT and anal biopsy at 1 and 3 months follow-up after the end of treatment. Pre- and post-treatment PET/CT data sets were compared. Results At pre-treatment assessment, anal cancer was identified by PET/CT in 47 patients (88.7%) and by CT in 40 patients (75%). The detection rates rose to 97.9% with PET/CT and to 82.9% with CT (P = 0.042) when the 5 patients who had undergone surgery prior to this assessment and whose margins were positive at histological examination were censored. Perirectal and/or pelvic nodes were visualized by PET/CT in 14 patients (26.4%) and by CT in 7 (17.5%). Sentinel node biopsy was superior to both PET/CT and CT in detecting inguinal lymph nodes. PET/CT upstaged 39% of patients and downstaged 25%. Radiation fields were changed in 11% of patients. PET/CT at 3 months was more accurate than PET/CT at 1 month in evaluating outcomes after chemoradiotherapy treatment: sensitivity was 100 vs. 66.6%, and specificity was 97.4 vs. 92.5%, respectively. The median follow-up was 20.3 months. Conclusions In this series, PET/CT detected the primary tumor more often than CT. Staging of perirectal/pelvic or inguinal lymph nodes was better with PET/CT; however, upstaging related to lymph node metastases might have been overestimated. Sentinel node biopsy was more accurate in staging inguinal lymph nodes. PET/CT should be performed at 3 months after the completion of treatment for assessing treatment efficacy.