Primary adenocarcinoma of the anus: a 22-year SEER population database analysis

Abstract

e15072 Background: Most anal canal cancers consist of squamous cell carcinoma (SCCA). Adenocarcinoma (AdenoCa) is rare and accounts for approximately 10% of anal cancers. A search of the SEER database (1973 to 2005) was carried out to evaluate the pattern of radiation (RT) and surgical treatment. Impact of the treatment on overall survival (OS) was evaluated. Methods: The search of the SEER database revealed 1,008 pts who had pathologically confirmed anal cancers with either SCCA or AdenoCa. All pts had single diagnosis of anal cancer with localized disease without nodal involvement. Excluded were pts with unknown use of surgery or radiation. Kaplan-Meier estimates and Cox-Mantel model were used to calculate and compare survival rates. Results: Median age of all pts was 57 years (range 29 to 99). For the SCCA group, median age was 57 years (range 29 to 99), which was younger than the AdenoCa group with median age of 74 years (range 37 to 92). Among the 1,008 pts, 954 had SCCA (94.6%), and 54 had AdenoCa (5.4%). Within the SCCA group, 14 (1.5%) had abdominoperineal resection (APR) in combination with external beam RT, and 795 (83.3%) had RT only with non-APR local surgical treatment inclusive of excision. Remaining 145 SCCA pts (15.2%) had non-APR local surgical treatment only without RT or had no treatment. Within the AdenoCa group, 10 (18.5%) had APR in combination with external beam RT, and 21 (38.9%) had RT only with non-APR local surgical treatment inclusive of excision. Remaining 23 AdenoCa pts (42.6%) had non-APR local surgical treatment only without RT. None of the adenoCa pt had no treatment. OS at 10 years was superior for pts with SCCA vs. AdenoCa (64.9% vs. 25.8%, p<0.05). Among the SCCA subset, there was no signficant difference in the 10-yr OS between the APR versus the RT pts (71% vs. 65%, p=0.78). On the other hand, among the AdenoCa subset, pts who had APR had better 10-yr OS than RT pts (53.8% vs. 0%, p=0.03) Conclusions: For localized anal SCCA, RT yielded equivalent overall survival as compared to APR. On the other hand, pts with localized anal adenoCa appeared to do worse when APR was omitted. RT only without APR might not be sufficient treatment in these patients. This database lacks information on use of chemotherapy and local disease control. Omission of APR in pts with anal canal adenoCa should be cautiously weighed. No significant financial relationships to disclose.