The inguinal lymph nodes as regional lymph nodes in anal canal adenocarcinomas: a nationwide database analysis in Japan

PurposeTo establish if it is appropriate to treat the inguinal lymph node (LN) of anal canal adenocarcinoma (ACA) as the intermediate LN according to the Japanese classification.MethodsThe characteristics of 346 ACA patients were examined from the nationwide registry. The effect of LN dissection was evaluated using the therapeutic value index (TVI). Furthermore, the prognostic classification ability of N factors and stage was evaluated using Akaike's information criterion (AIC), the concordance index (C-index), and the 5-year overall survival (OS) rate.ResultsThe rate of metastasis of the inguinal LN was 7.5% and the TVI was 3.05. Evaluation using AIC and the C-index showed better results when the inguinal LN was treated as the intermediate LN. The 5-year OS rate for 66 patients with perirectal or intermediate LN metastasis, 7 with inguinal LN metastasis, and 13 with inguinal and perirectal or intermediate LN metastasis were 49.2%, 68.6%, and 47.6%, respectively. When inguinal LN metastases were treated as N3, the 5-year OS rates were 66.7% for those with T1N3 and T2N3 disease, and 49.2% for those with T3N3 disease.ConclusionsThe inguinal LN of ACA was evaluated and staged as the intermediate LN to devise an appropriate treatment strategy.