Lymph node dissection in resectable perihilar cholangiocarcinoma: a systematic review

Background Perihilar cholangiocarcinoma is usually unresectable at the time of diagnosis. Only few patients are candidates for a potential curative treatment. For those patients, prognosis is strongly related to negative resection margin and lymph node status. Thus, a certain benchmark of lymph node count is necessary to secure relevant lymph node recovery and to avoid understaging. However, the required minimum number of retrieved lymph nodes remains unclear for perihilar cholangiocarcinoma. The 7th American Joint Committee on Cancer tumor, nodes, metastases edition increased the requirement for the histologic examination of lymph nodes in perihilar cholangiocarcinoma patients from 3 to 15. The applicability of such recommendation appears difficult and questionable. Therefore, the purpose of this systematic review is to evaluate the number of retrieved lymph nodes for staging of patients undergoing surgery for perihilar cholangiocarcinoma. Methods The MEDLINE, EMBASE, and The Cochrane Library databases were systematically screened up to December 2014. All studies reporting the number of lymph node count in perihilar cholangiocarcinoma were included and assessed for eligibility. Results A total of 725 abstracts were screened and 20 studies were included for analysis, comprising almost 4,000 patients. The cumulative median lymph node count was 7 (2 to 24). A median lymph node count greater than or equal to 15 was reported in 9% of perihilar cholangiocarcinoma patients and could only be achieved in extended lymphadenectomy. Subgroup analysis revealed a median lymph node count of 7 (range 7 to 9), which was associated with the detection of most lymph node positive patients and showed the lowest risk for understaging patients. Lymph node count greater than or equal to 15 did not increase detection rate of lymph node positive patients. Conclusions This systematic analysis suggests that lymph node count greater than or equal to 7 is adequate for prognostic staging, while lymph node count greater than or equal to 15 does not improve detection of patients with positive lymph nodes.