The concept of "borderline resectable" was recently introduced to the field of surgery for pancreatic cancer, and surgical outcomes for this disease with extremely dismal prognosis have improved since the introduction of this concept. However, no such concept has yet been introduced to the field of surgery for hilar cholangiocarcinoma (HCca).

To determine a definition and criteria for "borderline resectable" in the field of surgery for HCca.

Retrospective analysis of 88 patients undergoing curative-intent surgery for HCca at our institution between May 1992 and December 2008 to clarify independent prognostic factors.

Survival outcomes were obtained for these 88 patients, with a 5-year overall survival rate of 31.8%. Independent factors predictive of cancer death were determined by multivariate analysis to be the presence of regional lymph node metastasis (LNM) and pathological confirmed vascular invasion (VI). Cumulative survival rates of 23 patients with both LNM and VI who underwent surgery were significantly worse than those of the remaining 65 surgically treated patients and similar to those of 26 patients who were considered to have unresectable disease and treated with non-surgical multidisciplinary treatment during the same study period.

Outcomes of surgery for cases of HCca showing regional LNM and VI were no better than those of non-surgical treatment for unresectable disease. Coexistence of these two factors indicates oncologically dismal condition and thus such cases should be considered "borderline resectable." Treatments additional to surgery are required for "borderline resectable" cases to obtain better outcomes.