Higher Tumor Burden Neutralizes Negative Margin Status in Hepatectomy for Colorectal Cancer Liver Metastasis.

OBJECTIVE: The aim of this study was to examine if the prognostic significance of margin status in hepatectomy for colorectal cancer liver metastasis (CRLM) varies for different levels of tumor burden because hepatectomy indications for CRLM have been recently expanded to include patients with a higher tumor burden in whom achieving an R0 resection is difficult.

METHODS: Clinicopathological variables in an exploration cohort of 290 patients receiving hepatectomy in Japan for CRLM were investigated. R0 resection was defined as a margin width > 0 mm. Tumor burden was assessed using the recently introduced Tumor Burden Score (TBS), which was calculated as TBS2  = (maximum tumor diameter in cm)2  + (number of lesions)2 . The principal findings were validated using a cohort from the United States.

RESULTS: R1 resection rates significantly increased as TBS increased: 4/86 (4.7%) in patients with TBS < 3, 29/171 (17.0%) in patients with TBS ≥ 3 and < 9, and 9/33 (27.3%) in patients with TBS ≥ 9 (p < 0.001). R0 resection was significantly superior to R1 resection in patients with TBS ≥ 5; however, this was not the case for TBS ≥ 6, as confirmed by both univariate and multivariate analyses. Furthermore, prehepatectomy chemotherapy was associated with significantly improved survival for patients with TBS ≥ 8. Analysis of the validation cohort yielded similar results.

CONCLUSIONS: R0 resection appeared to have a positive impact on prognosis among patients with low tumor burden; however, this was not the case for patients with high tumor burden. As such, systemic treatment, in addition to surgery, may be central to achieving satisfactory outcomes in the latter patient population.