Reappraisal of the T Category for Solitary Intrahepatic Cholangiocarcinoma by Tumor Size in 611 Early-Stage (T1-2N0M0) Patients After Hepatectomy: a Surveillance, Epidemiology, and End Results (SEER) Analysis.

Background: The association between tumor size and survival in patients with intrahepatic cholangiocarcinoma (ICC) after hepatectomy is controversial, and the T category in the American Joint Committee on Cancer (AJCC) stage for ICC is a topic of debate.

Methods: Data from 611 T1-2N0M0 ICC patients classified by the AJCC 8th edition who underwent hepatectomy were extracted from the Surveillance, Epidemiology, and End Results (SEER) database during 1988-2015. Cancer-specific survival was evaluated using Kaplan-Meier analysis. The optimal cutoff value of solitary tumor size was used an adjusted p value approach to discriminating patient survival.

Results: In the AJCC 8th staging system, using a 5-cm cut-off value of tumor size for solitary ICC without vascular invasion (S/VI-) was not associated with survival in T1 category (p = 0.201), and multifocal ICC with vascular invasion had a worse survival than solitary ICC with vascular invasion (S/VI+) in T2 category (p = 0.014). Tumor size was a prognostic factor for both S/VI- and S/VI+, the optimal cutoff value of tumor size was obtained 8 cm for S/VI- and 3 cm for S/VI+. S/VI- ≤ 8 cm had a similar survival to S/VI+ ≤ 3 cm (p = 0.126), S/VI- > 8 cm had a similar survival to S/VI+ > 3 cm (p = 0.655), and multifocal ICC had a similar survival with S/VI- > 8 cm (p = 0.159) and S/VI+ > 3 cm (p = 0.196). When the cohort was divided into two groups-new T1 (S/VI- ≤ 8 cm and S/VI+ ≤ 3 cm) and new T2 (S/VI- > 8 cm, S/VI+ > 3 cm and multifocal ICC)-significant survival difference was observed (p < 0.0001).

Conclusions: The discriminatory power of the AJCC 8th edition for solitary ICC could be further enhanced by subdividing tumors according to size and vascular invasion (8 cm for S/VI- and 3 cm for S/VI+).