Depth of tumor invasion better predicts prognosis than the current American Joint Committee on Cancer T classification for distal bile duct carcinoma

Abstract

Background: The American Joint Committee on Cancer (AJCC) T classification system for cholangiocarcinoma does not take into account the unique pathologic features of the bile duct. As such, the current AJCC T classification for distal cholangiocarcinoma may be inaccurate.

Methods: A total of 147 patients with distal cholangiocarcinoma were identified from a single institution database. The prognostic importance of depth of tumor invasion relative to the AJCC T classification system was assessed.

Results: The AJCC T classification was T1 (n = 11, 7.5%), T2 (n = 6, 4.1%), T3 (n = 73, 49.7%), or T4 (n = 57, 38.8%). When cases were analyzed according to depth of tumor invasion, most lesions were > or =5 mm (<5 mm, 9.5%; range, 5-12, 51.0%; >12 mm, 39.5%). The AJCC T classification was not associated with survival outcome (median survival, T1, 40.1 months; T2, 14.8 months; T3, 16.5 months; T4, 20.2 months; P = .17). In contrast, depth of tumor invasion was associated with a worse outcome as tumor depth increased (median survival, <5 mm, not reached; range, 5-12, 28.9 months; >12 mm, 12.9 months; P = .001). On multivariate analyses, tumor depth remained the factor most associated with outcome (<5 mm; hazard ratio [HR] = referent vs 5-12 mm; HR = 3.8 vs >12 mm; HR = 6.7 mm; P = .001).

Conclusion: The AJCC T classification for distal cholangiocarcinoma does not accurately predict prognosis. Depth of the bile duct carcinoma invasion is a better alternative method to determine prognosis and should be incorporated into the pathologic assessment of resected distal cholangiocarcinoma.

Fig 1

Kaplan-Meier survival analysis stratified according to the current 6th edition of the AJCC Cancer Staging Manual T classification staging scheme. There was no significant survival difference among the groups (P = .17).

Fig 2

Kaplan-Meier survival analysis stratified according to depth of tumor invasion. Unlike the American Joint Committee on Cancer (AJCC) T classification, depth of tumor invasion was a strong predictor of long-term outcome. The 5-year survival rates of patients with distal cholangiocarcinoma lesions measuring <5 mm, 5–12 mm, and >12 mm were 69.3%, 21.5%, and 4.1%, respectively (P < .0001).

Fig 3

Kaplan-Meier survival analysis stratified according to the current 6th edition of the AJCC Cancer Staging Manual stage grouping scheme. There was no significant survival difference among the stage groups (P = .15).

Fig 4

Kaplan-Meier survival analysis based on our proposed stage grouping that incorporates depth of tumor invasion. Unlike the American Joint Committee on Cancer (AJCC) stage grouping, the proposed new stage grouping was a strong predictor of long-term outcome. The 5-year survival rates of patients with distal cholangiocarcinoma of proposed stages I, II, and III were 69.3%, 28.7%, and 8.5%, respectively (P < .0001).