Stage Evaluation of Cystic Duct Cancer

Abstract

Purpose: Cystic duct cancers (CDCs) have been classified as extrahepatic bile duct cancers or gallbladder cancers (GBCs); however, it is unclear whether their clinical behavior is similar to that of distal extrahepatic bile duct cancers (DBDCs) or GBCs.

Materials and methods: T category of the CDCs was classified using current T category scheme of the GBCs and DBDCs, and clinicopathological factors were compared among 38 CDCs, 345 GBCs, and 349 DBDCs. We modified Nakata's classifications (type 1, confined within cystic duct [CD]; combined types 2-4, extension beyond CD) and compared them.

Results: No significant overall survival (OS) difference was observed between the patients with CDC, GBC, and DBDC. The T category of GBC staging was more accurate at distinguishing OS in patients with CDC than the DBDC staging. Patients with T3 CDC and GBC showed a significant OS difference when using the T category for GBC staging, while those with T1-T2 CDC and GBC showed no significant difference. In contrast, the T category of DBDC staging did not show any significant OS difference between patients with T1-T2 CDC and DBDC or T3 CDC and DBDC. Patients with type 1 CDC had significantly better OS than those with combined types.

Conclusion: Unlike GBCs and DBDCs, CDCs exhibit distinct clinicopathological characteristics. The OS is better when the CDC confines within the CD, compared to when it extends beyond it. Therefore, we propose a new T category scheme (T1, confined to CD; T2, invaded beyond CD) for better classifying CDCs.

Keywords: Cystic duct; Distal extrahepatic bile duct; Gallbladder; Neoplasms; T category.

Fig. 1.

Schematic drawing, and representative gross, radiologic, and microscopic images of cystic duct cancers based on original Nakata’s classification. CBD, common bile duct; CD, cystic duct; GB, gallbladder.

Fig. 2.

The overall survival (OS) comparisons according to cystic duct cancer (CDC) according to the T category of gallbladder cancer (GBC) (A) and distal extrahepatic bile duct cancer (DBDC) (B) schemes. (A) When the OS was compared according to the T category of the GBC scheme, the median OS time in CDC patients with T3 was 24.0 months. In contrast, those with T1-T2 CDC did not reach the median OS (5-year OS rate, 57.1%). A significant OS difference was observed (p=0.029). (B) When the OS was compared according to the T category of the DBDC scheme, the median OS times in CDC patients with T1-T2 and T3 categories were 26.0 and 43.0 months, respectively. No significant survival difference was observed (p=0.779).

Fig. 3.

The overall survival comparisons among cystic duct cancer (CDC), gallbladder cancer (GBC), and distal extrahepatic bile duct cancer (DBDC) patients based on the T1-T2 and T3 categories of the GBC and DBDC scheme were applied. (A) When the GBC scheme was applied, overall survival rates were not different between patients with T1–T2 GBC and T1-T2 CDC (p=0.721). (B) However, patients with T3 CDC had significantly better overall survival than those with T3 GBC (p=0.008). When the DBDC scheme was implemented, the overall survival rates were not different between patients with T1-T2 DBDC and T1-T2 CDC (p=0.168) (C) and between patients with T3 CDC and T3 DBDC (p=0.522) (D).

Fig. 4.

The overall survival comparisons of 30 patients with debated cystic duct cancer (CDC), T1-T2 and T3 gallbladder cancers (GBCs), and T1-T2 and T3 distal extrahepatic bile duct cancers (DBDCs). The overall survival of the patients with 30 debated CDC group (5-year overall survival, 28.4%) was worse than those with T1-T2 DBDC (48.8%, p=0.065) but better than those with T3 GBC (14.6%, p=0.006). In addition, patients with T1-T2 GBC (64.5%) had a better overall survival than those with T1-T2 DBDC (48.8%, p=0.003).

Fig. 5.

The overall survival comparisons of patients with cystic duct cancer (CDC) by the original (A) and modified (B) Nakata’s classification. (A) Patients with type 1 CDC had a tendency toward better overall survival than those with other types (p=0.056, overall comparison). A tendency of overall survival difference was observed between types 1 and 2 CDCs (p=0.228), types 1 and 3 CDCs (p=0.060), and types 1 and 4 CDCs (p=0.060) by pair-wise comparisons. However, no significant overall survival difference was observed between patients with types 2 and 3 (p=0.399), types 2 and 4 (p=0.938), and types 3 and 4 (p=0.690) CDCs. (B) Cases with types 2, 3, and 4 CDCs were merged into a combined group, and its overall survival compared with type 1 CDC. Patients with type 1 CDC had significantly better overall survival than those in the combined group (p=0.010).

Fig. 6.

Proposed schematic representation of the new system for cystic duct cancer. (A) pT1: confinement in cystic duct. (B) pT2: invades adjacent organ or structure beyond the cystic duct.