ICC arises from intrahepatic bile duct cells and must be differentiated from HCC in clinical practice. A considerable amount of clinical and basic research has focused on HCC. However, the research on ICC generally inadequate, and the studies that have been conducted have small sample sizes9. The present study revealed some epidemiological, clinical pathological and prognostic characteristics of ICC from multiple aspects, indicating that ICC warrants sufficient attention. In this study, in the 102445 patients enrolled in between 1973 and 2014, the ratio of HCC to ICC was approximately 7.11:1, and the overall number of HCC cases was still significantly higher than the number of ICC cases. The proportions of male and female ICC patients were similar (50.6:49.4), while males accounted for a large proportion (75.7%) of the HCC patients. At the time of detection, more HCC patients (43.2%) were in the localized stage, while 30.4% of the ICC patients were already in the distant metastasis stage, and ICC was more poorly differentiated than HCC. In terms of the incidence trend, the incidence of HCC decreased by approximately 1.33% per year from 2011 to 2014, but the incidence of ICC increased rapidly, with an annual growth rate of 7.31% from 2002 to 2014. Some scholars believe that the current increase in ICC incidence may be due to the advantage of modern diagnostic methods to identify earlier lesions and biliary malignancies that were not previously diagnosed10. Of course, the increased incidence of ICC may be related to the increase in some newly recognized risk factors, such as viral hepatitis and nonviral chronic liver disease11,12. In addition, although the survival of the ICC patients increased over time, their median survival was still only 14 months. Currently, there is a lack of effective treatment for ICC to prolong patient outcomes13.
In addition to differences in pathogenesis, tissue origin, and clinical pathology, HCC and ICC also have significant differences in prognosis. Our study showed that the survival time of ICC patients was worse than that of HCC patients (median survival time of 14 vs. 19 months, p ≤ 0.01), which may be related to the high degree of malignancy in ICC. However, there is still a lack of clinical and basic research on ICC, which is worthy of further in-depth study. Compared with HCC, most cases of ICC are at an advanced stage when the cancer is discovered, the postoperative recurrence rate is high, and the overall treatment efficacy is poor14. Previous studies reported that the postoperative 5-year survival rate of ICC was approximately 20%, and the recurrence rate was approximately 50%7. Our results indicate that active surgery is still necessary. The competitive risk prognostic model used in this study showed that surgery could prolong the survival of ICC patients at different stages. Especially for stage III and IV patients, conservative treatment was considered suitable in the past. Currently, R0 resection surgery is the only effective treatment for ICC15. Unfortunately, studies have shown that only about 20–40% of ICC patients can be surgically removed16. Whether patients with intermediate and advanced ICC need aggressive surgical resection needs further discussion. Currently, intrahepatic metastasis is considered the most common type of ICC metastasis, followed by lymph node metastasis. Lymph node metastasis is widely regarded as a poor prognostic factor in ICC patients15. However, the need for active lymph node dissection in ICC is still controversial17. The controversy has focused on whether routine lymph node dissection should be performed and the extent of lymph node dissection15,18. Many scholars believe that lymph node dissection can benefit ICC patients and prolong their survival 19,20. It is believed that routine lymphadenectomy can reduce local recurrence and prolong the prognosis of patients4,21,22. However, Uenishi et al.23 believe that routine lymph node dissection cannot improve the overall survival rate of ICC patients and has a high incidence of surgical complications. Kim et al. also hold this viewpoint 24. Previous studies have shown that lymph node metastasis is an independent poor prognostic factor for ICC patients.25. The data considered in the present study showed that for patients with lymph node metastasis, active lymph node dissection was also beneficial. The median survival times of patients who underwent lymph node dissection and those who did not were 14 months and 5 months, respectively, and the difference was significant (p ≤ 0.01). This view is consistent with Bridgewater et al., who believe that intraoperative regional lymph node dissection can reduce the postoperative local recurrence rate and the biliary obstruction caused by lymph node invasion. In our experience, lymphadenectomy should be performed regardless of whether locally positive lymph nodes are found on preoperative examination or during surgery.