Introduction:
This population-based study aims to evaluate the survival benefits of radiotherapy, chemotherapy, chemoradiotherapy, and non-chemoradiotherapy in patients with unresectable intrahepatic cholangiocarcinoma (ICC)_

Material and methods:
Methods: We utilized the Surveillance, Epidemiology, and End Results (SEER) database's SEER*stat software (version 8.3.5) to gather patient data diagnosed with unresectable ICC from 2000 to 2018. Survival curves were plotted using the Kaplan-Meier method, comparing the overall survival (OS) and cancer-specific survival (CSS) among patients who underwent radiotherapy, chemotherapy, chemoradiotherapy, or no therapy at all. Univariate and multivariate Cox regression models were employed to analyze the prognostic factors affecting these unresectable ICC patients.

Results:
Results: From 2000 to 2018, we identified 11,753 cases of unresectable ICC from the SEER database. Out of these, 4,531 patients (38.5%) underwent chemotherapy alone, 482 patients (4.1%) underwent radiotherapy alone, and 996 patients (8.5%) received a combination of both. A total of 5,744 patients (48.9%) did not receive chemoradiotherapy. The median OS for patients receiving chemotherapy alone was 8 months (95% CI, 8-9 months), radiotherapy alone was 7 months (95% CI, 6-8 months), chemoradiotherapy was 12 months (95% CI, 11-13 months), and for those not receiving chemoradiotherapy was 3 months (95% CI, 3-3 months). The CSS findings were consistent with the OS results. The Cox regression models indicated that patient age, sex, grade classification, tumor diameter, and treatment modality were independent prognostic factors for unresectable ICC patients (P<0.05).

Conclusions:
Conclusion: Chemoradiotherapy can enhance the OS and CSS of patients with unresectable ICC, compared to the use of chemotherapy or radiotherapy alone.