Outcomes of combined HCC-cholangiocarcinoma with adjuvant chemotherapy: An NCDB cohort.

4166 Background: Combined (or mixed) hepatocellular carcinoma-cholangiocarcinomas (cHCC-CCA) are rare liver tumors that are associated with poor prognosis. Patients (pts) presenting with limited disease are candidates for curative intent surgery. However, the role of adjuvant chemotherapy is not established. Methods: This retrospective review was based on the National Cancer Data Base (NCDB) participant user file (PUF) from 2014 to 2022. Patients were identified using International Classification of Diseases for Oncology, 3rd Edition (ICD-O-3) topography (C22.0–22.1) and histology code 8180 for cHCC-CCA. Adjuvant chemotherapy was defined as chemotherapy administered on or after 6 weeks from surgery. Patients who had neoadjuvant chemo were excluded. Analytical stage variable captures data from pathological stage, and if pathological stage is missing, then clinical stage is captured. Pathological stage data were available only for 13% of pts. Hence, analytical stage was used with about 31% data available. Frequency and proportions were reported for categorical variables. Median overall survival (mOS) and corresponding 95% confidence intervals were reported using Kaplan-Meier (KM) estimates. Cox’s proportional hazard model was used to report the adjusted and unadjusted analysis of OS. Hazard ratio (HR) and 95% confidence intervals were reported. All statistical analysis were performed using SAS version 9.4 software. Analysis of the NCDB PUF is exempt from IRB review. Results: 2815 pts with cHCC-CCA were identified, of which 2174 pts data were used for final analysis. 394 (18.1%) pts received adjuvant chemotherapy and 1780 (81.9%) did not receive any chemotherapy. 90% were above age 50 years; 76.2% were Caucasians and 67.7% were Male. Of those who received adjuvant chemotherapy, 162 (41.1%) received chemotherapy as single agent and 203 (51.5%) received chemotherapy as multiple agents. Among 668 data on analytic stage, 28.3% were stage 1, 36.8% were stage 2, 20.9% were stage 3 and 14.1% were stage 4. LVI data was also available for 549 patients. Of these, 38.1% had LVI present. Adjuvant chemotherapy was associated with improved OS compared to no chemotherapy (HR = 0.87 (95% CI: 0.77 – 0.99) p = 0.0296) in the entire population. Adjusted OS analysis for adjuvant chemotherapy with analytical stage showed significant survival benefit with adjuvant chemotherapy (HR = 0.73 (9%% CI: 0.56 – 0.96), p = 0.0261). Further adjustment for LVI was not performed due to large missing data. Conclusions: Adjuvant chemotherapy is not currently a standard for pts with cHCC-CCA after curative intent surgery. However, it appears to be associated with improved survival. Prospective studies evaluating the role of adjuvant therapy in this pt population are needed.