MSS06 Presentation Time: 4:10 PM

Purpose Hepatobiliary cancers are rare neoplasms that often present in an inoperable state. In 2020 there were an estimated, newly diagnosed 42,810 "liver and intrahepatic bile duct" cancers and 11,980 "gallbladder and other biliary" cancers. Patients often present with malignant biliary tract obstruction in the setting of locally advanced or metastatic disease and radiation is reserved for palliative reasons. In some patients who are dispositioned to liver transplant (LTX), radiation can be used as a bridging therapy. The purpose of this study was to look at our institutions experience in treating patients with a combination of external beam radiation (EBRT) and hepatobiliary brachytherapy (BT) as they await LTX. Materials and Methods Medical records were retrospectively reviewed at our institution and patients diagnosed with cholangiocarcinoma who were also treated with hepatobiliary brachytherapy were included. These patients were considered for LTX. Results Between 2019 and 2021 a total of 6 patients were treated with EBRT and BT. Median age was 69.5 (range 60-86) and median follow up was 15 months (range 3-33). 3 patients (50%) presented with nodal disease at initial workup while 0 patients were metastatic. The 3 patients with nodal disease all received chemotherapy prior to radiation with median time to RT being 10 months in these patients. In the node negative patients, median time to EBRT was 1 month after diagnosis. 5 patients underwent conventionally fractionated EBRT, 45 Gy in 25 fractions, while 1 patient underwent stereotactic body radiotherapy (SBRT), 30 Gy in 5 fractions. All patients received concurrent chemotherapy. After completion of EBRT or SBRT, all patients underwent BT, 15 Gy in 5 fractions. Afterwards, 5 patients received adjuvant maintenance chemotherapy. While on maintenance chemotherapy, 4 patients progressed to have metastatic disease. 2 patients were able to undergo LTX, 7 months and 13 months after BT. In these patients, final pathology showed that there was no viable tumor in the areas where they were treated with BT. At most recent follow up, 1 of the patients who underwent LTX was alive while the other was deceased from unknown causes. Otherwise, 2 other patients were alive but with metastatic disease, 1 was deceased, and 1 was lost to follow up but with metastatic disease. Median survival in this cohort was 19 months and overall survival was 50%. Conclusions In well selected patients whose goal is to undergo LTX, EBRT and BT can be used as a bridging therapy. Though this is a small cohort, BT did demonstrate high rates of local control in patients able to undergo LTX.