Intrahepatic cholangiocarcinoma: a dose threshold evaluation in those undergoing transarterial radioembolization.

Background: Intrahepatic cholangiocarcinoma (ICC) is a rare primary hepatic malignancy. One of the treatment strategies which has shown some promise is transarterial radioembolization (TARE). However, data on dose thresholds, arguably the most important aspect of the procedure itself, is still limited. The study aims to evaluate the relationship between dose to tumor and radiologic response in intrahepatic cholangiocarcinoma patients undergoing transarterial radioembolization. Methods: Twenty-patients who underwent treatment for 26 tumors were retrospectively reviewed. Radiologic response at 3-month was evaluated and post yttrium-90 bremsstrahlung single photon emission computerized tomography computed tomography was evaluated to determine tumor dose. Other factors such as particle load and activity per particle were evaluated. Results: The mean tumor dose for those with progressive disease or stable disease, partial response, and complete response (CR) by European Association for the Study of Liver (EASL) criteria for the glass cohort was 294±0, 465.4±292.4 and 951.8±666.5 Gy respectively (P=0.039). A receiver operating characteristic (ROC) curve analysis of tumor dose demonstrated an area under the curve (AUC) of 0.738 (P=0.038) with Youden-index analysis demonstrated a cutoff point of >541.7 Gy (sensitivity: 55.56%; specificity: 92.86%) for the glass cohort. Significantly longer survival was noted in those who achieved a CR [HR: 4.79 (95% CI: 1.41-16.25)] and those treated with glass as compared to resin [HR: 5.02 (95% CI: 1.23-20.55), P=0.025]. Of the 17 treatments in 13 patients which were done concomitantly with chemotherapy 7/17 (41.2%) required a delay in chemotherapy, however all patients reinitiated chemotherapy after a delay. Conclusions: There appears to be a relationship between tumor dose and radiologic response, with this study suggesting a target of ≥541.7 Gy being warranted in patients receiving treatment with glass microspheres.