53 - Post-treatment PET/CT Dosimetry as a Predictor of Survival and Response in Patients with cholangiocarcinoma Treated with 90Y TARE Using Resin Microspheres

To evaluate the efficacy of TARE treatment of IHCC with ⁹⁰Y resin microspheres using a single-compartment model and correlate posttreatment PET/CT dosimetry with outcomes.

Materials and Methods:

This retrospective single–center study included consecutive adult patients with IHCC who underwent TARE with ⁹⁰Y resin microspheres prescribed using single compartment model between December 2019 and May 2024, who had posttreatment PET/CT (n=29). Per-lesion and overall response rates (complete response [CR], objective response, disease control, and duration of response) were assessed at imaging using the Response Evaluation Criteria in Solid Tumors, and overall survival (OS) was assessed using Kaplan-Meier analysis.

Results:

Among 29 patients (median age, 71 years (IQR, 65-77 years); 19 male patients) with IHCC, median tumor size was 6.4 cm (3.1 - 8.4), median tumor absorbed dose on PET/CT was 218 Gy (162 – 414), 83% of patients were treatment-naive, 15/29 patients had radiation segmentectomy while the remaining had radiation lobectomy. At 3 months, per lesion and overall (per- patient) CR was achieved in 18 (69%) and 15 (58%) of 29 patients, respectively. At 6 months, per- lesion rates of objective response and disease control were 95% and 100%, respectively, and per-patient rates were both 65%. There was no statistically significant difference in 3-month response between patients with D50 ≥ 300 (8 of 25 patients) Gy and those with D50 < 300 Gy (251 vs 163, p value = 0.5). At 3 months, using a delivered activity cut point of 1.5 GBq (AUC, 0.81 [95% CI: 0.63, 0.96]) predicted CR with 89% sensitivity. 6 patients had posttreatment liver surgery. Complete pathological necrosis was observed in 1 patient, while the remaining 5 patients had extensive necrosis ( > 90 %). Median overall survival was 14 months (95%CI:12, 28). OS probabilities were 56% (95% CI: 37, 84), 28% (12%-62%) and 14% (95% CI: 4, 49) at 1, 2 and 3-years posttreatment, respectively. Median TTP was 8.6 months (95% CI: 6.3, not reached). OS and PFS were higher in patients with D50 ≥ 300 Gy compared to those receiving < 300 Gy (p value = 0.04, and 0.01, respectively).

Conclusion:

Among patients with IHCC treated with ⁹⁰Y TARE, CR was achieved in 69% and 75% of patients at 3 and 6 months, respectively. In patients whose tumors received 300 Gy or more according to posttreatment dosimetry, a survival benefit was noted.