(Saturday, 3/30/2019)
Room: Exhibit Hall
Purpose: Yttrium-90 (Y-90) microspheres are used for the treatment of unresectable hepatic metastases. This study examines whether dosimetry related factors serve as prognostic indicators of clinical outcome, including overall survival (OS) and progression-free survival (PFS).
Methods: 32 patients with hepatic metastases treated with Y-90 were included in this study. Treatment dose was prescribed and the initial activity required to deliver such dose was calculated. OS and PFS probabilities were determined using Kaplan-Meier actuarial analysis. Median Y-90 activity administered, pulmonary shunt, and resulting lung activity were calculated. Patients were stratified into high and low activity groups with respect to each parameter’s median value. Statistical differences of OS and PFS between the two groups were compared using log-rank test.
Results: All tumors were metastatic with the most common primary site being colorectal adenocarcinoma (68.8%). Median follow-up duration was 10.5 months. Median Y-90 activity delivered was (40.8 ± 22.3 mCi). Fourteen patients received activity higher than the median value (46.3 ± 23.4 mCi). Eighteen patients received lower activity (30.1 ± 7.5 mCi; p < 0.001). Higher median PFS was observed with higher activity compared to lower activity (28.2 ± 3.9 vs. 9.3 ± 1.4 months, p < 0.001). The trend showed higher activity improved median OS (28.4 ± 3.7 vs. 10.8 ± 3.6 months, p = 0.068). Median OS probability was 80.8 % for high activity vs. 57.1 % for low activity at the median follow-up time.
Conclusion: Our results suggest that the initial activity delivered to patients could potentially serve as a prognostic indicator of PFS. More patients and longer follow-up time need to be included in a future analysis to determine whether total activity could also be used as OS indicator. Other dosimetric parameters such as lung activity and pulmonary shunt did not correlate with OS and PFS.
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