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Whereas malignancies including HCC and colorectal cancer metastatic to the liver have evidence guiding optimal dose-response thresholds for Y90 radioembolization, 90Y in the treatment of intrahepatic cholangiocarcinoma (ICC) lacks clear guidelines regarding personalized dosimetry. This retrospective study aims to establish a preliminary dose-response threshold for optimizing tumor control post-90Y radioembolization with resin microspheres. A total of 33 patients were reviewed for this study, of which 25 patients met inclusion criteria (diagnosis of ICC, availability of planning SPECT/CT, availability of follow-up imaging at 1 month, 90Y-radioembolic treatment with resin microbeads, and no concurrent systemic therapy). Of these, 17 patients - representing 28 treated hepatic lobes - were not censored due to exclusion criteria (prior intra-arterial therapy, additional intra-arterial therapy before follow-up imaging, and/or tumor not differentiable from background liver). At the 1-month time point when evaluated by RECIST criteria there were 25 responders (SD, PR, or CR) and 3 non-responders (PD). 90Y resin microsphere dose-response relationship was explored by via 3 analyses: identifying the threshold at which AUC was maximized using logistic regression, identifying the minimal dose above which we saw no non-responders, and exploring a potential upper-limit for safe dosing. Dose-response analyses performed in Python. The responder group received significantly (p110 Gy and the dose at which AUC was maximized was 97 Gy. No significant Spearman's correlation was seen between radioembolic dose delivered to normal liver and lab-based hepatotoxicity CTCAE measures at follow-up in either the complete cohort (p >0.6), nor in the subcohort of patients undergoing first-time unilateral treatment (p >0.7), though we did not a trend toward significant (p< 0.09) increases in bilirubin with higher radioembolic doses. Our study suggests that a dose of no less than 110 Gy should be delivered for radioembolic treatment of ICC with Y90 resin microspheres. Further research is warranted to validate these findings in a larger cohort, investigate whether this relationship holds over longer follow-up periods, and ascertain the upper limit of the maximum safe dose.
Rincón-Hekking et al. (Wed,) studied this question.