90Y Radioembolization Dose Required for HCC Tumor Response
Tumor response can be predicted after Yttrium-90 (90Y) radioembolization in patients with hepatocellular carcinoma (HCC) by analyzing the delivered tumoral radiation dose by internal pair-production positron emission tomography (PET) dosimetry, according to a study published in the International Journal of Radiation Oncology.
“Dosimetry remains one of the greatest challenges in optimizing treatment of liver malignancies by 90Y radioembolization,” the authors wrote in the study.
In this prospective study, 35 patients with primary and secondary liver tumors undergoing 90Y treatment from 2012 to 2014 were recruited; 27 patients with HCC with a total of 38 tumor lesions met the inclusion criteria and were included for analysis.
All patients underwent technically successful 90Y radioembolization with 20 patients (74%) receiving lobar treatment and 7 patients (26%) receiving segmental treatment. Immediately after radioembolization, time-of-flight PET imaging was performed and voxel values were converted into 90Y activity. PET images were used to determine radioemolization dose and image segmentation was performed with volumetric analysis of dose deposition within tumors. Radiologic response to treatment was assessed by imaging at 1 month follow-up, then ever 3 months after treatment.
According to modified RECIST 1.1 response criteria, objective response was achieved in 84% of the treated HCC tumors, with 55% demonstrating complete response and 29% demonstrating partial response. In the remaining 6 nonresponders, 4 had stable disease (11%) and 2 had progressive disease (11%).
Responders had a higher median 90Y tumor dose than nonresponders (225 Gy vs 83 Gy, P < 0.01). Logistic regression models show tumor dose (P = 0.002) strongly predicted objective response. All nonresponders had tumor dose <200 Gy.
“This study is hypothesis generating in suggesting a 90Y dose threshold with acceptable specificity for HCC response. We observed an 84% objective response for HCC, and our findings suggest a 200-Gy threshold as being specific for treatment response. Larger follow-up observational studies will be needed to validate dose thresholds that translate to meaningful clinical outcomes,” the researchers concluded.
Chan KT, Alessio AM, Johnson GE, et al. Prospective trial using internal pair-production positron emission tomography to establish the yttrium-90 radioembolization dose required for response of hepatocellular carcinoma. Int J Radiat Oncol Biol Phys. 2018;101(2):358-365. doi: 10.1016/j.ijrobp.2018.01.116. Epub Feb 9 2018.