Prospective Study of Systemic Yttrium-90 Elution during Radioembolization of Hepatic Metastases

Clinical question
Does blood radioactivity differ based on Y90 delivery method?

Take away point
Y90 delivery with 50% contrast in saline solution resulted in a significant blood radioactivity increase compared to delivery in D5W.

Reference
Alexander ES, Pantel AR, Carlin SD, Beckmann N, Mick R, Pryma DA, Soulen MC. Prospective Study of Systemic Yttrium-90 Elution during Radioembolization of Hepatic Metastases. J Vasc Interv Radiol. 2020 Dec;31(12):2007-2013.e1. doi: 10.1016/j.jvir.2020.08.011. Epub 2020 Nov 2. PMID: 33143997.

Click here for abstract

Study design
Single center prospective

Funding Source
None

Setting
Academic hospital. University of Pennsylvania, Philadelphia, PA

Figure


Figure. Fraction of free 90Y in the blood was significantly higher for patients treated with dilute contrast medium than in those treated with D5W (median, 0.5% of injected activity vs 0.2%; P 1⁄4 .001).

Summary

Manufacturers advise administering Y90 with D5W or sterile water to avoid exposing the resin microspheres to ionic solutions. Because Y90 is incorporated on the resin microspheres by an ion exchange reaction, exposure to ionic solutions may elute Y90 from the microsphere and lead to systemic delivery. Administration with sterile water or D5W and using intermittent contrast injection hinders real time monitoring and may increase the risk of non-target delivery due to early stasis or reflux. An alternative is to administer the microspheres with a nonionic contrast instead of D5W or sterile water, to allow real time visualization. The purpose of this investigation was to estimate and compare blood radioactivity after resin microsphere Y90 delivery flushed with dilute nonionic contrast compared to D5W

The authors prospectively evaluated 20 patients with hepatic metastases during their first Y90 radioembolization treatment. Y90 was dosed via the body surface area method. Microspheres were delivered either by flushing with D5W and intermittent contrast injection per the manufacturer instructions or by flushing with dilute 50% Isovue 300 in saline. Blood was drawn prior to the treatment, immediately after Y90 delivery, and at 10, 20, 60, and 120 minutes after Y90 delivery. Patients were observed for 1 month to evaluate for adverse events. Blood samples were analyzed using a gamma counter to measure counts per minute. The percent of radioactivity elution in the blood was calculated.

10 participants received Y90 with D5W and 10 participants received Y90 with diluted 50% Isovue 300. The percentage of free Y90 in the blood was significantly greater in subjects who received Y90 with Isovue 300 compared to D5W. Y90 flushed with dilute 50% Isovue was associated with shorter fluoroscopy times and lower air kerma compared to delivery with D5W . Technical success rate was 100%. One D5W treatment and two Isovue treatments were terminated early for stasis. There were zero immediate procedural complications. 12 participants experienced an adverse event at one month, eight of which were postembolization syndrome.

Commentary

The authors prospectively evaluated 20 patients receiving Y90 with either D5W, as per the manufacturer’s recommendation, or with Isovue 300 mixed with saline. Interestingly, the fraction of free Y90 in the blood was higher when the dose was flushed with Isovue 300, as the nonionic contrast should not theoretically contribute to Y90 elution. However, as the authors described, the blood radioactivity difference is of uncertain clinical significance because of the small absolute dose. Further, the increase in blood radioactivity may be offset to a degree by the decrease in fluoro time. Also, this study did not demonstrate a discrepancy in non-target embolization or early termination for stasis between the two delivery methods, a finding that has been described in other, larger studies. If this difference does in fact exist, then the lack of real time observation and the risk of non-target embolization when delivering 90 without contrast is worrying. If found to be safe, Y90 delivery with contrast provides a solution to the problem. As the authors mention, the study is limited by the small sample size, lack of patient randomization to treatment groups, and the relatively short 2-hour sampling time compared to the 64.1 hour Y90 half-life. Further evaluation with a larger, randomized cohort, and lengthier blood radioactivity analysis, would help to better clarify the safety and feasibility of Y90 delivery with dilute contrast as a solution.

Post Author
Maxwell Cretcher, D.O.
Integrated Interventional Radiology Resident, PGY-4
Department of Interventional Radiology
Dotter Interventional Institute, Oregon Health and Science University
@MCretcher