Experts point to size threshold below which drug-eluting embolics lose optimum embolic effect

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While there is a trend towards using smaller sized particles to obtain better results with embolization, clinical and research experts at the recently held Global Embolization Symposium and Technologies (GEST EU; 24–27 June, Seville, Spain) agreed that there appeared to be a lower size limit, <100µm, below which drug-eluting beads did not have an effective embolic effect.

J Irurzun, Alicante, Spain, speaking on the distinguishing characteristics of drug-eluting embolics noted that there was a need to “verify the limits in the trend” towards using smaller sized drug-eluting embolics. He suggested that there was a need to understand the peculiarities (and characteristics) of individual drug-eluting embolics as well as to obtain a good suspension and slow infusion of 1–3ml/minute.

Julian Namur, Jouy en Josas, France, speaking on the in vivo behaviour of drug-eluting embolics told delegates that below a certain size, drug-eluting embolics did appear to be less effective.

In relation to the published literature, Hasmukh J Parjapati and colleagues’ paper published in the American Journal of Roentgenology (AJR) in December 2014, that set out to investigate the overall survival, efficacy, and safety of small (100–300µm) vs large (300–500 and 500–700µm) doxorubicin TACE using drug-eluting beads in patients with unresectable hepatocellular carcinoma (HCC), showed that TACE with 100–300µm sized drug-eluting beads is associated with significantly higher survival rate and lower complications than TACE with 300–500 and 500–700µm sized DEB.

At GEST EU 2015, Irurzun also noted that there was a case to repeat the PRECISION V trial using TACE with drug-eluting beads in the size range of 100–300µm.

The PRECISION V randomised trial compared conventional transarterial chemoembolization (cTACE) with TACE using DC Bead (BTG) for the treatment of cirrhotic patients with HCC. Two hundred and twelve patients with Child-Pugh A/B cirrhosis and large and/or multinodular, unresectable HCCs were randomised to receive TACE with DC Bead loaded with doxorubicin or cTACE with doxorubicin. Results from the trial showed that the hypothesis of superiority for DC Bead was not met. However, patients with Child-Pugh B, ECOG 1, bilobar disease, and recurrent disease showed a significant increase in objective response (p=0.038) compared to cTACE. DC Bead was associated with improved tolerability, with a significant reduction in serious liver toxicity (p<0.001) and a significantly lower rate of doxorubicin-related side effects (p=0.0001). The investigators concluded that TACE with DC Bead and doxorubicin is safe and effective in the treatment of HCC and offers a benefit to patients with more advanced disease.

Katerina Malagari, Athens, Greece, one of the investigators on the PRECISION V trial, echoed Irurzun’s views and told Interventional News that there did appear to be a size threshold around >100µm, below which drug-eluting embolics appeared to lose their embolic effect. There is, however, data demonstrating that between 100µm and 300µm, “there is increased effectiveness for these embolic agents,” she said. “In the light of this data, there is a case to be made for repeating the PRECISION V randomised trial in a using TACE with drug-eluting beads that are sized between 100 and 300µm, rather than 500 and 700µm as were those that were used in the original PRECISION V trial,” she noted.