Liquid-filled balloon brachytherapy using Ga-68 is effective and safe because of the short 68-minute half-life - Results of a feasibility study in the porcine coronary overstretch model

Background-Liquid-filled balloons for coronary brachytherapy provide signif icant advantages over solid sources in dose homogeneity but carry the risk of life-threatening radiointoxication after balloon rupture and laboratory contamination in case of a spill. We hypothesized that the positron emitter Ga-68, with a half-life of only 68 minutes, was well suited to overcome th ese safety obstacles while providing full therapeutic efficacy. Methods and Results-The feasibility, efficacy, and safety of Ga-68 liquid-f illed balloon brachytherapy were investigated in the porcine coronary overs tretch model. Four groups of 5 balloon-induced coronary lesions were irradi ated with 8, 12, 16, and 24 Gy targeted to the adventitia. Ten unirradiated lesions served as controls. Segments treated with 16 or 24 Gy exhibited ma rked suppression of neointimal proliferation at 28-day follow-up, with quan titative parameters of intraluminal proliferation reduced to <20%. This ben eficial effect was not compromised by untoward edge effects. Uninjured but irradiated vessels did not show histological signs of radiation damage. The 68Ga whole-body dose due to balloon rupture was estimated to be 5 rem/50 m Ci treatment activity and compared favorably with that of Re-188 (78 rem/50 mCi). Conclusions-Ga-68 positron radiation suppresses neointimal proliferation at doses of 16 and 24 Gy. This biological efficacy, coupled with the attracti ve safety profile, suggests the selection of Ga-68 as an attractive isotope for liquid-filled balloon brachytherapy.