Combined gas embolization and chemotherapy can result in complete tumor regression in a murine hepatocellular carcinoma model

Hepatocellular carcinoma (HCC) is an intractable cancer with a high mortality rate. Transarterial chemoembolization (TACE), a non-curative method, is the first line therapy for intermediate stage patients. This effectively extends patient survival but requires a complicated intraarterial catheterization procedure and is poorly suited to repeated administration. Here, we investigate gas chemoembolization, a less invasive, more easily administered transient occlusion method that circumvents these limitations. We examined the efficacy of repeated embolization combined with systemically administered doxorubicin, the most common chemotherapeutic in TACE, or tirapazamine, a hypoxia-activated cytotoxic agent, in an ectopic xenograft model of HCC. Emboli were generated in situ using acoustic droplet vaporization, the noninvasive focused ultrasound-mediated conversion of intravenously administered perfluorocarbon microdroplets into microbubbles. Gas embolization alone significantly reduced the Ki67 index and tumor viability (11.6 ± 6.71% non-necrotic vs 100% in control; p < 0.01) after 3 treatments, as assessed by histological analysis. Mice treated for three weeks exhibited significant tumor regression compared to control (23.8 ± 5.37% of initial volume vs 427 ± 49.7% in controls, p < 0.01), irrespective of the chosen chemotherapeutic agent. However, an additional three weeks of monitoring post-treatment elucidated a significant difference in the tumor recurrence rate, with combined gas embolization and doxorubicin resulting in the best treatment outcomes (60% complete regression). While doxorubicin administration resulted in significant cardiotoxicity (p < 0.01), it strongly interacted with the droplet shells, reducing the systemic dose by 11.4%. Overall, gas chemoembolization shows promise as a developmental therapy and merits further study in more complex tumor models.