Cabozantinib Continues to Improve PFS in RAI-Refractory DTC

Francis P. Worden, MD, professor of medicine at the University of Michigan Rogel Cancer Center, Ann Arbor, Michigan, discusses the efficacy findings from the phase 3 COSMIC-311 study (NCT03690388) of cabozantinib (Cabometyx) in thyroid cancer.

The phase 3 COSMIC-311 study randomized patients aged 16 years and older with radioiodine-refractory differentiated thyroid cancer (RAIR-DTC) in a 2:1 ratio to receive either oral cabozantinib (Cabometyx) tablets at a dose of 60 mg/day or a placebo. Patients must have progressed on prior lenvatinib (Lenvima) and/or sorafenib (Nexavar) in order to be eligible in the study.

According to Woren, treatment with cabozantinib maintained a progression-free survival (PFS) improvement compared with placebo when used for the treatment of patients with RAIR-DTC, irrespective of the duration of prior lenvatinib.

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0:10 | The median progression-free survival on placebo was 1.9 months, and on the cabozantinib arm, and it was 11 months, so that was exceeding the expectations. The study was stopped early and declared a positive trial. Had it originally been based on response alone, the study probably would have been negative. I think it was well conducted in looking at those dual end points.

0:38 | This study also shows in that placebo arm that patients, if you look at the Kaplan-Meier plots, they are dropping off quickly in terms of of death and progression on the placebo arm, because we're talking about a group of patients that now has transforming disease or more aggressive disease and those people are in need of therapy. That does provide the benefit here. What's also important if we look at the subgroup analysis from the study is, interestingly enough, the people who attained the best benefit in progression-free survival were those who received prior sorafenib compared with lenvatinib. I think that goes back to the data that we had previously talked about with robust responses we see with lenvatinib and improvement in progression-free survival. Patients, when treated with placebo vs cabozantinib, did better with cabozantinib, but their overall progression-free survival was not necessarily as robust as with sorafenib.