Evaluating cabozantinib plus docetaxel and prednisone in patients with metastatic castration resistant prostate cancer

The study evaluated outcomes of combining cabozantinib (Cabometyx) with docetaxel (Taxotere) and prednisone (Deltasone) in treating patients with metastatic castration-resistant prostate cancer (mCRPC). The main finding was that the combination was safe and could possibly be effective in such patients.

Docetaxel was the first chemotherapy to improve survival in men with mCRPC. Cabozantinib shrinks several types of tumors by preventing the growth of new blood vessels. Previously, cabozantinib failed to improve survival compared to prednisone in men with mCRPC. Previous studies suggested that the effectiveness of docetaxel can be enhanced in combination with cabozantinib. However, studies adding cabozantinib to docetaxel-prednisone (DP) and further comparing it with DP are lacking.

This study included 44 adult men with mCRPC. They received three cabozantinib doses (20, 40, and 60 mg/day) added to DP. The maximum tolerated dose (MTD) of cabozantinib was determined as 40mg/day. MTD is the highest dose of a drug that does not cause side effects that cannot be tolerated. Then, participants were split into 2 groups. 13 patients received cabozantinib plus DP and 12 patients received DP alone. Patients were followed up for 18 months.

The average time until cancer worsened was 21 months under cabozantinib combination therapy and 6.6 months on DP. On average, patients were estimated to survive for 23.8 months on cabozantinib combination and 15.6 months on DP. The average overall survival for 12-months was 84.6% under cabozantinib-DP and 50.5% on DP alone.

Prostate specific antigen (PSA) is a protein in the blood used to evaluate cancer progression. A reduction in PSA levels means a reduction in cancer. 69% of patients in cabozantinib-DP had a more than 50% reduction in PSA levels compared to 25% on DP alone. 

The study concluded that cabozantinib can be safely added to DP for treating mCRPC, with promising effectiveness.

The study was conducted in two hospitals only. There was a very small number of participants. Larger studies are needed to further evaluate this combination.