Alternative hormone therapy with enzalutamide – effective regardless of metastasis site

This study examined the effects of enzalutamide (Xtandi) with respect to the site of metastatic castration-resistant prostate cancer. Researchers concluded that enzalutamide is a safe and effective treatment for all sites of metastases studied.

When prostate cancer spreads outside of the prostate (also called metastatic prostate cancer), tumors can form in distant parts of the body. The most common site of metastatic prostate cancer is on the bone. Bone tumors can cause significant pain and impact quality of life. Metastatic prostate cancer can also affect distant organs, including the lungs and liver (visceral disease). Visceral disease is often associated with poorer clinical outcomes.

The current standard treatment for metastatic prostate cancer is hormone therapy. By reducing levels of male hormones active in cancer growth (such as testosterone), survival can be increased. However, cancer can continue to spread despite standard hormone therapy. This is referred to as metastatic castration-resistant prostate cancer (mCRPC).

New hormonal treatments, such as enzalutamide, are being investigated as a possible treatment option for mCRPC. In a large trial, enzalutamide was shown to improve overall survival and cancer progression. Further studies are needed to determine the effects of enzalutamide with respect to the site or extent of metastatic or visceral disease. 

This study analyzed the results of a late-phase trial examining the effects of enzalutamide in mCRPC. In the trial, 1,717 men with mCRPC were randomly assigned to receive treatment with enzalutamide or placebo (a control drug with no active effect). None of the men previously received chemotherapy. This analysis divided men according to the site of metastatic disease. 88% of men had bone or lymph node metastasis (non-visceral group). 12% of men had visceral disease of the lung or liver (visceral group). The benefit of enzalutamide was compared between the two groups. Treatment outcomes were followed for an average of 2 years.

Enzalutamide significantly reduced the risk of progression or death compared to placebo. The benefit was similar in both patient groups. The risk of progression or death was reduced by 82% in the non-visceral group, and by 72% in the visceral group. Average survival was significantly longer with enzalutamide than with placebo. Survival was enhanced regardless of visceral disease or not. Disease progression was also significantly slowed in both groups.

The extent of metastatic disease had no effect on treatment effectivity. Men with fewer (less than 4) or many (4 or more) bone metastases similarly benefited from enzalutamide treatment. Among men where cancer spread to lymph nodes only, enzalutamide reduced the risk of progression or death by 91%.

Fatigue, back pain and high blood pressure were most commonly associated with enzalutamide. The overall rate of side effects was similar between the patient groups studied.

Researchers concluded that enzalutamide is a safe and effective treatment for mCRPC with or without visceral disease.