Study Shows Pseudoprogression in mCRPC Enzalutamide-Treated Men

A multi-institutional group of clinical researchers, led by the Duke Cancer Institute’s Andrew Armstrong, MD, McS, FACP, published a new report this month in JAMA Oncology describing the association between new unconfirmed bone lesions and outcomes in men with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide.

The study, a secondary analysis of the PREVAIL and AFFIRM randomized clinical trials, analyzed 1,672 enzalutamide-treated men who developed new unconfirmed bone lesions that could potentially lead to premature discontinuation of therapy. 

Study results suggested that men with mCRPC, whose disease initially responded to enzalutamide yet displayed new unconfirmed lesions in follow-up bone scans, may have pseudoprogression, a further sign of healing still indicative of a favorable treatment response.

“Scans can at times be misleading in their assessments of prostate cancer that has spread to the bone,” said Armstrong. “Some patients who are responding well to hormonal therapies such as enzalutamide can develop new lesions, but these are not always associated with worse outcomes and may indicate healing of previously hard to see bone metastases. This phenomenon is called bone scan flare, and it should not be the only reason to stop a therapy for a patient who is otherwise responding well to treatment.  Nearly 25% of men treated with enzalutamide for metastatic prostate cancer experienced a bone scan flare, suggesting that this is quite common.”

However, study results also indicated that men previously treated with docetaxel may be an exception. Investigators observed, patients treated with docetaxel prior to enzalutamide experienced worse overall survival with new unconfirmed bone lesions.   

“Currently, typical bone scans do not image the cancer directly,” explained Armstrong. “Newer PET-based imaging tests do, so it is critical to continue developing these imaging tests for more advanced disease settings. To enhance our understanding of advanced disease, we need to develop better imaging technologies.”

In addition to Armstrong, study authors include Mohammed Al-Adhami, Ping Lin, Teresa Parli, Jennifer Sugg, Joyce Steinberg, Bertrand Tombal, Cora Sternberg, Johann de Bono, Howard Scher and Tomasz Beer.

The study received support from Pfizer and Astellas Pharma.