Safety and Efficacy of Oral Testosterone Undecanoate Followed by Enzalutamide as Therapy for Men With Metastatic Castrate Resistant Prostate Cancer

Previous studies of high dose testosterone therapy given intramuscularly to men with metastatic castrate resistant prostate cancer suggest that high serum levels of testosterone may be required for clinical response. This injection regimen was given as one dose of 400mg injection every 28 days, which initially produces high serum testosterone levels but these levels drop to a varying degree in some men over the 28-day cycle. In this 30 patient trial will analyze the effects of oral testosterone therapy in men with metastatic castrate resistant prostate cancer taken on a schedule of seven days of oral testosterone therapy followed by seven days of no therapy for a twenty-eight day cycle. This therapy will be given for three 28 day cycles consecutively followed by radiographic scans to evaluate the metastatic disease. Patients will be allowed to continue on this therapy until the patients show signs of radiographic progression. If the patients show signs of radiographic progression after the first three cycles, the patients will stop taking the oral testosterone therapy and begin taking enzalutamide therapy. Enzalutamide therapy will be taken for three 28 day cycles, then radiographic scans will be taken. If there are no signs of radiographic progression, patients can continue to take enzalutamide therapy for an additional 3 cycles while on study. Patients with continued PSA or objective response will come off study but continue on enzalutamide as standard of care therapy. This study will help the investigators to understand if treating these men with the highest FDA approved dose of oral testosterone therapy will achieve similar and sustained high levels of serum testosterone that will produce similar or enhanced therapeutic response to the therapy when compared to the serum testosterone levels found in the previous injection therapy trials.