Looks like the FDA is ready for that long holiday weekend. On Friday afternoon, the agency approved Xtandi (enzalutamide, MDV3100) for metastatic prostate cancer (read the FDA's announcement).The approval comes after the FDA granted it priority review back in July to ensure that it would make a decision on the drug within six months. The approval came several months ahead of schedule. The hormonal drug, which showed an impressive 4.8 month increase in survival in a phase 3 study, is specifically for patients with metastatic prostate cancer who have been previously treated with docetaxel.The AFFIRM trial randomized patients two to one with the experimental treatment versus placebo. The trial included 1,199 patients with metastatic prostate cancer that had progressed after treatment with docetaxel and hormonal therapies. The study results were published back in August in the New England Journal of Medicine).The authors noted that: "At the time that this placebo-controlled study was designed and initiated, no life-prolonging treatment was available for men with progressive prostate cancer after docetaxel therapy; however, during the study period, both cabazitaxel and abiraterone acetate plus prednisone were approved for use." You also have Provenge, the prostate cancer vaccine, in the mix as well.It will be interesting to see how this "abundance of riches" in prostate cancer will ultimately play out. When the study was presented earlier this year at the ASCO Genitourinary Cancer Symposium, researchers also noted Xtandi promoted tumor shrinkage and a significant decline in PSA levels. The drug also delayed cancer growth by five months. Side effects, which included diarrhea, fatigue and hot flashes, were well-tolerated and had similar rates of toxicity to the placebo arm.Common side effects with Xtandi include fatigue, diarrhea and hot flashes. Rare occurrences of seizures have also been noted.