The Food and Drug Administration on Monday expanded approval of Johnson & Johnson’s prostate cancer pill Zytiga for men with an earlier stage of the disease.

The agency said in a statement that Zytiga is now approved for late-stage prostate cancer patients who have not yet received chemotherapy, based on study results showing it can extend life by up to five months when taken by men in that group.

The FDA previously approved the drug in April 2011 for men with prostate cancer who have already taken the chemotherapy drug docetaxel.

Zytiga works by decreasing the male hormone testosterone. Testosterone stimulates the growth of prostate tumors, and treatment often includes drugs aimed at cutting the body’s testosterone production. While older drugs can block about 90 percent of the hormone, scientists say Zytiga blocks virtually all of it, which can help slow the disease.

The FDA approved the new indication based on a J&J study of 1,088 men with late-stage prostate cancer who had not already received chemotherapy.

The typical patient taking Zytiga survived five months longer than the typical patient taking a fake pill, or placebo.

When the study was stopped, the median time until cancer worsened in the group getting dummy pills was about eight months.

Those on Zytiga were faring much better, so researchers could not yet report how long it would take their cancers to worsen.

FDA cancer drugs chief Dr. Richard Pazdur said the FDA’s approval “provides patients and health care providers the option of using Zytiga earlier in the course of treatment.”

Common side effects with the drug include fatigue, joint swelling, diarrhea, vomiting, cough and shortness of breath.

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The Associated Press