Men whose prostate cancer comes back in blood tests get no benefit from starting hormone therapy right away, also known as chemical castration, compared with waiting for the disease to progress, a study has found.
In a look at 2,012 men whose prostate cancer relapsed, those who delayed hormone treatment were no more likely to die over five and 10 years than those who started therapy immediately, researchers at the Harvard School of Public Health found. The results were released Wednesday ahead of the American Society of Clinical Oncology’s annual meeting later this month.
The findings mean that men whose cancer only shows up in an early blood test, and not in scans or examinations, may be able to wait before starting therapy that comes with significant side effects such as impotence, researchers said.
“For both groups and both outcomes, the survival is very similar,” said Xabier Garcia-Albeniz, an epidemiologist at Harvard School of Public Health in Boston and a study author.
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About 60,000 men a year in the United States have prostate cancer that relapses and shows up in blood tests before it becomes evident in scans or symptoms, said Peter Yu, president-elect of ASCO. The researchers emphasized that more work needs to be done and the study may not have accounted for differences in doctors’ decisions to treat patients based on risk factors not accounted for in the study.
Prostate cancer is often slow growing, meaning that many patients might be able to delay therapy. The new study will open discussion between patients and their doctors about what to do, Yu said.
“Up to now we’ve not had clear evidence, or some evidence, that delaying treatment until there are clear signs of disease is the safe thing to do,” he said on a call with reporters.
Side effects of androgen deprivation therapy include impotence, bone weakness, hot flashes, mental dullness and loss of muscle mass.
“None of those by themselves are extremely serious in most patients, but cumulatively they really impact most men’s quality of life,” said William Oh, a physician and the chief of hematology and medical oncology at Mount Sinai Hospital in New York.
In the study, 85.1 percent of men who started treatment immediately survived over five years, compared with 87.2 percent who delayed therapy. Over 10 years, 71.6 percent of men in both groups were alive.
Drugs used in androgen deprivation therapy include AstraZeneca’s Zoladex, which sold $996 million in 2013. The medicines can be given in injections from once a month to once a year.
“What this suggests is we probably pull the trigger on androgen deprivation therapy a little too soon,” Oh said in a telephone interview. “Nobody’s ever shown that starting right away makes any difference. The sooner you start it, the longer they’re on this therapy.”
When prostate cancer is detected initially, it can be treated with surgery or localized radiation. About one-third of men eventually relapse, Oh said, and doctors use a blood test for a protein called prostate-specific antigen, or PSA, as an early screening tool to see if the cancer has returned.
An estimated 233,000 new cases will be diagnosed in the U.S. this year, and 29,480 men will die of the disease, according to the National Cancer Institute. The growth of the cancer cells is driven by male hormones, most of which are made by the testicles. Decreasing production of hormones, or blocking them from getting to the cancers, can slow the cancer’s growth or shrink it.