A new study suggests that men with early stage prostate cancer may benefit with drugs that can slow or stop the cancer’s progress. Less than 10 percent of the 100,000 men each year who are diagnosed with early-stage prostate cancer and have the option of leaving the cancer in place. Rest get it removed using surgery or radiation. But those treatments can have serious side effects like impotence and incontinence.
The study, published on Monday in The Lancet, involved a drug, dutasteride, that is marketed to shrink prostates when they enlarge as men grow older. Two previous studies suggested that dutasteride and a similar drug, finasteride, could actually protect men from prostate cancer, but the Food and Drug Administration (FDA) declined requests to allow the drugs to be marketed for cancer prevention, citing concerns that they may protect against early cancers but spur the growth of dangerous later-stage ones.
For the new study Dr. Neil. E. Fleshner of the University of Toronto and his team randomly assigned 302 men between the ages of 48 and 82 with early-stage prostate cancer to take dutasteride or a placebo while being monitored for progression of the disease, but not treated, an approach known as active surveillance. Three years later, the cancer had progressed in 54 men in the dutasteride group, or 38 percent, and in 70 men in the placebo group, or 48 percent. Dutasteride slashes levels of prostate specific antigen, or P.S.A., in half. And blood tests for P.S.A. are part of active surveillance as well as the way most men first learn they have the cancer.
It’s “good news” for men who have low-risk prostate cancer because aggressive treatment, such as surgery and radiation, “can have a major impact on their quality of life, with risks of impotence and incontinence,” said Dr. Neil Fleshner.
But the study had limitations. It was small, and three years is a short time for a cancer that tends to progress over many years. And even though the patients and their doctors were not told who was taking the drug and who was taking the placebo, it was easy to figure out.
The evidence that dutasteride might be slowing or stopping the growth of prostate cancers or even shrinking the tumors came from biopsies of the study subjects. Prostate biopsies of those taking dutasteride were less likely to find cancer than biopsies of men who were taking the placebo.
That result is consistent with the results of the previous studies suggesting dutasteride might prevent cancer, noted Dr. Ian Thompson, a prostate cancer expert at the University of Texas Health Science Center at San Antonio, who was not associated with the study. “This study potentially affects 100,000 patients or more annually,” Dr. Thompson said. “For those of us who deal with this disease, this is potentially a big deal.”
Dr. Peter Albertsen, a prostate cancer expert at the University of Connecticut, who also was not associated with the new study, said dutasteride’s effect on P.S.A. levels could be helpful. It might make men taking the drug less likely to worry that their cancer is growing and have biopsies to check. “The more often you biopsy people, the more likely you are to find slightly increased disease or some other reason to claim disease progression,” Dr. Albertsen said. Active surveillance, he added, “means we follow patients until either the patient or doctor is scared that the disease is progressing.” Yet Dr. Albertsen worries that dutasteride might fuel the growth of dangerous and deadly prostate cancers, which tempers his enthusiasm for the drug.
In an editorial accompanying the paper, Dr. Chris Parker of the Royal Marsden, a London cancer center, expressed a similar concern. The problem, he said, may be the extensive prostate screening with P.S.A. tests, which is leading one American man in five to end up with a diagnosis of prostate cancer. The solution, Dr. Parker wrote, is to “try to avoid not only treating but also diagnosing low-risk disease.” In the meantime, he wrote, “dutasteride cannot be recommended as an adjunct to active surveillance.”
The study was funded by GlaxoSmithKline, which manufactures Avodart, a brand-name version of dutasteride. Prostate Cancer Canada estimates that 25,000 new cases of prostate cancer will be diagnosed this year and 4,100 men will die from the disease. About one-third of prostate cancer cases are considered aggressive and fast-growing.