Prostate cancer, the most common cancer among American men, continues to be overtreated in the wake of late-2011 medical guidelines recommending that doctors simply monitor some nonaggressive forms of the disease, according to two new studies published in the Journal of the American Medical Association (JAMA). 

Only one-fifth of men older than 65 diagnosed between 2006 and 2009 with low-risk prostate cancers got the recommended, noninvasive "watch-and-wait" treatment, according to one of the studies.

Treatment Depends on the Doctor

The researchers — doctors at the MD Anderson Cancer Center in Houston — wanted to know why. They found that doctors who performed radiation and surgical treatments were more likely to prescribe them to patients with nonaggressive cancers.

At one extreme, one urologist treated all but 5 percent of patients, while at the other, one urologist treated just 40 percent. Patients of urologists who also treated higher-risk prostate cancers were more likely to get the same invasive treatments. And consulting radiation oncologists were even more likely than urologists to treat nonaggressive cancers.

Doctors and other experts note that patients, uneasy doing nothing about the dreaded C-word, sometimes ask for more aggressive treatments. This study suggests that doctors, whether influenced by financial incentives or by a genuine belief that more is better, also drive more aggressive interventions.

But overtreating might be on the decline, the study also showed: Doctors who graduated from medical school more recently were less likely than their older colleagues to treat nonaggressive prostate cancers.

Read More: Surgery Isn't Always the Best Solution for Prostate Cancer »

Hormone Treatment No Better Than Monitoring

Even treatments perceived as less invasive don’t produce better outcomes for patients than monitoring low-risk cancers, according to the second JAMA study.  

If doctors don’t prescribe surgery or radiation for low-risk cancers in older men, they often prescribe androgen deprivation treatment, or ADT, in which drugs lower the patient’s levels of male hormones, including testosterone. Because male hormones feed prostate tumors, the treatment slows the cancer’s growth for a time.

But treatment with ADT alone does not improve survival rates over the watch-and-wait approach that’s increasingly recommended, according to a 15-year analysis of more than 65,000 American men older than 65 diagnosed with non-metastasized prostate cancers. (The study does not challenge the use of ADT in high-risk patients or in combination with other treatments, such as shrinking a tumor before treating it with radiation.)

Though it’s less invasive than radiation or surgery, ADT does have side effects. Some, such as sexual dysfunction and depression, affect the patient’s quality of life and others, such as weight gain and increased cholesterol, increase the patient’s risk of other health problems.

“Because of the potential side effects of osteoporosis, diabetes, and decreased muscle tone, clinicians must carefully consider the rationale behind ADT treatment if used as the primary therapy for older patients,” said Grace Lu-Yao, a cancer epidemiologist at Rutgers University and the lead author of the paper.

Learn More: All You Need to Know About Prostate Cancer »

In a comment published alongside the two studies in JAMA Internal Medicine, Drs. Quoc-Dien Trinh and Deborah Schrag of the Dana-Farber Cancer Institute in Boston emphasized the findings.

“There is no compelling evidence to prescribe ADT alone for men with localized prostate cancer,” they wrote.

Research May Sell Patients on ‘Watch-and-Wait’

Lu-Yao said it is too soon to tell if the use of ADT has waned since the new treatment guidelines came out in 2011. But she hopes the research will encourage doctors as well as patients to wait to treat low-risk prostate cancers.

“With a growing body of evidence, hopefully it will be more persuasive for both physicians and patients that this treatment really isn’t helpful,” Lu-Yao said.