Old age is no hindrance to benefiting from prostate cancer surgery and radiation therapy, according to a new U.S. study that shows men over 75 often get less effective treatment than their younger peers.

"It seems men in this age group are often undertreated, and that in turn may contribute to the higher mortality from prostate cancer among older men," said Dr. Matthew Cooperberg of the University of California, San Francisco, who led the research.

Prostate cancer is one of the most common cancers in men, affecting about 160 per 100,000 men in the U.S. every year and killing a sixth of them.

Cooperberg and colleagues reviewed data from 40 urology practices across the U.S., including nearly 12,000 patients with prostate cancer.

They found 60 percent of those aged 75 and over received only hormone treatment for high-risk tumors, even though that's not considered a cure, and eight percent were followed by their doctors with no active treatment.

By contrast, hormone treatment for such cancers was given to just between 18 and 26 percent of younger patients, and no more than one percent of them were put on watchful waiting.

"If you look at the national practice pattern, there is no question that older men are treated very differently," Cooperberg told Reuters Health. "Age is a stronger driver of treatment pattern than risk, and I think that's troubling."

Men with low-risk disease often do fine without aggressive treatment, he added. "Treatment really should be guided by disease risk, not by patients' chronologic age."

At first glance, age did appear to be tied to cancer deaths, suggesting older men fared worse. But when the researchers adjusted their calculations based on the kind of treatment people got, age no longer mattered.

Among 629 men aged 70 and older with high-risk cancer, about one in five died of prostate cancer within six years of their diagnosis. Those who had so-called local treatment, such as prostate cancer surgery or radiation, were 46 percent less likely to die from their cancer than those who had hormone therapy or were put on watchful waiting.

"Elderly men are becoming healthier and healthier," said Dr. Bob Djavan, who heads the urology department at the New York University School of Medicine and was not involved in the new study.

"A guy who is 70 today may become 85, so why should I not offer him curative treatment?" he said, adding that rather than age, what matters is cancer stage and life expectancy.

"You need to live 10 to 15 years to see a survival benefit," he noted.

So far, there are no randomized studies to demonstrate that local treatment actually makes men less likely to die from cancer, but observational studies hint of it. And since all treatment also comes with side effects, incontinence and sexual problems with surgery, for instance, or bone and muscle problems with hormone therapy, the right treatment option should be considered on a patient-by-patient basis, doctors say.

"Today we shouldn't think like we did 20 or 30 years ago: let's operate on the young guys and drop the old guys," said Djavan. "If you have a guy with high-risk disease, no matter how old he is he may benefit from surgery."