Important news for men with prostate cancer: first, the cancer tends to grow so slowly that only a fraction of patients actually die from it.

Second, men with low-grade cancer who opt for close monitoring instead of surgery to remove the prostate do not seem to suffer anxiety and distress from living with ‘‘untreated’’ cancer.

Those are the take-home messages of two studies appearing in medical journals this week.

Prostate cancer, the second most common cancer in men after lung cancer, is increasingly being diagnosed at earlier stages, mainly because of more widespread screening programs.

While many prostate tumors grow very slowly and take years to cause harm, many men nevertheless undergo aggressive surgery and radiation, and end up living with the side effects of treatment - including impotence and incontinence - for a cancer that may never have killed them. Figuring out which cancers will become deadly is difficult, however.

Dr. Peter Scardino of Memorial Sloan-Kettering Cancer Center in New York and colleagues studied more than 12,600 men with prostate cancer, including some with a particularly aggressive form. All the men had their prostates removed.

In the Journal of Clinical Oncology, the researchers report that 15 years later, only 12 percent had died from cancer. On the other hand, 38 percent had died from other causes.

The study “shows a remarkably low risk of dying of prostate cancer within 15 years for treated men, and supports the concept that men with slow-growing cancers may not need immediate treatment,” Scardino told Reuters.

In the United States, however, less than 2 percent of men under age 65 choose to have doctors closely monitor their cancer instead of having surgery and radiation, according to Dr. Scardino and his colleagues.

In a separate study, Dr. Roderick C. N. van den Bergh at Erasmus University Medical Center in Rotterdam, the Netherlands and colleagues questioned 150 men with low-grade prostate cancer who did opt for such “active surveillance” instead of radical therapy. In active surveillance, patients can undergo treatments if and when the disease worsens, the authors note.

In fact, when these patients’ answers were compared with answers from patients who received other types of treatments, it turned out that most of the active surveillance patients were less conflicted about their decisions, less depressed and less anxious.

The cause-effect is a bit murky, of course: Dr. van den Bergh admitted to Reuters Health that it’s possible the men in the study were able to choose the active surveillance approach “because they suffer low anxiety and distress.”

Even so, he said, “The take-home message of the article is that men with a supposedly low-risk form of prostate cancer who chose to actively survey the disease instead of radically treating it - a ‘treatment’ strategy that is quickly gaining in popularity since the aim is to avoid unnecessary, possibly (incapacitating) treatments - do not seem to show increased levels of anxiety and distress when compared to men who receive other forms of treatment (like surgery or radiation therapy).”

“This potential psychological burden was supposed to be a major disadvantage of active surveillance,” Dr. van den Bergh continued. “Active surveillance seems therefore to be a feasible option with regards to anxiety and distress issues.”

SOURCES: Journal of Clinical Oncology, July 27, 2009, and Cancer, September 1, 2009.