Most older men with early-stage prostate cancer will not need treatment or will die of another cause before their cancer progresses significantly, according to a presentation at The American Society of Clinical Oncology's 2008 Genitourinary Cancers Symposium.

The current study is one of the first conducted during the current era of prostate-specific antigen level screening to describe the natural history of disease that is not immediately treated. This is important because the screening can detect cancer 6 to 13 years earlier than traditional diagnostic methods, and researchers have found that biochemically diagnosed cancers can often differ in stage and biology.

In this study, the investigators examined data on 9,018 men from the U.S. Surveillance, Epidemiology and End Results (SEER) database who had been diagnosed with stage I or II prostate cancer between 1992 and 2002 and who did not receive local therapy such as surgery or radiation therapy or hormonal therapy within six months of diagnosis. The median age of the men at diagnosis was 77.

The researchers found that prostate cancers in the study group were generally slow growing. Most of the men did not have any therapy, and approximately two of three died of other causes or did not experience cancer progression that required surgery or radiation therapy. Of the 2,675 men who had some treatment, the median time between diagnosis and start of cancer therapy was 10.6 years (127 months).

As expected, men with less aggressive disease (low or moderate grade) fared better than those with high-grade cancers. After 10 years, 3 to 7 percent of those with low or moderate-grade disease had died of prostate cancer compared with 23 percent of men with high-grade cancers.

Grace Lu-Yao, PhD, the presenter, noted that the clinical outcomes of this study population were also substantially more favorable than those observed in previous studies, perhaps because the use of antigen tests resulted in earlier detection of prostate cancer.

"Because prostate cancer therapies are associated with significant side effects, our data can help patients make better informed decisions about the most appropriate approach for them and potentially avoid treatment without adversely affecting their health," said Grace Lu-Yao, PhD, cancer epidemiologist at The Cancer Institute of New Jersey, associate professor at UMDNJ-Robert Wood Johnson Medical School and School of Public Health and the study's lead author.

Lu-Yao added that men who choose not to undergo treatment should be carefully monitored for rising prostate-specific antigen level and other signs of cancer growth.