Surgery to remove small, low-risk prostate cancer tumors can be safely delayed for years without an increased risk of death, according to results from a large long-term study published Monday.

With the advent of early screening for prostate cancer in the late 1980s, doctors have been able to detect tumors at much earlier stages, noted Harvard professor Martin Sanda, who co-authored the research published in the Journal of Clinical Oncology.

But while the so-called prostate-specific antigen (PSA) testing "has enabled us to successfully begin aggressive treatment of high-risk cancers at an earlier stage, it has also resulted in the diagnosis of cancers that are so small they pose no near-term danger and possibly no long-term danger," he said.

Sanda and his team studied the health of 51,529 men since 1986, with participants responding to a health questionnaire every two years. In total, 3,331 of the men reported getting a prostate cancer diagnosis between 1986 and 2007.

Out of this group, 342 men, just over 10 percent, opted to defer treatment for one year or longer, and 10 to 15 years later, half of the men still had not undergone any treatment.

Compared to the patients who opted for aggressive treatment such as surgery or radiotherapy, Sanda's team found that deaths attributed to the cancer "were very low among the men with low-risk tumors."

The research showed only two percent of those who deferred treatment died of the disease, compared with one percent of the men who began treatment immediately following their cancer diagnosis.