When Prostate cancer remains confined to the gland, it’s safe to take a conservative approach to treatment, new research suggests.

The findings show that, contrary to another recent study, the death rate from localized prostate cancer does not increase sharply 15 years after diagnosis - which probably makes intensive therapy unnecessary.

In the previous study, reported last year, a substantial minority of early stage cancers became more aggressive after 15 years of watchful waiting.

The authors of that report said their results supported the idea of “early radical treatment, notably among patients with an estimated life expectancy exceeding 15 years.”

By contrast, the findings published in this week’s Journal of the American Medical Association do not show a long-term increase in mortality rates and, therefore, do not support this view.

Dr. Peter C. Albertsen, from the University of Connecticut in Farmington, and colleagues suggest that two factors contribute to the opposite conclusions reached by each study: tumor classification and cause of death determination.

The increased mortality rate seen in the previous study may “reflect a classification artifact involving a small number of patients,” Albertsen’s team writes.

Also, the previous study used review of medical records to determine the cause of death, whereas the current one employed death certificate analysis. “Misclassification of a small number of patients in either study may explain the different findings at years 15 and 20.”

Albertsen’s group analyzed data from the Connecticut Tumor Registry on 767 men diagnosed with localized Prostate cancer between 1971 and 1984. The men were treated with watchful waiting, or with immediate or delayed hormonal therapy, and were followed for an average of 24 years.

During the first 15 years of follow-up, the death rate due to prostate cancer was equivalent to 33 per 1000 persons per year. After 15 years, the rate fell to 18 per 1000 persons per year.

“Men with low-grade prostate cancer have only a small risk of Prostate cancer progression even after 20 years of management by observation or androgen withdrawal therapy alone,” the investigators conclude.

SOURCE: Journal of the American Medical Association, May 4, 2005.