Loss of a tumor suppresser gene called Rb may be the first step in the development of prostate cancer, according to findings from experiments in mice.

Loss of the Rb gene has been seen in as many as 60 percent of clinical cases of prostate cancer, Dr. Norman M. Greenberg and colleagues note in the September 1st issue of Cancer Research.

Most genes exist as two copies - one on each chromosome pair.

The team found that deletion of even one Rb gene in the prostate of mice caused pre-cancerous changes. However, after 1 year, the lesions had not become malignant and were considered to represent an early stage of the disease.

“The long-term goal,” Greenberg, of the Fred Hutchinson Cancer Research Center, Seattle, told Reuters Health, is to “distinguish patients with early-stage disease who are most likely to progress from those less likely to progress.”

“If we can determine with reasonable certainty that a patient only has reduced levels of Rb in the prostate, and no other changes, this would be consistent with the early form of the disease and would indicate that aggressive therapy was likely not needed,” Greenberg continued.

A safe, minimally invasive test to monitor the genetic make-up of a patients’ prostate would greatly help doctors manage prostate cancer, he concluded. “Providing aggressive therapy only to those who need it would also reduce health care costs.”

SOURCE: Cancer Research, September 1, 2004.