Doctors eventually may be able to divide prostate cancer -- which is now treated as a single disease -- into different types and offer targeted therapies, thanks to an important genetic discovery.

If further research confirms these findings, published today in the journal Science, the discovery eventually might lead to better tests for prostate cancer as well as targeted therapies, says one of the study's authors, Mark Rubin, chief of urologic pathology at Brigham and Women's Hospital in Boston.

"This is amazing," says Michael Heinrich, a professor at the Oregon Health & Science University Cancer Institute, who was not involved in the study. "This is the Rosetta stone of prostate cancer. Cracking the code lets you read the whole library. The implications of this are huge in a lot of different ways."

Specific Genes Fuse

About 232,000 men a year are diagnosed with prostate cancer.

Until now, doctors thought it was the result of lots of random genetic mutations, Heinrich says. This study, however, suggests for the first time that prostate cancer begins after specific genes fuse.

Doctors found these merged genes in nearly 80% of 29 prostate cancer samples, says Arul Chinnaiyan, a professor at the University of Michigan Medical School who directed the study. None of the 50 samples of non-cancerous tissue had the genes, he says.

This may allow doctors to begin to divide prostate cancer -- which is now treated as a single disease -- into different types. Doctors have been treating breast cancer this way for years: They prescribe the drug Herceptin to women whose tumors make too much of certain protein, and they give the drug tamoxifen to those whose tumors respond to hormones.

Critical First Step

So far, Chinnaiyan and his colleagues have found fused genes only in prostate tissue. They are trying to see whether they can detect the genes in blood or urine, which could allow them to develop a more accurate diagnostic test for prostate cancer.

Chinnaiyan also hopes the genes will tell doctors which tumors are deadly and require aggressive treatment. That could allow men whose tumors are relatively harmless to avoid treatment and its side effects. Doctors now have few good ways to tell these men apart, leading about half to undergo unnecessary therapy, says Otis Brawley, medical director of Grady Health System's Georgia Cancer Center for Excellence.

Chinnaiyan says his discovery may allow doctors to develop new treatments. Chronic myeloid leukemia patients can live for years without serious side effects thanks to the drug Gleevec, which was developed after scientists discovered the cancer's genetic roots.

Brian Druker, the scientist who developed Gleevec, says it could take years or even decades to develop a targeted therapy for prostate cancer. But these genes at least give scientists a target, a critical first step. "This is incredibly important," Druker said in an e-mail. "Finding the cause gives us hope for finding a cure."