A lethal form of prostate cancer is far more common than previously thought, leading researchers believe that more specific diagnoses could lead to better treatment and survival rates, according to a UCSF study published Monday.

The study looked at 202 men with prostate cancer who had spread beyond the prostate and were resistant to standard treatment. It turned out that about 17 percent of these cases of metastatic prostate cancer were a more deadly subtype with specific genetic mutations. Previously, researchers believed that less than 1 percent of all prostate cancers were in this category.

The findings, published in the Journal of Clinical Oncology, suggest that this type of cancer – called treatment-emergent small-celled neuroendocrine prostate cancer or t-SCNC – could be treated more successfully with targeted medications.

"Think of advanced, hormone-treatment-resistant prostate cancer as a pie," Dr. Rahul Aggarwal, Assistant Professor of Medicine at the UCSF Department of Hematology and Oncology and one of the authors of the study. "Instead of treating these advanced cases homogeneously, as is the case with today's standard treatments, we want to divide the pie into tumor features."

In this way, it could be possible to develop treatments that are tailored to individual tumors based on their unique genetic mutations and other properties, he said.

In breast cancer, he said, there is already a clear understanding of subtypes, and there are several treatments available for them.

"We're trying to get to the same place in prostate cancer," Aggarwal said.

He added that understanding the prevalence of this aggressive form of prostate cancer will help to inspire studies to treat it.

Only men have a prostate, which is a gland associated with semen production just below the bladder.

Usually, prostate cancer is treated with hormones and chemotherapy, according to the study. In cancers that were resistant to conventional treatment, patients with t-SCNC died on average nearly eight months earlier, after their treatment failed, than patients without this type of cancer.

Nearly 30,000 men die every year from prostate cancer, with about 1 in 10 cases spreading beyond the prostate at the time of diagnosis.

Jill Tucker is a staff member of the San Francisco Chronicle. Email: jtucker@sfchronicle.com Twitter: @jilltucker


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