Better genetic tests fine tune cancer therapy

By Deena Beasley - Analysis

CHICAGO (Reuters) - New cancer research is moving medicine closer to more reliable use of genetic tests to help decide which drugs to use -- good news for patients, but potentially less lucrative for drug companies.

Before now, only certain breast cancer patients have had the option of a drug determined by their genetic makeup. Genentech Inc's Herceptin and GlaxoSmithKline's Tykerb are approved for only the 25 percent to 30 percent of breast cancer patients whose tumors generate a protein called HER-2.

Research released at a meeting here of the American Society of Clinical Oncology on Sunday gives doctors insight into which patients will be helped by Erbitux, the targeted cancer therapy developed by ImClone Systems Inc.

"We have struggled with how to afford these targeted drugs. Part of the answer is to determine who will benefit," said Dr. Julie Gralow, a breast cancer specialist at the University of Washington.

Aside from biomarkers for targeted cancer drugs, data from the oncology meeting examined tailoring chemotherapy drugs to cancer patients and testing for a specific genetic marker that may be a way for doctors to predict which patients will have their cancer get worse after being treating with anemia drugs.

The Erbitux study, looking at a subset of subjects from a large clinical trial, found that colon cancer patients whose tumors contained the normal, or wild-type, version of a gene known as KRAS were significantly helped by Erbitux, while those with a mutated KRAS gene saw no benefit from the drug, also known as cetuximab.

Patients given Erbitux and chemotherapy had a 15 percent reduction in the risk of tumor growth, compared to those on chemotherapy alone, but the benefit climbed to 32 percent when looking only at patients with the normal KRAS gene.

"I believe it is now warranted to test all patients. KRAS mutants should not receive cetuximab," said Dr. Gail Eckhardt, a medical oncology professor at the University of Colorado.