Gene profiles might guide chemotherapy

From Chicago, at a meeting of the American Society of Clinical Oncology

Profiles of genetic variations in cancer patients could help oncologists predict the outcome of chemotherapy and, in some cases, indicate the most effective course of treatment, two new studies suggest.

Sarada Gurubhagavatula of Massachusetts General Hospital in Boston and her colleagues analyzed blood from 103 patients who had received chemotherapy for advanced lung cancer. The scientists looked for variations in two genes, dubbed XPD and XRCC1, that encode proteins governing DNA repair.

The scientists compared each patient’s genetic profile with his or her progress against cancer while getting chemotherapy. The analysis revealed that 13 patients who had certain forms of both genes survived only 6.8 months on chemotherapy, while 26 people with the most common forms of both genes lived an average of 20.4 months. The remaining patients, who had versions of these genes that apparently compromised DNA repair only slightly, survived 11 to 17 months.

In another study, Mark Ratain of the University of Chicago reports that having one of two known forms of the gene UGT1A1 precipitates a dangerous side effect in some colon cancer patients receiving irinotecan–a frontline chemotherapy drug. In these people, irinotecan induces a sharp drop in white blood cell count, a side effect that opens the door to infections.

Creating a genetic profile of a patient before treatment could avert this complication by revealing which patients shouldn’t get the drug, Ratain says. He notes that the University of Chicago Medical Center has already started compiling some patients’ genetic profiles.

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