For years now, drug companies and journalists have been touted the new era of personalized medicine. This is one of those things that always seems to be arriving, but is taking its time getting here. The industry has sunk a huge pile of money into biomarker research, and it's safe to say that it hasn't paid off yet - although, at the same time, one still has to think that it should, eventually.
Nature Biotechnology has a good article that shows how tricky the whole business can be. HER2 is one of the more validated cancer biomarkers, and there's a drug (Herceptin) that's targeted specifically for breast cancer patients that express it. So how's that going? Not so well:
A recent study from the University of California, San Francisco, reveals that one in five HER2 tests gives the wrong answer1. Furthermore, the article, which reviews the medical literature, reports that as many as two-thirds of breast cancer patients who should be tested for HER2 are not, and consequently a significant fraction of women treated with Genentech's Herceptin (trastuzumab) have never been tested for HER2 overexpression.
The health benefit provider Wellpoint, of Indianapolis, might dispute that finding. According to Genentech staff scientist Mark Sliwkowski, the insurer has data showing that 98% of its breast cancer patients are tested. However, doctors differ in their views on testing before prescribing Herceptin. “Some doctors don't know how to interpret test results, they prefer just to prescribe it and assess the patient's progress,” says Michael Liebman of the patient stratification company Strategic Medicine of Kennett Square, Pennsylvania.
More than a decade after the drug received US Food and Drug Administration (FDA) approval, the personalized medicine paradigm clearly has holes. . .
That it does. As the article goes on to explain, there are doubts about how good many of the existing HER2 tests are, worries about how they don't always agree, questions about whether some HER2-negative patients might be benefiting from Herceptin anyway, and more questions about those results due to uncertainties about the tests. That's the state of the art right there, folks, and it's clear that we have a long way to go. I don't see any reason why biomarkers (of various kinds, not just genetic) won't help us figure out which patients should be getting which drugs, but don't let anyone tell you that we're there yet.