Scientists have created a gene profiling test that may someday help reveal which people with early lung cancer are likely to suffer a relapse and would benefit most from chemotherapy. Separately, other researchers found that several new tumour profiling tests for breast cancer, including two already in general use, are similar in accuracy and should allow many women to avoid unnecessary chemo.
The lung cancer test needs far more testing, but is potentially breakthrough research building on years of work to develop personalized cancer treatments. Its accuracy so far (about 80 percent) is better than what we have, but inevitably, it’s not as good as we would like.
Both studies were reported in yesterday’s New England Journal of Medicine. Treatment guidelines for cancer have been relatively crude, i.e. based on a tumour’s size, whether it has spread, and other specific tumour characteristics.
As a result, many women with early breast cancer get chemo even though the vast majority would do fine without it. It is the opposite with early-stage lung cancer: even though about a third of patients will get worse and die, few get chemo because doctors can’t tell which ones will benefit, and the treatment itself carries risks. Chemotherapy can damage the liver, heart and other organs, and in some cases can kill.
Doctors hope that growing knowledge about the genes fueling these cancers will lead to better ways to tell who really needs chemo. The newly emerging tumour profile tests are tools to let them do that.
To develop the lung cancer test, Duke University researchers examined 198 tumour samples and analyzed 133 genes whose activity correlated with how aggressive the cancer was. Essentially, they created a fingerprint unique to the individual patient (that) predicts survival chances. Patients were scored as having a low or a high risk of recurrence based on the test, and results were compared to what actually happened to them.
The test was 93 percent accurate on the half of patients whose tumour samples came from Duke and 75 percent accurate on the rest. Current best tests to estimate risk based on tissue characteristics are about 60 percent accurate,
A larger study of 1,200 lung cancer patients will start in early 2007 to further evaluate the Duke test. After surgery to remove the initial tumour, patients will get chemotherapy or not, depending on their test score, and then will be followed for a few years to see how they do.
In the other study, researchers at the University of North Carolina at Chapel Hill compared how five gene profiling tests performed at predicting outcomes of 295 breast cancer patients. Although the tests used different sets of genes, four were remarkably similar in accuracy and better than tests used now that are based on tumour characteristics.
They agreed 80 percent of the time, indicating they all are ultimately tracking the same biological processes affecting tumour growth. Two of the four tests have been widely available for two years, and two large international studies have been launched to establish their ultimate accuracy and usefulness.
The tests can be automated and standardized for wide use, eliminating the variability that exists when pathologists have to evaluate the appearance of tumour cells under a microscope. Such tests in the future could potentially allow 30 percent to 50 percent of women to skip chemotherapy for breast cancer based on their gene profile.
New England Journal of Medicine
American Cancer Society