Results of a new study published in the Journal of the National Cancer Institute call into question the ability of a model developed from microarray data to accurately predict outcomes from tamoxifen treatment in breast cancer patients.

Data from microarray studies have been used to develop predictive models for treatment outcome in breast cancers. One recent study identified two genes - HOXB13 and IL17BR - whose gene expression could be used to predict response to tamoxifen treatment in women with estrogen receptor-positive breast cancer.

James F. Reid, of the Fondazione Istituto FIRC di Oncologia Molecolare in Milan, Italy, and colleagues attempted to validate this predictive model using an independent cohort of 58 patients with resectable estrogen receptor-positive breast cancer. They assessed the expression of the HOXB13 and IL17BR genes and the association between their expression and outcome by use of four statistical tests.

The authors could not validate the performance of the two-gene predictor with their cohort of samples nor could they develop a model with good predictive accuracy using the available independent microarray datasets. They conclude that treatment-response predictive models have poor performance with the small sample sizes of patients and the informative genes currently available.

In an editorial, Richard Simon, D.Sc., of the National Cancer Institute, provides possible explanations for the inconsistencies in the results of the two studies and makes recommendations about how these types of studies could be improved.

SOURCE:
Journal of the National Cancer Institute, June 14, 2005