A biomarker reflecting expression levels of two genes in tumor tissue may be able to predict which women treated for estrogen receptor (ER)-positive breast cancer should receive a second estrogen-blocking medication after completing tamoxifen treatment. In a report published online in the Journal of the National Cancer Institute, Massachusetts General Hospital Cancer Center investigators find that the HOXB13/IL17BR ratio can indicate which women are at risk for cancer recurrence after tamoxifen and which are most likely to benefit from continuing treatment with the aromatase inhibitor letrozol.
Previous research by the team discovered that the ratio between levels of expression of two genes—HOXB13 and IL17BR—in tumor tissue predicted the risk of recurrence of ER-positive, lymph-node-negative breast cancer, whether or not the patient was treated with tamoxifen. The current study of patients from MA.17, the highly successful clinical trial of letrozole, was designed to evaluate the usefulness of the HOXB13/IL17BR ratio both for prognosis and for identifying who could benefit from continued treatment with letrozole.
Investigators analyzed primary tumor samples and patient data from the placebo-controlled MA.17 trial, which confirmed the ability of extended letrozole therapy to improve survival after the completion of tamoxifen treatment. Tissue samples were available from 83 patients whose tumors recurred during the study period—31 who had received letrozole and 52 in the placebo group—and 166 patients with no recurrence—91 who had received letrozole and 75 the placebo. Analysis of tumor samples revealed that a high HOXB13/IL17BR ratio, meaning the expression level of HOXB13 is greater than that of ILBR17, predicts an increased risk for tumor recurrence after tamoxifen therapy, but that risk drops significantly if a patient receives letrozole. Read the article.
