Prosigna Breast Cancer Prognostic Gene Signature Assay study published in JCO

NanoString Technologies, Inc. (NASDAQ: NSTG), a provider of life science tools for translational research and molecular diagnostic products, today announced that the TransATAC clinical validation study for its Prosigna Breast Cancer Prognostic Gene Signature Assay, which is based on the PAM50 gene signature, was published in the Journal of Clinical Oncology (JCO). This study, portions of which were initially presented at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium, evaluated the ability of three breast cancer tests to predict risk of distant recurrence after endocrine therapy in postmenopausal women with hormone receptor-positive (HR+) early-stage breast cancer. The authors of the study concluded that the PAM50-based assay provides more prognostic information in endocrine treated patients with HR+ node negative disease than Oncotype DX^®, with better differentiation of intermediate and high-risk groups.

“The publication of the TransATAC study is an important milestone in our ongoing effort to enable genomic testing for breast cancer in local laboratories worldwide”

The study included 1,017 samples from the landmark ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial of postmenopausal women with HR+ early-stage breast cancer treated with five years of endocrine therapy. The study was performed on RNA extracted from tumor samples by Genomic Health, Inc. for validation of the Oncotype DX^® Breast Cancer Assay. The goals of the TransATAC study were to determine if the PAM50 gene signature added prognostic information to clinical-pathological variables and to compare the performance of the PAM50 risk of recurrence (ROR) score, the Oncotype DX recurrence score (RS), and the IHC4 score, derived from immunohistochemical assessment of ER, PR, HER2 and Ki67 genes, in indicating risk of distant recurrence after endocrine therapy. All primary and secondary endpoints of the study were met.

Authors of the study reported that the PAM50 ROR score added prognostic information about the risk of 10-year distant recurrence in addition to that provided by standard clinical-pathological variables in the analysis of all patients studied (p < 0.001). Similar results were achieved in all three prospectively defined clinically important subsets of patients: node-negative (p < 0.001), node-positive (p = 0.002), and HER2-negative (p < 0.001). In addition, the study reported that patients with Luminal A subtype had a lower risk of recurrence than those with the Luminal B subtype further supporting the biological differences between these groups.

The authors also concluded that the PAM50 ROR score provided more prognostic information than the widely used Oncotype DX RS. Compared to Oncotype DX RS, PAM50 ROR score categorized fewer patients as intermediate-risk and more as high-risk when using prospectively defined risk cutoffs for low, intermediate and high risk of <10%, 10% to 20% and >20% estimated risk of recurrence, respectively. Moreover, the authors concluded that the PAM50 ROR score provided at least as much information as the IHC4 and may provide more information than IHC4 in the node negative/HER2 negative patient group.

"The publication of the TransATAC study is an important milestone in our ongoing effort to enable genomic testing for breast cancer in local laboratories worldwide," said Brad Gray, President and Chief Executive Officer of NanoString Technologies. "We look forward to discussing the results and conclusions of this study with oncologists, pathologists, and payers in the European Union and other countries that recognize the CE Mark, as we continue with our commercial launch in those regions."