Quantitative Gene Expression by Recurrence Score in ER-Positive Breast Cancer, by Age

Sandra M. Swain, Raquel Nunes, Carl Yoshizawa, Megan Rothney, Amy P. Sing

Breast cancer in young women (<50 years) has been associated with an increased risk of recurrence and decreased survival compared with patients older than 50. The objective of this analysis was to determine, from a large database of patients with early-stage breast cancer, if the Recurrence Score(®) result (Oncotype DX(®), Genomic Health, Inc, Redwood City, CA, USA) provided clinically meaningful differences in predicted risk of recurrence in younger-compared with older-patients. Tumor samples from patients with estrogen receptor (ER)-positive breast cancers that were successfully processed in the Genomic Health central lab between June 2004 and December 2013 for Recurrence Score and quantitative gene expression of ER, progesterone receptor (PR), and Her/2neu, were included. Descriptive statistics were used to describe the distribution of scores by age group: <40, 40-49, 50-59, 60-69, and ≥70 years, nodal status, and histologic subtype. Specimens from 394,031 patients [3.3% (n = 13,029) aged <40 years; 15.6% (n = 61,643) aged ≥70 years] were included; 81.6% of patients had invasive ductal carcinoma. Nodal status was specified for 362,001 patients (87.0% negative). Median Recurrence Score results were similar across risk groups. Low (<18)- and high (≥31)- risk Recurrence Score results were seen in 58.5% and 8.5% of patients, respectively. A greater proportion of patients aged <40 (14.1%) than ≥70 (8.8%) years had a high-risk score. ER expression increased as a function of age and PR single-gene and invasion gene group expression were similar across age groups. These data indicate that in patients with ER-positive breast cancer, age alone does not reflect the underlying individual tumor biology, suggesting that the Recurrence Score result may add potentially useful information for personalized treatment decisions. Genomic Health, Inc.