The 70-gene signature genetic test (MammaPrint) has been shown to improve prediction of clinical outcomes in women with early-stage breast cancer. Researchers in Europe combined the test with standard clinical–pathological criteria in selecting patients for adjuvant chemotherapy, and examined treatment outcomes.
In the randomized, phase III study, 6693 women with early-stage breast cancer were categorized by their genomic risk (using the 70-gene signature) and their clinical risk (using a modified version of Adjuvant Online). Women at low clinical and genomic risk did not receive chemotherapy and those at high clinical and genomic risk received chemotherapy. In patients with discordant risk results, either the genomic risk or the clinical risk was used to determine if chemotherapy administration was warranted.
The primary goal was to assess whether, among patients with high-risk clinical features and a low-risk gene-expression profile who did not receive chemotherapy, the lower boundary of the 95% confidence interval for the rate of 5-year survival without distant metastasis would be 92% (ie, the noninferiority boundary) or higher.
A quarter of the women (1550) were at high clinical risk and low genomic risk. At 5 years, the rate of survival without distant metastasis in this group was 94.7% among those not receiving chemotherapy. The absolute difference in this survival rate between these patients and those who received chemotherapy was 1.5%, with the rate being lower without chemotherapy. Similar rates of survival without distant metastasis were reported in the subgroup of patients who had estrogen-receptor–positive, HER2–negative, and either node-negative or node-positive disease.
The researchers concluded that about 46% of women with breast cancer who are at high clinical risk may not require chemotherapy. More information on the study is available here.
Cardoso F, van’t Veer LJ, Bogaerts J, et al. 70-gene signature as an aid to treatment decisions in early-stage breast cancer. N Eng J Med. 2016;375:717-729.