STOCKHOLM — The genetic assay MammaPrint was able to identify a substantial proportion of women with small, early-stage breast tumors who were at risk for distant metastases, according to a study in 319 women.
The study included women with lymph node-negative T1 breast cancer, a group generally regarded as low-risk patients. Among 39 women with tumors smaller than 11 mm, 19 (49%) had a good-prognosis signature as determined by the MammaPrint assay, and 20 (51%) had a poor-prognosis signature.
Overall, the 10-year distant metastasis-free survival rate was greater than 90% among those with a good-prognosis signature, compared with 60% among those with a poor-prognosis signature, according to results reported in a poster presentation at the European Society for Medical Oncology Congress.
In the 280 women with tumors measuring 11-20 mm, the probability of remaining free of distant metastases at 10 years was 85% for those with a good-prognosis signature and 60% for those with a poor-prognosis signature.
The probability of remaining metastasis free was significantly different between prognosis-signature groups for either tumor size. “We've already shown that MammaPrint can distinguish high-risk patients with poor survival rates, but even in patients who are considered clinically to have a good outcome, we see that 50% of these patients actually have a poor prognosis,” coinvestigator Dr. Femke de Snoo, director of medical affairs, Agendia BV, Amsterdam, said in an interview.
The MammaPrint breast cancer prognostic test measures the expression of 70 genes in tumor samples. It is cleared for use by the Food and Drug Administration, and made by Agendia BV, which sponsored the study.
In an effort to underscore that the MammaPrint assay adds information to all risk categories, the investigators performed a subgroup analysis in 145 women with lymph node-negative, estrogen receptor-positive, grade 2 tumors.
The 10-year overall survival rate was significantly different among 90 women with a good-prognosis signature, as compared with 55 women with a poor-prognosis signature (92% vs. 60%), according to the investigators, led by Dr. Annuska M. Glas, also of Agendia BV.
Poster discussant Dr. Fabrice André of the Gustave-Roussy Institute in Villejuif, France, said that the number of women with small tumors of the breast is increasing with mass screening. If the current data are reproduced in cross-validation retrospective studies, MammaPrint could be used in clinical practice to identify women who are eligible for chemotherapy among this good-prognosis population, Dr. André said. He cautioned, however, that randomized, controlled trials are needed before molecular assays should be used to decrease the use of adjuvant treatment in this population.
We've shown that MammaPrint can distinguish high-risk patients with poor survival rates. DR. DE SNOO