41 Pathologic Complete Response (pCR) Rates According to MammaPrint and BluePrint Test Results Are Consistent Among Pre and Postmenopausal Patients

Pat Whitworth, MD¹

¹Ascension Saint Thomas Hospital Midtown, Nashville, TN.

Background

Increased use of multigene expression profiling has enabled refinement of early-stage breast cancer management. Clinical trials have demonstrated that risk-of-recurrence testing identifies those patients with breast cancer who will derive benefit from adjuvant chemotherapy and those who can avoid it without affecting long-term clinical outcomes. Recent subanalyses of premenopausal patients suggest a significant clinical benefit to adjuvant chemotherapy in this patient group; however, it has yet to be demonstrated whether this is due to a direct cytotoxic effect or secondary ovarian suppression. Here, we report the first age-based analysis of the 70-gene (MammaPrint; MP) and 80-gene (BluePrint; BP) assays in the preoperative setting.

Materials and Methods

The prospective NBRST trial (NCT0147910) evaluated the utility of MP and BP in the preoperative treatment setting. From 2011 to 2014, the study enrolled 1072 patients from 67 institutions and included women with invasive breast cancer of any pathology-defined subtype, regardless of hormone or HER2 receptor status. Patients received neoadjuvant chemotherapy or neoadjuvant endocrine therapy, according to National Comprehensive Cancer Network guideline recommendations. Median follow-up for distant metastasis–free survival was 5.0 years.

Results

In the study, 41.8% of patients were 50 years or younger and 58.2% were aged >50 years. MP classified 16% of patients as low risk and 84% of patients as high risk. BP classified 49.2% of tumors as luminal, 16.2% as HER2 positive, and 34.6% as basal subtype. MP further stratified luminal tumors into A (32.6%) and B (67.4%) subtypes. MP classified 13.8% of patients <50 years and 18.1% of patients aged >50 years as low risk. Among the 4 molecular subtypes, there was no significant difference in pathologic complete response rate based on an age-50 cutoff (Table).

Conclusions

As expected, pCR rates varied according to molecular subtype. MP and BP accurately predicted pCR in patients with tumors of all subtypes, regardless of age, supporting their use to better tailor preoperative treatment and timing for surgery.