BluePrint in combination with MammaPrint molecular subtyping reclassified more than 20% of breast cancer patients into a different subgroup compared with conventional assessment, according to the results of the prospective Neoadjuvant Breast Registry Symphony Trial (NBRST). In Annals of Surgical Oncology, Whitworth et al reported that this reclassification of patients led to an improved distribution of response rates and a more accurate picture of which patients were likely to respond (or not respond) to neoadjuvant chemotherapy for breast cancer.
Selection of the appropriate therapy for a woman with breast cancer can be guided by accurate classification of the tumor by molecular subtype. Currently, however, conventional assessment methods such as immunohistochemistry and fluorescence in situ hybridization (FISH) lack standardization and the interpretation of test results differs among laboratories.
Thus, investigators have turned to other potentially more effective approaches to molecular subtyping. BluePrint, a novel molecular profile, is a multigene classifier, determining the mRNA levels of 80 genes. In combination with MammaPrint (risk stratification by multigene assays), BluePrint can classify patients with breast cancer into three subtypes based on functional molecular pathways: luminal (A or B), HER2, and basal.
In the NBRST study, the investigators attempted to predict chemosensitivity in women with histologically proven breast cancer with the 80-gene BluePrint functional subtype profile vs conventional subtyping. Chemosensitivity was defined as pathologic complete response or the absence of invasive carcinoma in both the breast and axilla at microscopic examination of the resected specimen.
More than 400 women with breast cancer who had started or were scheduled to start neoadjuvant chemotherapy or hormone therapy took part in the multicenter NBRST study. All of them had definitive surgical resection. The age of study participants ranged from 22 to 80 years, with a median age of 52 years. Most of the patients (85%) had T2 or T3 tumors.
Patients who had undergone an excisional biopsy or axillary dissection or who had confirmed distant metastases were excluded from the study. Also, those who had received prior chemotherapy, radiotherapy, or endocrine therapy for breast cancer were ineligible for study participation.
Microarray analysis for the 80-gene BluePrint subtype and the 70-gene MammaPrint profiles was conducted at Agendia Laboratory, which was blinded to both clinical and pathologic data. BluePrint and MammaPrint analysis categorized the study patients as follows: 59 (14%) were luminal A, 153 (36%) were luminal B, 74 (17%) were HER2, and 140 (33%) were basal.
Reclassification to Different Molecular Subgroup
In total, 22% (94 of 426 patients) were reclassified in a different BluePrint/MammaPrint molecular subgroup compared with conventional subtyping. For instance, 37 of 211 patients (18%) of conventionally determined hormone receptor–positive/HER2-negative patients were reassigned by BluePrint as basal (35) or HER2-positive (2). In addition, 53 of 123 conventionally determined HER2-positive patients (43%) were reclassified as luminal (36) or basal (17).
As for response rates to neoadjuvant chemotherapy, the investigators reported an overall pathologic complete response rate of 25% (99 of 403 patients). Six percent of patients with luminal breast tumors had a pathologic complete response rate (2% for luminal A, 7% for luminal B).
More than half of the 74 patients with BluePrint-determined HER2-positive tumors had a pathologic complete response, which the investigators noted was significantly superior (P = .047) to the 38% of conventionally assigned HER2-positive patients.
Use of the multigene classifier BluePrint may assist oncologists in accurately identifying which patients with breast cancer may benefit from neoadjuvant chemotherapy and which ones are less likely to do so. According to the investigators, there are potential clinical implications for two particular groups of reassigned patients via BluePrint molecular subtyping: (1) those who were conventionally assigned as HER2-positive but not classified as such by BluePrint, and (2) those who were considered to have hormone receptor–positive/HER2-negative disease via conventional assessment but were reclassified to basal disease by BluePrint.
“This reclassification of patients leads to an improved distribution of response rates in the different subgroups of patients: a lower pathologic complete response rate for BluePrint luminal patients compared with [immumohistochemistry]/FISH-defined conventional luminal patients, with more responsive patients reassigned to the HER2 and basal categories,” concluded the investigators.
Pat Whitworth, MD, of the Department of Surgery, Nashville Breast Center, Nashville, Tennessee, is the corresponding author of the article in Annals of Surgical Oncology.
Lisette Stork-Sloots, MSc, and Femke A. de Snoo, MD, PhD, are employees of Agendia NV, Amsterdam, The Netherlands. The other authors disclosed no potential conflicts of interest.
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