Abstract P6-01-02: Using MammaPrint on Core Needle Biopsy to Guide Neoadjuvant Chemotherapy for Invasive Breast Carcinoma
Authors: Drapalik Lauren M. , Singh Rashi , Simpson Ashley , Rock Lisa , Shenk Robert , Amin Amanda L. , Miller Megan E. 
Published: March 2023

Abstract
Introduction: MammaPrint, a 70-gene assay used to predict breast cancer recurrence, is typically obtained on the surgical specimen to guide the use of adjuvant chemotherapy. However, MammaPrint results obtained at the time of diagnosis on core biopsy specimen could allow consideration of neoadjuvant chemotherapy (NAC), particularly for tumors that may not traditionally be considered for NAC such as invasive lobular carcinoma (ILC). We hypothesized that MammaPrint scores correlate with pathologic complete response (pCR) and can predict NAC response independent of histology type.
Methods: The National Cancer Database was used to identify patients with AJCC Stage I-III unilateral HR+/HER2- breast cancer with MammaPrint scores treated 2010-2018. Patients were stratified by histology: invasive ductal carcinoma (IDC) and ILC; and by MammaPrint score for 5-year breast cancer recurrence: Low Risk (1%) and High Risk (12%). Descriptive statistics identified clinical and treatment differences between groups. Logistic regression was used to identify factors associated with chemotherapy receipt and sequence. A subset analysis of patients receiving NAC compared pCR rates by MammaPrint score and histology type.
Results: Of 10,999 patients, 9,351 (85%) were diagnosed with IDC and 1,648 (15%) with ILC. ILC were larger at presentation: 40% of ILC were cT2 or greater vs. 29% of IDC (p&lt; 0.001). However, 90% of patients in both groups had cN0 disease. The majority of ILC were grade II (67% ILC vs. 52% IDC, p&lt; 0.001). High Risk MammaPrint scores were significantly more common in IDC tumors: 44% IDC vs 25% ILC (p&lt; 0.001). Mastectomy and axillary lymph node dissection (ALND) were performed more often for ILC than IDC (unilateral mastectomy 32% vs. 21%, bilateral mastectomy 17% vs. 12%, ALND 29% vs. 24%; all p&lt; 0.001). Conversely, chemotherapy (38% vs. 30%, p&lt; 0.001) and radiation (69% vs. 64%, p&lt; 0.001) were more frequently used to treat IDC than ILC. In the subset analysis of patients who received NAC (n = 715), tumors with High Risk MammaPrint scores had more favorable in-breast and axillary responses than those with Low Risk scores for both ILC and IDC (Table 1). Furthermore, only tumors with High Risk Mammaprint scores achieved an overall pCR: 7% IDC and 5% ILC. There were no significant differences in pCR rates by histology type. On multivariable logistic regression, High Risk MammaPrint score was positively associated with the receipt of NAC (OR 4.3, p&lt; 0.001) and adjuvant chemotherapy (OR 24.8, p&lt; 0.001). NAC, adjuvant chemotherapy, and any chemotherapy were also strongly associated with node-positive disease and tumor size &gt;2cm, but not IDC vs. ILC histology.
Conclusions: Superior response to NAC was observed in tumors with High Risk MammaPrint score regardless of histology type, indicating a correlation between pCR rates and genomic assay results. Greater use of NAC guided by High Risk Mammaprint score obtained on core needle biopsy may allow patients with invasive breast cancer to undergo less extensive breast and axillary surgery. Further prospective studies using MammaPrint testing on core biopsy specimens could validate these findings in clinical practice.
Table 1. Response to neoadjuvant chemotherapy by MammaPrint score for patients with Invasive breast carcinoma, NCDB 2010–2018
Citation Format: Lauren M. Drapalik, Rashi Singh, Ashley Simpson, Lisa Rock, Robert Shenk, Amanda L. Amin, Megan E. Miller. Using MammaPrint on Core Needle Biopsy to Guide Neoadjuvant Chemotherapy for Invasive Breast Carcinoma [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P6-01-02.