E27: Using the combined 70- and 80-gene signatures on core needle biopsy to guide neoadjuvant chemotherapy recommendations for invasive breast cancer in a Black population: Can we identify those who benefit most at time of diagnosis?

Neoadjuvant chemotherapy (NAC) is increasingly being used in both early stage and locally advanced breast cancer (BC) to track patient response to treatment, downstage tumors, reduce surgical morbidity and improve long-term outcomes. Ideal candidates for NAC may be difficult to identify, especially among the hormone receptor positive subgroups. The 70-gene MammaPrint (MP) and 80-gene BluePrint (BP) genomic signatures are increasingly being used on core needle biopsy (CNB) to guide treatment decisions. This has not been extensively studied in primarily Black patient populations. We hypothesized that Black patients with genomically high-risk tumors, as defined within the MP index and/or by BP subtypes, would be more likely to be recommended for NAC and achieve tumor downstaging and/or pathologic complete response (pCR).

Methods:

After IRB approval, we retrospectively identified all Black patients diagnosed with invasive BC at a public New York City hospital between 2021 and 2023 who had MP/BP sent on CNB. Some underwent surgery first, while others were recommended for NAC followed by definitive surgery. Descriptive statistics identified treatment differences between MP and BP subgroups.

Results:

Out of the total cohort of 85 Black patients, 82 (96.5%) were female. Mean age was 60.4. 57 (67.1%) underwent surgery first while 28 (32.9%) received NAC [Table 1].  25/28 (89.2%) who underwent NAC were genomically high risk by MP, whereas only 3/28 (10.8%) were genomically low risk by MP (p< 0.001).  Within the MP index, most patients that underwent surgery first were MP Low or UltraLow (34/57, 59.6%), whereas most patients that received NAC were MP High 2 (14/28, 50%, p< 0.001). 16/19 (84.2%) patients that received NAC and had definitive surgery had pathologic downstaging in the breast and/or axilla (p=0.086), and furthermore, 10/19 (52.6%) achieved pCR.  8/10 of these were MP High2 (p=0.038), and 6/10 were BP Basal [Table 1].

Conclusions: Black patients with genomically higher-risk tumors, defined by MP and/or BP on CNB, were more frequently recommended for NAC over those with lower-risk tumors.  Moreover, MP High 2 and BP Luminal B/Basal/Her2 subtype tumors more frequently received NAC, and subsequently downstaged and/or achieved a pCR. MP/BP on CNB can be an important tool to aid in the treatment planning of Black patients with BC in order to more confidently predict potential downstaging and/or pCR.