Can Genomic Testing Help Refine Choosing Wisely the Omission of Axillary Staging in cN0 Breast Cancer?

Choosing Wisely (CW) recommends women age ≥70 y with cT1-2cN0 ER+/HER2-invasive breast cancer (BC) should forgo routine axillary staging with sentinel lymph node biopsy (SLN) at the time of breast surgery. Despite this longstanding recommendation, acceptance of SLN omission has not been widely adopted. Genomic assays, such as MammaPrint (MP), may supplement the decision to apply CW. We hypothesized that having MP on BC core needle biopsy (CNB) meeting CW could provide additional information to aid in decision-making about the need for axillary staging with SLN.

A retrospective single-institution review was conducted for women with BC meeting CW criteria, who also had MP performed on CNB from 2020 to 2021. Categorical characteristics were compared using the chi-square test. Continuous variables were compared using the Mann-Whitney U-test.

MP was available on CNB for 238 BC meeting CW criteria: 70% low risk and 30% high risk. Axillary staging was performed in 195 (82%). Eighty-one percent were pathologically node-negative and 19% were pathologically node-positive. The MP score did not correlate with pathologic nodal stage (P = 0.52). The rate of high nodal burden (pN2) was extremely low (n = 1, 0.5%). The only significant correlation with pathological node positivity was older age (P = 0.03). Appropriately, high-risk MP was strongly associated with increased recurrence risk (n = 4, P = 0.008).

Having MP on CNB does not provide clinically meaningful information about the pN stage and does not further refine which BC patients within CW could benefit from escalation to SLN or delineate a group more likely to be pathologically node-negative.