Evaluation of risk stratification using gene expression assays in patients with breast cancer receiving neoadjuvant chemotherapy

Purpose: To evaluate the association of various gene expression assays with pathologic complete response (pCR) in the setting of neoadjuvant chemotherapy among patients with breast cancer Methods: The National Cancer Database (NCDB) was queried for women diagnosed between 2010 and 2017 with stage I-III breast cancer who underwent neoadjuvant chemotherapy and either 21-gene recurrence score (RS) or 70-gene signature (GS). Logistic multivariable analysis (MVA) was performed to identify variables associated with pCR. Results: A total of 3009 patients met our inclusion criteria. The median follow up was 48.0 months (interquartile range 32.2–66.7 months). On logistic MVA for all patients, those with a high risk from GS (adjusted odds ratio [aOR] 3.23, 95% confidence interval [CI] 1.49–8.13, p = 0.006) or with RS ≥ 31 (aOR 1.99, 95% CI 1.41–2.82, p < 0.001) were more likely to have pCR. When compared to RS ≥ 31, a high risk from GS was not associated with pCR (aOR 1.01, 95% CI 0.75–1.37, p = 0.94). However, among those with favorable hormone receptor status, similar findings were noted, except that those with a high risk group from GS were less likely to have pCR compared to those with RS ≥ 31 (aOR 0.65, 95% CI 0.43–0.96, p = 0.03). When analyses were repeated using a high risk group from RS defined as RS ≥ 26 among those with favorable hormone receptor status, RS ≥ 26 was not associated with pCR when compared to the high risk from GS (aOR 0.74, 0.50–1.07, p = 0.12). Conclusions: To our knowledge, this is the largest study using a nationwide oncology database suggesting that high recurrence risk groups in both assays were associated with pCR. Among those with favorable hormone receptor status, RS ≥ 31 may be a more selective prognostic marker for pCR.