Omission of chemotherapy for low-grade, luminal A N1 breast cancer: Patterns of care and clinical outcomes

Purpose: Multiple ongoing randomized studies are assessing the impact of omission of chemotherapy (CT) in low-risk node-positive Luminal A breast. The goal of this investigation was to evaluate trends and practice patterns of adjuvant CT use in Luminal A pT1-3N1 breast cancer, along with determining the clinical benefit from adjuvant CT in this patient population. Methods: The National Cancer Data Base was queried (2004–2014) for women with pT1-3N1 luminal A invasive ductal carcinoma receiving adjuvant hormonal therapy (HT). Multivariable logistic regression ascertained factors associated with adjuvant CT administration. Kaplan-Meier analysis evaluated overall survival (OS) between patients treated with CT/HT vs. HT alone, while sub-stratifying patients by age. Results: Of 8548 total patients, 5182 (61%) received CT/HT, while 3366 (39%) received HT alone. A steady rise in omission of adjuvant CT was observed, from 14% (2004–2005) to 41% (2012–2014). A decision not to use CT was more likely in more recent time periods, in older patients, at academic centers, following lumpectomy, and with lower T classification (p < 0.05 for all). CT was associated with higher OS in all patients (p < 0.001) and women ≤50 years old (p = 0.030), but not for ages 51–60 (p = 0.116), 61–70 (p = 0.222), or >70 (p = 0.239). Conclusions: Using CT for Luminal A N1 breast cancer is decreasing over time, primarily in older patients and at academic centers. Although CT is still associated with an OS advantage in all patients, subgroup analysis demonstrated no OS benefit in women >50 years of age. These results have implications on the ongoing randomized trials.