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Breast

E79: Neoadjuvant Chemotherapy in T1cN0 Triple Negative Breast Cancer

Introduction: Neoadjuvant chemotherapy (NAC) is increasingly utilized in triple negative breast cancer (TNBC) to minimize surgical intervention and stratify patients for adjuvant therapy based on response (pathologic complete response [pCR] versus residual disease [RD]). However, in T1cN0 TNBC patients, the optimal treatment strategy with or without NAC is unclear due to the risk of overtreatment and missing pathologic response data. Therefore, we aimed to characterize NAC utilization over time, identify predictors of NAC receipt, and report pCR rate in this group.

Methods: Females, age 18 and older, diagnosed with stage 1-3 TNBC who received surgery within 8 months in the National Cancer Database (2004-2018) were included. Characteristics and treatment were compared between three groups: no expected NAC (T1a/bN0), unclear NAC expectation (T1cN0 patients), and expected NAC (T2+/N+). pCR was defined as ypT and ypN. Predictors of NAC and trends of NAC utilization over time in the T1cN0 group were described.

Results: 75,402 TNBC patients were included; 16,983 (22.5%) cT1a/bN0, 28,926 (38.4%) cT1cN0, and 29,493 (39.1%) cT2+/N+. NAC was given to 3.7% of T1a/bN0, 9.9% of T1cN0, and 50.5% of T2+/N+ patients. In T1cN0 patients, partial mastectomy was performed in 63.1%, and axillary dissection was performed in 16.4%. pCR was achieved in 33.4% of T1a/bN0, 37.3% of T1cN0, and 28.9% of T2+/N+ patients. In the T1cN0 group, insured patients (odds ratio [OR] 1.74, 95% confidence interval [CI] 1.05-2.89) and higher grade tumors (2 versus 1, OR 5.87, 95% CI 3.55-9.71; 3 versus 1, OR 6.89, 95% CI 4.20-11.3) were more likely to receive NAC. Older patients (OR 0.89, 95% CI 0.88-0.89), Black patients (OR 0.74, 95% CI 0.63-0.87), increasing comorbidities, lobular versus ductal histology (OR 0.35, 95% CI 0.14-0.91), and patients in the Northeast (OR 0.72, 95% CI 0.60-0.87) and the West (OR 0.78, 95% CI 0.64-0.95) versus the South were less likely to receive NAC. After adjusting for comorbidities and facility characteristics, higher grade (grade 3 versus 1, OR 2.80, 95% CI 1.04-7.56) was predictive of pCR. Older (OR 0.95, 95% CI 0.94-0.96) and Black (OR 0.77, 95% CI 0.65-0.92) versus White T1cN0 patients were more likely to have RD. NAC utilization for T1cN0 patients increased from 0% in 2004 to 15.4% in 2017 (Figure, p=0.005).

Conclusions: NAC utilization in T1cN0 TNBC patients increased over the study period and appears to be driven by a combination of tumor characteristics, patient factors, and facility preferences. Future studies are warranted to assess optimal treatment strategy and address disparities in NAC use.

Learning Objectives:

  • List predictors of neoadjuvant chemotherapy receipt in T1cN0 triple negative breast cancer patients
  • List predictors of pathologic complete response in T1cN0 triple negative breast cancer patients after neoadjuvant chemotherapy
  • Describe trend over time for utilization of neoadjuvant chemotherapy in T1cN0 triple negative breast cancer patients