Impact of 21-Gene Expression Assay on Clinical Outcomes in Node-Negative ≤ T1b Breast Cancer

  • Maria Pomponio
  • Luke Keele
  • Elizabeth Hilt
  • Laura Burkbauer
  • Macy Goldbach
  • Susanna Nazarian
  • Kevin Fox
  • Julia TchouEmail author
Breast Oncology



Prior to the advent of Oncotype DX 21-gene recurrence score (oDX) assay, the National Comprehensive Cancer Network (NCCN) guideline supported omission of adjuvant chemotherapy in patients with ≤ 1 cm (T1b) hormone receptor-positive (HR +), human epidermal growth factor receptor 2 (HER2−) node tumors. However, around 30% of these patients would have an oDX recurrence score that warrants consideration of adjuvant chemotherapy. To clarify the potential benefit of oDX in these patients, we performed a retrospective analysis comparing clinical outcomes of women with T1a or T1b, N0 HR + HER2− according to performance of oDX.

Patients and Methods

After receiving institutional review board (IRB) approval, an institutional database was queried to identify patients with HR + HER2− ≤ T1bN0 tumors (n = 2307) diagnosed between 2009 and 2018. Patients were further stratified by recurrence score (RS) defined as low (< 18), intermediate (18–30), or high (> 30). Log-rank, Kaplan–Meier, and inverse probability of treatment weighting (IPW) analyses were used to compare disease-free survival (DFS) and overall survival (OS) across groups.


Performance of oDX (n = 1149, 49.8%) was associated with larger tumors, younger age, and White race. On univariate analysis, performance of oDX was associated with improved OS (P < 0.01). On multivariate IPW analysis, performance of oDX lengthened DFS by an average of 16.5 months, while OS was similar between groups (P < 0.01 and P = 0.73). The improved DFS was mainly driven by those with tumors ≥ T1b.


Overall, outcomes were excellent regardless of oDX testing. Performance of oDX testing was associated with improved DFS in patients with tumors ≥ T1b. Our results support routine use of oDX testing in patients with tumors ≥ T1b.



Authors have no financial relationships or conflicts of interest relevant to this article to disclose.


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Copyright information

© Society of Surgical Oncology 2019

Authors and Affiliations

  1. 1.Division of Endocrine and Oncologic Surgery, Department of Surgery, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaUSA
  2. 2.Division of Epidemiology and Biostatistics, Department of Surgery, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaUSA
  3. 3.Division of Hematology Oncology, Department of Medicine, Perelman School of MedicineUniversity of PennsylvaniaPhiladelphiaUSA

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