Impact of adjuvant chemotherapy on survival of women with T1N0M0, hormone receptor negative breast cancer

Background: The benefit of adjuvant chemotherapy in women with T1N0M0 breast cancers is unclear. While gene expression-based prognostic assays may aid management of women with early estrogen receptor (ER) positive tumors, therapeutic decision-making in women with early stage ER negative tumors remains fraught with difficulties. We investigated the association between adjuvant chemotherapy and overall survival in women with T1N0M0, hormone receptor negative breast cancers.

Method: All newly diagnosed breast cancer patients with node-negative and hormone receptor negative tumors measuring≤2cm at the University Malaya Medical Centre (Malaysia) from 1993 to 2013 were included. Mortality of patients with and without adjuvant chemotherapy were compared and adjusted for possible confounders using propensity score.

Results: Of 6732 breast cancer patients, 341 (5.1%) had small (≤2cm), node-negative and hormone receptor negative tumors at diagnosis. Among them, only 214 (62.8%) received adjuvant chemotherapy. Five-year overall survival was 88.1% (95% confidence interval (CI): 82.0%-94.2%) for patients receiving chemotherapy and 89.6% (95% CI: 85.1%-94.1%) for patients without chemotherapy. Chemotherapy was not associated with survival following adjustment for age, ethnicity, tumor size, tumor grade, HER2 status, lympho-vascular invasion, type of surgery and radiotherapy administration. However, chemotherapy was associated with a significant survival advantage (adjusted hazard ratio: 0.35, 95%CI: 0.14-0.91) in a subgroup of women with high-grade tumors.

Conclusion: Adjuvant chemotherapy does not appear to be associated with a survival benefit in women with T1N0M0, hormone receptor negative breast cancer except in those with high-grade tumors.