Abstract PS13-23: Evaluation of a beneficial effect of adjuvant chemotherapy in patients with stage I triple-negative breast cancer: A population-based study using the SEER 18 database
Authors: Wang Yang , Zhang Bailin 
Published: February 2021

Abstract
Background:Triple-negative breast cancer (TNBC), a subtype of breast cancer, due to the lack of an effective therapy target, the only postoperative approach that seems to work for TNBC is chemotherapy treatment. For TNBC that is less than 1 cm and has no lymph node metastasis, administering chemotherapy is controversial at present. The word "consider" is used in the description of the National Comprehensive Cancer Network (NCCN), and the level of evidence is IIb. The Chinese Society of Clinical Oncology (CSCO) guidelines do not provide a specific recommendation for this group of patients but recommend that all patients with TNBC should receive postoperative chemotherapy. In this study, the SEER database was used to evaluate the benefit of chemotherapy. The results will help confirm whether patients with stage T1aN0M0 and T1bN0M0 TNBC should be administered adjuvant chemotherapy.Purpose To evaluate the effect of adjuvant chemotherapy on improving the prognosis of patients with stage I triple-negative breast cancer (TNBC).Methods TNBC patients diagnosed in the SEER 18 database from 2010 to 2015 were included. Kaplan-Meier plots and log-rank tests were used to compare the differences in breast cancer-specific survival (BCSS) and overall survival (OS) between subgroups of variables. A Cox proportional hazard model was used to determine the prognostic factors affecting BCSS and OS.Results A total of 9,256 patients were enrolled in this study. Among these patients, 380 died from breast cancer, and 703 died from all causes. Patients who received chemotherapy had significantly better BCSS and OS than those who did not receive chemotherapy for stage T1cN0M0 (BCSS, hazard ratio (HR) = 0.68, 95% confidence interval (CI) = 0.51-0.90; OS, HR = 0.54, 95% CI = 0.44-0.67) and stage IB (BCSS, HR = 0.39, 95% CI = 0.16-0.95; OS, HR = 0.41, 95% CI = 0.19-0.87) disease. Patients who received chemotherapy did not have significantly better BCSS or OS than those who did not receive chemotherapy for stage T1aN0M0 or T1bN0M0 disease. The patients who received chemotherapy in the poorly differentiated and undifferentiated groups had better BCSS (HR = 0.68, 95% CI = 0.52-0.88) and OS (HR = 0.54, 95% CI = 0.44-0.66) than the patients who did not receive chemotherapy.Conclusion According to current clinical guidelines, patients with stage T1bN0M0 TNBC are probably overtreated. The prognosis of these patients with stage T1aN0M0 or T1bN0M0 disease is good enough that adjuvant chemotherapy cannot improve it further.
TABLE: The effect of adjuvant chemotherapy on BCSS stratified by the tumor stageStageChemotherapyCasesDeath from breast cancerlog-rank PUnivariate CoxMultivariate CoxaHR (95%CI)PHR (95%CI)PT1aN0M00.446No857121.00(reference)1.00(reference)Yes24651.50(0.53-4.25)0.4491.17(0.33-4.12)0.808T1bN0M00.700No886281.00(reference)1.00(reference)Yes1341370.91(0.56-1.48)0.7001.00(0.57-1.74)0.999T1cN0M02.73×10-5No1410971.00(reference)1.00(reference)Yes41891710.59(0.46-0.76)3.41×10-50.68(0.51-0.90)0.007IBNo49100.0031.00(reference)1.00(reference)Yes278200.33(0.16-0.71)0.0050.39(0.16-0.95)0.038a Adjusted by age, laterality, grade, total number of malignant tumors per patient and radiotherapy.Patients who received chemotherapy had significantly better BCSS than those who did not receive chemotherapy for stage T1cN0M0 and stage IB disease. In contrast, no significant associations of chemotherapy with BCSS were observed for stage T1aN0M0 or stage T1bN0M0 disease.
Citation Format: Yang Wang, Bailin Zhang. Evaluation of a beneficial effect of adjuvant chemotherapy in patients with stage I triple-negative breast cancer: A population-based study using the SEER 18 database [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS13-23.