Adjuvant chemotherapy and survival in women aged 70 years and older with triple-negative breast cancer: a Swedish population-based propensity score-matched analysis

BACKGROUND: Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer associated with poor survival, in which adjuvant systemic treatments are limited to chemotherapy. Due to competing mortality risks and comorbidities, older patients with TNBC are often undertreated with adjuvant chemotherapy, and clinical trials on this problem are scarce, despite a growing patient population. This study aimed to assess outcomes for patients aged 70 years and older with TNBC with or without chemotherapy in a national population-based registry, to provide information that can assist in treatment decisions for these patients. METHODS: In this population-based registry study, data on all patients aged 70 years and older diagnosed with primary early TNBC (larger than 5 mm in diameter and without distant metastasis) and surgically treated between Jan 1, 2009, and Dec 31, 2016, were retrieved from the Swedish National Breast Cancer Register, the Swedish Patient Register, and the Swedish Cause of Death Register. Patients with incomplete data (on oestrogen receptor, progesterone receptor, or human epidermal growth factor receptor 2 status, surgical procedure in the breast, or information about chemotherapy) were excluded. A propensity score-matched (PSM) model was used to examine the outcomes of adjuvant chemotherapy on 5-year breast cancer-specific survival (BCSS) and 5-year overall survival (OS), adjusted for age, tumour size, tumour grade, nodal status, and comorbidities. FINDINGS: Of 1130 women eligible for analysis, 368 (32·6%) received adjuvant chemotherapy, 45 (4·0%) received neoadjuvant treatment, and 717 (63·5%) did not receive chemotherapy. 5-year BCSS was significantly improved in patients who received adjuvant chemotherapy (85% [95% CI 81-89]) compared with patients who did not receive chemotherapy (68% [64-72]; p<0·0001). A similar benefit was observed in 5-year OS (79% [95% CI 75-84] vs 49% [45-53]; p<0·0001). In our PSM analysis, 5-year BCSS in patients treated with adjuvant chemotherapy was 83% (95% CI 78-89), versus 73% (67-80; p=0·014) in patients not treated with chemotherapy. 5-year OS in patients treated with adjuvant chemotherapy was 75% (95% CI 69-82), versus 63% (57-71; p=0·029) in patients who did not receive chemotherapy. INTERPRETATION: In this PSM registry analysis of surgically treated female patients aged 70 years and older with TNBC without distant metastasis, we identified a significant benefit both in 5-year BCSS and 5-year OS with adjuvant chemotherapy versus no chemotherapy, which persisted when adjusting for age and comorbidities. These results underline the importance of considering adjuvant chemotherapy in older patients. FUNDING: Knut and Alice Wallenberg Foundation, Assar Gabrielsson Foundation.