Abstract
Background: Assessing the survival benefit of neoadjuvant chemotherapy (NAC) in triple-negative breast cancer (TNBC) patients is typically evaluated through clinical trials. Clinical trials are limited by their highly controlled context, often limiting the generalisability of findings. Globally, there is a lack of population-based evaluations of ‘optimal care’ for those diagnosed with TNBC, the most aggressive breast cancer type with no targeted treatment. The main advance in clinical practice for TNBC treatment has been the use of NAC, with its use now recommended even for small triple-negative tumours. In this study, we use a Queensland (Australia) population-based study to identify TNBC patients who received NAC and achieved pathological complete response (pCR) to examine associations with overall survival (OS) and breast cancer-specific survival (BCSS). Methods: All women diagnosed with invasive TNBC between 2017 to 2019 in Queensland, Australia, were identified from the Queensland Oncology Repository (a state-wide database) and followed up to Feb 17, 2024, for OS and up to Dec 31, 2021, for BCSS. Stage IV and patients who had not undergone any treatment were excluded. pCR was defined as no residual invasive breast cancer after NAC regardless of lymph node status. Multivariable logistic regression models were developed using Directed Acyclic Graphs (DAGs) to identify confounding variables to be included in models and were used to assess the likelihood of being treated with NAC and achieving pCR. Survival rates for OS and BCSS were estimated for no NAC versus NAC with pCR and NAC without pCR using Kaplan-Meier, and adjusted hazard ratio (HR) were estimated using flexible parametric survival models to account for time-varying hazards; at one-year, two-year, and four-year survival, adjusting for age, geographic region, prognostic stage, and hospital type (public vs private). Results: A total of 1,021 TNBC cases were included in the analysis. Overall, 21.5% had received NAC, with NAC more common in 2019 (27.3%) compared to 2017 (16.1%) and more common in those living in major cities (24.4%) and outer regional/rural areas (21.9%) than those in inner regional areas (12.6%). Patients who received NAC (versus those who did not) were younger (mean ± SD 49.0 ± 13.0 vs. 61.4 ± 14.6 years) and were more commonly diagnosed with stage IIIa-IIIc (70.5% vs 53.1%). Among those who had NAC, 42.4% achieved pCR, with higher rates of pCR in 2019 (53.8%) compared to 2017 (31.5%). pCR was more common in those with stage IIa-IIb (62.5%) versus stage IIIa-IIIc (34.9%). The median follow-up was 4.96 years (range, 0.01-7.12) for OS and 3.21 years (range, 0.14-4.99) for BCSS. Compared to those who did not receive NAC, those who did and achieved pCR had better OS (HR 0.27 to 0.41; p>0.05) at 1-, 2- and 4-years post-diagnosis, whereas those who did not achieve pCR had significantly poorer OS (HR 2.22 to 3.57; p<0.05) at all follow-up years. Similar trends were observed for BCSS. Conclusion: The best survival was observed in patients who received NAC and achieved pCR. In this population-based sample, survival differences in those with pCR versus those without were similar to that observed in clinical trials. Receipt of NAC however, differed by age and geographical region, with those living in inner regional areas being less likely to receive NAC. Equitable access to current optimal care is essential for addressing survival disparities, while continued research into tailored treatments for TNBC is vital for improving outcomes for those who do not benefit from current treatments.
Citation Format: Larissa Vaz-Goncalves, Louise Marquart-Wilson, Melinda Protani, Jodi Saunus, Julie Moore, Michelle Morris, Marina Reeves. Neoadjuvant chemotherapy and survival outcomes in triple-negative breast cancer: a population-based study (Queensland, Australia) [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-11-22.