Early progression of breast cancer during neoadjuvant chemotherapy may predict poorer prognoses.

Background: In Finland, breast cancers treated with neoadjuvant chemotherapy (NACT) are usually locally advanced and/or have an inflammatory phenotype. We evaluated early NACT responses in breast tumours and lymph nodes and their correlation with survival.Material and methods: We collected a retrospective dataset of 145 patients with very high-risk but non-metastasised breast cancers that were treated with NACT in a Finnish University Hospital between September 2013 and January 2019. The patients underwent magnetic resonance imaging (MRI) scans before beginning NACT and after every second NACT cycle thereafter.Results: The total pathological complete response rate was only 10.7% and breast cancer-specific survival (BCSS) at 24 months was 93.0%. The 2-year breast cancer-specific survival (BCSS) rate was 93.0%, but this varied from 86.5% for the triple-negative subtype to 100.0% for the luminal A-like subtype. Enlargement of the malignant axillary lymph nodes during the first two NACT cycles was associated with poor BCSS rates in HER2-negative patients (p = .00003 in the univariate analysis; hazard ratio = 26.3; 95% confidence interval = 2.66-259.6; p = .005 in the multivariate analysis). Furthermore, progression in the combined diameters of the breast tumours and axillary lymph nodes during the period between a patient's pre-treatment MRI and her MRI after two NACT cycles was also correlated with worse BCSS rates in both univariate and multivariate analyses.Conclusions: An early MRI assessment after two NACT cycles, specifically of the tumour's axillary lymph nodes, has the potential to predict short-term BCSS in patients with locally advanced HER2-negative breast cancers.