Complete response in the axilla and the non-triple negative subtype are favourable prognostic factors for survival outcomes in inflammatory breast cancer

Aim: To assess real-world outcomes and prognostic factors of non-metastatic inflammatory breast cancer according to immunohistochemistry (IHC)-based subtype and treatment regimen.

Methods: An institutional retrospective analysis of patients treated with neoadjuvant systemic treatment (NAST) for stage III inflammatory breast cancer diagnosed between 2001 and 2018 was performed. The survival outcomes in relation to patient characteristics, tumour characteristics, treatment modality and response to NAST were analyzed.

Results: 225 patients fulfilled the inclusion criteria, 90% of patients were node-positive. IHC-based subtypes: 39.1% were HR+/HER2-, 19.1% HR+/HER2+, 23.1% HR-/HER2+ and 18.7% HR-/HER2-. Treatment was multimodal: NAST (100%), surgery (94.2%) and radiotherapy (94.2%). 53.3% of patients received adjuvant endocrine therapy, 34.3% (neo)adjuvant trastuzumab. Tri-modality therapy was applied in 89.3% of patients. Following NAST, a pathologic complete remission (pCR) in the breast was found in 16.9%, in the axilla in 29.7% and in both the breast and axilla in 10.3% of patients. The axillary pCR rate was significantly higher in HR- subtypes. Median overall survival (OS) was 8.9, 7.2, 5.8 and 2.3 years (p < 0.001) for HR+/HER2-, HR+/HER2+, HR-/HER2+ and HR-/HER2- subtype, respectively. On multivariate analysis, IHC-based subtype, age and axillary pCR were found as independent prognostic factors for RFS and OS. pCR rate and median OS improved over time, 5.8% vs 14.7% and 4.7 vs 10.0 years (2001-2009 vs. 2010-2018), respectively.

Conclusions: Axillary pCR and the non-triple-negative IHC-based subtype are favourable prognostic factors for RFS and OS in inflammatory breast cancer. Introduction of taxanes and antiHER2 drugs contributed to improved pCR rate and OS.