Abstract 201P
Background
The 70-gene signature (MammaPrint®) has been validated to aid adjuvant chemotherapy decisions in early-stage breast cancer. In patients with clinically high/genomic low-risk disease, chemotherapy can be safely omitted. However, there is still a need to increase the likelihood of breast-conserving surgery (BCS). We aim to evaluate the efficacy of neoadjuvant endocrine treatment (NET) in patients with clinically high/genomic low-risk disease regarding radiological response, pathological response, and rate of BCS.
Methods
A single-center retrospective analysis was performed of breast cancer patients diagnosed between 2015 and 2019 with a low 70-gene signature score who were treated with NET. Response was assessed using MRI or ultrasound according to RECIST. Major pathological response was defined as no residual invasive tumor cells left in breast and axilla or <10% residual invasive disease in the breast and axilla.
Results
Fifty-one patients were included with a median age of 53 (37-77), of which 24 (45%) were premenopausal. The median tumour size was 29 mm (17-48). Ten patients had lymph node-positive disease. Based on the St. Gallen criteria. 30 patients were classified as luminal A and 21 as luminal B. Tamoxifen was started in pre- and an aromatase inhibitor in postmenopausal patients, with a median duration of 8 months (4-14) until surgery. Four patients switched therapy because of stable or progressive disease at 3-month evaluation. Radiological complete response was observed in seven patients (14%), partial response in 32 (64%) and stable disease in 10 (20%) patients. Major pathological response was observed in 12.5% of the cases. Of the eleven patients in whom mastectomy had been indicated initially, seven (7/11; 64%) were eligible for BCS after NET. Because of lymph node-positive disease or a second progressive lesion found post-operatively, five (10%) patients received adjuvant chemotherapy.
Conclusions
Based on this relatively small series, treating patients with a low-risk 70-gene signature with neoadjuvant endocrine therapy seems feasible. The pathological response rate and conversion to breast-conserving surgery are of clinical relevance and deserve validation in a larger study.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Netherlands Cancer Institute/Antoni van Leeuwenhoek hospital (NKI-AVL).
Funding
Has not received any funding.
Disclosure
S. Linn: Advisory/Consultancy, Research grant/Funding (institution), instutional support: AstraZeneca; Advisory/Consultancy, instutional support: Cergentis; Advisory/Consultancy, instutional support: IBM; Advisory/Consultancy, Research grant/Funding (institution), instutional support: Pfizer; Advisory/Consultancy, Research grant/Funding (institution), instutional support (non-financial): Roche; Research grant/Funding (institution): Agendia; Research grant/Funding (institution): Eurocept-pharmaceuticals; Research grant/Funding (institution), instutional support (non-financial): Genentech; Research grant/Funding (institution), instutional support (non-financial): Novartis; Research grant/Funding (institution), instutional support (non-financial): Tesaro; Research grant/Funding (institution), instutional support (non-financial): Immunomedics; Non-remunerated activity/ies, instutional support: Bayer. M. Kok: Advisory/Consultancy, Research grant/Funding (institution): BMS; Advisory/Consultancy, Research grant/Funding (institution): Roche; Advisory/Consultancy: MSD; Advisory/Consultancy: Daiichi; Research grant/Funding (institution): AstraZeneca. All other authors have declared no conflicts of interest.