Mammacarcinoom Neoadjuvante Systeemtherapie

The results of neoadjuvant systemic therapy (NST) in primary breast cancer patients are promising. Down staging of the tumour by NST results in an increased rate of breast conserving surgery (BCS) 1,2, and thereby less morbidity, improved cosmetic outcomes and better quality of life3,4. NST also benefits axillary down staging (ADS) with less extensive axillary surgery and its postoperative complications.

In the Netherlands criteria for NST are currently not well defined, resulting in different indications between hospitals5. This is likely to result in different treatment outcomes such as surgical treatment of the breast or axilla, differences in the amount of radiotherapy, cosmetic outcomes or quality of life.

With this study we want to investigate the next three questions considering NST in primary breast cancer patients.

1. What are the different reasons for applying NST in primary breast cancer patients in the Netherlands?
2 a. How often does NST result in conversion to BCT from a mastectomy in different tumor types?
2 b. What are the surgical outcomes (volumes, margins, re-excisions)?
3. How often does NST result in axillary down staging by which an ALND is omitted in the different tumor types?

This will be a snapshot study, this is an hypotheses-generating design, without restraining to many in- or exclusion criteria. Thereby, this design generates a population-based overview, which rapidly provides insight in current clinical practice on a national scale.

There will be two timepoints for collection data for this Snapshot registration, one at the multidisciplinary team discussion (MTD) pre-NST staging and one after the finale pathology results. Research data will be collected through our Snapshot score form and stored in Castor, an electronic database, according to Good Clinical Practice standards and will be handled confidentially and anonymously

With this study we aim to provide societal and ethical justification. This is an observational research project, patients included in this research will not undergo any intervention or treatment as part of the research project. Therefore, this study is not WMO-compulsory.