TAO-Towards Optimal (Neo)Adjuvant Systemic Therapy of Stage III Triple-negative Breast Cancer

This prospective, national, multi-centre study will include patients with stage III triple-negative breast cancer (TNBC) who are planned to start with standard (neo)adjuvant systemic treatment. The study will gather clinico-pathological, treatment and follow-up information of participating patients through Dutch databases. Participating patients will be asked to complete cancer specific and more generic quality of life questionnaires at nine time points during and after their anticancer treatment in a mobile application. For all patients who have consented to additional blood collection, to assess the course of dynamic ctDNA during (neo)adjuvant chemotherapy and its relation with outcome, two tubes will be collected at four different time points.

Inclusion Criteria: * Patients aged 18 years or older * Histologically confirmed adenocarcinoma of the breast * Assumed clinical or pathological stage III (TNM) breast cancer * Breast tumor must be: * HER2-negative: i.e. either score 0 or 1 at immunohistochemistry or score 2 at immunohistochemistry and negative at in situ hybridization (ISH, CISH or FISH) * Hormone receptor negative i.e. an estrogen receptor (ER) of \