This is a multicenter, open labeled, phase 2 clinical trial, where patients are stratified to one of two treatment groups based on upfront TP53 mutation status; i.e. TP53 mutated vs. TP53 wt disease, and treated with dose-dense cyclphosphamide. Furthermore, patients included are stratified based on tumor stage; i.e. locally advanced breast cancer (M0 disease) or metastatic breast cancer (M1 disease). All participating cancer centers will prospectively include patients with breast cancer fulfilling the inclusion criteria.
If patients do not respond to the experimental treatment as outlined in the protocol, treatment with dose-dense cyclophosphamide will be terminated, and further cancer treatment will continue at the treating oncologist's discretion. The response data for all patients who have received at least one chemotherapy course will be included in the final efficacy analysis.
Tumor tissue, blood samples and radiology data will be collected before therapy starts, if therapy needs to be changed, and for patients with locally advanced breast cancer: at surgery. Response data will be evaluated closely during treatment, with clinical assessment of tumor size every two weeks for patients with locally advanced breast cancer and by radiology every eight weeks for patients with metastatic breast cancer. Evaluation of side effects/tolerance will be performed at every clinical visit, i.e. every two weeks for all patients included in the p53 trial.