Short summary

Cohort study on early breast cancer patients investigating a possible effect of neoadjuvant therapy (NAT) on invasive disease-free survival compared to only adjuvant therapy. In the study period NAT was recommended in the event of locally advanced breast cancer to reduce the need for extensive surgery. However, some patients with early breast cancer were also offered NAT if the preliminary investigations demonstrated that the patients would receive adjuvant therapy after the operation.

Rationale

Chemotherapy is an important part of the neoadjuvant or adjuvant treatment in many early breast cancer patients. In 2019 55 % of Danish breast cancer patients received chemotherapy. Studies have demonstrated that neoadjuvant therapy (NAT) can minimize or eliminate the tumour in both the breast and axilla resulting in less extensive surgery. However, it is still debated whether NAT improve survival compared to adjuvant therapy. The aim of the study is to investigate whether NAT increases invasive disease-free survival in breast cancer (and in whom) in the era of polychemo- and HER2 targeted neoadjuvant therapy compared to adjuvant therapy with a minimum 5-year follow up.

Description of the cohort

Vejle Hospital were pioneers in implementing NAT for early breast cancer in Denmark. In the study period NAT was also considered when the tumour was ≤ 5 cm and one of the following:

1. TNBC and HER2 positive

2. The patient´s preoperative prognostic histopathology (malignancy grade, nodal involvement), age indicated that adjuvant therapy would be part of the treatment.

The reference group of patients that received AT will be identified through the Danish Breast Cancer Group (DBCG). Propensity score matching will be applied. - 1:n (variable) to achieve exchangeability.

Inclusion criteria:

-Women > 18 years diagnosed with breast cancer

-Between 01.01.2004-30.09.2016 (min 5-year follow-up)

-operable tumours < 5 cm

-NAT or AT

Exclusion criteria:

-Previously diagnosed with breast cancer

-LABC, metastatic disease at the time of diagnosis.

-Only endocrine neoadjuvant therapy

Data and biological material

Clinical data will be extracted through RKKP/DBCG. Additional histopathological data will be extracted through DPDB. Information on recurrence will be found through RKKP/DBCG cross-checked with DPDB and the Danish National Patient Registry (DNPR). Information on survival and emigration will be accessed through the National Registries, Danish Civil Registration System (CRS) and Cause of Death Registry (DAR).

Collaborating researchers and departments

Department of Surgery, Vejle Hospital

• Hans B. Rahr

Department of Clinical Oncology, Regional Hospital Gødstrup

• Troels Bechmann

Department of Plastic and Breast Surgery Aarhus University Hospital,

• Marianne Djernes Lautrup

Department of Breast Surgery, Gentofte Hospital

• Tove Tvedskov

Department of Pathology

• Trine Tram