The MARECA (national study of management of breast cancer locoregional recurrence and oncological outcomes) study: protocol for a prospective, multicentre cohort study.

<h4>Background</h4>Despite a UK 5-year breast cancer survival rate of 86.6%, patients may develop breast cancer recurrence within the same breast after breast conserving surgery, as well as in the remaining skin or chest wall after mastectomy or in the ipsilateral lymph glands. These recurrences, collectively termed locoregional recurrence (LRR), occur in around 8% of patients within 10 years of their original diagnosis. Currently, there is a lack of robust information on the presentation and prevalence of LRR with no UK-specific clinical guidelines available for the optimal management of this patient group. Additionally, there is a need to identify patterns of LRR presentation and their progression, which will enable prognostic factors to be determined. This will subsequently enable the tailoring of treatment and improve patient outcome.<h4>Methods</h4>The MARECA study is a prospective, multicentre cohort study recruiting patients diagnosed with breast cancer LRR +/- associated distant metastases. Over 50 UK breast units are participating in the study with the aim of recruiting at least 500 patients over a recruitment period of 24 months. The data collected will detail the tumour pathology, imaging results, surgical treatment, radiotherapy and systemic therapy of the primary and recurrent breast cancer. Study follow-up will be for up to 5 years following LRR diagnosis to determine subsequent oncological outcomes and evaluate potential prognostic factors.<h4>Discussion</h4>This study will address the current knowledge gap and identify subgroups of patients who have less successful treatment outcomes. The results will determine the current management of LRR and the prognosis of patients diagnosed with breast cancer LRR +/- distant metastases in the UK, with the aim of establishing best practice and informing future national guidelines. The results will direct future research and inform the design of additional interventional trials and translational studies.