3000 - Breast Reconstruction and Radiotherapy: A Nationwide Cohort Study on Care Evaluation and Optimization (CONRAD study)

Purpose/Objective(s): All breast reconstruction (BR) options following mastectomy have an increased complication risk if combined with radiotherapy. Up to now, only a few high-quality studies have addressed patient satisfaction and complication risks, both in terms of timing of BR (prior to or after radiotherapy (i.e., immediate or delayed)) and type of BR (implant or autologous). As radiotherapy is indicated or considered in a significant number of patients and a growing number of patients desire BR, this issue is becoming increasingly relevant. With the nationwide CONRAD study, we aim to identify the most ideal treatment strategy by comparing different BR options in terms of patient-reported outcomes (PROs), complications, and cost-effectiveness. These results will enable us to improve shared decision-making and cost-effectiveness of BR strategies in the setting of radiotherapy.

Materials/Methods: The CONRAD study is a nationwide retro- and prospective observational cohort study. All patients, 18 years or older, treated with mastectomy and radiotherapy for breast cancer with/without (any type of) BR are eligible for inclusion. Retrospectively, patients not treated with radiotherapy will also be included. The primary objective is to assess PROs (using the validated questionnaires BREAST-Q and EQ-5D-5L) at 1 year. Secondary objectives include PROs at 3, and 5 years, complication rates prior to and after radiotherapy, cost-effectiveness in terms of incremental cost-effectiveness ratios, time to adjuvant oncological treatment, breast cancer recurrence at 3 and 5 years and recurrence free interval, disease free survival, and overall survival at 3 and 5 years. Multivariable linear regression models will be used to estimate the association of treatment strategy (consisting of BR type and radiotherapy treatment) with the different outcome measures, adjusted for relevant patient, tumor, and treatment characteristics. Additionally, as data is collected longitudinally, mixed effects models will be used. To detect a clinically relevant difference (medium effect size) in BREAST-Q results (8 points), 150 patients will be required per treatment group. Therefore, the accrual for the prospective cohort is targeted at 750 patients (300 patients with immediate BR (150 autologous, 150 implant), 300 patients with delayed BR (150 autologous, 150 implant) and 150 patients without BR). Patients will be included over a 2 year period in 25-30 institutions. Retrospectively, the entire cohort will involve 8.000-10.000 patients treated between 2015 and 2016. The first results of this study are anticipated in 2027.

Results: TBD.

Conclusion: The nationwide CONRAD study will enable us to compare different BR options in the setting of radiotherapy (considering all relevant aspects, i.e., health gains, complications, and cost-effectiveness). As a result, breast cancer care can be optimized by improving shared decision-making and efficiency.