The GeDI project-a German DIBH database

Background: Studies indicate that all left-sided breast cancer patients benefit from the deep inspiration breath hold technique (DIBH), however, not all patients experience the same benefit. A meta-analysis performed by Latty et al. reviewed 18 studies evaluating DIBH, which demonstrated a relative reduction of mean dose (Dmean) to the heart ranging from 26.2% to 75% as compared to irradiation in free breathing. However, as most papers report averages rather than patient-by-patient analyses, outliers remain unidentified. Thus, a lack of data and knowledge exists in determining selection criteria to predict individual patient benefit from DIBH.

Methods: We are planning to establish a large retrospective database of breast cancer patients treated with deep inspiration breath hold (DIBH) radiotherapy techniques. Data will be collected anonymized from all participating centres. A detailed analysis of:

1. Differences in OAR sparing by anatomical conditions
2. Differences in OAR sparing by used DIBH techniques (free breathing, RPM, surface scanning with camera or laser systems etc)
3. Differences in OAR sparing by fractionation schedules (normalized to EQD2)
4. Differences in OAR sparing by PTV volumes and CTV definitions

but not limited to, will be performed.

Discussion: Patient data will be stratified according to different anatomical conditions (such as large breasts vs. small breasts), radiation techniques, fractionation schedules and PTV volumes (for e.g. chest wall after mastectomy vs. breast only vs. breast and lymphatics etc). This multicentre database will allow for the first time an in depth analysis of the impact of DIBH. It will enhance our knowledge on outliers and will provide selection criteria to predict individual patient benefit from DIBH.