Whole Breast + Lymph Node Irradiation: Prone Compared to Supine Position in 15 or 5 Fractions

Locoregional radiotherapy after lumpectomy and axillary node dissection diminishes the locoregional recurrence risk at 10 years by 21,2 % in women with pathologically confirmed lymph node involvement. Excess dose to organs at risk can lead to acute and late side effects, such as tissue damage, organ malfunction and secondary cancers. Radiotherapy in prone position has helped reduce these risks for whole breast radiotherapy only, but has not yet been adequately investigated for patients also requiring regional nodal irradiation. One of the reasons is that there is no optimal patient support device available to allow regional nodal irradiation in prone position. To this end, a novel positioning device was developed at our center, allowing regional nodal irradiation in prone position. It was called the crawl breast couch because the patient position resembles a phase from the crawl swimming technique. A previous planning study by Deseyne et al. using this device shows a benefit (i.e. reduced dose) for the ipsilateral lung, the thyroid, as well as a minor benefit for the right lung, and contralateral breast (which already receive very low relative doses) while maintaining similar target coverage when compared to supine positioning. Apart from the paradigm shift from supine to prone radiotherapy, in recent years, it has become clear that breast cancer cells are more sensitive to fraction dose than originally presumed. Large randomized trials confirm this hypothesis: moderate hypofractionation schemes in 15 or 16 fractions are at least equivalent in tumor control and toxicity although the total dose is lower than the traditional 50 Gy in 25 fractions. Further acceleration to 5 fractions is expected to have an even larger radiobiological advantage regarding tumor control. Additional advantages are patient comfort and a better use of radiotherapy resources. This randomized trial with 2 x 2 factorial design tests 2 interventions for patients with breast cancer requiring whole-breast and regional nodal irradiation: radiotherapy in prone position with a specifically designed patient support device called the crawl breast couch, and accelerated radiotherapy in 5 fractions. The standard arm in this trial is supine hypofractionated radiotherapy. The goal of this trial is to evaluate the effect of the prone crawl treatment position and/or accelerated schedule on acute and late toxicities, as well as quality of life and time management for breast cancer patients receiving whole breast and regional nodal irradiation after breast conserving surgery.