Rapid Prototyping, Design and Early Testing of a Novel Device for Supine Positioning of Large Volume or Pendulous Breasts in Radiotherapy

Here we describe the development of a novel device for breast positioning in supine radiotherapy that reduces breast sag and skin folds for patients with large or pendulous breasts. The overall aim of this work is to provide a practical and robust means of reducing high grade skin toxicity (moist desquamation) which tends to occur in skin folds. Participants with breast cup size D or greater were recruited to this ethics board approved prototype design study. Brassiere size, cup size, breast diameter, body mass index, height, weight, skin folds and torso dimensions were measured. Participants were positioned in treatment position on a breast board, with arms above the head and skin folds were identified and measured. 3D optical surface imaging provided initial design ideas and a rapid prototyping process using 3D printing was employed to arrive at a suitable design. The final clinical device consists of a curved carbon fibre breast support scoop suspended from a rigid frame that is compatible with commercially available breast boards. In addition to reducing skin folds, the device better positions the breast on the chest wall to help minimize the volume of normal tissue being irradiated and facilitates rapid setup. We present results of preliminary testing of the device, including dose buildup incurred by the carbon fibre scoop, skin fold reduction data and treatment planning data from CT simulations with and without the device. Surface dose with the device in place remains less than 80% of the prescription dose to the breast. Skin folds were reduced and reductions in irradiated volumes of lung and body were achieved compared with clinical plans without the supportive device. The novel breast support shows great potential to address a long-standing problem for a significant population of patients undergoing radiotherapy for breast cancer.