Abstract
Post-mastectomy Radiotherapy (PMRT) is advised for patients who have high-risk breast cancer disease. The radiation Tumour Volume (TV) is the chestwall, inclusive of the skin. The aim is to deliver a maximum dose to the TV, whilst minimising the dose to the Organs at Risk (OAR). It is beneficial to treat patients with a left-sided tumour by using a gating technique called Deep Inspiration Breath-hold (DIBH). This technique minimises the dose to the heart, as it displaces the heart away from the chestwall as the patient breathes in.
Due to the skin-sparing effect of high-energy photons, the TV in PMRT can be underdosed. A tissue-equivalent material, called a bolus, can be placed on the skin to counteract this effect and to improve the dose that is received in the superficial skin region. Unfortunately, the commercial sheet bolus that is currently used does not completely conform to the irregular shape of the chestwall, which causes air gaps that can compromise the accuracy of the surface dose (π·π·ππππππππ).
Several studies have demonstrated that the three-dimensional (3D)-printed bolus offers improved accuracy and a reduction of the air gaps, when compared to the commercial sheet bolus, as it can conform precisely to a patientβs shape. However, the search for the optimal 3D-printed material is ongoing. The experiences of the staff and patients have been under-researched; however, these are crucial outcomes that need to be measured, in order to obtain the successful adoption of the 3D-printed bolus in the clinic. Unaddressed questions remain, when the 3D-printed bolus is combined with certain techniques, such as DIBH.
This research was conducted at a Private Radiotherapy Unit that is based in the KwaZulu-Natal (KZN) Midlands. A quantitative, quasi-experimental comparative design was used, which compared the two 3D-printed bolus types, a semi-rigid elastomer, Thermoplastic Polyurethane (TPU), as well as a flexible silicone. Nineteen patient participants were randomly assigned into two different arms, and the application of the two bolus types was alternated daily. Each patient was imaged before the treatment, whilst in DIBH, with one of the 3D-printed bolus types being applied to their skin. The conformity of each bolus was calculated by measuring the volume and thickness of the visible air gaps on the images that were generated. The time taken to apply each bolus was recorded by the Radiation Therapists (RTs). Both the patients and the participating RTs completed a questionnaire to rate their experience of the two 3D-printed bolus types...