Abstract
BackgroundFor patients with high risk breast cancer and mastectomy, radiotherapy is the treatment of choice to improve survival and local control. Target dose is mainly limited due to skin reactions. The feasibility of using 4 MV beams for chest wall treatment was studied and compared to standard 6 MV bolus radiotherapy.MethodsPost-mastectomy IMRT was planned on an Alderson-phantom using 4 and 6 MV photon beams without/with a 0.5 cm thick bolus. Dose was measured using TLDs placed at 8 locations in 1 and 3 mm depth to represent skin and superficial target dose, respectively.Results4 MV and 6 MV beams with bolus perform equally regarding target coverage. The minimum and mean superficial target dose for the 6 MV and 4 MV were 93.0% and 94.7%, and 93.1% and 94.4%, respectively. Regarding skin dose the 4 MV photon beam was advantageous. The minimum and mean skin dose for the 6 MV and 4 MV was 76.7% and 81.6%, and 69.4% and 72.9%, respectively. The TPS was able to predict dose in the build-up region with a precision of around 5%.ConclusionsThe use of 4 MV photon beams are a good alternative for treating the thoracic wall without the need to place a bolus on the patient. The main limitation of 4 MV beams is the limited dose rate.
Highlights
For patients with high risk breast cancer and mastectomy, radiotherapy is the treatment of choice to improve survival and local control
For patients with high risk breast cancer and mastectomy, postoperative radiotherapy is the treatment of choice to improve local control and survival [1,2,3]
The 2005 Oxford meta-analysis shows that for node positive patients post-mastectomy radiotherapy (PMRT) decrease significantly the risk of chest wall recurrence from 21% to 7.8% and that this improvement is correlated with an improvement of survival [3]
Summary
For patients with high risk breast cancer and mastectomy, radiotherapy is the treatment of choice to improve survival and local control. For patients with high risk breast cancer and mastectomy, postoperative radiotherapy is the treatment of choice to improve local control and survival [1,2,3]. Post-mastectomy radiotherapy (PMRT) is administered using low energy photon beams Another possibility to improve the chest wall dose distribution for PMRT would be using a photon energy lower than 6 MV x-rays. The purpose of the present study is to calculate and measure skin and target dose distributions in an Alderson Rando phantom irradiated with 4 MV x-rays without bolus, and with 6 MV with and without bolus
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