Exploration of a Methodology For Evaluating Variation in On-Treatment Positioning and Dosimetric Consequences for VMAT Breast Patients

The study examines the development and scrutiny of an all-encompassing methodology aimed at appraising the fluctuations in on-treatment positioning and the subsequent dosimetric implications for patients undergoing Volumetric Modulated Arc Therapy (VMAT) for breast cancer treatment. The utilisation of VMAT in breast cancer therapy has showcased the potential for optimised dose delivery while demanding meticulous attention to patient setup accuracy and its potential impact on dose distribution. A method was developed that employed harnessing daily Cone-Beam Computed Tomography (CBCT) scans acquired during treatment, to evaluate day-to-day positional fluctuations in Volumetric Modulated Arc Therapy (VMAT) for 5 patients with left and rightsided breast cancer (FB and DIBH cases) at the Illawarra Cancer Care Centre (ICCC). The methodology aimed to scrutinise the precision of patient setup, acknowledging its pivotal role in treatment accuracy.