CLINICAL EXPERIENCE WITH IMAGE-GUIDED RADIOTHERAPY IN AN ACCELERATED PARTIAL BREAST INTENSITY-MODULATED RADIOTHERAPY PROTOCOL

Purpose To explore the feasibility of fiducial markers for the use of image-guided radiotherapy (IGRT) in an accelerated partial breast intensity modulated radiotherapy protocol. Methods and Materials Nineteen patients consented to an institutional review board approved protocol of accelerated partial breast intensity-modulated radiotherapy with fiducial marker placement and treatment with IGRT. Patients (1 patient with bilateral breast cancer; 20 total breasts) underwent ultrasound guided implantation of three 1.2- × 3-mm gold markers placed around the surgical cavity. For each patient, table shifts (inferior/superior, right/left lateral, and anterior/posterior) and minimum, maximum, mean error with standard deviation were recorded for each of the 10 BID treatments. The dose contribution of daily orthogonal films was also examined. Results All IGRT patients underwent successful marker placement. In all, 200 IGRT treatment sessions were performed. The average vector displacement was 4 mm (range, 2–7 mm). The average superior/inferior shift was 2 mm (range, 0–5 mm), the average lateral shift was 2 mm (range, 1–4 mm), and the average anterior/posterior shift was 3 mm (range, 1 5 mm). Conclusions This study shows that the use of IGRT can be successfully used in an accelerated partial breast intensity-modulated radiotherapy protocol. The authors believe that this technique has increased daily treatment accuracy and permitted reduction in the margin added to the clinical target volume to form the planning target volume.