Accelerated Partial-Breast Intensity-Modulated Radiotherapy Results in Improved Dose Distribution When Compared With Three-Dimensional Treatment-Planning Techniques

Purpose To compare dose distribution and normal tissue sparing in partial-breast treatment using three-dimensional conformal radiotherapy (3D-CRT) vs. intensity-modulated radiotherapy (IMRT). Methods and Materials Sixty-three patients with Tis-1N0M0 breast cancer were treated on a Phase II prospective accelerated partial-breast IMRT protocol at two facilities between April 2004 and January 2006. Fifty-six patients had data sets sufficient to adequately contour all structures. These cases were subsequently replanned with 3D-CRT techniques using the same contours, to compare the dose distribution patterns of 3D-CRT vs. IMRT. Results The average planning target volume (PTV) to ipsilateral breast (IB) ratio was 24% (range, 7–58%). The average volume of IB receiving 25%, 50%, 75%, and 100% of the prescribed dose was 4.0%, 5.0%, 5.5%, and 10.5% less with IMRT than with 3D ( p < 0.01). The dose reduction to normal breast was further improved in the subset of patients whose PTV to IB ratio was >25%, and in patients with contoured breast volume