How Important Is a Reproducible Breath Hold for Deep Inspiration Breath Hold Breast Radiation Therapy?

Abstract

Deep inspiration breath hold (DIBH) for left-sided breast cancer has been shown to reduce heart dose. Surface imaging helps to ensure accurate breast positioning, but it does not guarantee a reproducible breath hold (BH) at DIBH treatments. We examine the effects of variable BH positions for DIBH treatments. Twenty-five patients who underwent free breathing (FB) and DIBH scans were reviewed. Four plans were created for each patient: FB, DIBH, FB_DIBH (the DIBH plans were copied to the FB images and recalculated, and image registration was based on breast tissue), and P_DIBH (a partial BH with the heart shifted midway between the FB and DIBH positions). The FB_DIBH plans give a "worst-case" scenario for surface imaging DIBH, where the breast is aligned by surface imaging but the patient is not holding their breath. Kolmogorov-Smirnov tests were used to compare the dose metrics. The DIBH plans gave lower heart dose and comparable breast coverage versus FB in all cases. The FB_DIBH plans showed no significant difference versus FB plans for breast coverage, mean heart dose, or maximum heart dose (P≥.10). The mean heart dose differed between FB_DIBH and FB by <2 Gy for all cases, and the maximum heart dose differed by <2 Gy for 21 cases. The P_DIBH plans showed significantly lower mean heart dose than FB (P<.01). The mean heart doses for the P_DIBH plans were <FB for 22 cases, the maximum dose was <FB for 18 cases. A DIBH plan delivered to a FB patient setup with surface imaging will yield dosimetry similar to that of a plan created and delivered FB. A DIBH plan delivered with even a partial BH can give reduced heart dose compared with FB techniques.