A Comprehensive Evaluation of Setup Uncertainties and Margin Optimization Using Deep Inspiration Breath-Hold Versus Free-Breathing Techniques in Breast Carcinoma.

Abstract

PurposeTo systematically evaluate and compare geometric setup errors and calculate optimal planning target volume (PTV) margins for patients with left-sided breast carcinoma treated with three-dimensional conformal radiotherapy (3D-CRT) using free-breathing (FB) versus deep inspiration breath-hold (DIBH) techniques.Materials and methodsA retrospective analysis was conducted on 103 postoperative breast carcinoma patients (n = 47 in the FB group; n = 56 in the DIBH group). Daily setup verification was performed using paired kilovoltage (kV) orthogonal images, yielding 348 analysed fractions. Setup deviations were measured in anterior-posterior (AP), superior-inferior (SI), and right-left (RL) directions. PTV margins were derived using the Van Herk formula.ResultsIn the FB group, systematic errors were 0.16 cm (AP), 0.17 cm (SI), and 0.17 cm (RL), with random errors of 0.28 cm, 0.37 cm, and 0.29 cm, respectively. In the DIBH group, systematic errors were 0.14 cm (AP), 0.16 cm (SI), and 0.16 cm (RL), with random errors of 0.25 cm, 0.29 cm, and 0.27 cm, respectively. DIBH significantly reduced setup errors in the SI direction (p = 1.1 x 10-5). Calculated PTV margins for DIBH were smaller, particularly in the SI axis (0.61 cm vs. 0.69 cm).ConclusionDIBH significantly mitigates random setup errors in the longitudinal direction by stabilizing diaphragmatic motion, allowing for reduced PTV margins and improved sparing of organs at risk.