Abstract
<title>Abstract</title> <p>Background Deep-inspiration breath-hold (DIBH) can reduce cardiac, left anterior descending coronary artery (LAD), and ipsilateral lung exposure during radiotherapy for left-sided breast cancer. However, the relative dosimetric differences among active breathing coordinator-assisted DIBH (ABC-DIBH), surface-guided radiotherapy-assisted DIBH (SGRT-DIBH), and voluntary DIBH (vDIBH) remain unclear. This study systematically evaluated the comparative dosimetric effects of FB, ABC-DIBH, SGRT-DIBH, and vDIBH for cardiac, LAD, and left lung protection in left-sided breast cancer radiotherapy. Methods PubMed, Embase, the Cochrane Central Register of Controlled Trials, Web of Science, and CNKI were searched from inception to May 13, 2026. Original studies comparing DIBH with free breathing (FB) or comparing eligible DIBH techniques, and reporting extractable cardiac, LAD, or left lung dosimetric outcomes, were included. A frequentist random-effects network meta-analysis was performed. Mean differences (MDs) with 95% confidence intervals (CIs) were used as effect measures, and P-scores were used to support treatment ranking. Heterogeneity, inconsistency, small-study effects, and robustness were also assessed. Results Fifty-eight studies involving 4136 patients with left-sided breast cancer were included, forming an evidence network of 4 treatment nodes and 13 dosimetric outcomes. Compared with FB, ABC-DIBH, SGRT-DIBH, and vDIBH generally showed lower cardiac, LAD, and left lung doses across the primary outcomes. ABC-DIBH ranked most favorably for Heart Dmean (MD -1.77 Gy, 95% CI -1.98 to -1.56; P-score 0.941) and LAD Dmean (MD -9.24 Gy, 95% CI -11.21 to -7.27; P-score 0.884). SGRT-DIBH ranked most favorably for Heart Dmax (MD -14.43 Gy, 95% CI -18.32 to -10.54; P-score 0.956) and LAD Dmax (MD -16.89 Gy, 95% CI -21.15 to -12.62; P-score 0.993). vDIBH ranked most favorably for Left lung Dmean (MD -1.16 Gy, 95% CI -1.58 to -0.74; P-score 0.820) and Left lung V20 (MD -3.00 percentage points, 95% CI -4.08 to -1.92; P-score 0.877). Prespecified sensitivity analyses did not change the direction of the primary effects. Most primary outcomes showed no evident global inconsistency, whereas inconsistency signals were observed for two secondary outcomes, Heart V30 and Left lung V5. Conclusions ABC-DIBH, SGRT-DIBH, and vDIBH were all associated with lower cardiac, LAD, and left lung exposure than FB in radiotherapy for left-sided breast cancer, but their relative advantages were outcome-dependent. Current evidence suggests that the main dosimetric benefit is achieved by implementing DIBH itself, while the choice of a specific DIBH technique should consider the organ-at-risk endpoint, dosimetric priority, patient breath-hold capability, equipment availability, and clinical workflow. These findings support dosimetry-oriented technique selection but do not establish definitive superiority in long-term clinical outcomes.</p>