AbstractPurposeThis study aimed to investigate the accuracy of three fixation methods in patients with left breast cancer receiving whole breast radiotherapy: conventional breast bracket (BB), breast bracket combined with deep inspiration breath holding (DIBH), and cervical‐thoracic integrated bracket (CTIB) combined with DIBH.MethodsFrom January 2023 to September 2023, 84 patients who underwent left breast cancer radiotherapy with supraclavicular radiation after conservative surgery were included in this study, of which 25 patients were fixed by conventional BB, 34 patients by BB & DIBH, and 25 patients by CTIB & DIBH. Image registration was conducted around the treatment area, using the sternoclavicular joint and acromioclavicular joint as landmarks. Systematic and random errors were calculated to assess the accuracy of these fixation methods.ResultsCompared to the conventional BB group, the CTIB & DIBH group demonstrated significant improvements in accuracy across multiple dimensions, including left–right, superior‐posterior, and anterior–posterior directions, as well as rotational errors in the sagittal and coronal planes. The CTIB & DIBH group showed a significant reduction of setup error in the anterior–posterior direction compared to the BB & DIBH group. The displacement of the acromioclavicular joint varied, with the CTIB & DIBH method showing more favorable outcomes.ConclusionDIBH method exhibited lower setup errors and more effective fixation of the acromioclavicular joint, especially when combined with CTIB, making it a recommended fixation method in adjuvant radiotherapy following breast‐conserving surgery.