Evaluating the setup accuracy and workflow efficiency of tattooless surface-guided radiation therapy for breast cancer.

[PURPOSE] To evaluate the setup accuracy and workflow efficiency of a fully tattooless surface-guided radiation therapy (SGRT) workflow across different breast radiotherapy techniques and determine the impact of image-guided radiation therapy (IGRT) frequency on these outcomes.

[METHODS] In total, 324 patients had undergone whole-breast irradiation (WBI) under free breathing, WBI with deep inspiration breath-hold (DIBH), or chest wall and regional nodal irradiation (RNI) after mastectomy, all guided via AlignRT. A tattooless workflow was consistently applied during simulation and treatment. Based on the implementation period, patients were categorized into daily IGRT (dIGRT) and periodic IGRT (pIGRT) groups. Setup accuracy was evaluated using residual 3D vector errors after IGRT, and treatment duration was derived from AlignRT monitoring-on logs.

[RESULTS] Mean 3D vector errors (95% confidence interval) were 1.4 mm (1.4-1.5) for WBI, 1.3 mm (1.2-1.4) for DIBH, and 3.6 mm (3.5-3.7) for RNI. The proportions of fractions within 5 mm were 97.1%, 94.4%, and 81.9%, respectively. No significant accuracy differences were observed between dIGRT and pIGRT. In RNI, longer monitoring-on times correlated with greater setup errors, particularly in the dIGRT group. Monitoring-on time was significantly reduced with pIGRT compared to dIGRT (mean reduction: 0.7-2.4 min) and showed a gradual decline across fractions.

[CONCLUSION] A fully tattooless SGRT workflow ensures accurate and efficient patient setup for breast radiotherapy. Periodic IGRT maintains high precision while reducing treatment time, supporting its clinical feasibility and optimized integration into routine practice.