Surface-guided radiation therapy for breast cancer: more precise positioning

Introduction Hypofractionated radiation therapy for breast cancer requires highly precise delivery through the use of image-guided radiotherapy (IGRT). Surface-guided radiation therapy (SGRT) is being increasingly used for patient positioning in breast radiotherapy. We aimed to assess the role of SGRT for verification of breast radiotherapy and the tumour bed. Materials and methods Prospective study of 252 patients with early stage breast cancer. A total of 1170 determinations of daily positioning were performed. Breast surface positioning was determined with SGRT (AlignRT) and correlated with the surgical clips in the tumour bed, verified by IGRT (ExacTrac). Results SGRT improved surface matching by a mean of 5.3 points compared to conventional skin markers (98.0 vs. 92.7), a statistically significant difference (p < 0.01, Wilcoxon Test). For surface matching values > 95%, >= 3 clips coincided in 99.7% of the determinations and all markers coincided in 92.5%. For surface matching rates > 90%, the location of >= 3 clips coincided in 99.55% of determinations. Conclusions SGRT improves patient positioning accuracy compared to skin markers. Optimal breast SGRT can accurately verify the localisation of the tumour bed, ensuring matching with >= 3 surgical clips. SGRT can eliminate unwanted radiation from IGRT verification systems.