Feasibility assessment of real-time surface-guided intrafraction radiotherapy for prostate cancer without immobilization

Abstract Background Real-time position movement management in the intrafraction of radiotherapy has become a focus of precision radiotherapy. Real-time surface-guided radiotherapy by optical surface monitoring system (OSMS) has been widely used in multiple tumours, but its application in the intrafraction of radiotherapy for prostate cancer without immobilization is rarely reported. Methods Five patients of prostate cancer without immobilization were enrolled in this study. During 165 fractions of radiotherapy, cone-beam computed tomography (CBCT) was used to verify the set-up position before radiotherapy and correct the 6 degrees of freedom (6-DOF) errors. The 6-DOF real-time mean intrafractional motion was monitored by OSMS in the intrafraction of radiotherapy with thresholds of ± 3mm and ± 1°, and Post-treatment verified by the CBCT(V-CBCT). Spss22.0 statistical software was used to test the data of OSMS and VCBCT, P < 0.05 was statistically significant. Results The set-up errors by CBCT were Lat (1.78 ± 1.15) mm, Lng (3.24 ± 1.37) mm, Vrt (2.72 ± 1.49) mm, Rtn (0.56 ± 0.43) °, Roll (0.31 ± 0.32) °, Pitch (0.32 ± 0.39) °. OSMS monitoring intrafraction real-time position movement mean errors were Lat (0.52 ± 0.53) mm, Lng (0.76 ± 0.49) mm, Vrt (1.02 ± 0.71) mm, Rtn (0.27 ± 0.24) °, Roll (0.31 ± 0.32) °, Pitch (0.58 ± 0.43) °. Post-treatment CBCT verification errors were Lat (0.56 ± 0.57) mm, Lng (0.82 ± 0.54) mm, Vrt (1.01 ± 0.58) mm, Rtn (0.27 ± 0.19) °, Roll (0.32 ± 0.36) °, Pitch (0.60 ± 0.45) °. There was no significant difference between intrafraction OSMS real-time position movement mean error and after CBCT verification error (p > 0.05). Conclusions The OSMS is an accurate tool for real-time position movement management in prostate cancer radiotherapy without immobilization.