A bias-free, automated planning tool for technique comparison in radiotherapy - application to nasopharyngeal carcinoma treatments

Abstract

In this study a novel, user-independent automated planning technique was developed to objectively compare volumetric-modulated arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) for nasopharyngeal carcinoma planning, and to determine which technique offers a greater benefit for parotid-sparing and dose escalation strategies. Ten patients were investigated, with a standard prescription of three dose levels to the target volumes (70, 63, and 56 Gy), using a simultaneous integrated boost in 33 fractions. The automated tool was used to investigate three planning strategies with both IMRT and VMAT: clinically acceptable plan creation, parotid dose sparing, and dose escalation. Clinically acceptable plans were achieved for all patients using both techniques. For parotid-sparing, automated planning reduced the mean dose to a greater extent using VMAT rather than IMRT (17.0 Gy and 19.6 Gy, respectively, p < 0.01). For dose escalation to the mean of the main clinical target volume, neither VMAT nor IMRT offered a significant benefit over the other. The OAR-limiting prescriptions for VMAT ranged from 84-98 Gy, compared to 76-110 Gy for IMRT. Employing a user-independent planning technique, it was possible to objectively compare VMAT and IMRT for nasopharyngeal carcinoma treatment strategies. VMAT offers a parotid-sparing improvement, but no significant benefit was observed for dose escalation to the primary target.