Evaluation of dose distribution differences from five algorithms implemented in three commercial treatment planning systems for lung SBRT

Early stage lung cancer is increasingly being treated using stereotactic body radiation therapy (SBRT). Several advanced treatment planning algorithms are now available in various commercial treatment planning systems. This work compares the dose distributions calculated for the same treatment plan using, five algorithms, in three different treatment planning systems. All plans were normalized to ensure the prescription dose covers 95% of the planning target volume (PTV). Dose to the planning target volume (PTV) was compared using near-minimum dose (D-98%), near-maximum dose (D-2%) and dose homogeneity, while dose fall-off was compared using D(2c)m and R-50. Dose to the lung was compared using V-5Gy, V-20Gy and mean lung dose. Statistical analysis shows that dose distributions calculated using Eclipse's Acuros XB and RayStation's Monte Carlo were significantly different from the other dose distributions for the PTV dose parameters investigated. For lung dosimetric parameters, this difference persisted for volumetric modulated arc therapy (VMAT) plans but not for conformal arc plans. While normal tissue complication probability (NTCP) differences were significant for some of the algorithms for VMAT delivery approaches, they were not significantly different for any algorithm for conformal arc plans. All parameters investigated here were within 5% between all algorithms. The results show that, while some small dosimetric differences can be expected around the PTV, the dose distribution to the rest of the treatment area, especially the lungs, should not be clinically-relevant when switching between one of the five algorithms investigated.