Comparative Dosimetry and Biological Risk Assessment of Lung Oligometastasis SBRT: VMAT, Helical Tomotherapy, and CyberKnife

PurposeTo compare the dosimetry and biological risk of volumetric modulated arc therapy (VMAT), helical tomotherapy (HT) and cyberKnife (CK) in the treatment of lung oligometastases.Methods and materialsThis retrospective study included a cohort of 21 lung oligometastasis patients, each with 2 or 3 lesions, who had previously undergone stereotactic body radiation therapy (SBRT). VMAT, HT and CK plans were made for each patient. The dose distribution of planning target volume (PTV) and organs at risk (OARs) were evaluated. Three biological risks were evaluated, namely radiation pneumonitis (RP), coronary artery disease (CAD) and congestive heart failure (CHF). Monitor Units (MUs) and beam-on-time were also recorded.ResultsAll techniques were able to produce clinically deliverable plans. The expected biological risks for VMAT plans, CK plans, and HT plans were 6.69%, 5.05%, 5.88% for RP, 1.20%, 1.15%, and 1.17% for CAD, 1.26%, 1.19%, and 1.22% for CHF. The expected risks of RP were slightly lower in CK plans compared to VMAT and HT plans (p < 0.001), with VMAT plans showing the highest expected risks. For central lung cancer, the expected CAD risks of CK and HT plans were lower than those of VMAT plans (p < 0.05). The delivery efficiency of VMAT plans was significantly higher than that of CK plans and HT plans.ConclusionsAll three techniques, VMAT, HT, and CK, meet the therapeutic requirements for target coverage and dose constraints for OARs. Although there are statistical differences, the difference between the expected risk values of RP and CAD is very small, so the clinical manifestations may not show differences.