On the use of single-isocenter VMAT plans for SBRT treatment of synchronous multiple lung lesions: Plan quality, treatment efficiency, and early clinical outcomes

Cone-beam computed tomography (CT)-guided volumetric-modulated arc therapy (VMAT) plans for stereotactic body radiotherapy (SBRT) treatment of synchronous multiple lung lesions with a flattening filter-free (FFF) beam is a safe and highly effective treatment option for oligometastases lung cancer patients. Fourteen patients with metastatic non–small-cell lung cancer (NSCLC) lesions (two to five) received a single-isocenter VMAT SBRT treatment in our clinic. Four-dimensional (4D) CT-based treatment plans were generated using advanced AcurosXB-based dose calculation algorithm using heterogeneity corrections with a single isocenter placed between/among the lesions. Compared to 10X-FFF and traditional flattened 6X (6X-FF) beams, 6X-FFF beam produced highly conformal radiosurgical dose distribution to each target volume, reduced dose to adjacent organs at risk (OAR), and significantly reduced the lung SBRT fraction duration to < 3.5 min/fraction for 54/50 Gy treatments in 3/5 fractions — significantly improving patient convenience and clinic workflow. Early follow-up CT imaging (mean, 9 months) results show high local control rates (100%) with no acute lung or rib toxicity. Longer clinical follow up in a larger patient cohort is ongoing to further validate the outcomes of this treatment approach.