5 fractions showing optimized doses to critical organs as well as target volume (PTV). (E) Radiation dose constraints used for treatment planning. Kidney Cancer Journal 75 With a 98% local tumor control rate after a median followup of 28 months, according to this report, SAbR seems to be more effective and certainly less invasive than thermal ablation. There was a measurable size reduction in 38 lesions, including complete remission in 19 while the renal function remained stable. The authors can only speculate on what their results might look like when patients are followed for the long term. However, even if renal function were to fail after a longer followup, the patients still would have experienced a prolonged period free from hemodialysis. Ongoing Trials Seek to Extend Findings Two ongoing trials are recruiting patients to continue investigations into the use of SAbR. One is being conducted at the University of Texas Southwestern Medical Center where patients with enlarging (>4mm growth within the past year) early renal cancers will undergo treatment of SAbR of 36Gy in 3 or 40Gy in 5 fractions. The primary endpoint of this single arm phase II trial is local control at 1 year which will be evaluated with radiographic scans and a tumor biopsy one year after treatment carefully evaluating the proliferative capability of baseline compared to post-treatment bi-opsy to confirm tumor nonviability. The estimated study completion date is December of 2018. The Clinical Trials.gov identifier is NCT021 41919.32 A second ongoing study, also phase II single arm, TROG 15.03 FASTRACKII,33 is being conduced in Australia, has an accrual target of 70 patients and is scheduled for completion in September of 2021. All participants will be assessed at regular intervals post treatment in order to estimate the activity and efficacy of the technique, tolerability, survival, distant failure rate, and change of renal function after SAbR. SAbR dose fractionation in this study depends on tumor size: fraction schedule 1: 26Gy in 1 Figure 3. SAbR plan for IVC tumor thrombus. (A-C) Representative axial, sagittal, and coronal images of the SAbR treatment plan with isodose lines showing dose distribution and coverage of the IVC-TT. (D) Radiation dose volume histogram from SAbR plan of 50 Gy in
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