Patients were simulated using CT imaging with both 3D and 4D scans to account for respiratory motion. Photon (x-ray) beams with photon energies of 6 MV were used. All patients received a simulation CT scan used to contour the gross tumor volume (GTV). No margin was added for clinical target volume (CTV). GTV were defined either on MIP (Maximum Intensity Projection) images or using GTVs at 3 phases (inspiration, expiration and midphase) of the respiratory cycle to create an ITV. An additional 0.5 cm in the axial plane and 0.5 to 1.0 cm in the longitudinal plane (craniocaudal) was added to the each GTV to create the planning target volume (PTV).
SBRT dose/fractionation treatment regimens ranged from 34 to 54 Gy in 1 to 10 fractions using photons. The treatment goals were 54 Gy in 3 fractions for peripheral lesions and 50 Gy in 5 fractions central lesions. Treatment dose and fractionation was per physician discretion and was adjusted based on tumor size, location, organs at risk, patient comorbidities, and prior treatment. Per protocol, treatments delivered with > 10 Gy per fraction had a minimum of 48-h interfraction interval. Treatments with ≤ 10 Gy per fraction had a minimum 24-h interfraction interval. Treatments were completed over 14 days for 3 fraction treatments and over 21 days for > 5 fraction treatment schedules.
Local recurrence (LR) was assessed radiographically and was defined as tumor recurrence or increased size of the treated tumor, based on Response Evaluation Criteria in Solid Tumors (RECIST) criteria on CT imaging, within the radiation PTV [10 (link)]. Time to LR was measured from the end of SBRT to the time of tumor recurrence or last follow up. Local progression-free survival was defined as the time from end of SBRT to the time of LR. Overall survival (OS) was measured from the end of radiation to the time of death.
Adverse radiation events due to SBRT were graded based on the Common Terminology Criteria for Adverse Events, version 4.0.
SBRT dose/fractionation treatment regimens ranged from 34 to 54 Gy in 1 to 10 fractions using photons. The treatment goals were 54 Gy in 3 fractions for peripheral lesions and 50 Gy in 5 fractions central lesions. Treatment dose and fractionation was per physician discretion and was adjusted based on tumor size, location, organs at risk, patient comorbidities, and prior treatment. Per protocol, treatments delivered with > 10 Gy per fraction had a minimum of 48-h interfraction interval. Treatments with ≤ 10 Gy per fraction had a minimum 24-h interfraction interval. Treatments were completed over 14 days for 3 fraction treatments and over 21 days for > 5 fraction treatment schedules.
Local recurrence (LR) was assessed radiographically and was defined as tumor recurrence or increased size of the treated tumor, based on Response Evaluation Criteria in Solid Tumors (RECIST) criteria on CT imaging, within the radiation PTV [10 (link)]. Time to LR was measured from the end of SBRT to the time of tumor recurrence or last follow up. Local progression-free survival was defined as the time from end of SBRT to the time of LR. Overall survival (OS) was measured from the end of radiation to the time of death.
Adverse radiation events due to SBRT were graded based on the Common Terminology Criteria for Adverse Events, version 4.0.
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