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SU‐GG‐J‐17: Technical Aspects of a Simple and Effective Method to Perform Stereotactic Body Radiation Therapy (SBRT) in Lung Cancer Patients without 4D‐Ct and Gating
Author(s) -
Jani S,
Glazebrook S,
Volpp B,
Weinstein G
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3468240
Subject(s) - isocenter , medicine , lung cancer , nuclear medicine , radiosurgery , lung , radiation therapy , gating , radiology , image guided radiation therapy , lung tumor , medical physics , oncology , physiology
Purpose : In recent years, there has been considerable debate about the necessity of using respiratory gating and 4D ‐CT to perform SBRT, a fast‐growing practice with high risk to patients. Here, we describe the technical aspects of a method to perform SBRT in lung patients without the use of respiratory gating and 4D‐CT. Methods and Materials : After two years of slow dose escalation, we launched our SBRT program in 4/2009 and have enrolled 10 patients (11 lesions) so far. Each patient underwent a CT‐guided placement of a Visicoil marker. Patients were immobilized with a homegrown method utilizing a Vac‐loc and Aquaplast body cast; then underwent a fluoroscopic exam with a C‐Arm to determine tumor motion. Normal tissues dose limits were set using RTOG/ M.D. Anderson guidelines on lung SBRT. About two‐third of lesions (7/11) were treated with 50 Gy in 4–5 fractions, the remainder with >5 fractions due to increased risk of complications. Treatments were carried out at a BrainLab Novalis system with ExacTrac image guidance. Prior to treatment, a series of x‐rays were taken with the patient in “breath‐in and hold” and “breath‐out and hold” positions. The mid‐point of tumor motion was established and used to determine the treatment isocenter. Results : Average target dimensions were 19cc (GTV) and 73cc (PTV). The lung DVH (V‐20), based on whole lung‐GTV, ranged from 3.1% to 11% with an average of 7.8%. Tumor motion observed at the treatment machine using ExacTrac x rays matched to within 3 mm of the fluoroscopic value. Patient follow‐up (9/10) showed no evidence of Grade III toxicity and no progression of disease in any patient. Conclusions : Respiratory gating and 4D‐CT are not essential components of SBRT. As pointed out by recent ASTRO/ACR guidelines, the truly critical aspect is rigurous QA of each process.