1020 - Prospective Study of Surface Guided Radiation Therapy (SGRT) Alone or in Combination with Fiducials for Free Breathing (FB) vs. Breath Hold (BH) Stereotactic Body Radiation Therapy (SBRT) Treatments of the Lung
Presenter(s)
J. H. Heinzerling II1, B. J. Moeller1, M. Robinson2, V. V. Thakkar1, R. S. Prabhu1, M. C. Ward1, C. D. Corso1, J. Gregory2, C. J. Hampton2, R. D. Foster2, J. Singh2, and K. Mileham2; 1Atrium Health Levine Cancer, Wake Forest School of Medicine, and Southeast Radiation Oncology Group, Charlotte, NC, 2Atrium Health Levine Cancer, Wake Forest School of Medicine, Charlotte, NC
Purpose/Objective(s): Respiratory motion management with BH is one technique to limit normal lung and other organ dose during SBRT treatments of the lung. Surface guidance (SGRT) has been utilized for BH in larger targets such as breast cancer, but its reliability in BH treatments of small targets has not been investigated or compared to FB treatments. We report the primary endpoint of a prospective trial evaluating BH vs. FB SBRT treatment of the early stage non-small cell lung cancer (NSCLC) and lung metastases utilizing SGRT alone or in combination with fiducials.
Materials/Methods: An IRB approved prospective study was conducted in patients (pts) with primary stage I NSCLC or lung metastasis undergoing SBRT. Eligible pts had at least 1 cm of respiratory associated motion on FB 4DCT. Pts were then assigned to receive either BH or FB technique based on radiation treatment center and technology available for FB vs. BH treatments. BH was performed either with SGRT alone or SGRT in combination with fiducials and continuous imaging during treatment. Reliability of BH was evaluated with mid-treatment cone beam CT (CBCT) and subsequent shifts recorded for comparison of BH techniques. The primary endpoint was incidence of grade 2 or higher SBRT and fiducial related pulmonary toxicities in each cohort. Secondary endpoints included reliability of gated SBRT treatments utilizing SGRT alone vs. SGRT with fiducials, changes in pulmonary function tests (PFTs) from baseline to 6 months, and local control (LC). Mean shifts for reliability were estimated from mixed models with fixed effects for fraction number and cohort and a random effect for pt. PFT differences from baseline to 6 months were compared between cohorts with Kruskal-Wallis tests.
Results: 45 pts were enrolled with 15 undergoing FB SBRT, 25 undergoing BH SBRT with SGRT alone and 5 treated with BH SBRT with both SGRT and fiducials. Median follow up was 25.4 months (range 0.1 to 70.5 months). Most pts received 54 Gy in 3 fractions. Mean shifts on mid-treatment CBCT for BH performed with SGRT alone vs. SGRT with fiducials were not significantly different with mean shifts <3mm for translational and <1 degree for rotation. There were no adverse events (AEs) related to fiducial placement. Pulmonary AEs associated with SBRT were very low with only 1 (4%) grade 2+ or higher pulmonary AE in the BH SBRT with SGRT alone cohort, and a total of 3 (12%) SBRT related grade 2+ toxicities in the SBRT BH cohort vs. 1 (7%) in the FB SBRT cohort. PFT decline was modest in all 3 cohorts and did not show significant differences in FEV1 or DLCO decline at 6 months. One local failure has been reported to date, which was in the SBRT BH with SGRT alone cohort (LC 96% at 2 years).
Conclusion: SGRT alone provides a reliable technique for BH SBRT treatments of the lung with excellent LC. Fiducial placement did not significantly change reliability of BH SBRT treatments. No significant toxicity differences or PFT changes between baseline and 6 months were seen in this comparison of FB vs. BH SBRT.