(P107) Vero SBRT Treatment of Moving Lung Tumors

April 30, 2015

Overall, 40%-thresholded 18F-FDG PET contours nonsignificantly enlarge PTVs when multiphase free-breathing, inspiration, and expiration breath-hold scans are used for Vero SBRT. Whether 18F-FDG PET contours improve local control of moving lung tumors treated by Vero SBRT needs further study.

Charles A. Kunos, MD, PhD, John P. Shanahan, MS; Summa Cancer Institute

PURPOSE: Intrafraction motion management of moving lung tumors during stereotactic ablative body radiotherapy (SBRT) remains challenging. We investigated whether 40%-thresholded 2-[18F] fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET) images enhanced intrafraction tracking capabilities of the Vero SBRT platform.

MATERIALS AND METHODS: Three patients with six total moving lung tumors had gross tumor volume (GTV) contours created on free-breathing, end-inspiration, and end-expiration breath-hold computed tomography (CT) images. A thresholded 40% maximum standard uptake value 18F-FDG PET contour was generated. The four individual contours contributed to a single image-guided internal target volume (ITV). Vero SBRT treatment planning was conducted on the free-breathing CT dataset, with the ITV expanded all around by 5 mm for a final planning target volume (PTV). The prescription for each lesion was 40 Gy in four fractions of 10 Gy given every other day. Non-coplanar radiation doses were determined using a Monte Carlo algorithm. T-test statistics were calculated to compare parameter means.

RESULTS: The PTV was 23 cm3 on average (standard deviation [SD] = 18 cm3) without the 18F-FDG PET contour and 36 cm3 on average (SD = 32 cm3) with the 18F-FDG PET contour (P = .41). The lung V20 Gy was 2.6% on average (SD = 0.9%) without the 18F-FDG PET contour and 2.8% on average (SD = 0.5%) with the 18F-FDG PET contour (P = .68). Vero SBRT gimbal pan-and-tilt range of 4 cm was not exceeded by the addition of the 18F-FDG PET contour to the ITV.

CONCLUSIONS: Overall, 40%-thresholded 18F-FDG PET contours nonsignificantly enlarge PTVs when multiphase free-breathing, inspiration, and expiration breath-hold scans are used for Vero SBRT. Whether 18F-FDG PET contours improve local control of moving lung tumors treated by Vero SBRT needs further study.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org