Nikola Cihoric MD, Abstract Co-Author: Nothing to Disclose

Bernd Klaeser MD, Abstract Co-Author: Nothing to Disclose

Michaeal Topfer MD, Abstract Co-Author: Nothing to Disclose

Martin Frueh MD, Abstract Co-Author: Nothing to Disclose

Marco Malthaner PhD, Abstract Co-Author: Nothing to Disclose

Daniel Schmidhalter PhD, Abstract Co-Author: Nothing to Disclose

Natalie D. Klass MD, Abstract Co-Author: Nothing to Disclose

Ludwig Plasswilm MD, PhD, Abstract Co-Author: Nothing to Disclose

Ernst Born PhD, Abstract Co-Author: Nothing to Disclose

Norbert Blumstein MD, Abstract Co-Author: Nothing to Disclose

Thomas Krause, Abstract Co-Author: Nothing to Disclose

Daniel M. Aebersold MD PhD, Abstract Co-Author: Nothing to Disclose

Michael Schmuecking MD, Presenter: Nothing to Disclose

To evaluate the role of BED and F-18 FDG PET/CT for target volume delineation and clinical outcome after SBRT 47 lung lesions were analyzed prospectively.

Inclusion criteria: histologically proven NSCLC stage I or hypermetabolic oligometastatic lung lesions. Peripheral or central localization, maximal tumor diameter of 50mm. Karnofsky index > 60%. Medically inoperable. Moving of the lung lesion during breathing less than 5mm as detected by 4D-CT. Initial staging: whole body and deep inspiration breath hold F-18 FDG PET/CT in radiation treatment position, MRI of the brain. Radiation treatment planning: 4D-CT and angio-CT in radiation treatment position for target volume delineation. Using 4D-CT for target volume delineation, a Boolean operation was used to sum the multiple gross target volumes (GTV) delineated in diagnostic lung window to form an internal target volume (ITV). The planning target volume (PTV) was derived by a three-dimensional isotropic expansion of the ITV by 5mm to account for both microscopic extension and daily setup errors. Prescription dose varied from 5x7Gy to 5x12Gy, depending on the location of the lesion. 80% prescription isodose line = PTV. Median time for follow-up: 12 months, maximal time: 34 months.

For 38/47 lung lesions, the ITV derived by Boolean operation was identical or smaller than the ITV derived by non-gated PET, in 9/47 lesions bigger due to spiculae as seen in the diagnostic lung window. Actuarial local control after 2 years: for all patients: 91%. BED > 100Gy vs. BED < 100Gy: 100% vs. 71% (log rank test: p = 0.04). Coverage of microscopic extension: with 5x7Gy: 13%, with 5x12Gy 78%. No treatment related deaths, no grade 3/4 toxicities. Pneumonitis grade 1-2: 3%.

If treated with a BED > 100Gy, our preliminary data suggest a high long term local control at low rates of treatment-related toxicity. The microscopic extension beyond the GTV is covered sufficiently. Non-gated F-18 FDG PET/CT in radiation treatment position is helpful for the ITV delineation of lung lesions and may be used to evaluate the magnitude of the daily setup errors prior to radiation treatment.

To achieve a long term control, a SBRT delivery of a BED < 100Gy should be avoided due to low doses within the GTV and insufficient coverage of the microscopic extension beyond the GTV.

Cihoric, N, Klaeser, B, Topfer, M, Frueh, M, Malthaner, M, Schmidhalter, D, Klass, N, Plasswilm, L, Born, E, Blumstein, N, Krause, T, Aebersold, D, Schmuecking, M, What is the Role of BED and Margin Concept in SBRT of Lung Lesions?.  Radiological Society of North America 2012 Scientific Assembly and Annual Meeting, November 25 - November 30, 2012 ,Chicago IL. http://archive.rsna.org/2012/12022093.html