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ORAL 36 - Translational Science/Radiation (ID 151)
- Event: WCLC 2015
- Type: Oral Session
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
ORAL36.06 - 4D-VQ-PET/CT Imaging Allows Strong Correlation Between Radiotherapy Dose and Change in Lung Ventilation, Perfusion and Density (ID 211)
16:45 - 18:15 | Author(s): N. Hardcastle
Ga-V/Q PET/CT is a novel imaging modality for assessment of perfusion(Q), ventilation(V) and lung density changes in the context of radiotherapy (RT) for non-small cell lung cancer.
In a prospective clinical trial, 20 patients underwent 4D-V/Q PET/CT before treatment, 4 weeks into treatment and 3 months after definitive lung RT. Eligible patients were prescribed 60 Gy in 30 fractions with or without concurrent chemotherapy. Functional images were registered to the RT planning 4D-CT and isodose volumes averaged into 10 Gy bins. Within each dose bin, relative loss in SUV was recorded for ventilation and perfusion, and loss in air-filled fraction was recorded to assess RT-induced lung fibrosis. A dose-effect relationship was described using both linear and 2-parameter logistic fit models and goodness of fit assessed using Akaike Information Criterion (AIC).
A total of 179 imaging datasets were available for analysis (1 scan unrecoverable). An almost perfectly linear dose-response relationship was observed for perfusion and air-filled fraction (r = 0.99, p < 0.01), with ventilation also strongly linear (r = 0.95, p < 0.01) [Figure]. Logistic models did not provide a better fit as evaluated by AIC [Table]. Perfusion, ventilation and the air-filled fraction changed by -7.5% ± 0.3%, -7.1% ± 0.6% and 4.9% ± 0.02% per 10 Gy, respectively. Within high-dose regions, higher baseline SUV was associated with greater rate of loss. At 50Gy and 60Gy the rate of loss was 1.35% (p = 0.07) and 1.73% (p = 0.05) per SUV, respectively. Of 8/20 patients with peri-tumoral reperfusion / re-ventilation during treatment, 7/8 did not sustain this effect post-treatment. Figure 1 Figure 2
RT induced regional lung functional deficits occur in a dose dependent manner and can be estimated using simple linear models with 4D-V/Q PET/CT imaging. These findings may inform functional lung sparing by planning RT using this novel imaging technology.
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