Prediction of clinical outcome after stereotactic body radiotherapy for non-small cell lung cancer using diffusion-weighted MRI and ¹⁸F-FDG PET

Highlights: • We evaluated DW-MRI and FDG-PET as prognostic factor for NSCLC treated with SBRT. • Lower ADC value was relevant to disease progression after SBRT. • Higher SUV_max was relevant to disease progression after SBRT. • Using both values in combination was a better predictor. - Abstract: Purpose/objectives: To evaluate the use of diffusion-weighted magnetic resonance imaging (DW-MRI) and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for predicting disease progression (DP) among patients with non-small cell lung carcinoma (NSCLC) treated with stereotactic body radiotherapy (SBRT). Materials/methods: Fifteen patients with histologically confirmed stage I NSCLC who underwent pre-treatment DW-MRI and PET and were treated with SBRT were enrolled. The mean apparent diffusion coefficient (ADC) value and maximum standardised uptake value (SUV_max) were measured at the target lesion and evaluated for correlations with DP. Results: The median pre-treatment ADC value was 1.04 × 10⁻³ (range 0.83–1.29 × 10⁻³) mm²/s, and the median pre-treatment SUV_max was 9.9 (range 1.6–30). There was no correlation between the ADC value and SUV_max. The group with the lower ADC value (≤1.05 × 10⁻³ mm²/s) and that with a higher SUV_max (≥7.9) tended to have poor DP, but neither trend was statistically significant (p = 0.09 and 0.32, respectively). The combination of the ADC value and SUV_max was a statistically significant predictor of DP (p = 0.036). Conclusion: A low ADC value on pre-treatment DW-MRI and a high SUV_max may be associated with poor DP in NSCLC patients treated with SBRT. Using both values in combination was a better predictor