Assessment of treatment response after lung stereotactic body radiotherapy using diffusion weighted magnetic resonance imaging and positron emission tomography: A pilot study

Background and purpose: There is no early predictor of treatment response after lung stereotactic body radiotherapy (SBRT). We conducted this pilot study to evaluate whether serial diffusion weighted magnetic resonance imaging (DW-MRI) or positron emission tomography (PET) could predict response after SBRT. Material and methods: Early stage non-small cell lung cancer patients who received SBRT were eligible. DW-MRI and PET were undertaken pretreatment and every 3 months after SBRT in the first year. Patients with <1 year of follow-up were excluded from the analysis. The apparent diffusion coefficient (ADC) value and maximum standardized uptake value (SUVmax) of tumors were measured and compared between groups with or without local recurrence (LR). Results: Fifteen patients were enrolled and the data of 14 patients were analyzed. The median ADC value was significantly lower in patients with LR (n = 3) than in those without LR (n = 11) at 3 and 6 months (1.11 vs. 1.54 and 0.98 vs. 1.69 [x10(-3) mm(2)/s]; p = 0.039 and 0.012, respectively) while there was no significant difference pretreatment and at 9 and 12 months after treatment. No significant difference was observed in the SUVmax at any time point. Conclusions: DW-MRI could be an early predictor of treatment response after lung SBRT.