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 (SUV_max) 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 [×10⁻³ mm²/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 SUV_max at any time point. Conclusions: DW-MRI could be an early predictor of treatment response after lung SBRT.