Prognostic value of dual-time-point ¹⁸ F-FDG PET in fibrotic idiopathic interstitial pneumonia

Purpose : The aim of this prospective study was to clarify whether dual-time-point [ 18 F]-2-fluoro-2-deoxy- D -glucose positron emission tomography ( 18 F-FDG PET) imaging results are useful to predict long-term survival of idiopathic pulmonary fibrosis (IPF) and fibrotic nonspecific interstitial pneumonia (f-NSIP) patients. Methods : Seventy patients with IPF (n=43) or f-NSIP (n=27) underwent 18 F-FDG PET examinations at 2 time points; 60 minutes (early imaging) and 180 minutes (delayed imaging) after 18 F-FDG injection. Standardized uptake value (SUV) at each point and the retention index value (RI-SUV) calculated from those were evaluated, then the results were compared with survival and serial trends in pulmonary function indices. Results : The early SUV value for lung lesions in patients with f-NSIP (1.31±0.45) was significantly higher than that in those with IPF (1.09±0.31, P =0.014), whereas the delayed SUV and RI-SUV values were not significantly different. There was no significant difference in survival between the patients groups ( P =0.24). The 3-year survival of all patients (IPF and f-NSIP) negative for RI-SUV (<0%) was 96.7% as compared to 50.8% for those with positive RI-SUV (≥0%; P <0.0001). Positive RI-SUV was shown to be a robust predictor of survival in both groups (IPF, HR 4.67, 95% CI 1.23-17.8, P =0.023; f-NSIP, HR 8.88, 95% CI 1.04-75.9, P =0.046) when compared with baseline FVC, DL CO , and pathological diagnosis. Conclusion : Our results demonstrate that positive RI-SUV is strongly predictive of long-term survival and changes in pulmonary function in patients with IPF or f-NSIP.