To explore the imaging features of ¹⁸F-fluorodeoxyglucose (FDG) PET/CT (high-resolution CT, HRCT) imaging in focal organizing pneumonia (FOP).

Patients with solid nodular FOP (n=45; 33 males, 12 females, age (58±9) years) and early peripheral non-mucinous solid lung adenocarcinoma (n=47; 21 males, 26 females, age (63±10) years) confirmed by postsurgical pathology between May 2012 and December 2018 in Zhongshan Hospital, Fudan University were retrospectively analyzed. All patients underwent ¹⁸F-FDG PET/CT (HRCT) imaging followed by surgery within 3 weeks. The imaging findings and characteristics of the lesions were recorded. Differences of the maximum standardized uptake value (SUV_max) and maximum diameter between FOP and adenocarcinoma were analyzed by Mann-Whitney U test or t′ test. Spearman correlation or Pearson correlation analysis was performed to analyze the relation between SUV_max and maximum diameter. Binary logistic regression analysis was performed to identify the predictive factors for FOP. Finally, the receiver operating characteristic (ROC) curve analysis was used for evaluation of diagnostic efficiency.

The SUV_max of FOP was lower than that of lung adenocarcinoma (3.1(1.7, 4.9) vs 6.5(3.8, 9.3); z=-4.598, P<0.01), and the maximum diameter of FOP was smaller than that of lung adenocarcinoma ((18.0±6.3) mmvs (21.8±4.3) mm; t′=-3.424, P<0.01). The SUV_max was positively correlated with the maximum diameter in FOP group (r_s=0.509, P<0.01), while the SUV_max of lung adenocarcinoma was not correlated with the lesion size (r=0.076, P>0.05). HRCT of the PET/CT system showed the fusiform shape were more common in FOP (χ²=9.549, P<0.05). Multivariate regression analysis identified that SUV_max≤7.1, diameter≤18.3 mm, and fusiform shape were independent factors to predict FOP, with odds ratio (OR) of 10.585, 4.674, 9.073, respectively (all P<0.05). ROC curve analysis showed that the area under the curve (AUC) of SUV_max≤7.1 combined with diameter≤18.3 mm and fusiform nodule was 0.860, and the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 97.8%(44/45), 70.2%(33/47), 75.9%(44/58), 97.1%(33/34), and 83.7%(77/92), respectively.

SUV_max≤ 7.1 combined with maximum diameter≤ 18.3 mm and fusiform shape may predict solid nodular FOP.

Cryptoenic organizing pneumonia; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose