Does 18F-FDG Uptake by Respiratory Muscles on PET/CT Correlate with Chronic Obstructive Pulmonary Disease?

Abstract

(18)F-FDG muscle uptake is evident in some benign physiologic processes as seen in the respiratory muscles of patients with chronic obstructive pulmonary disease (COPD) and labored breathing. The purpose of this study was to correlate the presence of COPD with the patterns of (18)F-FDG uptake by muscles as demonstrated by PET/CT scans. (18)F-FDG PET/CT scans and pulmonary function tests (PFTs) were performed for 63 consecutive patients with newly diagnosed or highly suspected lung cancer. Presurgical pulmonary function tests by way of spirometry examinations were performed as the standard of care. Patients were grouped into those with normal spirometry findings and those with mild to very severe COPD. The guidelines of the Global Initiative for Chronic Obstructive Lung Disease were used for staging COPD and obstructive impairment. A nuclear medicine physician and 2 residents who did not know the COPD status retrospectively reviewed PET/CT scans and kept a log for cases of increased (18)F-FDG uptake in the respiratory muscles (diaphragm, intercostal muscles, and scalene muscles). The χ(2) test and Cramer V were used to evaluate the correlation between increased (18)F-FDG uptake by muscles and the presence of COPD. Sixty-three patients underwent both (18)F-FDG PET/CT and PFT within 1 mo of each another without interval therapy. Of the 63 patients, 26 (41%) had no spirometric obstruction and 37 (59%) had spirometric obstruction. Of these, 30 (81%) had a previously established diagnosis of COPD (1 mild, 26 moderate, 9 severe, and 1 very severe). Excessive (18)F-FDG uptake was seen in at least 2 of the 3 muscles (diaphragm and intercostal muscles) in 27 (73%) of the 37 patients with COPD and obstructive ventilatory impairment. The severity of COPD and obstruction showed a significant correlation with the presence of abnormal (18)F-FDG uptake by any of the 3 muscle types, particularly when 2 groups of muscles were involved (Cramer V = 0.60, χ(2) P < 0.001). Our study revealed a strong correlation between increased (18)F-FDG uptake by respiratory muscles and the presence of COPD.