Severity of pulmonary involvement and (18)F-FDG PET activity in sarcoidosis

Assessing inflammatory activity is useful in the management of persistent symptomatic sarcoidosis patients. (18)F-FDG PET (PET) has been shown to be a sensitive technique to assess inflammatory activity in sarcoidosis. The aim of this study was to evaluate whether the severity of pulmonary involvement is associated with PET activity in persistent symptomatic sarcoidosis patients.

Over a 5-year period, relevant clinical data including laboratory and lung function test results were gathered from the medical records of 95 sarcoidosis patients with persistent disabling symptoms who underwent both a PET and HRCT. HRCT scans were classified using a semiquantitative scoring system and PET findings as positive or negative, respectively.

PET was positive in 77/95 patients, of whom 56 demonstrated pulmonary PET-positivity. HRCT scores were high (7.1 ± 3.6) in patients with positive pulmonary PET findings (n = 56) compared to patients with negative pulmonary PET findings (n = 39; 3.0 ± 2.9; p < 0.001). DLCO (65 ± 20% predicted) and FVC (85 ± 24% predicted) were low in patients with pulmonary PET-positivity versus those with negative pulmonary PET findings (79 ± 16% predicted; p = 0.001 and 96 ± 22% predicted; p = 0.044, respectively). Interestingly, out of the 26 patients with fibrotic changes, 22 (85%) had positive pulmonary PET findings, of whom 18/22 (82%) showed extrathoracic PET-positive lesions and 16/22 (73%) showed signs of serological inflammation.

The severity of the pulmonary involvement, assessed by HRCT features and lung function parameters, appeared to be associated with PET activity in sarcoidosis. The majority of patients with fibrotic changes demonstrated inflammatory activity at pulmonary and extrathoracic sites.