Outcome of PET-Negative Solid Pulmonary Nodules: A Retrospective Study

Abstract

It was observed that malignancy had been found on follow-up in patients with PET-negative solid solitary pulmonary nodules (SPN). A retrospective analysis was performed to observe the natural history and malignant potential of these lesions, which, in routine practice, are presumed to be inactive. Patients with an incidentally-discovered solid solitary pulmonary nodule who then had a negative follow-up PET/CT from 2005 to 2015 were identified using a text-based search methodology. These patients' charts were mined to determine the rate of development of subsequent malignancy from these index nodules. Of the patients with initially PET-negative solitary pulmonary nodule (n = 62, 43.5% women, mean age 65), 44 had clinical follow-up of the index lesion. 8 (7 pathology-proven) subsequent malignancies were identified with a mean time to diagnosis of 37.6 (±31.3) months. There were no statistically significant predictors of subsequent development of cancer (including age, gender, and smoking status). Upon follow up, 18.2% of the initially queried solid PET-negative nodules developed subsequent malignancy at an average time of 37.6 months, suggesting the continued need for follow-up of these initially PET-negative nodules beyond the 2 years currently suggested in popular guidelines. Importantly, these findings also remind radiologists that a negative PET/CT is not a surrogate for tissue diagnosis in the case of non-FDG avid SPN.