Follow-Up of Small (4 mm or Less) Incidentally Detected Nodules by Computed Tomography in Oncology Patients: A Retrospective Review

Introduction: It is often not possible to determine whether small nodules detected on computed tomography (CT) in oncology patients are metastatic. We evaluated a group of oncology patients to determine the outcome of small pulmonary nodules and whether they can be ignored in the therapeutic decision process. Materials and Methods: Radiology reports of thoracic CTs from a 2-year period were searched for keywords indicating a small pulmonary nodule. All CT images were evaluated by two thoracic radiologists for nodules 4 mm or less. There were 102 cases that met criteria for inclusion. Results: Forty-seven had follow-up CT of less than 365 days, and 55 had follow-up CT for more than 365 days. For those with less than 365 days, the observed nodule was increased (17, 36%), increased and new nodules (9, 19%); stable (19, 40%); stable but new nodules developed (1); and decreased (1). For those with greater than 365 days follow-up, the observed nodule was increased (3, 5%); stable (51, 93%); and stable but new nodule developed (1). Combined, 28% of patient';s nodules increased (90% were within 365 days; 25% within 203 days; and 14% within 14 days). Conclusion: In oncologic patients, 28% of small pulmonary nodules detected at initial CT will increase in size, suggesting metastasis. This increase in size tends to occur early, and follow-up CT in 3 months and 6 months would be appropriate in further evaluation. Small nodules that are stable in size for more than 365 days are unlikely to be pulmonary metastasis.