Introduction A solitary pulmonary nodule is defined as a single, radiolographically visible lesion that is within and surrounded on all sides by pulmonary parenchyma. It is a widely held concept that a nodule that remains stable for 2 years is benign. This is based on data that are currently being reconsidered. Our hypothesis is that such nodules are, in fact, benign.
Methods All patients seen at the Oklahoma City VA thoracic oncology clinic between 1999 and 2004 were evaluated. Those with a radiographically stable lung nodule after a 2-year follow-up were included in our analysis. Imaging beyond the 2-year stability period and the clinical outcome of the patients were reviewed.
Results A total of 915 patients were evaluated in our clinic during the 5- year period. Twenty-nine patients were discharged after the 2-year follow-up, at which time they were deemed to have a benign lesion based on the 2-year stability rule. Of those, one patient, a nursing home resident, died, and another was lost for follow-up before any further imaging could be obtained. Twenty-seven patients, with a total of 29 nodules, were therefore included in our analysis. All patients were male, with an average age of 59 years. All were smokers, with an average of 51 pack-years. The size of the lesions ranged from 0.5 to 4.5 cm (mean 1.7 ± 0.9 cm). Most lesions occurred in the right upper lobe (38%) and the left upper lobe (24%). Beyond the 2-year stability period, follow-up imaging averaged 1.5 ± 1.4 years (10 patients had chest radiography, 16 had chest CT, and one patient had both). Of the 29 nodules, only one (3.4%, 95% confidence interval 0.09-17.7%) increased in size from 2.4 to 3 cm. Its doubling time was 1,719 days, suggesting a benign etiology. Twenty-six patients are still alive 2.2 years beyond the follow-up period. One patient, whose lesion remained stable, died in a nursing home 3.4 years after the stability period.
Conclusion Our data suggest that if a lung nodule is stable over a 2-year period, it is likely to be benign and will remain stable in size.
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