Prevalence and Predictability of Occult Satellite Nodules in Clinical Stage Ia Non-small Cell Lung Cancer following Lobectomy

We sought to assess the prevalence and clinical predictors of satellite nodules in patients undergoing lobectomy for clinical stage Ia disease.The National Cancer Database was queried for patients who underwent lobectomy for clinical stage cT1N0 NSCLC. Collaborative staging information was used to identify patients who were pathologically upstaged based on having separate tumor nodules in the same lobe as the primary tumor. Multivariable logistic regression was used to assess the association of clinical factors with the detection of separate nodules.A separate tumor nodule was recorded in 2.8% (n = 1284) of 45,842 clinical stage Ia patients treated with lobectomy or bilobectomy. Female gender (3.1% vs. male 2.5%; P = .002) and non-squamous histology (adenocarcinoma 3.2% and large cell neuroendocrine 3.0% vs. squamous cell 1.9% tumors; P < .001) were associated with the presence of separate nodules. The frequency increased for tumors larger than 3 cm (≤ 3cm, 2.7% vs. > 3cm, 3.8%; P < .001). Other factors associated with separate nodules were upper lobe location, pleural and/or lymphovascular invasion and occult lymph node disease. The best predictive model for separate nodules based on the available clinical variables resulted in an area under the curve of 0.645 (95% CI 0.629-0.660).Separate tumor nodules may be detected with a low but relatively consistent frequency across the spectrum of patients with clinical stage Ia NSCLC. The predictive ability using basic clinical factors in the database is limited.