Inclusion Criteria:

- age ≥ 40

- any smoking status, e.g. current, former, or never

- co-morbid conditions, e.g. COPD

- Nodule size ≥ 4 mm and ≤ 30 mm (up to Stage 2B eligible), any spiculation or ground
glass opacity

- Pathology: malignant - adenocarcinoma, squamous, or large cell

- Pathology: benign - inflammatory (e.g. granulomatous, infectious) or non-inflammatory
(e.g. hamartoma)

- Clinical stage, Primary tumor: ≤T2 (e.g. 1A, 1B, 2A and 2B)

- Clinical stage, Regional lymph nodes: N0 or N1 only

- Clinical stage, Distant metastasis: M0 only

Exclusion Criteria:

- prior malignancy within 5 years of lung nodule diagnosis

- No nodule size available

- No pathology data available for those with

- Current diagnosis of non-small cell lung cancer

- Clinical stage: Primary tumor ≥T3; Regional lymph nodes: ≥N2; 4 Distant metastasis:
≥M1