The prognostic significance of intranodal isolated tumor cells and micrometastases in patients with non–small cell carcinoma of the lung

To study whether isolated tumor cells and micrometastases, as defined by the current American Joint Committee on Cancer criteria for extrapulmonary neoplasms, have prognostic value for patients with resected non–small cell carcinoma of the lung. Intrathoracic lymph nodes (n = 1063) from 60 patients with non–small cell carcinoma of the lung were studied for the presence of metastases with serial histologic sections and keratin immunostains. Metastases were classified as isolated tumor cells, pN1mi, pN1, pN2mi, and pN2. Isolated tumor cells were smaller than 0.2 mm, while pN1mi and pN2mi measured 0.2 mm to 2 mm. Survival analysis was performed, stratifying by nodal status and stage. Isolated tumor cells were detected in 11 lymph nodes from 5 of 33 pN0 patients and in 9 pN1 and pN2 patients. The lymph nodes from 3 patients were reclassified as pN1mi. No pN2mi were detected. A survival model based on a stratification of the cohort into stages I to III was significant (chi-square = 7.426, df = 2, P = .024) but demonstrated considerable overlap between the survival curves of stage I and II patients. A model stratifying isolated tumor cells and pN1mi into stage I disease was significant (chi-square = 7.985, df = 2, P = .018) and showed no overlap between the survival curves of stage I and II patients. There were no significant survival function differences between patients with pN0, isolated tumor cells, and pN1mi. Patients with non–small cell carcinoma of the lung with isolated tumor cells and pN1mi have similar survivals to those with pN0, consistent with the findings reported for breast cancer patients. Future larger studies of patients with non–small cell carcinoma of the lung are needed to confirm whether current American Joint Committee on Cancer staging criteria should be modified to include the pN1mi category.