Detection of Occult Micrometastases in Patients With Clinical Stage I Non–Small-Cell Lung Cancer: A Prospective Analysis of Mature Results of CALGB 9761 (Alliance)

Abstract

Purpose Outcomes after resection of stage I non–small-cell lung cancer (NSCLC) are variable, potentially due to undetected occult micrometastases (OM). Cancer and Leukemia Group B 9761 was a prospectively designed study aimed at determining the prognostic significance of OM. Materials and Methods Between 1997 and 2002, 502 patients with suspected clinical stage I (T1-2N0M0) NSCLC were prospectively enrolled at 11 institutions. Primary tumor and lymph nodes (LNs) were collected and sent to a central site for molecular analysis. Both were assayed for OM using immunohistochemistry (IHC) for cytokeratin (AE1/AE3) and real-time reverse transcriptase polymerase chain reaction (RT-PCR) for carcinoembryonic antigen. Results Four hundred eighty-nine of the 502 enrolled patients underwent complete surgical staging. Three hundred four patients (61%) had pathologic stage I NSCLC (T1, 58%; T2, 42%) and were included in the final analysis. Fifty-six percent had adenocarcinomas, 34% had squamous cell carcinomas, and 10% had another histology. LNs from 298 patients were analyzed by IHC; 41 (14%) were IHC-positive (42% in N1 position, 58% in N2 position). Neither overall survival (OS) nor disease-free survival was associated with IHC positivity; however, patients who had IHC-positive N2 LNs had statistically significantly worse survival rates (hazard ratio, 2.04, P = .017). LNs from 256 patients were analyzed by RT-PCR; 176 (69%) were PCR-positive (52% in N1 position, 48% in N2 position). Neither OS nor disease-free survival was associated with PCR positivity. Conclusion NSCLC tumor markers can be detected in histologically negative LNs by AE1/AE3 IHC and carcinoembryonic antigen RT-PCR. In this prospective, multi-institutional trial, the presence of OM by IHC staining in N2 LNs of patients with NSCLC correlated with decreased OS. The clinical significance of this warrants further investigation.