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Lymph node involvement prognostic for survival in NSCLC, M1a disease
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Lymph node stage may have clinical significance and prognostic value for patients with non–small cell lung cancer and M1a disease, according to retrospective study results.
“Although the incidence of lung cancer has been stable in the past decade, nearly 40% of new cases were diagnosed at stage IV,” Chang Chen, MD, PhD, vice president of Shanghai Pulmonary Hospital and professor of thoracic surgery at Tongji University School of Medicine, and colleagues wrote. “In 2007, these large numbers of cases were subdivided and a new category of M1a was proposed in the seventh edition of TNM staging.”
Clinical staging guidelines defined M1a disease as metastases within the chest cavity, including pleural dissemination and contralateral pulmonary nodules.
Patients with M1a disease are classified as stage IV, regardless of lymph node status.
Chen and colleagues sought to determine whether identification of lymph node status held clinical value in terms of lung cancer–specific survival for this patient population.
The researchers used the SEER database to identify 39,731 patients (median age, 70 years; range, 23-103; 54.3% men) diagnosed with NSCLC and M1a disease between 2005 and 2012.
Patients were classified by lymph node (N) stage:
- N0 (n = 11,435), defined as no regional node metastasis;
- N1 (n = 2,683), defined as metastasis in ipsilateral peribronchial, perihilar and intrapulmonary lymph nodes;
- N2 (n = 18,977), defined as metastasis in ipsilateral mediastinal and/or subcarinal lymph nodes; and
- N3 (n = 6,636), defined as metastasis in contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph nodes.
Patients with N0 status had significantly longer lung cancer–specific survival than those with N1 status (P < .001), as did patients with N1 status compared with those with N2 status (P < .001).
Similar survival outcomes occurred among patients with N2 and N3 status.
A multivariate analysis showed that compared with N0 status, lymph node metastasis served as an independent prognostic factor for patients with N1 (HR = 1.14; 95% CI, 1.09-1.2), N2 (HR = 1.35; 95% CI, 1.31-1.39) and N3 status (HR = 1.39; 95% CI, 1.34-1.44).
The researchers performed a subgroup analysis, in which they stratified patients based on diagnosis period (2005-2008, n = 24,801; 2009-2012, n = 14,930).
Patients with N0 status achieved better survival outcomes than patients with N1 status in both time periods (2005-2008, P = .018; 2009-2012, P = .009), as did patients with N1 status compared with patients with N2 status (P < .001 for both periods).
Similar outcomes occurred for patients with N2 and N3 status regardless of diagnosis period.
The presence of lymph node metastasis remained a significant independent prognostic factor for patients with N1 (2005-2008, P < .001; 2009-2012, P = .002), N2 (P < .001 for both periods) and N3 status (P < .001 for both periods).
The researchers performed an additional subgroup analysis based on the presence of pleural dissemination (n = 31,294) or contralateral pulmonary nodules (n = 8,437). Patients with pleural dissemination were further divided by malignant pleural effusion (n = 29,197) and malignant pleural nodules (n = 2,097).
Patients with N0 status and pleural dissemination had significantly better survival than those with N1 status (P = .019), as did those with N1 status compared with N2 status (P < .001).
The researchers observed similar outcomes for patients with contralateral pulmonary nodules (N0 vs. N1, P = .001; N1 vs. N2, P < .001).
Further, patients with malignant pleural nodules and N2 status had significantly better lung cancer–specific survival than patients with N3 status (P = .003).
The researchers acknowledged several study limitations. Because the SEER database does not capture data on clinical and pathologic N staging, the researchers were unable to analyze these values in specific subgroup analyses.
The researchers further lacked data on treatment platforms, as well as functional status, comorbidities and molecular mutations.
“Our study found that the extent of lymph node metastasis has prognostic value for patients with M1a disease,” Chen and colleagues wrote. “Specifically, patients with M1a disease without lymph node involvement had the best survival, followed by those with N1 disease.” – by Cameron Kelsall
Disclosure: The researchers report no relevant financial disclosures.
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