Raja M. Flores, Thomas A. Routledge, Ennapadam Venkatraman, Joseph Dycoco, Yael Hirth, Valerie W. Rusch; Memorial Sloan-Kettering Cancer Center, New York, NY
Objective: MPM originates in the parietal pleura, however, the propensity to metastasize to N1 or N2 nodes and their corresponding prognostic value is unknown. The AJCC staging system groups N1 and N2 disease together as stage III. The goal of this study was to better define the prognostic value of specific nodal stations to improve stratification for clinical trials.Methods: Patients with biopsy proven MPM who underwent surgical resection with mediastinal nodal dissection or sampling were identified and clinical data was obtained from an institutional database. Nodal stations were defined by the AJCC lung cancer node map classification. Survival was analyzed by the Kaplan-Meier method, logrank test, and Cox proportional hazards analysis. A p-value of <.05 was considered statistically significant.
Results: From 1990 to 2005, 348 patients were identified: 279 men and 69 women, median age 67 years (range 26-85). EPP was performed in 223 cases and Pleurectomy/Decortication in 125. Survival differences were observed between N1/N2 negative, N1 positive patients with a median survival of 19 months versus N2 positive , N2/N1 positive, and internal mammary positive lymph node patients with a median survival of 10 months (p<0.01). A Cox model grouping all N2 and mammary positive versus N1 positive and N0 nodal stations demonstrated a HR of 1.7 (p<.0001) controlling for T3/T4 status (HR = 1.6, p=0.4), non-epithelioid histology (HR = 1.7, p<.0001), EPP (1.1, p=0.4), and male gender (HR 1.4, p=0.01) .
Conclusion: It appears that MPM has a greater propensity to metastasize to the N2 nodes, however, solitary metastasis to the N1 nodes portends a better prognosis than solitary metastasis to N2 nodes implying earlier stage disease, in addition the survival of internal mammary nodes parallels survival with N2 positive nodes. These differences should be taken into consideration for revision of the AJCC staging system.
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