Does the revised TNM staging system for lung cancer better estimate actuarial rates of local/regional recurrence after surgery?

Abstract

7072 Background: The International Association for the Study of Lung Cancer (IASLC) recently recommended changes to the TNM classification of lung cancers. For early-stage disease, increasing tumor size and nodal status are of primary prognostic relevance for overall survival. However, the ability of the old and the new staging system to predict the risk of local/regional recurrence (LRR) has not been evaluated. Therefore, we examined whether the proposed changes in AJCC 7 would refine the risk of LRR in patients who undergo surgery for early-stage NSCLC. Methods: The medical records and pertinent radiographs for all patients who underwent surgery for early-stage (N0-N1) NSCLC at Duke between 1995 and 2005 were reviewed. Patients undergoing suboptimal surgery (sublobar resections, positive margins), or those who received any preoperative therapy or postoperative radiation therapy were excluded. Disease recurrence at the surgical margin, ipsilateral hilum, and/or mediastinum was considered a LRR. Stage was assigned based on both AJCC 6 and AJCC 7. Actuarial rates of LRR were estimated using the Kaplan-Meier method. Results: Of 975 patients who underwent surgery during the time interval, 741 were eligible for this analysis. Surgery consisted of lobectomy in 91% (n=672) and pneumonectomy in 9% (n=69) of patients. 82% (n=605) of patients were pathologic N0 (pN0) and 18% (n=136) were pN1. Adjuvant chemotherapy was administered to 7% (n=52). Median follow-up was 35 months. Conversion from AJCC 6 to AJCC 7 resulted in 25% stage migration (upstaging in 15%; downstaging in 10%). For all patients, the 5-year actuarial risk of LRR was 20% (95% CI 17%-24%). 5-year rates of LRR for stage IA, IB, IIA, and IIB disease using AJCC 6 were 12%, 26%, 40%, and 27%, respectively. Using AJCC 7, corresponding rates were 12%, 21%, 34%, and 38%, respectively. Conclusions: The risk of LRR increases monotonically with stage in the new AJCC 7 system, but not for the older AJCC 6 system. Thus, the newer staging system is better in predicting the risk of LRR. This information will be valuable when designing future studies of postoperative RT. No significant financial relationships to disclose.