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Vol.47 No.1 contents | Japanese/English |
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- Original Article -
New TNM Classification for Non-small Cell Lung Cancer by Evaluating T Factor Based on Tumor Size and Visceral Pleural Invasion
Noriaki Sakakura1, Futoshi Ishiguro1, Tatsuya Katayama1, Katsuhiro Okuda1, Takayuki Fukui1, Shoichi Mori1, Shunzo Hatooka1, Masayuki Shinoda1, Tetsuya Mitsudomi11Department of Thoracic Surgery, Aichi Cancer Center Hospital
Objective. In the current TNM staging system for lung cancer, there is no significant difference in survival rate between stage IB and IIA. Furthermore, the number of patients with stage IIA is very small. In this study, we re-evaluated the T factor based on tumor size and visceral pleural invasion to try to solve these problems. Methods. We studied 1245 consecutive patients with non-small cell lung cancer who underwent pulmonary resection. For analysis in order to stratify T2 category into subcategories, pathological T2 category was divided according to the tumor size and the degree of visceral pleural invasion, classified according to the Japan Lung Cancer Society criteria (P factor). Of the patients with current IB disease, those with worse prognostic T2 tumor were classified as IIA disease. Results. The 5-year survival rates and number of patients by pathological stages according to the current TNM classification were as follows: 82.2% for IA (n=354), 64.6% for IB (n=311), 69.2% for IIA (n=39), and 45.5% for IIB (n=145). T2 category was divided according to the tumor size (≤3, >3 to ≤5, >5 cm) and the degree of visceral pleural invasion (P0-1 or P2). Patients with T2 tumor of >3 to ≤5 cm and P0-1 had better outcome than those with T2 tumor of >5 cm or P2, and the 5-year survival rates were 59.5% and 37.5-47.3%, respectively. Therefore, the better prognostic T2 groups were defined as subcategory T2a, and the worse ones as T2b. With regard to stage grouping of TNM subsets, T2aN0M0 was classified as the new IB, and T2bN0M0 was classified into the new IIA together with the current T1N1M0. The 5-year survival rates and number of patients in our modified classification were 70.6% for our proposed IB (n=163) and 60.4% for our proposed IIA (n=145). Conclusions. Of the patients with current IB disease, those with tumor greater than 5 cm or those with P2 tumor have poor prognosis. When these groups of patients are re-classified as new IIA disease, survival rates are stratified in the order of stages IA, IB, IIA, and IIB, and more uniform distribution in the number of patients is achieved.
key words: Lung cancer, TNM classification, Revision, Tumor size, Pleural invasion
Received: September 1, 2006
Accepted: October 18, 2006
JJLC 47 (1): 1-8, 2007
