Eiji Shinto1, Jin-Ichi Hida2, Hideyuki Ike3, Hirotoshi Kobayashi4, Yojiro Hashiguchi5, Kazuo Hase6, Hideki Ueno6, Kenichi Sugihara7. 1. Department of Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan. eiji-c@zf6.so-net.ne.jp. 2. Department of Surgery, Kindai University School of Medicine, Osaka, Japan. 3. Department of Surgery, Saiseikai Yokohamashi Nanbu Hospital, Yokohama, Japan. 4. Department of Surgery, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan. 5. Department of Surgery, Teikyo University School of Medicine, Tokyo, Japan. 6. Department of Surgery, National Defense Medical College, Tokorozawa, Saitama, Japan. 7. Tokyo Medical and Dental University, Tokyo, Japan.
Abstract
BACKGROUND: Complete mesocolic excision is becoming popular in colon cancer surgery in Western countries, and in the tumor-node-metastasis (TNM) classification of rectal cancer, a part of the lateral pelvic lymph nodes is classified as regional. However, the appropriateness of TNM staging according to the assessment of nodal status exclusively by extended lymphadenectomy remains unclear. PATIENTS AND METHODS: Using a nationwide multicenter database in Japan, we retrospectively analyzed 6866 patients with stage III colorectal cancer (CRC) treated with extended (D3) dissection. First, the best cutoff values for the number of metastatic nodes were explored. Second, the utility of the metastatic status of the main lymph nodes (i.e., at the origin of the feeding artery) and the lateral pelvic lymph nodes ("jN3" category in the Japanese staging system) as N staging criteria was evaluated. The modified N staging system that had the best risk stratification power was determined according to the Akaike information criterion (AIC). RESULTS: Excellent performance was noted when the number of metastatic nodes was categorized by cutoff values of "3/4" and "6/7." Categorization of nodal metastasis was proven the most clinically efficacious when classified as modified-N1 (N1 and jN3-negative), modified-N2a (N2a and jN3-negative), and modified-N2b (N2b and/or jN3-positive; AIC, 22,810.8), rather than the classification based on the TNM (AIC, 22,849.2) or Japanese staging system (AIC, 22,811.1). CONCLUSIONS: We structured a modified N staging system according to the number and extent of lymph node metastases. The modified system may be used in stage III cases for precise risk stratification.
BACKGROUND: Complete mesocolic excision is becoming popular in colon cancer surgery in Western countries, and in the tumor-node-metastasis (TNM) classification of rectal cancer, a part of the lateral pelvic lymph nodes is classified as regional. However, the appropriateness of TNM staging according to the assessment of nodal status exclusively by extended lymphadenectomy remains unclear. PATIENTS AND METHODS: Using a nationwide multicenter database in Japan, we retrospectively analyzed 6866 patients with stage III colorectal cancer (CRC) treated with extended (D3) dissection. First, the best cutoff values for the number of metastatic nodes were explored. Second, the utility of the metastatic status of the main lymph nodes (i.e., at the origin of the feeding artery) and the lateral pelvic lymph nodes ("jN3" category in the Japanese staging system) as N staging criteria was evaluated. The modified N staging system that had the best risk stratification power was determined according to the Akaike information criterion (AIC). RESULTS: Excellent performance was noted when the number of metastatic nodes was categorized by cutoff values of "3/4" and "6/7." Categorization of nodal metastasis was proven the most clinically efficacious when classified as modified-N1 (N1 and jN3-negative), modified-N2a (N2a and jN3-negative), and modified-N2b (N2b and/or jN3-positive; AIC, 22,810.8), rather than the classification based on the TNM (AIC, 22,849.2) or Japanese staging system (AIC, 22,811.1). CONCLUSIONS: We structured a modified N staging system according to the number and extent of lymph node metastases. The modified system may be used in stage III cases for precise risk stratification.