Validation of the new AJCC TNM staging system for gastric cancer in a large cohort of patients (n = 2,155): Focus on the T category
Introduction
The prognosis of resectable gastric cancer is mainly related to the depth of invasion (T category) and lymph node involvement (N category).1, 2, 3, 4 Following the International Union Against Cancer–American Joint Committee on Cancer (UICC-AJCC) TNM classification released in 2002,5 the T2 category – which is defined as a tumor involving the muscularis propria or subserosa5, 6 – is considered advanced disease but represents a stage with an intermediate prognosis between early gastric cancer (EGC, T1) and serosal involvement gastric carcinoma (T3). Whereas the survival rates of EGC are high (independently of the lymph node status)7, 8, 9 and those of T3 are low,1, 2, 10 the survival rate of T2 gastric cancer varies significantly in relation to other prognostic parameters (i.e. nodal metastasis).11, 12, 13, 14, 15, 16 Since 1998, the College of American Pathologists suggested that a subclassification of T2 into T2a (tumor with invasion of muscolaris propria) and T2b (tumor with invasion of subserosa) should be recommended because “postsurgical survival after resection for cure is significantly different for patients with T2a and T2b lesions”.17
The prognostic role of T2 subclassification is supported by several lines of evidence. In particular, this T category has been associated with variable nodal involvement rates, N-ratio values as well recurrence and mortality rates. It is unclear whether these findings depend upon the extent of lymphadenectomy.11, 12, 18, 19 In a recently published study performed on 189 patients curatively resected with extended lymphadenectomy, we confirmed that patients with T2a tumors have a significantly better 5-year overall survival as compared to those with T2b neoplasms, with T2 subcategorization being an independent prognostic value at multivariate analysis.20
Although the 2002 UICC-AJCC classification split the T2 category into T2a and T2b, these subcategories were not maintained in the TNM stage grouping.5 In the light of the above mentioned evidence regarding the prognostic value of T2 subcategorization, this gap of the 2002 TNM version will be filled by the 2010 TNM release. In particular, the new version redefines the T category as follows: T1a = mucosa, T1b = submucosa, T2 = muscolaris propria, T3 = subserosa (formerly known as T2b), T4a = perforates the serosa (formerly known as T3), T4b = infiltration of adjacent structures (formerly known as T4).21
In the present multicentric study we confirm that the subdivision of the T2 category (T2 and T3 in the new TNM classification) has a significant prognostic value independently of lymph node status in patients with gastric cancer.
Section snippets
Patients selection and data collection
In this retrospective multicentric study, data were collected from the medical records of 2155 patients who underwent radical resection (R0) for histologically confirmed T1-T4a gastric carcinoma from January 1988 through December 2006. Patients were operated at six Italian centers experienced in gastric cancer treatment: Clinica Chirurgica Generale 2, University of Padova (n = 352); First Division of General Surgery, University of Verona (n = 387), Institute of Surgical Sciences, University of
Patients and tumor characteristics
Clinical and pathological data of 686 patients classified T2/T3 are shown in Table 1.
The male-to-female ratio was approximately 3:2, with a median (range) age of 69 (27–94) years. In 39% of patients the tumor was limited to the muscolaris propria (T2), while in the remaining 61% of cases the tumor involved the subserosa (T3). A D2 or more extended lymphadenectomy was performed in 86% of patients, while a D1 lymphadenectomy was performed in 14% of patients.
The distribution of T2 and T3 was
Discussion
In this retrospective study, which involved six Italian centers experienced in gastric cancer surgery, we investigated the prognostic impact of the new T categories recently implemented in the latest version of the AJCC TNM classification,21 with special attention to the T2 and T3 (formerly T2a and T2b) subcategories, in patients who underwent radical resection for gastric carcinoma. Univariate analysis demonstrated that the 5-years OS rate of patients with T2 tumors was significantly higher
Acknowledgments
This study was supported by the Italian Veneto Region Associazione Italiana Ricerca sul Cancro (AIRC) grant 2009.
All Authors had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
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On behalf of the Italian Research Group for Gastric Cancer (G.I.R.C.G.).