A proposal for a new classification of T4 breast cancer as stage IIIC: a report from the Korean Breast Cancer Society
BACKGROUND The American Joint Committee on Cancer (AJCC) TNM classification for breast carcinoma had not been changed for 15 years, since the publication of the third edition in 1987. However, in the sixth edition, published in 2002, significant modifications were made with regard to the number of metastatic axillary lymph nodes. The authors investigated whether the sixth edition of the TNM classification provided more reliable prognostic information compared with the third edition. METHODS The records of 1230 patients who underwent surgery for invasive breast carcinoma between 1993 and 1999 were reviewed. Each patient was assigned to axillary lymph node and disease stage groups according to the 1987 and 2002 AJCC TNM classifications. Disease-free survival (DFS) curves were calculated and plotted using the Kaplan-Meier method and the two-sided log-rank test was used to compare the survival curves of the patient groups. RESULTS Of the 1067 patients who were classified as having Stages II and III disease according to the 1987 classification, 411 (38.5%) were shifted to higher disease stages using the 2002 classification. Among the 1987 Stage IIA, Stage IIB, and Stage IIIA patients, the DFS rates of the patients who were shifted to higher stages of disease were significantly worse than those of the patients for whom the stage of disease was not changed. Among those patients classified as having T4anyNM0 (Stage IIIB) disease according to the 1987 classification, there was no survival difference noted between those patients with T4N0,1,2M0 disease (who formed the Stage IIIB group) and those with T4N3M0 disease (who formed the Stage IIIC group) according to the new staging system. Of the 221 patients who formed the new Stage IIIC group, 12.2% were classified as having Stage IIA disease, 42.1% as having Stage IIB disease, 38.9% as having Stage IIIA disease, and 6.8% as having Stage IIIB disease according to the 1987 classification. The survival rates of these Stage IIA, Stage IIB, and Stage IIIA patients were not found to be significantly different; however, the survival of patients in the Stage IIIB group was found to be significantly worse than the survival of the patients in the other disease stage groupings, and the patients in the Stage IIIC group were not a prognostically homogeneous group. On the basis of these results, the authors placed patients with T4anyNM0 disease in the same group (Stage IIIB). When the 2002 classification was rearranged in this manner, patients with Stage IIIC disease formed a homogeneous group; the 5-year DFS rate of patients with Stage IIIB disease was found to be significantly worse than that for patients with Stage IIIC disease (P = 0.0011). CONCLUSIONS In the 2002 TNM classification for breast carcinoma, patients with T4anyNM0 disease should form a distinct stage grouping and this stage grouping (Stage IIIC) should be placed before Stage IV, and Stage IIIB disease groupings should include patients with T1,2,3N3M0 disease. In this way, the authors hope that the 2002 AJCC TNM classification, which provides more reliable prognostic information than the 1987 classification, will become more refined.