The importance of extracapsular extension of axillary lymph node metastases in breast cancer.

PURPOSE: To evaluate the prognostic value of extracapsular extension (ECE) of axillary lymph node metastases in 221 patients with axillary lymph node-positive, T1-T2 breast cancer treated at Dokuz Eylul University Hospital, Department of Radiation Oncology.

PATIENTS AND METHODS: The clinical records of patients with axillary node-positive, pathological stage II-III breast cancer examined at Dokuz Eylul University Hospital, Department of Radiation Oncology, between 1991-1999 were reviewed. All patients underwent modified radical mastectomy (MRM) or wide excision with axillary node dissection. Axillary surgery consisted of level I-II dissection. The number of lymph nodes dissected from the axilla was equal to or more than 10 in 92% of the patients. All 221 patients had pathological T1-T2 tumors. The number of involved lymph nodes was four or more in 112 51% patients and less than four in the remaining 109 (49%). In 127 (57.5%) patients, extracapsular extension was detected in axillary lymph nodes. Tangential radiotherapy fields were used to treat the breast or chest wall. Lymphatic irradiation was performed in 215 (97%) patients with fields covering both the supraclavicular and axillary regions. Median radiotherapy dose for lymph nodes was 5000 cGy in 25 fractions. The following factors were evaluated: age, menopausal status, histological tumor type, pathological stage, number of involved axillary lymph nodes, and extracapsular extension. The chi-square test was used to compare proportions of categorical covariates between groups of patients with and without ECE. Survival analyses were estimated with the Kaplan-Meier method. The Cox regression model was used for the analysis of prognostic factors.

RESULTS: The median follow-up for the survivors was 55 months (range, 19-23). The median age was 52 years (range, 28-75). In patients with extracapsular extension the percentages of pathological stage III (22% vs 4.3%, P < 0.0001 and involvement of four or more axillary nodes (25.5% vs 69.3%, p < 0.0000) were higher. Multivariate analysis revealed a significant correlation between the presence of ECE and disease-free survival (DFS) (P = 0.04) as well as distant metastases-free survival (DMFS) (P = 0.002), but there was no significant correlation between ECE and overall survival (OS). Only an elevated number of involved axillary lymph nodes significantly reduced the overall survival (P = 0.001).

CONCLUSION: The rate of extracapsular extension was found to be directly proportional to the number of axillary lymph nodes involved and the stage of disease. Extracapsular extension had significant prognostic value in both univariate and multivariate analysis for DFS and DMFS but not OS. The reason for ECE not affecting OS might be related to the much more dominant prognostic effect of the involvement of four or more axillary nodes on OS. Studies with more patients are needed to demonstrate that ECE is a likely independent prognostic factor for OS.