Prognosis of breast cancer: Evidence for interaction between c-erbB-2 overexpression and number of involved axillary lymph nodes

✍ Scribed by Dr. Indraneel Mittra; Alka A. Redkar; Rajan A. Badwe

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 484 KB
• Volume: 60
• Category: Article
• ISSN: 0022-4790
• DOI: 10.1002/jso.2930600208

✦ Synopsis

Abstract

The prognostic significance of c‐erbB‐2 oncogene amplification or overexpression in relation to axillary lymph node metastasis is controversial. We investigated this question in 159 cases of operable breast cancer: 56 patients with node negative disease and 103 patients with pathological involvement of axillary lymph nodes. c‐erbB‐2 overexpression was assessed by immunohistochemistry using a polyclonal antibody raised against a synthetic peptide fragment of the oncoprotein. The overall incidence of c‐erbB‐2 overexpression was 35%. c‐erbB‐2 overexpression was significantly related to survival when all patients were considered (P = 0.0124), and also for patients with positive axillary lymph nodes (P = 0.0026). c‐erbB‐2 overexpression had no influence on survival of node negative patients (P = 0.7972). A multivariate survival analysis using the Cox proportional hazard model revealed that number of involved lymph nodes, c‐erbB‐2 overexpression, ER status, and tumour size were independently related to prognosis (P = 0.0000, 0.0012, 0.0112, and 0.0204, respectively). When an interaction term was introduced in the Cox model between c‐erbB‐2 overexpression and number of involved axillary lymph nodes, a statistically highly significant interaction between these two factors was observed (P = 0.0002), suggesting that the expression of prognostic power of c‐erbB‐2 overactivity is related to the number of involved axillary lymph nodes. The 159 patients were then subdivided into three groups: node negative (‐ve) (56); 1–6 node positive ( + ve) (55); and ≥7 node +ve (48). This cutoff criterion gave the most numerically equitable distribution of the 159 patients into three groups. The relative risk of death increased stepwise from 0.86 (95% CI 0.26–2.78) for node negative patients, to 1.95 (95% CJ 0.82–63) for 1–6 node positive patients, to 2.23 (95% Cl 1.15–4.35) for >7 node positive patients. Our results suggest that the prognostic influence of c‐erbB‐2 overexpression increases arithmatically with increasing number of involved axillary lymph nodes. © 1995 Wiley‐Liss, Inc.