Do we need HER-2/neu testing for all patients with primary breast carcinoma?

BACKGROUND: HER-2/neu is a valuable prognostic marker in primary breast carcinoma. Controversy surrounds the correlation between HER-2/neu expression and other prognostic markers, as has been discussed in preclinical and clinical studies. The objective of the current study was to investigate the probability, calculated using parameters that are assessed routinely in clinical practice, that patients with breast carcinoma had positive HER-2/neu status.

METHODS: The authors evaluated HER-2/neu status in 923 consecutive patients with breast carcinoma by immunohistochemical methods. Correlations involving HER-2/neu status, estrogen receptor (ER) and progesterone receptor (PR) status, tumor grade, patient age, lymph node involvement, and tumor size were evaluated using the Mantel-Haenszel chi-square test and the Spearman correlation. The authors created a simple scoring system (i.e., the diagnostic instrument for validation of HER-2/neu score) to define subgroups of patients with breast carcinoma and to determine the likelihood of HER-2/neu positivity.

RESULTS: HER-2/neu overexpression was correlated significantly with negative ER (P = 0.0001) and PR status (P = 0.0001), Grade 3 (G3) lesions (P = 0.0001), and young age (P = 0.006). The likelihood of HER-2/neu positivity in a patient with positive ER and PR status and G1/G2 disease was approximately 6.1%.

CONCLUSIONS: The authors demonstrated in a large patient series that HER-2/neu overexpression was associated with negative hormone receptor status, G3, and young age. In a subgroup of patients presenting with hormone-responsive and G1/G2 tumors, the likelihood of HER-2/neu overexpression was very small. Therefore, the assessment of HER-2/neu status in this subgroup of patients with breast carcinoma may be considered unnecessary, unless the role of HER-2/neu status in adjuvant treatment has been proven.