Tissue expression and serum levels of the oncoprotein HER-2/neu in 157 primary breast tumours.

BACKGROUND

We studied HER-2 expression in paired serum and tissue samples, in 157 selected cases from 701 consecutive primary breast cancer patients with pre-treatment HER-2 extracellular domain (ECD) > or = 10 ng/ml, or < 10 ng/ml but showing a HER-2 ECD lead time before first metastasis.

PATIENTS AND METHODS

HER-2 ECD was measured by the Immuno 1 automated ELISA (Bayer). Tumour tissue was analysed by immunohistochemistry (IHC) with Dako A 0485 and CB 11 antibodies and scored with the Dako scoring system.

RESULTS

Mean HER-2 ECD was 12.48+/-7.08 ng/ml and 21/157 (13.4%) sera were > or = 15 ng/ml (cut-off). Forty tumours (25.48%) showed both invasive and intraductal components, 3 (1.91%) were pure in situ carcinomas and 114 (72.61%) were pure invasive tumours. Elevated HER-2 ECD concentration was related only to pT (p=0.0008), histological grade (p=0.0465), presence of comedonecrosis (p=0.0123) or comedo-type carcinoma (p=0.041) and was unrelated to the presence of an intraductal component. HER-2 ECD was > or = 15 ng/ml in 48% of Dako 3+ and 60% of CB 11 2+ and 3+ tumours. By logistic regression analysis, the significant parameters associated with HER-2 ECD concentration were pT (p=0.0038) and Dako 3+ scores (p=0.0005). In Dako 3+ or CB 11 2+3+ tumours, elevated mean HER-2 ECD concentrations were observed only when pT exceeded 28-30 mm (p=0.0062 and p=0.0036, respectively).

CONCLUSION

In breast tumours, a threshold in size and HER-2 overexpression is necessary to observe elevated concentrations of HER-2 ECD at diagnosis. This information may be useful when the primary tumour is not available for IHC.