The c-erbB-2 oncogene product in serum (serum c-erbB-2) was measured b
y an enzyme-immunoassay kit. The 12 U/ml cut-off level was estimated a
s the mean plus two standard deviations for 250 healthy women. With th
is cut-off level increased serum c-erbB-2 was found in 12.0% of primar
y breast cancer cases (n = 25), in 4.9% of non-recurrent breast cancer
patients (n = 82), and in 31.4% of patients with recurrent breast can
cer (n = 35). In patients with primary and recurrent breast cancer, wh
ose sera were assayed concurrently for serum c-erbB-2, CEA and CA15-3,
the positive rates of these markers were fairly similar. However, the
ir combined use significantly increased the sensitivity as compared to
the use of any one marker alone.