Tumour epidermal growth factor receptor, erbB-2 and cathepsin D in node-negative invasive breast cancer: their impact on the selection of patients for systemic adjuvant therapy.

Objective: To determine the feasibility and the economic impact of tumour EGFR, erbB-2 and cathepsin-D measurements in women with node-negative breast cancer.

Design: Consecutive tumour samples received at a regional steroid receptor laboratory from patients with node-negative breast cancer were evaluated with commercially available kits to determine EGFR, erbB-2 and cathepsin-D levels.

Setting: All node-negative patients whose tumours were submitted to the steroid receptor laboratory from November 1992 to March 1994 were included (n = 142). A control group of concurrent node-negative breast cancer patients from the London Regional Cancer Centre (LRCC) database were also evaluated to determine the representativeness of our sample.

Main outcome measure: To determine the proportion of patients who were positive for the 3 newer prognostic factors relative to their risk of relapse.

Results: We found 75 positive values in 69 patients (48.6%). We demonstrated that each factor identified a different high-risk subgroup. Epidermal growth factor receptor (EGFR) positivity (> 10 fmol/mg protein) was found in 16.3% of patients, with 19.9% of patients positive for erbB-2 (> 250 units/mg protein) and 17.3% positive for cathepsin D (> 70 pmol/mg protein). Between 10% and 23.2% more node-negative patients currently seen in a regional cancer centre could be offered systemic adjuvant chemotherapy based on a single positive new factor.

Conclusions: These tumour evaluations are straightforward using material already available in a regional steroid receptor laboratory or on tumour tissue available to pathologists. The economic impact is minimal; the 1995 cost of performing all 3 evaluations is Can$425-616 (US$304-440) per patient treated depending on the number of assays per run. Prospective clinical trials incorporating tumour EGFR, erbB-2 and cathepsin D are feasible and economically viable.