With the current arrangement for FISH testing external to the MUHC, the most cost-effective strategy is to screen all patients with IHC, followed by confirmatory testing with FISH of those patients with IHC scores of 2+ or 3+. Purchase of new equipment may be justified if it is decided to test all patients with FISH.
Recommendation: If it is assumed that trastuzumab therapy will be offered, it is recommended that all breast cancer cases be screened with IHC and those who have scores of 2+ or 3+ be tested by FISH to confirm their HER2 positive status. In the unusual event that a breast cancer patient approaches the hospital with a positive FISH test carried out outside the MUHC, an IHC test needs to be carried out to confirm the course of action.