The drug trastuzumab (Herceptin) is used to treat HER2-positive breast cancer (a type of breast cancer that overexpresses the HER2 gene and accounts for about 25% of all breast cancers). Trastuzumab therapy improves the chances of survival; however, it has deleterious side effects and is expensive. Thus, it is important to accurately determine the patientís HER2 status.
The challenge is to develop a testing strategy that is both accurate and economical. A false-negative test result can mean a woman will not receive a life-prolonging drug, and a false-positive result can lead to unnecessary, expensive drug treatment.
In a systematic review published in the Canadian Medical Association Journal, Dendukuri and colleagues compared the cost-effectiveness of 7 strategies (based on a combination of 2 tests) to diagnose HER2 status. They found that the most cost-effective strategy is to screen all women who have newly diagnosed breast cancer with immunohistochemistry and to confirm ambiguous or positive test scores with fluorescence in situ hybridization.
In a related commentary, Brian Goldman notes that the example of trastuzumab and the HER2 gene illustrates both the promise and the perils of gene patenting. Even though genes occur naturally in humans, it is the person who discovers a gene who usually holds the patent for it.
Any researcher or pharmaceutical company who wants to investigate or develop treatments based on that gene must obtain permission from the patent holder. Even testing for mutations in patented genes (e.g., BRCA1 and BRCA2) can be restricted by the patent holder.
Canadian Medical Association Journal, May 8, 2007