Assessment of a patient's HER-2/neu status is easy for staff in blood science laboratories to perform on a routine basis, and excludes the risk of subjective interpretation of results
The UK government has announced that all women in England who have been diagnosed with early stage breast cancer are to be tested for over-expression of HER-2/neu - the oncoprotein which is directly targeted by the tumouristatic drug Herceptin.
This follows in the wake of a landmark decision made recently by Somerset Coast Primary Care Trust which has, in exceptional circumstances, allowed an early stage breast cancer patient to receive the drug.
Currently, Herceptin is only authorised by the National Institute for Clinical Excellence (Nice) for use in advanced stage metastatic disease.
An application is reportedly being planned by Roche Pharmaceuticals, the manufacturer of Herceptin, for the drug to be licensed for early stage use in 2006.
Amid the controversy currently surrounding the length of time being taken by Nice to appraise and approve new cancer treatments, these latest developments have also served to bring the patchy availability and long waiting lists associated with HER-2/neu testing into the public eye.
The role of HER-2/neu testing.
Diagnostic assessment of a patient's HER-2/neu status is essential for guiding therapy with Herceptin.
Determination of HER-2/neu status has traditionally been accomplished using tissue testing techniques, whose availability is limited in some areas due to funding difficulties and perennial problems surrounding the recruitment and retention of specialist histology staff.
The in vitro diagnostic test now available from Bayer Diagnostics facilitates the quantitative determination of HER-2/neu in human serum using the automated Advia Centaur immunoassay system.
The ability to assess a patient's HER-2/neu status from blood samples offers clear advantages over tissue testing which relies on the analysis of biopsy specimens.
Whereas tissue testing facilitates retrospective assessment of material from a primary tumour which has been invasively removed at some time in the past, the serum assay provides a convenient means of obtaining dynamic real-time results using a simple non-invasive procedure which can be repeated at any time, guiding on-going treatment decisions.
In contrast to established histology methods such as fluorescence in situ hybridisation (Fish) and immunohistochemistry (IHC), this test is easy for staff in blood science laboratories to perform on a routine basis without special training, and (unlike IHC) excludes the risk of subjective interpretation of results.
It also overcomes the recognised problem of identifying patients whose original tissue biopsies were HER-2/neu negative or not tested or not available for testing or stored for a long time period, but who subsequently become positive after their cancers have spread.
Evidence for the use of serum HER-2/neu testing.
The current evidence supports the potential applications for serum HER-2/neu results in patient management as follows.
1) To establish candidacy for Herceptin based therapy at the time of clinically proven metastatic disease in those patients found to be serum HER-2/neu positive who were tissue negative at the time of primary diagnosis.
2) To obtain earlier diagnosis of metastatic disease; the data in the literature suggests a lead time of up to nine months before clinical signs of metastatic disease which then might initiate discussions on optimisation of therapy.
3) To establish a serum HER-2/neu baseline level in all patients diagnosed with metastatic breast cancer, allowing changes in disease status and prognosis to therapy offered to be monitored on an ongoing basis.
4) To establish a baseline level of serum HER-2/neu at the timepoint of diagnosis of breast cancer and prior to initiation of Herceptin treatment, enabling changes in levels to be monitored during the course of treatment and based on this discussions on therapy regimes.
The unique synergy which exists between serum HER-2/neu and Herceptin provides an excellent model for the future of personalised medicine whereby a biomarker is used to direct therapy on an individualised basis.
The potential of serum HER-2/neu measurement in detection, therapeutic decision-making and treatment monitoring in metastatic breast cancer is already being actively researched using the Bayer HER-2/neu assay in NHS laboratories at London's Kings College Hospital and Christie Hospital, Manchester, running on their Advia Centaur immunoassay systems.
Meanwhile, the Bayer test is already routinely available to private patients attending Wellington Hospital, Harley Street Clinic, Portland Hospital, Princess Grace Hospital, London Bridge Hospital and Lister Hospital in the UK, and through HCA Laboratories which provides a dedicated testing service to the Hospital Corporation of America using the Advia Centaur.
As public attention focuses increasingly on the treatment of breast cancer and interest in Herceptin grows, many other UK laboratories with Advia Centaur systems now have the opportunity to add serum HER-2/neu measurement to their testing repertoires.
(Please note that Bayer HealthCare is unable to provide medical advice to patients).
