Dew, Question for specificity
Dako markets the EGFr test because it’s a good business—not because it’s good science.
The statement is a bit of extreme. IHC testing is such a useful tool that not only is it used for EGFr testing, but also for HER2+ receptor testing. Breast cancer patients will not receive trastuzumab unless it's 3+ IHC (admittedly there is a small fraction of patients that are FISH+ but IHC2+). And the EGFr IHC testing is no different from HER2+ except for the ligand. Clearly, there are scientific values for the tests.
This is another way of saying the same thing: extremely low levels of EGFr (even levels below the level of detection of the commercial assay) may be sufficient to allow a patient to respond to an anti-EGFr drug.
This statement essentially mocks the collective intelligence of scientists at IMCLONE, BMS, Amgen, Dako and FDA. The line has to be drawn somewhere. I'd rather believe if the test is negative, it has to have high probability of identifying a negative sample, otherwise the assay is useless and should not have been marketed. If the specificity is 90%, then 90% of the EGFr-negative patients will not respond. Again, I ask how prevalent do oncologists treat without testing for EGFr positivity.
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