If the EGF-R mutation is an inherited one, it can be easily tested for, at any time, using some DNA extracted from the blood. If it is a mutation that is gained following birth, then an actual biopsy sample from the tumour is needed. Assuming that material is available, the test can be done at any time.
Second, I do not think that this test will have a huge impact on the income derived from the EGF-R inhibitors. If the test is validated and used, then the companies like AZN and OSIP will be able to offer a more tailored therapy with a heavily increased chance of therapeutic benefit. This will likely prompt the companies to increase the cost of their drugs in a manner analogous to Genzyme's enzyme therapies.
Furthermore, selecting a patient population that is very likely to benefit also means that you're focusing on a population that will take the drug for a longer average duration. Coupled with a price increase, the companies involved will do their best to make the economics work.
As for the FDA delaying Tarceva because they already offer Iressa... anything is possible, but I doubt it would fly. If I'm not mistaken, the patient populations that Iressa and Tarceva were tested on were not identical. Iressa patients had failed 2 previous regimens whereas, Tarceva's had failed at least 1. Furthermore, such an action by the FDA would really be a large blow to many of us biotech investors... especially if we can no longer count on life extension as a fundamental step towards FDA approval.
