Are EGFR Inhibitors Only Useful in Certain Patient Groups?

It's becoming more clear that some targeted therapies can be even more finely targeted, as highlighted in this summary of EGFR inhibitors.

Consider these findings from Iressa trials:
"EGFR inhibition response rate to Iressa was 27% in Japanese patients compared with only 10% in non-Japanese patients, but that this difference was not as significant as the differences in response rate favoring women over men, patients with adenocarcinomas over squamous carcinomas, and healthier patients over less healthy ones (“performance status”, or the ability to perform the activities of daily living without assistance or significant symptoms). The US-based IDEAL-2 trial also showed women receiving iressa to be more likely to have symptomatic improvement (50% vs. 31%) and significant tumor shrinkage (19% vs. 3%) compared with men, and also that patients with adenocarcinomas were more likely to have symptomatic improvement (43% vs. 30%) and tumor shrinkage (13% vs. 4%) compared with those who had squamous tumors. "

Good news (in terms of tumor shrinkage, but NOT survival) if you're a non-smoking Japanese woman with an adenocarcinoma, bad news if not.

Kind of amazing that this sort of knowledge is only coming to light ~3 years post-FDA approval. (I'm not suggesting that approval be delayed, just that with any approval, there's still many important outstanding questions.)

This also brings to mind the question of who is likely to sponsor the development of the relevant intelligence and diagnostics to further segment patients. You might guess that the makers of EGFR inhibitors would, but is it in their best interest to EXCLUDE potential customers? (Plus, there's enough competitors among EGFR inhibitors that no one is likely to want to pay to develop this market for the benefit of their competition.

(That being said, I'm pretty sure that I've seen press releases announcing that AZ has sponsored EGFR biomarker development, with CST, I think.)