As far as I recall the FDA warning on epo was issued on the basis on a study on Head-and-neck tumours showing a increased risk of failure of the external beam radiation in the epo-group vs. the controls (subjects were given epo during ebr to counter radiation induced anaemia).
This progressed into another FDA-warning on the use of epo for patients with widespread cancer disease. It was customary to administer epo to these patients as they would typically be anaemic as a result of increased haemolysis or red bone marrow displacement. It turned out that these patients fared worse than the patients treated with regular blood transfusions. Epo could, apart from raising the hct, also induce increased microvessel density in tumours (both increasing tumour oxygenitation) or act as a growth factor in tumours but this is a bit speculative. Epo-receptors may be wide spread in the human body, studies on the cognitive changes induced by epo have been done. The most likely conclusion on that matter is that epo somehow induces mythomanic tendencies
Saying that epo is carcinogenic in persons with no pre-existing cancer is (to my knowledge) unsubstantiated. Time will tell if we get a huge spike of cancers in 'previously healthy former elite athletes' in 20-30 years time.
Meanwhile, I'm keeping an eye open for the cancer statistics in the NBA and NFL - all that hgh has to kick start a significant amount of tumours - but perhaps that'll be masked by the increased amount of untimely sudden cardiac deaths caused by the 'roids and recreational drugs.