[sageridder]

I don't know that a difinative answer is possible.
On October 2, 1996, Armstrong was diagnosed with testicular cancer that had metastasized, spreading to his lungs and brain.Clinical conditions that give rise to tissue hypoxia including anemia, lung disease, or cyanotic heart disease, lead to increased levels of serum EPO.A primary elevation of EPO levels can also occur in association with renal diseases such as hydronephrosis or cysts, or certain tumors, resulting in erthrocytosis.EPO (rhu-EPO). Rhu-EPO has been used successfully in a variety of clinical situations to increase production of red blood cells. Currently, this agent is licensed for use in the treatment of the anemia of renal failure, the anemia associated with HIV infection in zidovudine (AZT) treated patients, and anemia associated with cancer chemotherapy.(source)

http://path.upmc.edu/consult/rla/july1995.html

So if it was there,which still seems questionable from the artical provided by Grojlach,There seem to be some factors from the cancer or possibly it's treatment that could have resulted in a positive test from the sample.