Wasn't that the point of one of Thorpe's comments in May? A rat was given a particularly nasty cancer; they let the cancer establish for a number of days; most rats would have died soon after; bavi was administered, but only for a specified treatment cycle.
The rat recovered and appeared to live to the end of a normal, healthy life cycle.
When they looked inside the rat after it died, they realized that a war had been going on because the virulent cancer was constantly trying to grow but the rat's immune system responded throughout the rest of the rats's natural life to keep the cancer at bay. The rat's cancer wasn't effectively masked by the presence of PS any longer.
That's what I remember. I believe it was in the Q&A.