Now at minute 1:42
of this video we now know that persistence means "once the cell begins to attack the tumor instead of dying the cell begins to proliferate in the body, makes new cells that will keep attacking the tumor
Read it slowly, several times and remember that this is being unleashed in solid cancer.
So if each cell instead of dying creates new cells which in turn each newly created cell creates new cells (and again and again.....) then the body of the metastatic cancer patients ends up with trillions of "soldiers" depending on the size of the initial dose.
So even a low dose might be good enough if the cells persist and the patient lives long enough for the persistence/ multiplier effect to kick in sufficient quantities.
Persistence should be read to mean multi-multplier.