so in summary from what little I know,I think the optimum result...

so in summary from what little I know,
I think the optimum result would be for:
a) injection of the virus into cancer cell,
b) virus multiplies and pops the cancer cell,
c) parts of the dead cell break off with virus inside,
d) parts of the dead cell are ingested by other cells,
e)i)if it is inside a normal cell the immune system will target the virus,
ii) if it is inside a cancer cell the immune system will not be able to target the virus
f) the virus will multiply inside the cancer cell and the cycle repeats.

Whether or not that is what's happening I can only speculate, but can only get back to the point made by VLA that kmsmith brought up about the virus being present for 4-5 weeks being a good thing.