Your answer is not very reassuring on the mutation front.
Considering that what you said can be translated to "we are curing cancer with an infectious disease that was modified to spread more slowly and kill cancer cells faster than it kills you", I don't think it is reassuring to the people that has to live day to day with the patient either.
It is a horrible necessity to have cancer patients be dosed with poison, but infecting themselves with something that can get to their families is in another league.
Spread more slowly is an understatement, a critical gene is deleted so that the virus cannot replicate in healthy cells. Also, it's a virus that causes cold sores. Not something you want your family to get for no reason, but not really horrifying either.
Considering that what you said can be translated to "we are curing cancer with an infectious disease that was modified to spread more slowly and kill cancer cells faster than it kills you", I don't think it is reassuring to the people that has to live day to day with the patient either.
It is a horrible necessity to have cancer patients be dosed with poison, but infecting themselves with something that can get to their families is in another league.