How would cancer interfere with hsv 1 and would it make it worse?

It might : Hsv one tends to pop up more often in people whose immune systems are not working effectively. A cancer patient, especially one on chemotherapy, will have a weak immune system. This would allow hsv one to become more active.

Benign to serious : Cancer and its treatment may render the immune system weak which in turn may lead to more frequent outbreaks. Rare complications such as from disseminated hsv may also be seen in the immunecompromised individual.