Sorry to hear that your cancer has returned. Glad that your treatments are going well.
Since you have treated your cats any eggs that hatch and make it to a host will die. The ones that don't make it to a host will die in a week or so from lack of food.
There are 3 ways to kill the eggs that are hidden. Water, Heat and chemical.
1) You can drown them by completely submerging everything in water. The tank (if that's what your using) can be partially submerged then flipped to submerge the top. Fill completely with water when submerging the bottom. 24+ hours recommended.
2) You can "cook" everything at 140 degrees for a couple of hours. Hard to do with the tank and possibly dangerous with any combustible items.
3) Not sure if it is available there but you can treat everything with a No Pest Strip. It will penetrate everything. Remove the snake and put the tank with everything still in it outside. Put the no Pest Strip in and cover it for 24 hours. Remove and let it air out for another 24 hours. Or if you can get a flea collar that is the kind that emits a toxic gas ( usually older types ) and put that in the tank to treat.