Hi,
Welcome to the club (nobody wants to be in).
Experts have recently published that no, side effects of BCG are not cumulative and do not get worse with time. Funny, that. I've noticed people complaining that they do seem to get worse with more treatments, especially women. That's after about 9 years of listening to bladder cancer survivors talk about their stuff.
Prove me wrong and the experts right, and I will be very happy for you!
Best,
Wendy