Hmmm, it could be that by 'in sitro' the doctor is referring to CIS, carcinoma in situ. This is actually an agressive form of bladder cancer, but BCG halts it about 75% of the time.
I hope your son has an experienced doctor who knows the territory because bladder cancer is a complicated disease, though very survivable. A careful approach must be used if someone has CIS. Were there also papillary tumors present? They often occur together, tumor and CIS. CIS does not appear as a tumor, but as a red patch and it's very difficult to stage properly as it can be invisible.
I'd want to know if that's what your dealing with. I'd also want an explanation for the bleeding, is it side effects from BCG or symptoms of tumor?
When people can't tolerate BCG, sometimes doctors give low dose BCG with Interferon as a combination, it's supposedly less toxic and just as good.
More info:
blcwebcafe.org/interferon.asp
Wendy