You should have every reason to hope that this is a managable condition. I've known many others with large high grade tumors, T1, that respond to BCG completely.
I hope the doctor is sure that he got it all, recent studies are saying that with large, high grade T1 tumors, it is wise to go back in a few weeks after the first TuR removal and do a second TUR before beginning treatment. If there is residual tumor it can effect treatment and prognosis.
There are some references to this info to be found on this page, in the side bar:
blcwebcafe.org/superficialblca.asp
, where at the bottom of the page are the latest European recommendations for T1 tumors: (excerpt)
*The visual judgement of urologists in superficial bladder tumors is very good.
*Second resection is indicated whenever insufficient material is delivered and in any T1 G3 tumor. In the last infiltrative tumors are regularly found. The treatment largely depends on prognostic parameters.
If the doctor or your mother are not amenable, don't worry, many tests have shown that BCG can also obliterate existing marker lesions that are left in the bladder just to study them.
Where is your mother being treated?