The implementation of GEM/DOC protocol to general hospitals is rather new. I started seeing the posting related to the protocol since two years ago here and there. The teaching university associated cancer hospital I know just started prescribing formally since December 2021. So, you many not find many replies. But, the protocol is 6 weeks induction treatment, followed by monthly for 12 months. Below is the result of a clinical trial involving many hospitals for GEM/DOC protocol was published in May 2020. It should answer to your questions.
276 patients with median age 73 years old. including only patients with recurrence during BCG treatment. between 2009 - 2018
9 patients quit the induction as the patients could not tolerate side effects
HG recurrence free survival 65% at 12 months and 52% at 24 months
Recurrence free survival 60% at 12 months and 46% at 24 months
10 patients (3.6%) had disease progression on TURBT for recurrence
42 patients (15.6) had radical cystectomy ( median 11.3 months from induction)
11 patients (4%) had progress to muscle invasive
best
www.auajournals.org/doi/10.1097/JU.0000000000000688