A very good question.
I think it is best to ask to Mayo AZ why they chose 5 weeks + 3 week, then 2 wks for remaining maintenance. I am very interested to know why Mayo AZ did not follow a consensus statement published in 2019, which recommended dose reduction to 1/2, 1/3 which several academic hospitals seemed to have followed. The current BCG shortage started when Sanofi abandoned the most popular intravesical BCG product business in 2016, peaked at 2019-2021 when MERCK took over Sanofi's customer with Onco-Tice. Mayo AZ must have accumulated their data with their own protocol and reason to continue with their protocol.
Tice BCG shortage
The BCG production facility in Durham, NC can produce maximum of 700-800K vials a year. The demand exceeds more than 1M vials. The reason the shortage subsided is because a) many academic hospitals implemented dose reduction & use of intravesical chemotherapy for intermediate risk NMIBC , b) several European countries switched from Tice to BCG-MEDAC which is manufactured by Medac Corp. in Germany as the main supplier, c) a few countries like Australia and New Zealand supplemented Tice with other BCGs. US and the UK are the only countries who decided to use only Tice BCG. US chose dose reduction and prioritized BCG for high risk. To UK, MERCK guaranteed 90% supply if Tice BCG remains sole source of BCG. Initially, UK recommended reduction of BCG treatment frequency, which later stopped the recommendation due to the result of NIMBUS clinical trial.
SWOG clinical trial (2000) led by Dr. Lamm
The clinical trial was to compare BCG treatment with 6 weeks induction course only vs 6 weeks + 3 weeks ( 7 times) maintenance (in total 27 instillations). It is difficult to compare SWOG protocol and Mayo AZ protocol.
As Allan mentioned only 16% were able complete the whole treatment mainly due to side effects.
NIMBUS clinical trial (2023-2019) led by European
The clinical trial was see if side effects could be reduced without affecting efficacy by reducing number of BCG instillations.
The standard BCG schedule was 6 wks of induction followed by 3 wks of maintenances at 3,6 and 12 month ( 15 installations). The reduced frequency BCG schedule was the induction at wks 1,2 and 6 followed by 2 wk (wks 1 and 3) of maintenance at 3,6, and 12 months (in total 9 instillation).
Result After 12 month of median follow-up, 46/170 or 27% of (reduced frequency group) versus 21/175 or 12% of (standard treatment group) had recurrence, hence it was determined that reduced frequency was inferior to standard frequency, and the trial was terminated at that point.
Note that the NIMBUS protocol is different from Mayo AZ.
Incidentally, in 2015, FDA and AUA got together and came up the definition of BCG Unresponsibe. Patient is considered as BCG unresponsive if there is recurrence in spite of the patient having received Adequate BCG treatment. FDA/AUA defined Adequate BCG treatment is when a patient receives (5 or 6) weeks induction and a (2 - 6) weeks maintenance treatment.
Mayo AZ sounds like a good place for NMIBC patients to be treated as they used flexible blue light cystoscopy after 5 weeks BCG treatment, then after the first 3 weeks maintenance treatment for your husband. I do understand the dilemma.