I Had Cis In 1987 And Have Been Followed Ever

I had cis in 1987 and have been followed ever since. I took BCG for quite a while. I had a positive cytology///had surgery on set if biopsies came back PUNLMP...So they did another cystoscoic with cysview and a no CIS was found...now they want to do BCG again. They told me that PUNLMP wantsnt treatable with BCG...and I was negative for CIS/...why BCG now