Sorry I didn't answer sooner, but I haven't been here recently.
In the 13 years I have been doing battle with high grade bladder cancer including CIS, I have never had a positive cytology. It's a good test, but one can't be lulled into complacency with a negative test.
With regard to how quickly bladder cancer can develop, my follow up biopsies just a few months after BCG for CIS were positive for high grade papillary carcinoma with invasion of the lamina propria. I wasted no time getting my bladder out before I developed invasive disease.
That being said, there's no indication that you have bladder cancer, but I had problems with kidney stones during all my treatments, so the best thing to do is follow up appropriately with the cystoscopy.
I hope by now you've had it done and it was negative for cancer.
-Warren
TaG3 + CIS 12/2000. TURB + Mitomycin C (No BCG)
Urethral stricture, urethroplasty 10/2009
CIS 11/2010 treated with BCG. CIS 5/2012 treated with BCG/interferon
T1G3 1/2013. Radical Cystectomy 3/5/2013, No invasive cancer. CIS in right ureter.
Incontinent. AUS implant 2/2014. AUS explant 5/2014
Pediatrician