A relationship may not imply cause and effect. One possible explanation is that IVT decreases the rate of early RC so that some patients who would have done better with RC delay RC until after their disease has spread. This may relate to understaging since IVT is intended for superficial disease and understaged patients won't find out they've been understaged initially until a recurrence shows invasion, a node or metastasis shows up, or the staging is changed at RC.
If this is the explanation, it isn't the IVT which decreases survival, but rather the delay in RC which treatment with IVT makes possible.
-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