Mistersac,
I wondered about that too. So many fine points about BC.
A clear explanation of why a TURBT may be advisable when only CIS is present is on page 1 & 2 of an article authored by Michael O'Donnell, a source I trust. Obviously, there is a range of CIS involvement, from minimal to extensive coverage of the bladder; physician judgment will determine the need to biopsy CIS.
O'Donnell cites the Prognostic Factor of CIS. My Urologist explains it thusly, "When I see lots of CIS on the surface, I have to wonder what is below".
CIS is always considered aggressive or high grade, and must be treated. It can't be both of those things and also be described as "only a superficial surface rash". O'Donnell explains:
"Tis — Tis (also called carcinoma in situ [CIS]) is characterized by severe cellular dysplasia in the absence of discrete tumor formation. Areas of mucosal involvement with Tis are often found in association with invasive disease. The presence of Tis in the mucosa adjacent to a Ta or T1 tumor appears to increase the risk for muscle invasive disease [5-8]. The potential prognostic significance associated with Tis is illustrated by a multicenter series 243 Treatment of non-muscle-invasive bladder cancer patients who underwent radical cystectomy for carcinoma in situ without more invasive disease [7].
"Staging based upon the cystectomy specimen revealed that Tis, T0, or Ta in 48, 8, and 8 percent of cases, respectively. However, T1, T2, T3, and T4 disease was detected in 13, 12, 5, and 6 percent of cases, respectively. Lymphovascular invasion and positive lymph nodes were found in 9 and 6 percent, respectively.
"The presence of Tis without invasive urothelial cancer is associated with a high incidence of progression to invasive disease, even after transurethral resection and treatment in intravesical BCG. In a retrospective, single institution series of 155 patients managed with transurethral resection and intravesical bacillus Calmette-Guerin (BCG), the five-year cumulative incidence of progression to cT1 or higher disease was 45 percent (95% CI 37-55) [8]."
Full article at:
ether.stanford.edu/urology/Treatment%20of%20non-muscle-invasive%20bladder%20cancer.pdf
Best
Jack