Despite years of training and lengthy experience, we commonly “miss” tumors in the bladder not due to lack of rigor in performing rigid and flexible cystoscopy, but rather due to the difficulty in seeing some of these tumors, and in particular carcinoma in situ.
In this excellent study, 104 patients underwent both white light imaging (WLI) and narrow band imaging NBI by the same surgeon. Patients with suspected active inflammation (e.g. urinary tract infection), prior BCG therapy, or bladder radiation were excluded. NBI is achieved using special optical filters placed into an otherwise typical white light source; the filters, when activated, narrow the bandwidth of the transmitted light; blue and green light, which have more superficial tissue penetrance are emphasized while the deeper penetrating red light is suppressed. As such the appearance of thickened or inflamed mucosa is enhanced; the superficial pattern of blood vessels is better seen. All of this occurs with the switch of a button or a foot pedal. No photodynamic dyes are given to the patient either prior to the cystoscopy or with the irrigating fluid. No special endoscopes are needed.
In the present study, NBI had a greater sensitivity (93% vs. 57%), negative predictive value (95% vs. 79%), and likelihood ratio of a negative test (0.10 vs. 0.50) than WLI; WLI had a higher specificity (86% vs. 71%) and a slightly better positive predictive value (69% vs. 63%) than NBI. However, what is most important to my mind is the question: In how many patients did the addition of NBI lead to a diagnosis of bladder cancer in the face of a negative WLI examination? In this study, in 27% of the patients, a bladder tumor was detected only by NBI. Indeed, among 63 patients with a negative urine cytology, 14% had either CIS (8 cases) or a T1G3 (1 case) detected solely by NBI.
In short, I am convinced and have now introduced NBI into my practice. I believe that its ease of use, coupled with its ability to facilitate the detection of bladder tumors in an additional one fourth of patients, makes NBI one of the most significant advances in endoscopy in the past 25 years.
Tatsugami K, Kuroiwa K, Kamoto T, Nishiyama H, Watanabe J, Ishikawa S, Shinohara N, Sazawa A, Fukushima S, Naito S
J Endourol. 2010 Nov;24(11):1807-11
10.1089/end.2010.0055
PubMed Abstract
PMID: 20707727
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