UAA Lecture: Singapore Urology Fair 2010

Seiji Naito
Kyushu University, Fukuoka, Japan

Narrow Band Imaging in Bladder Cancer

Seventy percent of bladder tumors have initial superficial presentations, but approximately 50–70% of them recur, with 10–30% showing grade or stage progression. The effective therapeutic outcome in the treatment of bladder tumor is defined by its early and certain detection. A previous report suggested that many cases of early recurrence were due to omission of the tumors during transurethral resection. Especially, carcinoma in situ (CIS) of the urinary bladder is often defined as a flat lesion involving the thickness of the urothelium, and its diagnosis by conventional cystoscopy is difficult. The early and definitive detection of CIS is important for an effective therapeutic outcome in the treatment of bladder tumors, because CIS is associated with greater risk of stage progression and reduced survival.

Several novel endoscopic imaging techniques have been developed for the detection of bladder tumors and the efficacy of fluorescence cystoscopy using dyes, such as 5-aminolevulinic acid (ALA), hexaminolevulinate 5-ALA (HAL) or hypericin have been reported. These studies showed that significantly more tumor lesions could be detected by fluorescence cystoscopy using dyes than with conventional cystoscopy using white light image (WLI). Fluorescence cystoscopy demonstrated a sensitivity of >90% and a specificity ranging from 40–90% for the detection of tumor lesions.

The narrow-band imaging (NBI) technique, in which modified optical filters are used in the light source of a video endoscope system, narrows the bandwidth of the spectral transmittance. NBI enhances the differences in penetration depth between wavelengths, because light penetration depth within the tissue is highly dependent on the wavelength; the shorter the wavelength, the more superficial the penetration. Blue light therefore penetrates most superficially, while red light penetrates deepest. In the NBI system, the relative intensity of the blue light is increased while the intensities of both red and green light are decreased to a minimum. This enhances contrast in images of capillaries in the surface layers of the mucosal membranes and the detailed patterns on the mucosal membranes, without the use of dyes. Recent reports have suggested that NBI cystoscopy is more effective than WLI cystoscopy for the detection of bladder tumors.

We also evaluated the clinical efficacy of the NBI system for detecting imperceptible and/or flat bladder carcinomas, which are difficult to detect with WLI. Since the sensitivity and negative predictive value of NBI are >90% and the likelihood ratio of a negative test is low, it is effective for identifying imperceptible and/or flat abnormal lesions without omission and is useful for exclusion diagnosis of bladder tumor including CIS. To compare the morbidity and efficacy between NBI and WRI, we are planning an international multi-center randomized study. Our data on the efficacy of NBI and outline of the multi-center study will be presented.