Narrow band imaging-assisted transurethral resection for non-muscle invasive bladder cancer significantly reduces residual tumour rate

This is the first report on the impact of NBI-TUR on residual tumour rate. It has been previously shown that NBI cystoscopy significantly improves NMIBC detection since additional tumours missed during WL cystoscopy were seen using NBI technology, in 22–56% of the patients [6, 14‐17]. Consequently, it is expected that NBI improves TUR quality by contributing to resection completeness, thereby reducing the residual tumour rate. In the current study we provide evidence to support this concept, showing that the residual tumour rate after NBI-TUR is significantly lower compared to standard WL-TUR (15 vs. 30.5%, respectively). Based on the logistic regression analysis, we can state that the odds for detecting a tumour up to 3 months after WL-TUR is 2.7 times higher than after NBI-TUR.

Potential limitations of our study are related to its design, namely the retrospective collection of the control group. First, it may be speculated that retrospectively collected data including baseline characteristics or information on TUR radicality was more difficult to retrieve. Nevertheless, there were no missing data on baseline characteristics, which underlines the documentation quality. In only two patients (1.7%) data on fFU was lacking, due to non-specific circumstances. For all other WL-cohort patients, results of fFU cystoscopy were well documented with an electronic report supplemented by bladder diagram, recorded still images of abnormal looking urothelium and bladder-wash out cytology. In cases with re-TUR, the surgical as well as the final pathological report were available electronically for all patients. Second, the WL-TUR cohort was treated in an earlier era than the NBI-patients, which may have influenced the outcome. However, the treatment strategy has not been altered over these years: the first EAU guidelines on bladder cancer already advocated a complete TUR, supplemented by the administration of one single chemotherapeutic intravesical instillation immediately after TUR, and adjuvant instillations in the intermediate- and high risk group [18]. This is illustrated by the similar number of patients with adjuvant courses of intravesical therapy. In addition, the type of adjuvant therapy was not significantly different for the two intervention groups (Table 1). Third, despite the fact that re-TUR is the best proof of absence of residual tumour, a re-TUR was not incorporated as a standard procedure in the study protocol due to the partly retrospective design of the study. Thus, most fFU data were based on outpatient flexible cystoscopy findings. Nevertheless, almost 33% of patients in the NBI group and 16% in the WL group had a re-TUR as part of routine management. It has to be noted that in all these patients, re-TUR was performed to ensure correct staging rather than due to doubt on radicality of the first TUR (which was an exclusion criterion). The difference in re-TUR ratios between the two groups may be explained by the relatively higher number of pT1 and/or grade 3 tumours in the NBI group (though not statistically significant), necessitating confirmation of non-muscle invasive disease.

To compare the effect of two interventions, it is crucial that groups are identical on potential confounders. In this study, we generated two comparable intervention groups by frequency matching based on the EORTC risk criteria and the single intravesical chemotherapy instillation status immediately after TUR. These two factors are considered the most important determinants of future bladder cancer recurrence [19, 20].

Attempting to decrease the well-known high number of early recurrences in NMIBC is of utmost importance because these recurrences necessitate meticulous follow-up with cystoscopy plus cytology and adjuvant courses of intravesical therapy in selected cases, all of which result in high patients’ burden and increased costs. In fact, it has been estimated that bladder cancer is one of the most expensive cancers of today’s medical practice, mainly due to the lifelong need for follow-up and repeated treatments [21]. Many studies have already proven that PDD is effective in reducing the early recurrence rate [22‐25]. However, there are some drawbacks of PDD that have restricted a widespread use. Since NBI does not require an intravesical fluorescent it has advantages over PDD, provided that the system proves to be equally effective. Theoretically, the expenditures probably will be lower, there is no risk of side-effects and the technique is immediately applicable without necessitating a special patient preparation.

Of course additional randomized and/or multicentre trials are warranted to confirm these first promising results. However, despite the lower level of evidence that the current study provides, it is important to have this evidence before investing time and money in constructing a randomised controlled trial. Partly triggered by the results of this trial, the clinical research office of the endourological society is currently doing a multicentre, international, randomised trial on the effect of NBI-assisted TUR on recurrence rates [26]. In addition, future studies have to investigate whether this improved outcome at 3 months will sustain at longer follow-up. Another interesting objective for future research could be to compare the effect of standard WL-TUR followed by adjuvant intravesical therapy with NBI-TUR without this adjuvant therapy. If the NBI-TUR can influence recurrence rate to such an extent that these intravesical therapies become redundant, this would have a major impact on healthcare, both for the patients (increased quality of life) as well as the economics (less healthcare costs).