Reduced recurrence of low-risk non-muscle-invasive bladder cancer is associated with low urine-specific gravity.

To investigate the association between urine-specific gravity and oncological outcomes in patients with non-muscle-invasive bladder cancer.

We identified 433 primary non-muscle-invasive bladder cancer patients who underwent transurethral resection between 2002 and 2016. The association between urine-specific gravity and tumor recurrence was statistically evaluated.

A total of 211 (48.7%) patients received adjuvant bacillus Calmette-Guérin therapy. During the median follow-up period of 60 months, 155 (35.8%) patients experienced at least one tumor recurrence. Of them all, 95 (21.9%) and 338 (78.1%) patients had high (>1.020) and low (≤1.020) urine-specific gravity, respectively. The Kaplan-Meier curve suggested that recurrence-free survival was significantly lower in patients with a high urine-specific gravity; however, the multivariate analysis failed to show that urine-specific gravity is significantly associated with tumor recurrence. In 222 (51.3%) patients who had not received bacillus Calmette-Guérin therapy, the Kaplan-Meier curve also suggested that recurrence-free survival was significantly lower in patients with a high urine-specific gravity. Multivariate analysis showed that age >70 years (hazard ratio 1.69, P = 0.02), grade 3 tumor (hazard ratio 1.81, P = 0.03) and high urine-specific gravity (hazard ratio 1.87, P < 0.01) were independent risk factors for tumor recurrence.

High urine-specific gravity is an independent risk factor for tumor recurrence in non-muscle-invasive bladder cancer patients who have not received bacillus Calmette-Guérin therapy. Our results suggest that hydration status might have some clinical impacts on bladder tumor recurrence.

International journal of urology : official journal of the Japanese Urological Association. 2020 Aug 13 [Epub ahead of print]

Tomohiro Iwasawa, Naoya Niwa, Kazuhiro Matsumoto, Akari Komatsuda, Hiroki Ide, Mototsugu Oya

Department of Urology, Tokyo Saiseikai Central Hospital, Tokyo, Japan., Department of Urology, Keio University School of Medicine, Tokyo, Japan.