Is obesity associated with worse outcomes after surgery to remove the bladder for cancer?

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Background and what this study adds: Little is known about the association between obesity and urothelial carcinoma of the bladder (UCB). Most studies have linked higher body mass index (BMI) to higher rates of perioperative complications. Only one previous study specifically examined obesity and bladder cancer-specific outcomes; it found no significant association between higher BMI and disease-specific survival among patients with UCB treated with radical cystectomy. That study was limited by a small sample and a high rate of preoperative therapies.

In contrast to that previous study, the present study found that obesity, defined as BMI ≥30 kg/m², was associated with features of biologically aggressive UCB and clinical outcomes after radical cystectomy. Even after adjustment for standard clinicopathological features, obesity remained an independent predictor of cancer recurrence, cancer-specific mortality and overall mortality.

The objective was to investigate the association between BMI and oncological outcomes after radical cystectomy (RC) for UCB in a large multi-institutional series. This retrospective study collected data from 4,118 patients treated with RC and pelvic lymphadenectomy for UCB. Patients who received preoperative chemotherapy or radiotherapy were excluded. Univariable and multivariable models examined the association of BMI with disease recurrence, cancer-specific mortality and overall mortality. BMI was analysed both as a continuous variable and in categories reported in the methods as <25, 25–29 and ≥30 kg/m².

Median BMI was 28.8 kg/m², with an interquartile range of 7.9. The results reported that 25.3% of patients had BMI <25 kg/m², 32.5% had BMI 25–29.9 kg/m², and 42.2% had BMI ≥30 kg/m². Compared with patients with lower BMI, those with higher BMI were older (P < 0.001), had higher tumour grade (P < 0.001), and were more likely to have positive soft tissue surgical margins (P = 0.006).

In multivariable analyses adjusted for standard clinicopathological features, BMI >30 was associated with higher risks of disease recurrence (hazard ratio [HR] 1.67, 95% confidence interval [CI] 1.46–1.91, P < 0.001), cancer-specific mortality (HR 1.43, 95% CI 1.24–1.66, P < 0.001), and overall mortality (HR 1.81, CI 1.60–2.05, P < 0.001).

The main limitation was the study's retrospective design. The conclusion links obesity to worse cancer-specific outcomes in patients treated with RC, although the supplied conclusion sentence is cut off after “for.”