AUA 2018: Predicting Perioperative Complications in Patients Receiving Radical Cystectomy Using Pre-Operative CT-Measured Adipose Tissue Indices

San Francisco, CA (UroToday.com) Obesity is a growing global epidemic associated with high morbidity and mortality. In 2013, some 2.1 billion individuals worldwide were estimated to be overweight or obese, defined as a body mass index (BMI) over 25 kg/m2 and 30 kg/m2, respectively. While increased BMI has been associated with increased risk of certain malignancies, the link between increased BMI and bladder cancer risk has presented equivocal results. Certain studies have demonstrated an increased risk of bladder cancer with increased BMI [1-3], while others have found no association [4-5]. 

Increased levels of visceral adipose tissue (VAT) have been associated with increased risk of cancers of the breast, colon, and prostate, but whether or not VAT or subcutaneous adipose tissue (SAT) can improve on BMI as a predictor of perioperative outcomes and survival for patients undergoing radical cystectomy has not been evaluated. As such, Michael Kim, a 3rd year medical student from Ontario, Canada, discussed the role of VAT and SAT with regards to outcomes after radical cystectomy. The author’s hypothesis was that patients with higher adipose tissue levels would have poorer perioperative and survival outcomes.

For this study, the authors identified 202 patients meeting inclusion criteria undergoing a radical cystectomy at the Princess Margaret Cancer Centre between 2000 and 2012. Cox proportional hazards models were used to calculate multivariate analyses based on the following covariates of interest: age, gender, BMI, tumour stage, smoking status, Charlson comorbidity index (CCI) and type of chemotherapy received. Kaplan Meier curves were used to assess disease-specific survival and overall survival for both VAT and SAT. Multivariable logistic regression analysis was used to generate odds ratios (OR) for predictors of 30-day grade III-V Clavien-Dindo (CD) complications, and linear regression analysis was used to assess predictors of increasing length of stay (LOS).
The median age among patients included was 70 (IQR 78-60) years, median VAT was 165 (IQR 223-114) cm2, median SAT was 233 (IQR 316-182) cm2, median LOS was 9 (IQR 12-7) days, and age-adjusted CCI score was 6 (IQR 8-5). Male patients constituted 76% of the study cohort, 59% were ever smokers, 71% had ≥pT2-4 disease, and 40% of patients received chemotherapy. There were 32 (16%) 30-day grade III-V complications. Over a median follow-up of 37 (IQR 54-27) months for alive patients, there were 43 (21%) bladder cancer specific deaths and 65 (32%) all-cause deaths. Adjusting for CCI score and smoking status, VAT was not predictive of grade III-V 30-day complications (OR 1.004, 95%CI 0.999-1.008), whereas SAT (OR 1.004, 95%CI 1.001-1.008) was predictive, with similar adjustments. VAT was predictive of increasing LOS (β-coeff 0.0233, 95%CI 0.0002-0.0463) when adjusted for CCI score and gender, whereas SAT was not (β-coeff 0.0159, 95%CI -0.0024-0.0342). Neither VAT nor SAT was predictive of DSS or OS on multiple scenario survival analyses.

The strength of this study is that it is the first to assess different obesity parameters for predicting postoperative outcomes among patients undergoing radical cystectomy. However, there are several limitations with this study as discussed with the authors. A larger study population could have been captured however the study institution is a referral center and as a result, staging CT images for certain patients were not uploaded to the central radical cystectomy database. Second, although single-slice CT has been previously validated for measuring adipose tissue levels, a more accurate measure could have been obtained with multiple slices. A scoring system may be proposed in patients with increasing obesity as measured by VAT, SAT, and sarcopenia in order to better stratify their risk of specific perioperative complications. The authors concluded with several take-home points from their study:
  • Higher VAT was predictive of longer post-operative LOS
  • SAT was predictive of worse complications (grade III-V) 30 days after RC
  • There was no difference in cancer-specific or overall survival between groups
  • VAT and SAT measurements may be useful in conjunction with existing modalities to improve pre-operative risk assessment for predicting immediate post-operative outcomes

Presented By: Michael Kim, Queen’s University, Kingston, ON, Canada
Co-Authors: Jaimin Bhatt, Zachary Klaassen, Bimal Bhindi, Thomas Hermanns, Patrick Richard, John Kachura, Robert Hamilton, Neil Fleshner, Antonio Finelli, Michael Jewett, Alexandre Zlotta, Girish Kulkarni, Toronto, Canada

References:
1. Koebnick, C., et al., Body mass index, physical activity, and bladder cancer in a large prospective study. Cancer Epidemiol Biomarkers Prev, 2008. 17(5): p. 1214-21.
2. Pan, S.Y., et al., Association of obesity and cancer risk in Canada. Am J Epidemiol, 2004. 159(3): p. 259-68.
3. Stewart, S.B. and S.J. Freedland, Influence of obesity on the incidence and treatment of genitourinary malignancies. Urol Oncol, 2011. 29(5): p. 476-86.
4. Calle, E.E., et al., Overweight, obesity, and mortality from cancer in a prospectively studied cohort of U.S. adults. N Engl J Med, 2003. 348(17): p. 1625-38.
5. Holick, C.N., et al., Prospective study of body mass index, height, physical activity and incidence of bladder cancer in US men and women. Int J Cancer, 2007. 120(1): p. 140-6.

Written by:  Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre Twitter: @zklaassen_md at the 2018 AUA Annual Meeting - May 18 - 21, 2018 – San Francisco, CA USA
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