Obesity linked to improved long-term survival post-nephrectomy

Patients with renal cell carcinoma (RCC) and a high body mass index (BMI) undergoing radical nephrectomy had improved overall survival outcomes compared with patients with a lower BMI, according to a meta-analysis presented during the 2023 AUA Annual Meeting.¹

“More research into the underlying biological and physiological mechanisms will enable better understanding of the effect of BMI, beyond mere association, on post-nephrectomy outcomes,” said Edmund Chiong, MD, PhD.

Describing the background for the study, presenting author Edmund Chiong, MD, PhD, National University of Singapore, said, “Recent research has shown that obesity is associated with improved survival rates in patients with renal cell carcinoma — this has been termed the ‘obesity paradox.’ We sought to evaluate the impact of BMI on oncological and surgical outcomes of patients who underwent nephrectomy.”

The investigators accrued patient data from 4 electronic databases. They targeted studies that addressed oncological and surgical outcomes following nephrectomy. The screening of studies and data extraction was conducted by 2 independent authors. If there was discrepancy, it was resolved by a third independent author. Overall the analysis included data from 21 studies.

The researchers defined obesity as having a BMI >25.

Results for oncologic outcomes showed that a higher BMI was predictive of a higher overall survival, with patients with a BMI >25 having a 30% lower risk of death versus patients with a BMI <25 (HR, 0.70; 95% CI, 0.58-0.85). Among patients with a BMI of 25-30 vs patients with a BMI <25, the hazard ratio for overall survival was 0.97 (95% CI, 0.64-1.46).

Regarding cancer-specific survival, patients with a BMI >25 had a 40% reduced risk of dying of kidney cancer versus patients with a BMI <25 (HR, 0.60; 95% CI, 0.50-0.73). Patients with a BMI of 25-30 also had a 40% reduced risk of dying of kidney cancer versus patients with a BMI <25 (95% CI, 0.37-0.97), and patients with a BMI >30 had a 35% reduced risk of dying of kidney cancer versus patients with a BMI <25 (HR, 0.65; 95% CI, 0.52-0.82).

And regarding recurrence-free survival, patients with a BMI >25 had a 28% lower risk of recurrence vs patients with a BMI <25 (HR, 0.72; 95% CI, 0.63-0.82), and patients with a BMI of 25-30 had a 45% lower risk of recurrence vs patients with a BMI <25 (HR, 0.55; 95%, CI 0.42-0.73).

Regarding surgical outcomes, Chiong said, “Lower BMI fared better in operation time and warm ischemic time (statistically significant), but the absolute difference of 22 minutes and 2 minutes, respectively, was not clinically significant. Lower BMI also tended to fare better in length of hospital stay, intra-operative or post-operative complications, blood transfusion requirements, and conversion to open, but the differences were not statistically significant.”

In his concluding remarks, Chiong said, “Our study suggests that in patients with renal cell carcinoma undergoing radical nephrectomy, higher BMI is associated with improved long-term oncological survival and similar perioperative outcomes as lower BMI. More research into the underlying biological and physiological mechanisms will enable better understanding of the effect of BMI, beyond mere association, on post-nephrectomy outcomes.”

Reference

1. Ong C, Law T, Mok A, et al. The impact of body mass index (BMI) on oncological and surgical outcomes of patients undergoing nephrectomy: a systematic review and meta-analysis. Presented at: 2023 AUA Annual Meeting. April 28-May 1, 2023; Chicago, IL. Abstract MP47-14. doi: 10.1097/JU.0000000000003293.14