Obesity not linked to lower renal function following partial nephrectomy

A retrospective chart review presented at the SUO 23rd Annual Meeting did not find an association between higher BMI and decreased kidney function after treatment with a partial nephrectomy for kidney cancer.¹

“What's important to understand about BMI and long-term renal function is we associate increases in BMI with decreases in renal function,” Lachlan Shiver, a medical student at the University of South Florida College of Medicine, said in an interview with CancerNetwork® about the findings.

“So, as BMI increases, you see an increase in the rate of chronic kidney disease. What my study and my findings find is that when you do partial nephrectomy for renal masses, we see that people with greater BMI in terms of renal function from a 0-month to 36-month post [partial nephrectomy setting], you don't really see a decrease in renal function that you'd expect to see, based on the increases in BMI.”

Partial nephrectomy is the standard of care in patients with renal masses less than 5 cm. However, obesity can be associated with chronic kidney disease and renal cell carcinoma. Therefore, the researchers aimed to evaluate the long-term renal outcome after partial nephrectomy.

The retrospective chart review included 1274 patients who underwent partial nephrectomy from 2009 to 2020 at Moffitt Cancer Center. In particular, they focused on the percentage of change in glomerular filtration rate (GFR) values at 1 to 3 months, 6 months, 9 to 12 months, 24 months, and 36 months after partial nephrectomy.

Body mass index (BMI) was stratified into 4 subgroups: <25 (normal; n = 172 [15%’), 25 to <30 (overweight; n = 384 [32%]), 30 to <40 (class I to II obesity; n = 488 [42%]), and >40. (class III obesity; n = 114 [11%]).

At 1 to 3 months, mean GFR declined -9.63% (P = .263), followed by -9.25% at 6 months (P = .087), -8.11% at 9 to 12 months (P = .019), -9.50% at 24 months (P = .275), and -7.96% at 36 months (P = .028). As a result, the researchers found no significant correlation between BMI subgroups and change from baseline GFR.

In addition, the researchers found that increasing BMI in the normal, overweight, class I to II obesity, and class III obesity subgroups was associated with higher rates of malignant pathology (P < .001) and an increase in median estimated blood loss (median, 100 ml vs 100 ml vs 150 ml vs and 200 ml, respectively; P < .001). However, they found no difference in median hospital stay length (4 vs 3.5 vs 4 vs 4 days, respectively; P = .610)) or 30-day rates of intervention or readmission to the hospital (19% vs 40% vs 51% vs 10%; P = .936).

“So I think what we can take away from this study is that just because your patient [has a higher BMI], doesn't mean that they're a poor candidate for a partial nephrectomy,” Shiver said.

As a next step, he added, the researchers hope to evaluate BMI’s effect on recurrence rates. “Right now we're looking not only at BMI and long-term renal function, we're also looking at BMI and recurrence rates. So the preliminary findings from that are it looks like BMI isn't even associated with greater recurrence,” Shiver concluded. “Which is interesting because BMI is associated with a higher rate of renal cancer, but it doesn't look like [it is associated with] recurrence.”

Reference:

1. Shiver L, Khan F, Wang C, et al. Measuring Outcomes in Partial Nephrectomies: The Impact of BMI on Long-Term Kidney Function. Presented at: Society of Urologic Oncology 23rd Annual Meeting; November 30-December 2, 2022; San Diego, California. Poster 200.