Spare Nephrons When GFR Is Very Low

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Data support use of partial nephrectomy for renal tumors when kidney function is severely impaired

Nephron-sparing techniques should be considered for patients with significantly diminished renal function who are undergoing nephrectomy for renal cortical tumors, according to researchers.

They evaluated the effect of baseline renal function and comorbidity index on survival in patients with localized renal tumors. In their retrospective analysis, they retrieved demographic, clinicopathologic, BMI, and comorbidity data for 1,479 patients who underwent partial or radical nephrectomy between January 4, 1995, and June 9, 2005.

The patients had a mean age of 62 years; 62% were male. The investigators used the abbreviated Modified Diet in Renal Disease Study equation to determine estimated glomerular filtration rate (eGFR) based on patients' last pre-operative serum creatinine measurement.

Over the 10-year period, median BMI increased from 27 to 28 kg/m2 and the median baseline eGFR fell from 70 to 63 mL/min/1.73 m2. The investigators found an association between year of surgery and baseline eGFR, even after adjusting for age, sex, comorbidity, BMI, and tumor size.

Baseline eGFR, BMI, and comorbidities were not associated with disease-free survival after controlling for tumor stage. This was not the case, however, for patients with moderately reduced and severely reduced baseline eGFR (45-60 and less than 45, respectively). Compared with patients having normal kidney function, patients who began with moderately and severely reduced eGFR were 1.5 times and 2.8 times more likely to die from any cause. Findings appear in Mayo Clinic Proceedings (2008;83:1101-1106).

“In patients who have the combination of kidney cancer and lowered kidney function, doctors should consider tissue-sparing surgery versus complete removal whenever it is technically feasible,” said lead investigator Joseph Pettus, MD, assistant professor of urology at Wake Forest University School of Medicine in Winston-Salem, N.C. “These findings underscore the importance of considering baseline kidney function when devising treatment plans for patients with kidney tumors.” Dr. Pettus conducted the research with colleagues at Memorial Sloan-Kettering Cancer Center in New York City before moving to Wake Forest.

Impaired kidney function itself, even without a diagnosis of cancer, is related to increased risk of death and hospitalization, Dr. Pettus said. The loss of kidney tissue with surgery to remove a malignant tumor further impairs kidney function. Memorial Sloan-Kettering researchers previously found that patients whose kidneys were completely removed were almost 12 times more likely to experience significantly impaired function in the remaining kidney than patients whose organs were partially removed.

“Sometimes the treatment is worse than the disease, at least in some patients,” Dr. Pettus told Renal & Urology News. “It is important to check the pre-op GFR; it might sway you one way or another in terms of how you want to treat these lesions. We really had never asked about the prognostic value of GFR levels prior to surgery in this patient population.” The new data suggest that not only are GFR levels important, they  are even more important than T stage, except with respect to advanced tumors, he said.

Dr. Pettus pointed out that death rates increased 323% among kidney cancer patients between 1983 and 2002, despite earlier diagnosis. Increasing rates of kidney cancer combined with a decline in kidney function among patients diagnosed with renal tumors could explain the decrease in survival, even among patients with early stages of kidney cancer, Dr. Pettus said.
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