Tumor diameter and decreased preoperative estimated glomerular filtration rate (eGFR) are independently correlated in patients undergoing surgery for renal cell carcinoma (RCC), researchers concluded.

In a study of 1,009 patients undergoing partial or radical nephrectomy for unilateral RCC, tumor diameter independently predicted decreased preoperative eGFR after controlling for race andhypertension. Decreased preoperative eGFR independently predicted increased tumor diameter, after controlling for race, smoking status, and histology.

“The relationship between renal function and RCC is currently poorly characterized, although the present study suggests that there may be an important link between these two apparently independent processes,” investigators led by Nicholas M. Donin, MD, of the Columbia University College of Physicians and Surgeons in New York, wrote in BJU International (2011;109:379-383).

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For more than three decades, researchers have recognized an association between end-stage renal disease and the development of renal cortical tumors, Dr. Donin and his colleagues noted. Observational studies have demonstrated consistently cancer develops more frequently in patients with severely decreased eGFR than in age- and exposure-matched controls.

Dr. Donin’s group said their study is the first to show an independent association between increased tumor size and decreased eGFR. In a discussion of possible mechanisms that could explain the relationship, they noted that as a tumor grows, it might destroy renal parenchyma, “either through frank invasion of parenchyma or via mechanically distorting the architecture of the kidney, compressing renal parenchyma, tubules, collecting ducts and the renal pelvis, thus preventing proper filtration.”

Another possibility is that chronic kidney disease may be the primary process and develop of RCC is secondary. CKD might initiate and/or enhance a tumor’s ability to grow because of some directly trophic factors present in the uremic state, the investigators postulated.

Commenting on the new study, Daniel J. Canter, MD, Assistant Professor of Urology at Emory University in Atlanta, stated that although the study was well done, thought-provoking, and hypothesis-producing, “the real-world day-to-day clinical significance needs more elucidation.”

“If the findings in this study are validated,” Dr. Canter told Renal & Urology News, “urologists need to be cognizant of the fact that patients with larger tumors are more likely to have worse renal function and treatment decision-making needs to be tailored appropriately.”

Study patients had a mean tumor diameter of 5.29 cm and a mean pre-operative eGFR of75 mL/min/1.73 m2. Dr. Canter pointed out that a scatter plot presented by the investigators indicates that nearly all patients had an eGFR greater than 40.  “What is lacking is a detailed analysis of patients’ chronic kidney disease stratified by tumor size,” Dr. Canter said. “In essence, what I expect we are seeing is an under-appreciation of the prevalence of CKD in this patient cohort, as almost all patients had CKD stage III or less.”

When Dr. Canter was a fellow at Fox Chase Cancer Center in Philadelphia, he and collaborators conducted a study using the center’s kidney database and found that in a population of 1,114 patients presenting with an enhancing renal mass, 22% of patients with a seemingly normal serum creatinine had CKD. “I expect we are seeing the same phenomenon here [in the new study]. However, the authors do present a novel finding in that decreasing eGFR appears to independently correlate with increasing tumor size.”

The new findings “provide further evidence of the need for nephron-sparing surgery when technically feasible,” Dr. Canter said. “Chronic kidney disease predisposes patients to significant cardiovascular and overall health risks, and preservation of renal parenchyma is paramount when approaching these patients with enhancing renal masses.”