BOSTON—Renal function may decline following radiation treatment involving the abdomen, according to researchers who noted that this decline might not be observed until at least a year after completion of radiotherapy (RT).

A team at Roswell Park Cancer Institute in Buffalo, N.Y., studied 129 patients who underwent 3D conformal RT directed at the abdomen for GI cancers. The researchers measured BP, hemoglobin, serum creatinine, and creatinine clearance prior to RT, during RT, and after RT in three- to six-month intervals. Creatinine clearance was calculated using the Cockcroft-Gault formula.

Of the 129 patients, 28 had at least 12 months of follow-up and the required laboratory data to calculate creatinine clearance. The patients had a median age of 60.5 years (range 37-78 years); 12 subjects were female. The primary RT sites were pancreas (17 patients), stomach (four), hepatobilary (three), duodenum (two), ampulla (one), and retroperitoneum (one). The median radiation dose was 45.9 Gy (range 41.4-50.4) given daily as 1.8 Gy per fraction.

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After a median follow-up of 16 months, mean creatinine clearance decreased by 22.5% in patients who received radiation to the abdominal area. This reduction in renal function appeared to occur between 12 and 18 months after completion of RT, the researchers noted. Post-RT mean creatinine clearance was 80.2 mL/min, a significant decrease from 103.5 mL/min prior to treatment, said lead researcher Gary Yang, MD, associate professor of radiation medicine. He reported findings here at the annual meeting of the American Society for Therapeutic Radiology and Oncology.

The researchers found no difference between pre- and post-RT serum creatinine and hemoglobin.

In addition, pre-RT baseline creatinine clearance was significantly associated with decreasing post-RT creatinine clearance. For each 1 mL/min decrease in baseline creatinine clearance, the mean post-RT creatinine clearance decreased by 0.4 mL/min after controlling for other factors. The researchers found no correlation between radiation dose and decline in creatinine clearance.

“This is the first time that we have been able to quantify how much the kidney is affected in this way,” Dr. Yang told Renal & Urology News. “However, there is a latency period for kidney function problems to manifest. Therefore, longer follow-up is needed.”