Detecting kidney cancer in its early stage is an important aspect of treating the disease, but it only happens by chance during CT scans. In most cases, kidney masses found by CT Scans aren’t even cancerous. A recent study conducted at Washington University School of Medicine in St. Louis has revealed that measuring certain protein biomarkers in urine samples is more than 95 percent accurate in identifying early-stage kidney cancer.

"These biomarkers are very sensitive and specific to kidney cancer," Dr. Evan D. Kharasch, the Russell D. and Mary B. Shelden Professor of Anesthesiology, said in a statement. "The most common way that we find kidney cancer is as an incidental, fortuitous finding when someone has a CT or MRI scan. It's not affordable to use such scans as a screening method, so our goal has been to develop a urine test to identify kidney cancer early."

Kharasch and his colleagues gathered urine samples from 720 patients from Barnes-Jewish Hospital who were scheduled to undergo abdominal CT scans for reasons that were unrelated to kidney cancer. These urine samples were compared to the sample of 80 healthy people and 19 patients who had been previously diagnosed with kidney cancer. The research team assessed the levels of two specific proteins – aquaporin-1 (AQP1) and perlipin-2 (PLIN2).

Findings showed that patients with elevated levels of both protein had also developed kidney cancer. Out of all 720 patients who had abdominal CT scans, three also had elevated levels of both proteins. While two of these patients were subsequently diagnosed with kidney cancer, the third died before any diagnosis could be made. Patients who did not have kidney cancer, but did have another form of cancer or kidney disease had normal levels of both proteins, suggesting the test could also be used to rule out kidney cancer.

"Each protein, or biomarker, individually pointed to patients who were likely to have kidney cancer, but the two together were more sensitive and specific than either by itself," Morrissey said. "When we put the two biomarkers together, we correctly identified the patients with kidney cancer and did not have any false positives."

According to the American Cancer Society, around 61,460 new cases of kidney cancer will be diagnosed in 2015. Kidney cancer is currently considered one of the 10 most common cancers in both men and women. Around 80 percent of patients with kidney cancer survive when it’s diagnosed early on before it has a chance to spread. However, when kidney cancer is not detected before it spreads, over 80 percent of patients die within the first five years of being diagnosed.

"By and large, patients don't know they have kidney cancer until they get symptoms, such a blood in the urine, a lump or pain in the side or the abdomen, swelling in the ankles or extreme fatigue," explained co-author Dr. Jeremiah Morrissey. "And by then, it's often too late for a cure. Metastatic kidney cancer is extremely difficult to treat, and if the disease is discovered after patients have developed symptoms, they almost always have metastases. So we're hoping to use the findings to quickly get a test developed that will identify patients at a time when their cancer can be more easily treated."

Source: Siegel M, Morrissey J, Kharasch E, et al. Evaluation of Urine Aquaporin-1 and Perilipin-2 Concentrations as Biomarkers to Screen for Renal Cell CarcinomaA Prospective Cohort Study. JAMA Oncology. 2015.