The researchers say a urine test meets these standards. Currently, kidney cancer is diagnosed after radiographic imaging of the kidney, which may include an ultrasound, CT scan and/or MRI. Biopsy of a kidney mass is often difficult to interpret or may give a false negative result, and therefore currently confirmation of radiographic results is primarily after surgical excision. There is no protein marker test for kidney cancer as there is for prostate cancer with the PSA test.
“We used a common laboratory procedure to test the urine of 50 patients with kidney cancer,” explained Fox Chase molecular biologist Paul Cairns, Ph.D., lead author of the study. “Forty-four of the 50 tests showed gene changes in the urine that were identical to the gene changes found in the tumor samples taken at the time of surgery.”
When the same test was conducted on the controls – urine from people without cancer – none showed the relevant gene alterations that were found in the urine from people with cancer.
“The test is remarkably accurate with no false-positives in this study,” said Robert G. Uzzo, M.D., a urologic surgeon at Fox Chase and co-author of the paper. “In addition, one of the most impressive outcomes of this research is that the test also identified 27 of the 30 patients with stage I disease. Finding these cancers early means earlier treatment and better prognosis.”
The researchers used a molecular DNA-based test called methylation-specific PCR (polymerase chain reaction) to detect genetic alterations that initiate and fuel the onset of cancer. The test searched for six cancer specific tumor-suppressor genes that were altered – causing them to falter in their critical role of preventing errant cell growth. These six genes are usually identified only after a pathologist’s review of tumor tissue.
“If these results are confirmed in larger studies, this urine-based test may play a vital role in kidney cancer diagnosis,” said Cairns.