Glycoprotein is potential bladder cancer marker

Anaheim, CA-A team of German researchers is pursuing promising research on oncofetal fibronectin as a potential marker for bladder cancer. If the protein proves useful, it has the advantage of already being used as a maker for other purposes, such as early miscarriage. Antibodies and reagents already exist for the protein, as does the foundation for a simple urine test that could produce results in less than 30 minutes.

"We have been studying oncofetal fibronectin as a marker for bladder cancer for about 3 or more years now, al-though it was isolated in bladder tissue samples perhaps 10 years ago. That was the finding that gave us the idea to look for it in urine," Kerstin Junker, MD, chief of the molecular biology laboratory at Freidrich Schiller University in Jena, Germany, told Urology Times.

Oncofetal fibronectin is a cell matrix glycoprotein that exists in several isoforms and is associated with the cell matrix that surrounds a number of different tumors. The marker shows promise, according to data presented here by Dr. Junker at the AUA annual meeting. Those data showed the urine test to have an overall sensitivity of 84% and a specificity of 51%.

Sensitivity of oncofetal fibronectin varied according to tumor stage, the researchers reported. It showed a 62% sensitivity to pTa tumors, but was 100% sensitive to pT1 and pT2-4 tumors. Further, its specificity was lower: 30% for pTa tumors, 80% for pT1 tumors, and 59.1% for pT2-4 tumors. Up to 70% of initial bladder cancer tumors are confined to the urothelium or have invaded the lamina propria.

Dr. Junker noted that the test's current sensitivity is an improvement over cytology, the current noninvasive gold standard. She said that the mechanics of the test permit a 20- to 30-minute response: a significant improvement in turnaround time compared to cytology. In addition, cytology suffers from a relatively low sensitivity, she noted.

A rapid, noninvasive tumor marker test would also have substantial utility in monitoring patients after treatment. The recurrence rate for superficial bladder cancers may be as high as 70%.

One challenge facing the German researchers is the problem of "noise" associated with the glycoprotein, which is over-expressed in a number of cancers, as well as in other disease states, such as BPH and diabetic retinopathy. Many of these diseases can be weeded out by other diagnostic means, but BPH might be problematic.

"We have to find out why the specificity is lower in BPH patients," Dr. Junker acknowledged in her presentation.

She would not offer a prediction on when the test might become available. The research team hopes to investigate the sensitivity and specificity of new cutoff points, which would require another round of prospective trials. If these were successful, a long, unpredictable approval procedure would follow, whether approval was being sought in Europe or the United States.

At best, the test, one of a number of tumor marker tests being investigated, would likely not be available for at least 3 years.