A new screening test for esophageal cancer could help doctors spot malignancy early on, when chemotherapy is most effective, increasing the odds of survival for a disease in which outcomes are statistically poor."At present, the key to successful treatment of esophageal cancer is early diagnosis and there is consequently great interest in the development of a screening test that will identify patients with asymptomatic esophageal malignant or premalignant disease," reported doctors in the online July issue of the British Journal of Cancer.
Patients with esophageal cancer are often diagnosed at an advanced stage because symptoms may not present until the cancer has had time to develop. Without treatment, the overall survival rate is about 6 months, and even with treatment, only about 5% live 5 years. However, if diagnosed early, 80% of those treated with chemotherapy can live up to 5 years—which is why an effective early screening test is warranted.
By looking for MCM proteins in exfoliated tumor cells, doctors in the United Kingdom who developed the new screening test, believe they can identify early signs of esophageal cancer. Proteins of the mini-chromosome maintenance (MCM) family play a critical role in the initiation of DNA replication, and when this role is disrupted—a sign of cancer—MCM tumor cells are shed from the esophagus. The screening test involves testing gastric samples from patients with a glowing liquid (immunofluorometric assay) which identifies the MCM proteins that may be present in the esophagus.
Prior to the MCM screening test, doctors would screen patients at high risk for esophageal cancer by endoscopy, but this is time consuming and of questionable effectiveness according to some doctors. High risk patients are those with Barrett’s esophagus—a change in the lining of the esophagus caused by chronic reflux of stomach contents, people with GERD, cigarette smokers, alcohol consumption, and old age. Doctors say screening all these patients for esophageal cancer with endoscopy is not cost-effective.
To study the effectiveness of the MCM screening test, doctors enrolled 40 patients between the ages of 40 and 90, who were undergoing gastroscopy – visualization of the esophagus and stomach through the use of a flexible tube with a camera at the end. All patients were being screened at Addenbrookes Hospital National Health Service Trust in Cambridge, UK because they had esophageal cancer symptoms.
During the gastroscopy procedure gastric samples were taken and run through the MCM protein screening test. The researchers reported that the test had a high specificity and sensitivity—that is it was able to diagnose most of the patients who had cancer with very little false positives.
"In other words, a randomly selected patient with esophageal cancer would have a 93% probability of having an immunofluorometric Mcm5 value that is larger than a randomly selected patient with a malignancy," reported the researchers.
Further evidence that the test is effective at diagnosing esophageal cancer was that the difference in MCM protein values was highest between those patients with tumors and those with no tumors. The researchers suggested it is likely that even small cases would be detected at an early stage.
Before the test can be offered to patients in doctors’ offices and hospitals, the researchers report that studies on large unselected populations need to be conducted to determine whether the MCM protein screening can be used to detect early curable tumors.
