Nick Mulcahy

January 18, 2012

January 18, 2012 (San Francisco, California) — A new immunoassay can detect early pancreatic cancer with fairly high specificity and sensitivity, according to researchers. However, this conclusion comes from a study with only 28 patients.

The new immunoassay is based on the antibody PAM4 and detects pancreatic ductal adenocarcinoma (PDAC). It correctly detected stage 1 PDAC in 18 of 28 patients (64%) previously diagnosed with the disease at that early stage.

These patients were a subset of a larger group of confirmed PDAC patients with all stages of disease. The PAM4 immunoassay was able to correctly detect 76% of this larger group of PDAC patients (225 of 298).

The study tested patients with other cancers (n = 99), patients with benign disease of the pancreas (n = 126), and healthy adults (n = 79). To assess how common the marker is, PAM4 antigen levels were evaluated in 602 individuals with the enzyme immunoassay.

But the researchers are focused on finding a biomarker for early-stage pancreatic cancer.

Early detection can improve survival, said lead author David V. Gold, PhD, director of laboratory administration and a senior member of the Garden State Cancer Center in Morris Plains, New Jersey.

He spoke at a press conference hosted by the 2012 Gastrointestinal Cancers Symposium, which begins this week.

The 5-year survival rate for patients with stage 1 disease is 20%, said Dr. Gold. This is considerably better than the 5-year survival rate of 2% to 3% seen in all of PDAC. "Early detection and improved therapy go hand in hand," he said.

"Pancreatic cancer symptoms are vague; the disease tends to develop and grow silently. By the time it is detected, it has often spread to other parts of the body, making it nearly impossible to cure. These study results are extremely encouraging and may eventually lead to improved detection of the disease in high-risk individuals," Dr. Gold said in a press statement.

Dr. Gold and his team combined the PAM4 immunoassay with the CA19-9 immunoassay, which is commonly used to monitor the course of the disease. Together, the 2 immunoassays were able to detect 85% of patients with PDAC. "We combined the results of the 2 assays and discovered a significant improvement in the detection of PDAC while maintaining a high level of specificity," said Dr. Gold. Unfortunately, there was no improvement with the combination in the rate of detection of early-stage patients.

The study results inspired praise from one expert not involved with the study. The test "shows tremendous promise," said Morton Kahlenberg, MD, from the University of Texas Health Science Center at San Antonio, who moderated the press conference.

Dr. Gold noted that the CA19-9 test is approved by the US Food and Drug Administration for monitoring pancreatic cancer progression, but that no test is approved for the detection and diagnosis of pancreatic cancer.

PAM4 Antibody Appears Mostly Restricted to PDAC

The study is a collaboration of researchers from the Garden State Cancer Center; the University of Göttingen in Germany; Johns Hopkins Medical Institutions in Baltimore, Maryland; and the New York University Medical Center in New York City.

Some of the patients in the study had cancer of the organs surrounding the pancreas. The investigators found that about half of patients with extrahepatic biliary (50%) and periampullary (48%) adenocarcinomas tested positive for the PAM4 protein. In the press statement, Dr. Gold said that this finding was not unexpected because these cancers originated in closely related organs.

The researchers also used the immunoassay to get a sense of how common the PAM4 protein is in other pancreatic disorders (n = 126). Nineteen percent of patients with benign pancreatic disease and 23% of those with chronic pancreatitis tested positive for the PAM4 protein.

"These results demonstrate that the reactivity of the PAM4 antibody is highly restricted to PDAC," said Dr. Gold.

"To the best of our knowledge, there are no biomarkers or target antigens that are expressed at a similarly high frequency and concentration in PDAC, and that show such specificity," he said.

According to press materials, the researchers are planning to use the PAM4 biomarker to screen patients who are considered to be at high risk for pancreatic cancer for the presence of PDAC at an early stage of tumor growth. The subjects include those with chronic pancreatitis, those with sudden-onset diabetes, and those with a family history of PDAC.

The study was supported in part by grants from the National Institutes of Health and the Turpin Foundation. Coauthor David M. Goldenberg, ScD, MD, is an employee of Immunomedics and owns stock in the company.

2012 Gastrointestinal Cancers Symposium (GICS). Abstract 151. To be presented January 20, 2012.

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