Novel liquid biopsy identifies combinations of mutations in early-stage pancreatic cancer

A novel blood assay successfully identified tumor-specific DNA and protein biomarkers in a cohort of patients with early-stage pancreatic cancer.

“Few patients with pancreatic cancer survive longer than 5 years, in part because most patients are identified only after their disease has progressed to an advanced stage,” Anne Marie Lennon, MD, PhD, associate professor of medicine at Johns Hopkins University School of Medicine and director of the institution’s multidisciplinary pancreatic cyst program, and colleagues wrote. “We have shown how combining mutations in circulating tumor DNA with protein markers can result in a screening test with improved sensitivity while retaining specificity.

“The combination was superior to any single marker,” Lennon added. “Moreover, the combination detected nearly two-thirds of pancreatic cancers that had no evidence of distant metastasis at the time of surgical resection.”

Lennon and colleagues combined blood assays for KRAS gene mutations and protein biomarkers to compare the combination with either marker alone. Their analysis — performed through an international multicenter collaboration with centers in the United States, Europe and Far East — included 221 patients with resectable pancreatic ductal adenocarcinomas and 182 controls without a known cancer.

The assay identified KRAS mutations in 30% of patients, of which 100% were concordant to that subsequently found in primary tumors. The sensitivity of the assay was increased to 64% with the use of KRAS in combination with four thresholded protein biomarkers.

Researchers reported a 99.5% specificity, as the assay yielded only one false-positive result among the healthy controls.

“This combinatorial approach may prove useful for the earlier detection of many cancer types,” Lennon and colleagues wrote. “One of the critical design features of our study was that we included only patients with resectable pancreatic cancers and excluded all patients with advanced disease. Although this exclusion reduces the sensitivity that could be achieved by evaluating all pancreatic cancer patients, regardless of stage, the resectable cases are the most important group with respect to evaluating a screening technology.”

HemOnc Today spoke with Lennon about the study findings, their potential implications and what still must be confirmed in subsequent research.

Question: How did the idea for this combined technique come about?

Answer: Our initial work was in circulating tumor DNA, which is highly specific. The sensitivity was good, but we wanted to make it even better. Proteins, such as CA19-9, often are used to look for recurrence but they are rarely used in screening due to false positives.

Q: Can you describe the technique?

A: We used a standard technique to identify protein markers, and we used the Safe-Sequencing System technique to identify circulating tumor DNA. This technique allows for the detection of an extremely low number of mutant DNA, while greatly decreasing false-positive results due to sequencing.

Q: What did you think you would find?

A: Our hypothesis was that we would increase the sensitivity by using both techniques. The issue was how to maintain a very high specificity, which is essential for a potential screening test.

Q: What did you find?

A: By using a combination of circulating tumor DNA and protein markers, we were able to identify 64% of patients with pancreatic cancer. There are two key points about this paper. First, we only included patients with resectable pancreatic cancer. Second, 20% of patients in this study had pancreatic cancer but no symptoms. The circulating tumor DNA and protein marker panel identified 60% of these patients, 70% of whom had no evidence of recurrence at the end of the study. We were able to maintain very high specificity by using much higher cutoff levels for the protein markers than are used in routine clinical practice. Although this decreased our sensitivity because we used two different techniques, the overall sensitivity remained good, while maintaining 99.5% specificity.

Q: What still needs to be confirmed in subsequent research?

A: These are exciting results; however, a prospective study is required before using them in clinical practice. – by Jennifer Southall

Reference:

Cohen JD, et al. Proc Natl Acad Sci. 2017;doi:10.1073/pnas.1704961114/-/DCSupplemental.

For more information:

Anne Marie Lennon, MD, PhD, can be reached at Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, MD 21205; email: amlennon@jhmi.edu.

Disclosure: Lennon reports no relevant financial disclosures.

A novel blood assay successfully identified tumor-specific DNA and protein biomarkers in a cohort of patients with early-stage pancreatic cancer.

“Few patients with pancreatic cancer survive longer than 5 years, in part because most patients are identified only after their disease has progressed to an advanced stage,” Anne Marie Lennon, MD, PhD, associate professor of medicine at Johns Hopkins University School of Medicine and director of the institution’s multidisciplinary pancreatic cyst program, and colleagues wrote. “We have shown how combining mutations in circulating tumor DNA with protein markers can result in a screening test with improved sensitivity while retaining specificity.

“The combination was superior to any single marker,” Lennon added. “Moreover, the combination detected nearly two-thirds of pancreatic cancers that had no evidence of distant metastasis at the time of surgical resection.”

Lennon and colleagues combined blood assays for KRAS gene mutations and protein biomarkers to compare the combination with either marker alone. Their analysis — performed through an international multicenter collaboration with centers in the United States, Europe and Far East — included 221 patients with resectable pancreatic ductal adenocarcinomas and 182 controls without a known cancer.

The assay identified KRAS mutations in 30% of patients, of which 100% were concordant to that subsequently found in primary tumors. The sensitivity of the assay was increased to 64% with the use of KRAS in combination with four thresholded protein biomarkers.

Researchers reported a 99.5% specificity, as the assay yielded only one false-positive result among the healthy controls.

“This combinatorial approach may prove useful for the earlier detection of many cancer types,” Lennon and colleagues wrote. “One of the critical design features of our study was that we included only patients with resectable pancreatic cancers and excluded all patients with advanced disease. Although this exclusion reduces the sensitivity that could be achieved by evaluating all pancreatic cancer patients, regardless of stage, the resectable cases are the most important group with respect to evaluating a screening technology.”

HemOnc Today spoke with Lennon about the study findings, their potential implications and what still must be confirmed in subsequent research.

Question: How did the idea for this combined technique come about?

Answer: Our initial work was in circulating tumor DNA, which is highly specific. The sensitivity was good, but we wanted to make it even better. Proteins, such as CA19-9, often are used to look for recurrence but they are rarely used in screening due to false positives.

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Q: Can you describe the technique?

A: We used a standard technique to identify protein markers, and we used the Safe-Sequencing System technique to identify circulating tumor DNA. This technique allows for the detection of an extremely low number of mutant DNA, while greatly decreasing false-positive results due to sequencing.

Q: What did you think you would find?

A: Our hypothesis was that we would increase the sensitivity by using both techniques. The issue was how to maintain a very high specificity, which is essential for a potential screening test.

Q: What did you find?

A: By using a combination of circulating tumor DNA and protein markers, we were able to identify 64% of patients with pancreatic cancer. There are two key points about this paper. First, we only included patients with resectable pancreatic cancer. Second, 20% of patients in this study had pancreatic cancer but no symptoms. The circulating tumor DNA and protein marker panel identified 60% of these patients, 70% of whom had no evidence of recurrence at the end of the study. We were able to maintain very high specificity by using much higher cutoff levels for the protein markers than are used in routine clinical practice. Although this decreased our sensitivity because we used two different techniques, the overall sensitivity remained good, while maintaining 99.5% specificity.

Q: What still needs to be confirmed in subsequent research?

A: These are exciting results; however, a prospective study is required before using them in clinical practice. – by Jennifer Southall

Reference:

Cohen JD, et al. Proc Natl Acad Sci. 2017;doi:10.1073/pnas.1704961114/-/DCSupplemental.

For more information:

Anne Marie Lennon, MD, PhD, can be reached at Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, MD 21205; email: amlennon@jhmi.edu.

Disclosure: Lennon reports no relevant financial disclosures.