A minimally invasive multicancer blood test used with standard-of-care screening is safe, effective, and feasible for use in routine clinical care, according to interim findings from a large, prospective study.
The DETECT-A blood test, an early version of the CancerSEEK test currently in development, effectively guided patient management in real time, in some cases leading to diagnosis of early cancer and potentially curative surgery in asymptomatic women with no history of cancer.
The study enrolled 10,006 women, aged 65-75 years, with no prior cancer diagnosis. After exclusion and loss to follow-up, 9,911 women remained.
There were 26 patients who had cancer detected by the DETECT-A blood test, 15 of whom underwent follow-up PET-CT imaging and 9 of whom underwent surgical excision. An additional 24 cancers were detected by standard screening, and 46 were detected by other means.
The positive predictive value of the blood test was 19%. When the blood test was combined with imaging, the positive predictive value was 41%.
Improving Upon Standard Screening
“Standard-of-care screening [was used] for three different organs: breast, lung, and colon. It was more sensitive for breast cancer,” Dr. Papadopoulos noted. “Blood testing, though, identified cancer in 10 different organs.”
In fact, the DETECT-A blood test detected 14 of 45 cancers in 7 organs for which no standard screening test is available.
In addition, 12 cancers in 3 organs (breast, lung, and colon) were first detected by DETECT-A rather than by standard screening. This increased the sensitivity of cancer detection from 47% with standard screening alone to 71% with standard screening plus blood testing.
“More important, 65% [of the cancers detected by blood test] were localized or regional, which have higher chance of successful treatment with intent to cure,” Dr. Papadopoulos said.
DETECT-A covers regions of 16 commonly mutated genes and 9 proteins known to be associated with cancer. In this study, 57% of cancers were detected by mutations.
Safety and Additional Screening
DETECT-A also proved safe, “without incurring a large number of futile invasive follow-up tests,” Dr. Papadopoulos said.
In fact, only 1% of patients without cancer underwent PET-CT imaging, and only 0.22% underwent a “futile” invasive follow-up procedure.
Three surgeries occurred in patients who were counted as false-positives, but the surgeries were determined to be indicated, Dr. Papadopoulos said. He explained that one was for large colonic polyps with high-grade dysplasia that could not be removed endoscopically, one was for an in situ carcinoma of the appendix, and one was for a 10-cm ovarian lesion that was found to be a mucinous cystadenoma.
The investigators also analyzed whether the availability of a “liquid biopsy” test like DETECT-A would inadvertently reduce patients’ use of standard screening and found that it did not. Mammography screening habits after receiving the baseline DETECT-A blood test did not differ significantly from those prior to study enrollment.
These findings are important because early detection is a key factor in reducing cancer-specific morbidity and mortality, and although minimally invasive screening tests, including liquid biopsies like DETECT-A, hold great promise, prospective clinical studies of these new methods are needed to ensure that the anticipated benefits outweigh the potential risks, Dr. Papadopoulos explained.
“The problem is that most cancers are detected at advanced stages when they are difficult to treat,” he said. “The earlier cancer is detected, the greater the chance of successful treatment.”
Unanswered Questions and Future Studies
This study demonstrates that it is feasible for a minimally invasive blood test to safely detect multiple cancer types in patients without a history of cancer and to enable treatment with curative intent, at least in a subset of individuals, Dr. Papadopoulos said. He added that the findings also inform the design of future randomized trials “to establish clinical utility, cost-effectiveness, and benefit-to-risk ratio of future tests.”
Further studies will also be required to determine the clinical validity and utility of the strategy of using liquid biopsy as a complement to standard-of-care screening, Dr. Papadopoulos said.
Invited discussant David G. Huntsman, MD, of the University of British Columbia in Vancouver, applauded the investigators, saying this study serves to “move the field forward.” However, it still isn’t clear how sensitivity and negative predictive value will be determined and what the optimal testing schedule is.
“This is a prospective study that will provide the data on how this assay will be used [and] whether it should be used going forward,” Dr. Huntsman said, noting that the “much bigger and more important question” is whether it improves survival.
Cost-effectiveness will also be critical, he said.
This research was supported by The Marcus Foundation, Lustgarten Foundation for Pancreatic Cancer Research, The Virginia and D.K. Ludwig Fund for Cancer Research, The Sol Goldman Center for Pancreatic Cancer Research, Susan Wojcicki and Dennis Troper, the Rolfe Foundation, The Conrad R. Hilton Foundation, The John Templeton Foundation, Burroughs Wellcome Career Award For Medical Scientists, and grants/contracts from the National Institutes of Health.
Dr. Papadopoulos disclosed relationships with Thrive Earlier Detection Inc., PGDx Inc., NeoPhore, Cage Pharma, and other companies. Dr. Huntsman is a founder, shareholder, and chief medical officer for Contextual Genomics.
SOURCE: Papadopoulos N et al. AACR 2020, Abstract CT022; Lennon AM et al. Science. 2020 Apr 28. pii: eabb9601. doi: 10.1126/science.abb9601.
This story originally appeared on MDedge.com.