Preparation for mass screening
A large-scale liquid biopsy study to detect cancer will begin in the USA
Elena Kleshchenko, PCR.news
The pros and cons of mass screening for various types of cancer have been discussed for a long time: it is necessary to find a balance between the cost of screening and its accuracy, to compare the benefits of early diagnosis and the possible damage from false positive results. In February 2022, President Joe Biden announced the resumption of the Cancer Moonshot program, which he started back in 2016, when he served as vice president. The goal of the program is to intensify the fight against cancer, in particular, to reduce the death rate from cancer by at least 50% over the next 25 years, to improve the quality of life of patients and their loved ones.
As part of this program, the National Cancer Institute (NCI) plans to evaluate the prospects of screening tests. Last week, NCI consultants approved a four—year pilot study worth $75 million - Cancer Screening Research Network/MultiCancer Early Detection Evaluation. It will be attended by at least 24,000 people and will be evaluated mainly by tests that detect trace amounts of tumor DNA and proteins in the blood (liquid biopsy). Based on the results, the NCI will decide whether to launch longer clinical trials — lasting 7-8 years, involving approximately 300,000 volunteers aged 45 to 70 years — to find out whether screening testing saves lives.
Tests for early detection of oncological diseases are being developed by dozens of companies, including Grail with the Galleri test and Exact Sciences (Cologuard, Oncotype Dx). The $949 Grail test is prescribed by a doctor, detects a wide range of oncological diseases and is intended for people over the age of 50 and others with an increased risk of developing cancer. Grail has also launched a trial involving 140,000 people in the UK.
First, the NCI will check the tests on blood samples of people who are known to have cancer, as well as people who probably do not have cancer. Then several tests will be included in a pilot clinical trial, which will begin in 2023 or 2024. Some participants will have a liquid biopsy to detect various types of cancer, and standard screening procedures, such as mammography, while the control group will receive only standard tests. If the pilot study is successful, the NCI will proceed with a larger study that will already assess the possible reduction in mortality.
Read more about these plans to the magazine Philip Castle, Director of the NCI Cancer Prevention Department, told ScienceInsider. It is necessary to work out the procedure for taking blood, delivering samples to the company and obtaining results. We also need to understand how ethical it is to randomize people into a control group where they will not receive potentially life-saving liquid biopsy tests (although whether they are life-saving remains to be seen).
When asked how the tests for the pilot study out of about two dozen will be selected, Castle replied: "They [developers] should have verified, published data and show reproducibility of the results. They should be able to fix the parameters of the test, the algorithm [which evaluates whether the result is positive or negative]. And they should also be able to do enough tests." As a result, two or three tests will be selected. It is unclear whether Grail and Exact Science tests will be among them.
Castle also listed what could go wrong: "The test can reduce the number of cases of late-stage cancer, but not reduce mortality. It can find sluggish diseases like PSA that you don't want to treat. [Positive prostate-specific antigen test results are often caused by harmless prostate neoplasms.] We are concerned about compliance with the diagnostic examination procedure [that is, whether a person with a positive result of a liquid biopsy will take further steps to confirm or exclude cancer]. Obviously, a person with a positive test will have anxiety, even if you have ruled out cancer. (...) And vice versa, if the test result is negative, won't people neglect the usual screening?"
Nevertheless, he considers this study necessary: "The most encouraging thing is that we do not yet have screening tests for deadly cancers, such as pancreatic and ovarian cancer. We're desperate. But we have to put aside emotions and do our due diligence to evaluate these technologies and allow ourselves to speak with confidence about what they can and cannot do."
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