Most cancers cannot be reliably diagnosed until symptoms begin. Although there are exceptions such as mammograms and pap smears, no reliable screening methods exist for most cancers. To improve the early detection of cancer, dozens of companies have devised a test method that can detect various signs of cancer in blood taken from a patient’s arm. Now, to check how effective these early cancer screening blood tests are in practice, a national clinical trial is scheduled to begin in the United States.
In a speech held in Boston on the 12th, President Biden of the United States emphasized that different methods of early diagnosis of cancer using blood tests and clinical trials organized in the future are the core of the ambitious cancer conquest plan ‘Cancer Moonshot’ in the United States. Cancer Moonshot is a federal plan to halve the number of cancer deaths in the United States over the next 25 years. President Biden’s speech this time was on the 60th anniversary of the announcement by the former President of the United States, John F. Kennedy, that he would send a man to the moon. The ‘Cancer Moonshot’ project was also inspired by the US lunar exploration programme.
A new clinical trial run by the National Cancer Institute will begin recruiting participants in 2024 and will test 24,000 healthy participants over four years to see how effective different blood testing methods are in detecting cancer. If the results of the clinical trials look promising, the scale of the trial will be expanded 10 times and a large scale clinical trial will start again.
Most ‘multiple cancer early detection (MCED)’ tests work by finding remnants of tumor cells that are destroyed after the immune system attacks them. Remnants of dead tumor cells appear in the bloodstream, and even if the patient is asymptomatic, their presence can be a sign of cancer. After that, if cancer is confirmed by imaging tests, a biopsy is also performed.
Only one type of multiple cancer early diagnosis (MCED) test is currently used in the United States. Galleri’s test, which claims to detect early signs of more than 50 cancers, is available with a prescription for $949. However, most insurances do not cover the Galerie test, as it is not FDA approved. The Galleri test found cancer in 35 of the 6,600 study participants who were estimated to be healthy, according to new data released by the developers of the Galleri test. In particular, 26 of them had cancer that was not diagnosed through regular check-ups.
Questions remain about how to interpret MCED test results. Only certain blood tests can tell exactly where in the body the cancer originated. To confirm the diagnosis, laboratory tests of potentially cancerous tissue must be carried out, but a biopsy cannot be carried out on the whole body. False positives are also a problem in whole cancer screening. The Galleri test, the closest MCED test to widespread use, also incorrectly labeled 57 healthy blood samples in the aforementioned study as having cancer.
There is also the risk that an early diagnosis of cancer can lead to hasty action. Some cancers are unlikely to metastasize to other tissues or are not life-threatening, but early detection can make patients undergo very difficult treatments, such as chemotherapy. Fortunately, some studies suggest that this problem can be reduced because lower-risk cancers actually show up less in the bloodstream.
The National Cancer Institute clinical trial will help determine how to interpret blood test results to diagnose cancer. It will also provide guidance on how cancer screening research should be initiated, with multiple companies flooding the field with new testing methods.
Timothy Rebbeck, professor of cancer prevention at Harvard University, said: “Most companies do not want to compare their test methods head-to-head with those of other companies,” said Timothy Rebbeck, professor of cancer prevention at Harvard University. So we need a neutral third party like the National Cancer Institute.”
Rebeck believes that the blood tests to be confirmed in the new clinical trial will be very useful for pancreatic, liver and ovarian cancers. Although these three cancers have a high mortality rate, there is no early diagnosis. But even if blood tests are proven to be effective in diagnosing cancer early, longer term clinical trials will be needed to determine whether the time saved by early diagnosis can actually save lives.
Still, Lebeck is optimistic about the ultimate goal of the Cancer Moonshot. “The idea of halving deaths from cancer seems very realistic,” he said.
