Top doctors warn against $1,000 blood tests that claim to detect 50 types of cancer - urging Americans not to skip critical screenings

Top doctors have warned against tests that claim to detect dozens of types of cancer, urging Americans that 'we don't have the evidence' and to stick to regular screenings.

Multi-cancer detection tests (MCDs) have emerged as potential alternatives to invasive tests like colonoscopies and mammograms. These tools, which mainly consist of blood draws, are meant to pick up on abnormal proteins and other cells consistent with cancer.

Similar to full-body MRI scans promoted by Kim Kardashian and Gwyneth Paltrow, many MCDs also claim to catch the disease before symptoms start, meaning cancer is detected in earlier stages.

However, researchers presenting at the American Society of Clinical Oncology meeting in Chicago this weekend said that while early studies are compelling, they would not recommend them for their patients and they're 'not quite ready' to be widely prescribed.

They also warned that MCDs run the risk of false positives, which could lead to patients undergoing a battery of unnecessary tests.  

And these tools are not covered by insurance, with just one test costing upward of $1,000. 

The warnings come as health officials lower screening age guidelines for colorectal and breast cancers to combat a surge in young people with the disease. 

Dr Chyke Doubeni, family medicine physician at Ohio State University, said in a presentation Friday: ‘We don’t have the evidence. I think these tests are not currently ready for primetime.'

'The risk of potential harm is there, however you look at it.'

Several recent reports on MCDs have shown promise, including two trials from the University of Oxford. In the first study, the team compared how proteins in blood samples from Brits diagnosed with cancer differed from those who did not have the disease.

They found 182 differing proteins on average three years before a cancer diagnosis.

In the second study, 40 proteins in the blood were found to influence someone's risk of getting nine different types of cancer: bladder, breast, endometrial, head and neck, lung, ovary, pancreas, kidney and malignant non-melanoma. 

Additionally, research published earlier this year found that the Galleri test, which claims to detect 50 types of cancer and is being trialed in the UK by the NHS, detected 18 types early-stage cancers and claimed to be 93 percent accurate. 

However, at the time Paul Pharoah, professor of cancer epidemiology at the Cedars-Sinai Medical Centre, said the 'holy grail' for early detection was still some distance away, as more in-depth research is needed.

'Many such tests have been developed or are in development. This paper reports on the initial results of the development of one such test,' he said. 'While the results show some promise, it is far too soon to be confident that this test will turn out to be useful for early cancer detection.'

Dr Robert A Smith, oncology researcher at the American Cancer Society, said in the presentation that a potential benefit of MCDs is that they could detect cancers at earlier stages.

'It would mean detecting the disease earlier in its natural history compared to symptoms, suggesting the prognosis would be better,' he said. 

However, he also noted that these 'should not replace regular screenings. 

MCDs also carry the risk of false positive results. Dr Jamie Renee Brewer, a medical oncologist at the FDA, said in the presentation: 'While the false positive rate is low, the intended audience is hundreds of millions of people.'

This could lead to patients needing to undergo a battery of unnecessary, costly and invasive tests like biopsies for a negative diagnosis. 

Dr Ernest Hawk, vice president, Cancer Prevention and Population Sciences at MD Anderson Cancer Center in Texas, said in a hospital blog post: 'Any positive blood tests require a subsequent diagnostic evaluation.'

'Endoscopy, radiologic imaging and biopsies all take additional time, add costs and may result in additional risks from the procedures themselves.

‘We need to ensure that with this cancer screening prevention test we are decreasing cancer incidents or improving cancer specific survival,' Dr Brewer said.

Dr Brewer even suggested that the FDA and other agencies could start more strictly monitoring the tests and placing limits on them before they hit the shelves. 

Earlier this month, the agency did show support for the Guardant Health Shield Test, which is designed to test for colorectal cancer, with the majority voting it safe. 

However, FDA committee member Dr Charity J Morgan said that while the test was 'better than nothing for patients who are getting nothing,' it 'is not better than a colonoscopy.'

Dr Jonathan M Marron, a pediatric oncologist at Boston Children's Hospital, said in the presentation that the research so far is headed in a positive direction, and along with caution, optimism is key.

‘MCDs may have value both now and in the future, but value remains to be clearly demonstrated.'

‘There remains a great deal of uncertainty.'