A cancer blood test that claims to detect more than 50 cancers is now at the centre of a debate. On September 23, 2026, an FDA advisory panel narrowly voted in favour of GRAIL's Galleri test. The discussion, however, was unusually divided over whether the evidence really supports calling it an "early detection" test. The FDA has not yet made its final approval decision. Much of the controversy comes from the large NHS-Galleri trial, which involved more than 140,000 people. Indian oncologists say the technology is exciting, but they want people to understand what these tests can and cannot do before relying on them. Doctors do agree that a single blood test for many cancers could fill a big gap in screening. However, the split within the FDA panel reflects the same concerns oncologists in India are raising: These tests are not ready to replace the screening methods we already trust. A simple blood draw that could flag these hidden cancers early would be a "game-changer," Dr. Nayak says. Finding a cancer while it is small and localized is what allows surgeons to operate with the aim of curing it. The convenience is another big plus. Dr. Suresh S, Medical Oncologist and HOD Oncology at Apollo Speciality Hospitals, Vanagaram, Chennai, points out that a blood draw involves no radiation and no uncomfortable procedure. "Patients are more willing to get screened regularly when it's just a blood draw," he says. Dr. Arun Kumar Giri, Director of Surgical Oncology at Aakash Healthcare, adds that testing for many cancers with one sample could improve participation in screening. Dr. Darshana Rane, Consultant Medical Oncology at HCG Cancer Hospital, Mumbai, notes that related blood tests are already proving useful for patients who have been treated for cancer. They can detect molecular residual disease, meaning a recurrence, months before it shows up on a scan. That is the false-negative problem. Dr. Amit Upadhyay, Director, Hematologist and Oncologist at PSRI Hospital, explains that a false negative happens when the test misses a cancer that is really there. The danger is false reassurance. A person who gets a clear result may ignore a lump, a cough or unexplained weight loss, and reach a doctor much later than they should. False positives are the other side of the problem. For MCED tests, specificity is about 98-99%. That sounds high, but it means one to two out of every 100 healthy people will be told there may be cancer when there is none. This leads to whole-body PET scans and anxiety, often with no cancer found, Dr. Rane explains. As per Dr. Giri, a false positive can set off "a cascade of unnecessary investigations." Dr. Upadhyay adds that this means more tests, more costs and more anxiety. This also means that people who go through a false alarm may avoid screening in future, which is counterproductive. All the doctors stress on one point: A blood test cannot confirm cancer. "A positive result never means cancer until confirmed by biopsy, colonoscopy or imaging," Dr. Rane says. A positive result only means a cancer-related signal was found, and further tests such as imaging, endoscopy or biopsy are needed to see if cancer is actually present. Basically, early detection is not a guarantee of cure if the cancer is aggressive or treatment options are limited. Doctors need to be honest about those limitations. For now, no major guideline body, including the US FDA, the US Preventive Services Task Force, NCCN or ICMR, recommends MCED tests for routine screening of the general population. The experts also remind people that the basics still matter most. Avoiding tobacco, maintaining a healthy weight and discussing family history with a doctor "remains far more effective than a commercial multi-cancer blood test." Dr. Giri sums it up simply: A negative result "cannot be taken as a guarantee that cancer is absent," and recommended screening should continue as advised by doctors. If these tests can improve their accuracy for Stage I and II disease, they could "revolutionize global cancer care." Until then, experts say, use them with care and not as a shortcut.