A blood test for more than 50 types of cancer that was billed as the holy grail of oncology has failed to achieve its main objective in a major clinical trial, according to data presented at the world’s largest cancer conference.

The goal of the study involving 142,000 NHS patients in the UK was to assess whether adding the multi-cancer early detection test Galleri to standard screening could shift diagnoses to earlier, more treatable stages.

But results from the trial, revealed for the first time on Saturday, showed it failed to meet its primary endpoint, which was to reduce late-stage cancer diagnoses.

Findings from the world’s first randomised controlled trial of a multi-cancer early detection (MCED) test were presented to doctors, scientists and cancer experts at the American Society of Clinical Oncology’s (Asco) annual meeting in Chicago.

Dr Julie Gralow, Asco’s chief medical officer and executive vice-president, said: “While the Galleri-NHS study results show some encouraging trends toward tumour downstaging, it is important to recognise that the trial did not statistically reduce late-stage cancers by its predefined primary endpoint.”

One delegate, a senior cancer figure who spoke to the Guardian on condition of anonymity, put it more bluntly. “The trial flopped,” the delegate said. “Clear and simple.”

The trial enrolled 142,942 people aged 50 to 77 with no cancer symptoms. Every participant had blood drawn once a year for three years and received the recommended cancer screening tests.

Half had their blood samples examined using the Galleri test. The other half were in the control group, and their blood was not analysed by the test.

Those in the first group who had a positive result from Galleri testing followed up with a doctor for diagnostic workup, as did all those in both groups who developed symptoms related to cancer.

The trial sought to evaluate a combined primary endpoint of stage three and stage four diagnoses in a pre-specified group of 12 cancers when the Galleri test was added to standard of care screening versus standard of care screening alone.

But the results showed there was no statistically significant reduction in advanced cancers in stages three to four among those who had the Galleri test compared with those who did not.

On Saturday, Grail, the California-based company behind the test, said it was encouraged by other findings from the trial. Researchers highlighted data from the study looking at stage four cancers alone that showed they fell by 14%, suggesting the most deadly cancers were being detected at an earlier stage.

“Galleri represents a potential transformational shift in cancer detection,” Grail’s chief scientific officer, Harpal Kumar, an ex-chief executive of Cancer Research UK, said.

But experts not involved with the trial were more sceptical.

Prof Richard Houlston, head of the division of genetics and epidemiology at the Institute of Cancer Research, London (ICR), said: “This is the largest randomised trial so far to evaluate a multi-cancer early detection blood test. However, the researchers have presented their findings far more positively than the overall results justify.

“The study’s main goal was to show a reduction in late-stage cancers overall, and this primary endpoint was not met. While some secondary findings are encouraging, in so far as a possible reduction in the most advanced cancers after repeated screening rounds, these results remain uncertain and should be interpreted cautiously.”

He added: “The failure to meet the primary endpoint is the crux of the issue here. Mortality outcomes will be available in a couple of years, examination of which will be warranted.

“However, on the basis of results from this and smaller trials, there is no evidence base upon which to justify implementation of Galleri at a population scale.”

Prof Peter Johnson, the national clinical director for cancer at NHS England, said: “We look forward to seeing the data from the trial in detail, to help us make decisions on what this could mean for the NHS in the future.”