Researchers have discovered proteins in the blood that could warn people of cancer more than seven years before it is diagnosed.

The scientists identified 618 proteins linked to 19 types of cancer including bowel, prostate and breast cancers.

Some 107 of the proteins were found in a group of people whose blood was collected at least seven years before diagnosis.

It is hoped the proteins could one day be targets for cancer prevention – instead of detection – and with further research lead to drugs to help stop the disease before it starts.

The two Cancer Research UK-funded studies from Oxford Population Health suggest the proteins could be involved at the earliest stages of cancer, and could be linked to being at risk of the disease.

Some could be used to detect cancer earlier than is currently possible, potentially making it possible to treat the disease at a much earlier stage, or prevent it altogether.

Professor Ruth Travis, senior molecular epidemiologist at Oxford Population Health and a senior author of both studies, said: “To be able to prevent cancer, we need to understand the factors driving the earliest stages of its development.

“These studies are important because they provide many new clues about the causes and biology of multiple cancers, including insights into what’s happening years before a cancer is diagnosed.

“We now have technology that can look at thousands of proteins across thousands of cancer cases, identifying which proteins have a role in the development of specific cancers, and which might have effects that are common to multiple cancer types.”

Dr Iain Foulkes, executive director of research and innovation at Cancer Research UK, said: “Preventing cancer means looking out for the earliest warning signs of the disease.

“That means intensive, painstaking research to find the molecular signals we should pay closest attention to.

“Discoveries from this research are the crucial first step towards offering preventative therapies which is the ultimate route for giving people longer, better lives, free from the fear of cancer.”

In the first study, scientists analysed blood samples from UK Biobank taken from more than 44,000 people, including 4,900 who subsequently had a cancer diagnosis.

​The team used proteomics – the study of proteins to help learn how cancer develops and spreads – to analyse a set of 1,463 proteins from a single sample of blood from each person.

They compared the proteins of people who were later diagnosed with cancer and others who were not, allowing them to identify differences and establish which were linked to cancer risk.

The scientists also identified 182 proteins that differed in the blood three years before a cancer diagnosis.

​In the second study, the researchers looked at genetic data from more than 300,000 cancer cases to analyse which blood proteins were involved in cancer development and could be targeted by new treatments.

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

According to the findings, although altering these proteins may increase or decrease the chances of someone developing cancer, in some cases it may lead to unintended side-effects.

The researchers stress that further research is needed to find out the exact role the proteins play in cancer development, which are the most reliable ones to test for, what tests could be developed to detect the proteins in a clinic, and which drugs could target the proteins.

A test called the Galleri test is being trialled in the NHS, but it works by detecting tumour DNA circulating in the blood.

Researchers suggest the proteins they have discovered could be targets for cancer prevention.

Prevention and early detection are needed to keep improving cancer survival.

The findings are published in the Nature Communications journal.