Cancer is now the top cause of death in industrialised countries, alongside cardiovascular disease. Many cancer diagnoses occur after the tumour has already developed extensively. This later diagnosis can significantly reduce the chance of recovery.

A new skin implant developed by researchers working with Professor Martin Fussenegger at the Department of Biosystems Science and Engineering at ETH Zurich could one day be used to detect four of the most common cancers: breast, prostate, lung and bowel, as well as kidney failure.

The synthetic gene network serves as an early warning system, recognising these cancers when the level of calcium in the blood is elevated due to the developing tumour, the researchers revealed. This network is integrated into human body cells by biotechnologists and is implanted under the skin to constantly monitor blood calcium level.

If the calcium levels exceed a particular threshold over a period of time, a signal is triggered to initiate production of the body's tanning pigment melanin in the genetically modified cells, creating a temporary brown mole that is visible to the naked eye. The mole will appear before the cancer can be detected through conventional diagnosis, the researchers noted.

Professor Fussenegger explained: "An implant carrier should then see a doctor for further evaluation after the mole appears." The mole acts a marker to show that clarification and, if necessary, treatment is needed.

The hope is that, in the future, the skin implant will become a viable part of early detection, to increase the chances of survival. Professor Fussenegger also believes the system will be cost-effective, as it enables self-monitoring.

The research is still very much in the early days and further tests are needed. So far, the researchers have tested the early warning system in a mouse model and on pig skin and it was found to be reliable during both tests.

According to the Daily Telegraph, it is thought that the system would be particularly useful for those genetically susceptible to cancer, such as those carrying the BRCA1 or BRCA2 mutation. There are also hopes that it could be used to detect other markers, such as chemical changes signalling the onset of dementia or hormone disorders.

Science communications officer at Cancer Research UK, Dr Catherine Pickworth, told the BBC that the use of "wearable tech" as used in the study was exciting but noted that the research was still in its early days.

She added: "This study in mice shows that a biomedical tattoo could detect changes in the amount of calcium in the blood, but we need to see if this holds true in people.

"High levels of calcium can be an indicator of cancer but also many other conditions, so this approach may one day help doctors identify when patients could benefit from further tests.

"Spotting cancer early is one of the most powerful ways of improving survival, so finding the best way to monitor people at high risk, or those in remission, is an important challenge."

The research has been published in the journal Science Translation Medicine.