The earlier cancer is detected, the better the outlook for the patient. Unfortunately, cancer is a crafty foe and does a good job of hiding its presence until it's too late. Now, researchers at ETH Zurich have developed a novel early warning system for four common types of cancer. An implant keeps watch for elevated levels of calcium in the blood, and warns the patient by growing an artificial mole on their skin.

Early detection of cancer can not only improve survival rates, it can reduce the intensity of the treatments and cut healthcare costs dramatically. To that end, scientists are working to develop techniques such as blood tests, injectable nanoparticles and lab-on-chip systems to get the jump on cancer before it gets out of hand.

The prototype system from ETH Zurich is one of the most unique ideas we've seen so far. It's made up of a genetic network integrated into human cells, encased in an implantable device. When this is inserted under the skin, it constantly checks the calcium levels in a person's blood. High calcium levels are an early biomarker for four of the most common kinds of cancer – prostate, lung, colon and breast.

When the implant detects elevated calcium levels for a prolonged period of time, it triggers the genetically-modified cells to begin producing extra melanin. This pigment is what darkens skin to form freckles and moles, creating a clearly-visible signal at the site of the implant, telling the person that something is wrong and they should visit a doctor. The mole will appear long before the cancer could normally be detected through other means, and means people won't wait until they feel sick or are in pain to get themselves checked out.

"Early detection increases the chance of survival significantly," says Martin Fussenegger, an author of the study. "Nowadays, people generally go to the doctor only when the tumour begins to cause problems. Unfortunately, by that point it is often too late."

For those who'd rather not have a big blemish pop up on their skin forever, the team says another version of the device could produce a mark that's only visible under red light. Hiding the signal might defeat the purpose of the self-diagnosis test, but it could at least make a regular check by a doctor easier.

So far the team has tested the device in mice and samples of pig skin, where it responded well to high calcium concentrations. One disadvantage to this technique is the fact that encapsulated living cells, like those used in the device, generally only last for around a year, before they'd need to be replaced. That means the implant would need to be reactivated annually, which might be a hassle – or a good excuse for a regular checkup, depending on how you look at it.

With further research, the team says the concept could be adapted to monitor other biomarkers besides calcium, to serve as early warning systems for other gradually-developing illnesses like neurodegenerative diseases and hormonal disorders. Unfortunately, a publicly-available device is still at least a decade away.

The research was published in the journal Science Translational Medicine.

Source: ETH Zurich