A single test developed by scientists could one day be used to detect a broad range of cancers at their very earliest stages.
The same system could then be used to deliver precision radiotherapy, they said.
A team, at the Gray Institute for Radiation Oncology and Biology at Oxford University, told the National Cancer Research Institute conference that they had been able to find breast cancer in mice weeks before a lump had been detected.
The scientists were looking for a protein, called gamma-H2AX, which is produced in response to damaged DNA. This tends to be one of the first steps on the road to a cell becoming cancerous.
They used an antibody that is the perfect partner to gamma-H2AX and able to seek it out in the body.
This was turned into a cancer test by attaching small amounts of radioactive material to the antibody. If the radiation gathered in one place it would be a sign of a potential tumour.
The test was conducted on genetically modified mice, which are highly susceptible to forming tumours.
Prof Katherine Vallis said lumps could be felt when the mice were about 120 days old, but they detected changes prior to that at 90 to 100 days - before a tumour is clinically apparent.
She told the BBC that gamma-H2AX was a "fairly general phenomenon" and it "would be the dream" to develop a single test for a wide range of cancers.
However this is still at a very early stage.
Adding more radiation to the antibody could convert the test to a treatment.
Prof Vallis said "it is attracted to DNA damage", where it then delivers a dose of radiation, causing more damage and attracting even more antibodies - it is a "self-amplifying system".
Eventually the doses of radiation should do so much damage to the cancerous cells that they would be killed.
"This early research reveals that tracking this important molecule could allow us to detect DNA damage throughout the body," she said.
"If larger studies confirm this, the protein could provide a new route to detect cancer at its very earliest stage - when it is easier to treat successfully," she added.