Cancer cells may spread earlier than thought

Cancer cells may spread around the body much earlier in the disease process than was previously thought, a new US study suggests.

Cancer spread (metastasis) was thought to only occur when the disease was advanced and cells had become more aggressive. But the latest study from the Memorial Sloan-Kettering Cancer Centre in New York suggests that apparently 'normal' cells may move away from the original tumour site and lie dormant in other parts of the body until cancer genes within the cells are switched on.

The researchers injected mice with breast cells that had been modified so that cancer genes could be switched on at various times.

*These are important but early results in mice. If they are confirmed by further studies they could reveal new ways of stopping cancer spread at an earlier stage.* - Liz Baker, senior science information officer, Cancer Research UK

They found that the cells travelled in the bloodstream to the lungs and were able to survive there in their 'normal' state for up to 16 weeks before the cancer genes were activated, after which the cells began to grow aggressively there.

According to the researchers, the finding could help to explain why breast cancer can spread in some people long after the initial tumour has been treated.

The discovery is likely to spark a rethink of the process by which cancer spreads around the body and could lead to new ways to treat the disease.

Lead researcher Dr Katrina Podsypanina commented: "These findings indicate that properties inherent in normal cells are sufficient for negotiating a significant portion of the metastatic cascade.

"The finding that metastatic disease can arise from untransformed mammary (breast) cells in the circulation refines our conception of cancer progression, and suggests that each step in the metastatic cascade should be examined to establish its functional requirements, including those performed by normal cells."

She added that recurrent cancers could be targeted by treatments that destroy cells that have moved away from the primary tumour site and are lying dormant before a secondary tumour begins to take hold.

Commenting on the study published in the journal Science, Liz Baker, senior science information officer at Cancer Research UK, said: "Learning more about the spread of cancer - or metastasis - is essential because it is harder to treat the disease once it has spread.

"These are important but early results in mice. If they are confirmed by further studies they could reveal new ways of stopping cancer spread at an earlier stage and improve the outcome for people affected by this disease."