GETTY The study was led by Dr. Srinivas Malladi at the Memorial Sloan Kettering Cancer Centre

The phenomenon of cancer returning even after successful treatment is more common than most people realise. Almost a quarter of women with HER2-positive breast cancer will experience a recurrence of their disease following surgery and chemotherapy. For lung cancer patients over 50 percent will become victims again.

Joan Massagué, Director of the Sloan Kettering Institute said: “From the time a tumour begins to form until it is surgically removed, it is shedding tumour cells into the body. Most of these cells die, but a few may not.” These stragglers go into stealth mode and often return later somewhere else in the body. In the medical professional this is referred to as latent or dormant metastasis.

GETTY Almost 25 percent of women who survived breast cancer will be diagnosed again

GETTY Over half of people who survive lung cancer will have a reoccurrence

Published in the journal Cell, Srinivas Malladi, a postdoctoral fellow in Dr. Massagué’s lab spent six years developing a model to track metastasis. He began by obtaining sample of tumour cells from patients with early-stage breast and lung cancers. These were then injected into mice. Nearly all of the transplanted cells died, however a few survived in the lungs and kidneys. He called these persistent survivors latency competent cancer (LCC) cells. Dr. Malladi studied these LLC cells and found that they had similar behavioural characteristics to stem cells, which divide periodically to repair our tissues. This LCC cells’ ability to divide and seed distant organs.

GETTY Dr. Malladi refers to the surviving cancerous cells as latency competent cancer (LCC) cells

He also found that a part of these cells produce a protein called a WNT inhibitor which blocks cell division, leaving them in a state of suspended animation. This delayed growth is the main reason some LLC cells are able to survive in the body for many years without detection. By not dividing, these cells avoid producing the molecules that body’s natural killer cells can detect. Dr. Massagué said: “The job of NK cells is to sniff out anything that looks funny, like cancer cells and kill it.”