US scientists, studying genetically engineered mice to develop medicine for cancer, have reported this finding. They found that the body's immune system keeps tumors dormant for many years.
It also kills off some cancer cells, but not quickly enough to shrink or destroy the tumour, reported the online edition of Daily Mail.
The finding was described by the medical experts as "startling" and could lead to treatments that would allow patients to live with "neutralised" cancer for the rest of their lives.
Doctors have known for long that cancer can lie dormant in the body for years before suddenly coming back to life. They were however not aware exactly how they could be kept in check.
The findings are a result of a study led by Professor Robert Schreiber at the Washington University School of Medicine and published Monday in the online version of the science journal Nature.
"Thanks to the animal model we have developed, scientists can now reproduce this condition of tumour dormancy in the laboratory and look directly at cancer cells being held in check by the immune system," Schreiber said.
"Further research and clinical validation of this process may also turn established cancer into a chronic condition, similar to other serious diseases that are controlled long-term by taking a medicine," the scientist said.