George Klein (1925-2016) was Professor Emeritus at the Microbiology and Tumor Biology Center at the Karolinska Institute in Stockholm, Sweden when he published a fascinating article in The Scientist. The article makes the point that approximately one in three people will be struck by cancer in their lifetime. But, the other side of that coin is that two out of three people remain unaffected. Even the majority of heavy smokers who bombard their lungs with carcinogens and tumor promoters over many years remain cancer-free.
A systematic review revealed that prostate cancer’s incidental findings at autopsy ranged from <5% in men under age 30 to almost 60% by age 70. A not-insignificant percentage of these cancers, when localized and low risk, do not progress to overt cancer during the person’s lifetime. This has led to a recommendation option of active surveillance as opposed to treatment.
It is also known that circulating tumor cells (CTCs) are present in many cancer patients. However, only a portion of these cells will enter and persist in distant parts of the body. These are known as disseminated tumor cells or DTCs. An only a fraction of them develop into secondary tumors (metastases).
- What keeps these micro-cancers in check?
They are kept in check by a mix of the