New Delhi, March 25: You must be wondering why cancer affects only some people and not others? According to a new research, random changes or 'mistakes' in DNA when cells are dividing cause nearly two-third of all cancers in humans.
According to a report in Times of India, these changes are neither caused by external factors like smoking or exposure to harmful chemicals, nor by hereditary factors. They are chance events occurring at the molecular level. In other words, cancer can strike anybody.
This upends prevailing wisdom that cancer is mostly a lifestyle related disease caused by external or environmental factors like smoking, harmful chemicals and conditions like obesity. While all these are valid and important risk increasing factors, random chance may be the real driver, if one goes by this new research.
The study involved a statistical analysis of cancer data from 69 countries including India, representing 4.8 billion people, more than half of the world's population. It was done by scientists from Johns Hopkins Kimmel Cancer Center at Baltimore, US, and published in the peer reviewed journal Science on March 24.
Human bodies grow by constant division of cells, starting from the first cell formed by fusion of the male sperm with the female egg. Every time a cell divides into two, the genetic code carrying DNA is copied. What the scientists are saying is that mistakes occur in this copying process that accumulate over time and ultimately cause cancer.
"These copying mistakes are a potent source of cancer mutations that historically have been scientifically undervalued, and this new work provides the first estimate of the fraction of mutations caused by these mistakes," said the paper's lead author Cristian Tomasetti.
The researchers studied all 32 cancer types and estimated that 66% of cancer mutations result from copying errors, 29% can be attributed to lifestyle or environmental factors, and the remaining 5% are inherited. They found a strong correlation between cancer incidence and normal cell divisions among 17 cancer types, regardless of the countries' environment or stage of economic development.
This means that lifestyle factors like smoking or exposure to toxic chemicals are also very important factors causing nearly a third of cancers.