Cancer as a Bad Bet

Scientists from the Johns Hopkins Kimmel Cancer Center (Maryland, USA) have developed a statistical model that measure the proportion of cancer incidence, across many tissue types, caused mainly by random mutations when stem cells divide.  By their measure, two-thirds of cancer incidence across tissues can be explained by ‘bad luck’ when these random mutations occur in genes that drive cancer growth.  Bert Vogelstein and colleagues charted the number of stem cell divisions in 31 tissues and compared these rates with the lifetime risks of cancer in the same tissues among Americans.  The statistical modeling revealed that more stem cell divisions correlate to increased cancer risk.  The study authors report that: “These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to ‘bad luck,’ that is, random mutations arising during DNA replication in normal, noncancerous stem cells.”