US researchers have concluded that in two-thirds of cancer cases, the cause can be as simple as "bad luck." Only a third could be blamed on family genes or environmental causes like smoking.
The journal Science carried a report Friday that random mutations were behind 22 types of cancer, including leukemia. Just nine other types were influenced by heredity and environmental factors.
Oncologist Dr. Bert Vogelstein, of the Johns Hopkins University School of Medicine in Baltimore, said that in the majority of cases cancer occurred "just because that person was unlucky."
"It's like losing the lottery," said Vogelstein, who studied 31 cancer types with Johns Hopkins biomathematician Cristian Tomasetti.
They scanned scientific literature for data on stem cell division over a person's lifetime. This process of cellular self-renewal occurs naturally and helps replace cells that die off in a specific organ.
Habits not to blame
"When someone gets cancer, immediately people want to know why," Vogelstein said. "And the real reason in many cases is not because you didn't behave well or were exposed to some bad environmental influence."
Tomasetti said harmful mutations occurred for "no particular reason other than randomness" as master cells, called stem cells, divide in various bodily tissues.
"We should focus more research and resources on finding ways to detect such cancers at early, curable stages," he said.
Alongside leukemia, the two-thirds of cases involving random mutation included pancreatic, bone, testicular, ovarian and brain cancer.
Rate of cell division
Generally speaking, said the researchers, tissues that undergo more divisions, thus increasing the probability of random mutations, were more prone to tumors.
The nine heredity or environmental induced types of cancer included colorectal cancer, skin cancer and smoking-related lung cancer.
The authors said breast and prostate cancers were not included in their study because that were unable to determine reliable stem cell division rates from the literature.
ipj/cmk (Reuters, AFP)