New research from Stony Brook University in New York suggests that only 10 to 30 percent of cancer is influenced by matters completely out of our hands. The remaining 70 to 90 percent are the result of environmental factors or behavioral choices. Although the findings go directly against a similar study published earlier this year, this conflicting research does prove one thing: We're still not entirely sure of why some people get cancer.

For a study published this month in the journal Nature, Stony Brook researchers used computer modeling, population data, and genetic approaches to better understand the root of cancer. In doing so, the team found patterns in which some individuals with lower cancer risk migrated to a high cancer risk due to strictly outside factors. Although cells do often mutate during cell division — the underlying cause of cancer — using ultraviolet light and mathematical models, the scientists realized that these mutations rarely built up to the point of causing cancer without the influence of external factors. Due to this, they concluded that most cases of cancer result from avoidable factors, such as toxic chemicals and radiation.

These findings directly contradict the results of a similar study published in January, which concluded that two-thirds of cancer incidences can be blamed on random mutation, unrelated to genetics, environmental or behavioral factors. According to the researcher, from Johns Hopkins University School of Medicine in Baltimore, often cancerous mutations will occur for “no particular reason other than randomness,” Reuters reported.

“The real reason in many cases is not because you didn't behave well or were exposed to some bad environmental influence, it's just because that person was unlucky,” said study co-author, Dr. Bert Vogelstein. “It's losing the lottery.”

For the new study, lead researcher Dr. Yusuf Hannun told BBC News that, while the bad luck hypothesis has valid points, we should not minimize the role that external factors play in our cancer risk. Comparing our cancer risk to a game of Russian roulette, Hannun explained that the intrinsic, or bad luck, risk of cancer is similar to one bullet in a gun chamber.

“Now, what a smoker does is add two or three more bullets to that revolver. And now, they pull the trigger,” Hannun said. “There is still an element of luck as not every smoker gets cancer, but they have stacked the odds against them.”

What We Do And Don't Know About Cancer

Fundamentally, cancer is caused by the unregulated division of faulty cells. When these cells divide enough they may eventually create a tumor, which in some cases can metastasize and spread the cancer to various parts of the body. When enough of the body tissue is damaged by the tumor growth, death can ensue. However, the disagreement among medical professionals as to why this cell division sometimes leads to cancer growth shows just how little we know about what is actually causing cancer.

Although it’s evident that a person’s cancer risk is a combination of genetics, environmental factors, and chance, it's unclear what specific role each individual factor plays. What’s more, it remains an anomaly as to why humans have about a 40 percent chance of developing cancer, but other animals, such as whales and elephants, have a less than 5 percent lifetime risk of cancer.

Regardless of the lack of clarity behind what causes cancer, scientists are clear as to how we can all lower our individual chances. Reducing meat consumption, maintaining a healthy body weight, and abstaining from smoking and drinking alcohol have been proven to reduce one's lifetime risk of cancer.

Source: Wu S, Powers S, Zhu W, Hannun YA. Although doctors known that cancer risk is a combination of genetics, environmental factors, and chance, it's unclear what role each factor plays in our individual risk. Nature. 2015.