March 28, 2017

Most cancer mutations are just 'bad luck'—but many cases are still preventable, study finds

Daily Briefing

About 66 percent of the cell mutations that could cause cancer result from DNA errors that occur as cells replicate themselves, meaning most cancer diagnoses aren't tied to genetic risk or environmental factors—they're simply "bad luck," according to a study published Thursday in Science.

Study details

The study is a follow up to research published in 2015 that triggered a lot of backlash and prompted questions about the researchers' methodology and funding, STAT News reports. In the latest study, Bert Vogelstein and Cristian Tomasetti of the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University addressed those concerns, while reaffirming their previous findings.

 "We all agree that 40 percent of cancers are preventable," Vogelstein said at a news conference, adding, "The question is, what about the other cancers that aren't known to be preventable?" To answer that question, the researchers looked at health records from 69 countries on 32 different types of cancer.

Findings

The researchers found that about:

  • 5 percent of cancers are caused by inherited genetic risks, such as variants on the BRCA gene that increase risk of breast and ovarian cancer in women;
  • 29 percent of cancers result from mutations caused by environmental factors, such as cancer-causing viruses and sun exposure; and
  • 66 percent of genetic mutations that could cause cancer result from random errors in individuals' DNA.

According to the study, the human body uses DNA to repair most of the genetic mutations, reducing the risk that the cells could cause a medical issue. However, DNA errors in cells that were not repaired could cause cancer, according to the researchers.

The researchers attributed a large share of individuals' cancer risk to those mutated cells and suggested there might not be much individuals can do to prevent cancers stemming from the mutations. They added that cancer risk as a result of the mutations varies depending on the type of cell in which the mutation occurs, and therefore the type of cancer the cell could produce, such as lung cancer or prostate cancer.

Overall, the findings mean that even if individuals lived in an environment with no cancer-causing entities and inherited gene mutations could be fixed, most cancers diagnosed today still would occur, according to "Science Now." Bert Vogelstein of Johns Hopkins University, the lead author of both the original and new studies, said the findings "could provide comfort to the millions of patients who developed cancer but led near-perfect [healthy] lifestyles," as well as "parents of children who have cancer" who might blame themselves for passing on genetic risk factors to their children or the environment in which they live.

Still, the researchers stressed that about 42 percent of total cancer cases could be prevented by improving individuals' lifestyles and environments. As such, they said humans should continue practicing behaviors that could reduce their cancer risk.

Discussion

Cristian Tomasetti, a biostatistician at Johns Hopkins University and co-author of the study, said the findings mark "a complete paradigm shift in how we think about cancer and what causes cancer."

Paul Meltzer, a geneticist at the National Cancer Institute's Center for Cancer Research, called the study a "very important theoretical work" that could shape future cancer research.

However, some researchers said the study overestimates the role unavoidable cell mutations play in cancer risk and underestimates environmental effects. Song Wu, a biostatistician at Stony Brook University, for instance, has pointed to research that found prostate cancer incidence among Japanese men increased when they moved to the United States. "There's clearly something happening in the environment," Wu said (Healy, "Science Now," Los Angeles Times, 3/23; Harris, "Shots," NPR, 3/23; Begley, STAT News, 3/23).

What they value: Five types of cancer patients

Cancer patients have more choices for their care than ever before. To attract patients in this fiercely competitive landscape, you must invest your limited resources in the right services—ones that will earn patients' trust and improve their experience.

Oncology Roundtable's analysis of our 2015 Cancer Patient Experience Survey revealed five distinct patient types—each with unique characteristics and preferences for their care. Our infographic is your guide to understanding the five types of patients and what they value in a cancer provider.

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