Our Process
We begin with a question or concern about what causes cancer, and end with a well-researched answer in plain language. What steps do we take to get there? Read about our process below.
Why did we create the Cancer FactFinder?
Cancer is one of the most researched topics online because most everyone has had some kind of personal experience with the disease.
When making decisions about lifestyle, nutrition and health to avoid a cancer diagnosis, we often turn to:
• Social media
• Internet searches
• Friends
• Family
But how do we know which information to trust? It is often difficult to know which information about what does and does not cause cancer is reliable.
We created the Cancer FactFinder to provide ready access to accurate information about cancer so people can make informed choices to avoid certain exposures or take positive steps to maximize their health.
How do we gather and process information
for the FactFinder?
We review summaries of evidence in a manner consistent with other major organizations and share what we know about how strong the evidence is and whether something is or is not associated with cancer.
We use the following systematic and stringent process to identify claims about cancer causes in studies of humans:
- Identifying topics. We find topics to add to the Cancer FactFinder by searching the Internet, social media and other sources and by hearing directly from users of our site with a claim about what does or does not cause cancer. Do you have a claim to suggest? Tell us HERE [link to form].
- Review topics. Our editorial staff verify or refute these claims about what does and does not cause cancer using the best available studies in humans and laboratory/supporting studies.
We search for cancer claims from the internet, social media, and other sources.
Once identified, our editorial staff verify or refute these claims using the best available studies in humans and laboratory/supporting studies. We go to reliable sources of scientific data, including medical and scientific journals, obtain expert opinions by leading scientists, and abstract information from reputable organizations such as the American Cancer Society and the National Institutes of Health.
To decide whether a claim is likely true or false, we limit our review to evidence that provides information on strength of association or causation. This means that the criteria we use to make our conclusions include information about exposures and factors that are known to cause cancer. However, causation can’t always be established. We also consider the evidence for reliable associations with cancer in humans based on epidemiological evidence. We also evaluate findings from toxicology studies and other supporting studies, in addition to the current epidemiological evidence.
We also base our conclusions about cancer causes primarily on epidemiological studies done in humans.
Experimental studies, including animal and laboratory investigations, can provide supportive information, but ultimately, human epidemiological evidence was used to determine cancer risk.
Note that not all associations with cancer can be found by epidemiological studies, so there are still unknowns about some claims of cancer causes, especially when it involves something that may or is known to contain cancer-causing agents (carcinogens).
Laboratory studies and supporting evidence are also limited since the subjects of study are not humans. While these conclusions may show an effect in animals, it cannot always be applied to humans since the subjects are different. These limitations are noted in individual claim descriptions.
We then summarize the information we have and discuss it with our editorial team. After a summary of the information is drafted, editors with specialized expertise edit and fact-check the written summary.
In the FactFinder claims, our conclusions are summarized in the following ways:
We share this summary with members of the community, including cancer survivors and advocates, to ensure the message is clear and addresses the points that may be of concern to the general readership—not just the experts in a field.
Once fully vetted, we share the information through this FactFinder site so that it is available to the general public.
Category Key
Each claim is labeled to convey the degree to which it is true or not true. See the symbols and explanations below.
Strong scientific evidence supports this claim.
Some studies support this claim, but the evidence is not yet conclusive.
There is currently no scientific research available to assess this claim. (Often because researchers don't think it's worth studying.)
The scientific community has studied this topic, but has not yet determined if there is a link to cancer or not.
Most available evidence does not support this claim, though it is not completely ruled out.
Strong scientific evidence suggests that this claim is false.
What information is not included in our summaries?
Experimental studies, including animal and laboratory investigations, can provide valuable information. We didn’t consider evidence from animal and laboratory studies here, even though regulators routinely use this type of experimental evidence to evaluate chemicals for safety in the U.S. and the European Union.
Since we did not include animal studies in our report, we may have missed some important information about factors that cause cancer. Because it is unethical to expose humans to a risky chemical in a study, animal and laboratory studies are the only way to determine whether some exposures cause cancer.
Figuring out the causes of cancer can require putting together information from many other sources, including observations when humans have been exposed through their everyday life, at work, or in accidents, and considering evidence from experiments in animals or cells. Evidence from cancer studies in humans often emerges only after people have been exposed for decades.