🔍 What people get wrong
What People Get Wrong About Cancer
Twelve beliefs about cancer that federal health agencies have looked at and answered. Some are false. A couple are more complicated than either side admits.
How to read this page
NCI keeps a page of common cancer myths and answers them directly. Most of what follows comes from there, or from the longer fact sheets NCI links to it.
Two things about the wording are worth noticing before you start.
First, agencies say "no evidence" rather than "impossible." That is not hedging for its own sake. It means studies looked and did not find something, which is the strongest thing science usually gets to say. When we quote it, we keep the hedge.
Second, a few of these are not simply false. Artificial sweeteners are the clearest example: different expert bodies have reached different conclusions from the same evidence, and NCI reports that disagreement rather than resolving it. A page that told you it was settled either way would be lying to you.
The myths themselves are listed below, each with the federal source it came from.
The two that do harm
Most items on this list are harmless to believe. Two are not.
The belief that attitude determines survival puts the blame for a disease onto the person who has it, and adds a job to their day that no evidence says will help. NCI found no convincing scientific evidence linking attitude to risk of developing or dying from cancer. Being frightened, angry, or exhausted during cancer treatment is not a failure and does not make anything worse.
The belief that a biopsy spreads cancer stops people getting diagnosed. NCI puts the chance that surgery causes cancer to spread as extremely low. A delayed diagnosis is a much more certain harm than a theoretical one.
What is actually worth your attention
If you came here looking for what to do rather than what to stop worrying about, the honest answer is that the myths above are mostly not where cancer risk lives.
The things federal agencies do establish are on three pages in this section: tobacco, vaccines that prevent cancer, and weight, alcohol, and food. Between them they cover most of what any one person can change.
And a large share of cancer risk is age and luck, which nobody can change at all. That is not a comfortable fact, but it is a fairer one than a list of things you should have avoided.
What people get wrong
Myth: Cancer is a death sentence.
What the evidence says: NCI's myths page states that five-year survival rates for some cancers, such as breast, prostate, and thyroid cancers, are now 90 percent or better. Outlook varies enormously by cancer type and stage, and group survival figures never describe an individual.
Read the sourceMyth: Eating sugar makes cancer worse.
What the evidence says: NCI states that no studies have shown that eating sugar will make your cancer worse, or that if you stop eating sugar your cancer will shrink or disappear.
Read the sourceMyth: Cancer is contagious.
What the evidence says: NCI states that in general, no: cancer is not a contagious disease that easily spreads from person to person. You cannot catch it from someone.
Read the sourceMyth: A biopsy or surgery makes cancer spread.
What the evidence says: NCI states that the chance surgery will cause cancer to spread to other parts of the body is extremely low. NCI separately addresses the related belief about air, stating that exposure to air will not make tumors grow faster or cause cancer to spread.
Read the sourceMyth: A positive attitude changes whether you get cancer or survive it.
What the evidence says: NCI states there is no convincing scientific evidence linking a person's attitude to their risk of developing or dying from cancer. This one matters, because the belief quietly blames people for their own illness.
Read the sourceMyth: Cell phones cause cancer.
What the evidence says: NCI states that cell phones emit a type of low-frequency energy that does not damage genes, and that the evidence to date suggests cell phone use does not cause brain or other cancers in humans. NCI notes brain cancer rates have been stable and that findings across studies have been inconsistent. IARC lists radiofrequency energy as possibly carcinogenic on limited evidence, which NCI reports without upgrading.
Read the sourceMyth: Power lines cause cancer.
What the evidence says: NCI states that the magnetic energy emitted by power lines is a low-frequency form of radiation that does not damage genes, and that no consistent evidence for an association between any source of non-ionizing electromagnetic fields and cancer has been found. NCI adds that no mechanism by which they could cause cancer has been identified.
Read the sourceMyth: Herbal products can cure cancer.
What the evidence says: NCI states that no herbal products have been shown to be effective for treating cancer. That is an absence of demonstrated benefit rather than a claim that every herb is dangerous, but some do interact with cancer treatment, which is a reason to tell your care team what you are taking.
Read the sourceMyth: If it runs in my family, I will get it. If it does not, I will not.
What the evidence says: Both halves are wrong. NCI states only about 5 to 10 percent of cancers are caused by harmful mutations inherited from a parent. NCI also states that about 39 percent of men and women will be diagnosed with cancer at some point in their lives, most of them without a relevant family history.
Read the sourceMyth: Antiperspirants and deodorants cause breast cancer.
What the evidence says: NCI states there is no evidence linking the chemicals typically found in antiperspirants and deodorants with changes in breast tissue, and that a 2014 review found no clear evidence that aluminum-containing products increase breast cancer risk.
Read the sourceMyth: Artificial sweeteners cause cancer.
What the evidence says: This is the most nuanced one on the list. NCI states there is no evidence that FDA-approved sweeteners cause cancer or other harms in people. On saccharin, NCI states the way it caused cancer in rats does not apply to humans, and it was delisted as a carcinogen in 2000. On aspartame, IARC classified it in 2023 as possibly carcinogenic on limited evidence, while a separate expert committee concluded it has not been found to have adverse effects after ingestion, and FDA cited significant shortcomings in the underlying studies. NCI describes the human results overall as inconsistent.
Read the source
Words on this page
- No evidence
- Studies looked and did not find it. That is not the same as proof it cannot happen, and agencies word it carefully for that reason.
- Ionizing radiation
- Radiation with enough energy to damage DNA, like X-rays. Cell phones and power lines do not produce it.
- Relative risk
- How much more likely something is compared with another group. It says nothing about how likely it was to begin with.
If you want more detail
These pages are longer and go further into the same topic.