Claims about cancer travel unusually fast. And most of them travel without a source.
So we opened the US National Cancer Institute's own page on common cancer myths — ⭐ a document where the agency writes out each misconception and answers it on the spot.
⭐⭐⭐ The first item on the list is “Is cancer a death sentence?”
“Five-year survival rates for some cancers, such as breast, prostate, and thyroid cancers, now are 90 percent or better.”
— National Cancer Institute, “Common Cancer Myths and Misconceptions”
⭐ What an agency chose to put first on a list of myths is the first clue to reading the document.
⭐⭐⭐ The “this makes cancer worse” claims
| The common claim | What NCI writes |
|---|---|
| ⭐ Eating sugar makes cancer worse | “No studies have shown that eating sugar will make your cancer worse or that… your cancer will shrink or disappear.” |
| ⚠️ Surgery or a biopsy spreads it | “The chance that surgery will cause cancer to spread to other parts of the body is extremely low.” |
| ⚠️ Exposure to air makes it worse | “Exposure to air will not make tumors grow faster or cause cancer to spread to other parts of the body.” |
| ⭐⭐ Attitude determines risk and survival | ⭐⭐ “There is no convincing scientific evidence that links a person's 'attitude' to their risk of developing or dying from cancer.” |
| Cancer is contagious | “In general, no. Cancer is not a contagious disease that easily spreads from person to person.” |
| ⭐⭐ The “attitude” item is the one to sit with. ⚠️ That belief puts the weight of “you didn't fight hard enough” on the patient. | |
⭐⭐⭐ Family history — the myth runs both ways
⭐ This is the only place a number appears in the document.
| The question | What NCI writes | ⭐ How to read it |
|---|---|---|
| ⭐ Someone in my family has cancer — am I likely to get it? | ⭐⭐ “Only about 5 to 10 percent of cancers are caused by harmful mutations that are inherited from a person's parents.” | ⭐ Most are not inherited |
| ⭐ No one in my family has had cancer — am I risk-free? | “Most cancers are caused by genetic changes that occur throughout a person's lifetime… from aging and exposure to environmental factors.” | ⚠️ No family history does not remove risk |
| ⭐⭐ That the two sit next to each other is the point. ⭐ The same figure delivers reassurance on one side and a warning on the other. | ||
⭐⭐ Invert “5 to 10 percent” and you get 90 to 95. ⭐ And for that side, the causes the document names are aging and exposure to environmental factors.
⭐⭐ The “this causes cancer” claims
| The common claim | What NCI writes | ⭐ Strength of wording |
|---|---|---|
| Cell phones cause cancer | “No, not according to the best studies completed so far… cell phones emit a type of low-frequency energy that does not damage genes.” | ⭐ “No” plus a qualifier |
| Power lines cause cancer | “No, not according to the best studies completed so far… magnetic energy… does not damage genes.” | ⭐ Same shape |
| Deodorant causes breast cancer | “The best studies so far have found no evidence linking the chemicals typically found in antiperspirants and deodorants with changes in breast tissue.” | ⚠️ “Found no evidence,” not “there is none” |
| Herbal products can cure cancer | “No herbal products have been shown to be effective for treating cancer.” | ⭐⭐ The flattest statement |
| ⭐⭐⭐ The right column is the point of this table. The agency distinguishes “no,” “extremely low,” “found no evidence” and “none.” ⚠️ The sorting is ours, but the wording is the document's. | ||
⭐⭐ “Studies found no evidence” and “there is none” are different statements. ⭐ The deodorant item is the first kind; the herbal item is the second. ⚠️ It is also the distinction most often lost when agency documents get quoted.
⭐ For Korean cancer statistics see cancer prevalence in Korea and the thyroid cancer article; national screening is in this one. What the family goes through after diagnosis is in caring for someone with cancer.
Questions people ask
Wouldn't cutting out sugar help anyway?
⚠️ What NCI writes is that no studies have shown that cutting sugar makes cancer shrink or disappear. ⚠️⚠️ That is not a statement that sugar is good for you — the item answers one question only: does it make cancer worse.
Should I delay a biopsy?
⚠️⚠️ The document points the other way — “the chance that surgery will cause cancer to spread to other parts of the body is extremely low.” ⚠️ Note it says “extremely low,” not zero, and whether to test is a decision for your clinical team.
Is the cell phone question settled?
⚠️ Look at the shape of the sentence — “No, not according to the best studies completed so far.” ⭐ The “no” carries a qualifier. ⚠️ This article has not deleted it.
Does attitude really make no difference at all?
⚠️ What NCI writes is that there is no convincing scientific evidence, and the subjects are “risk of developing” and “dying from” cancer. ⭐ It is not a statement about quality of life or getting through treatment. ⚠️ The document does not address that.
Do other agencies say the same?
⚠️⚠️ What we opened is one National Cancer Institute page. Equivalent pages from other national cancer agencies were not checked — noted below.
Sources
- ⭐⭐⭐ US National Cancer Institute — Common Cancer Myths and Misconceptions (checked August 2026). Source for the twelve items and their order, ⭐ “five-year survival rates for some cancers, such as breast, prostate, and thyroid cancers, now are 90 percent or better,” the answers on sugar, contagion, surgery, attitude, air exposure, cell phones, power lines, herbal products and deodorants, ⭐⭐ “only about 5 to 10 percent of cancers are caused by harmful mutations that are inherited from a person's parents,” and “most cancers are caused by genetic changes that occur throughout a person's lifetime… from aging and exposure to environmental factors.”
- ⭐⭐ US National Cancer Institute — caregiver guidance (related document) — Support for Caregivers of Cancer Patients (checked August 2026), covered in the caregiver article. Where we confirmed that the same agency keeps separate documents for the patient side and the family side.
- ⭐ Checked directly. The “strength of wording” column (separating “no,” “extremely low,” “found no evidence” and “none”) and “the two family-history items invert each other” are our reading of the source; ⚠️ the document does not sort them that way. ⭐ That family history is the only item carrying a figure is also our own check.
What we could not verify
- ⚠️⚠️ Equivalent documents from other agencies. How other national cancer bodies handle these myths was not checked. This article carries one US page.
- ⚠️⚠️ The studies behind each answer. The NCI page states conclusions without listing individual studies, and this article goes no further.
- ⚠️ The basis of the survival figure. Which period or population “90 percent or better” refers to is not on the page. Korean figures are in a separate article.
- ⚠️ Myths not on this page. Only the listed items are carried here. Nothing is claimed about beliefs the page does not address.
- ⚠️ Choice of treatment. Neither the document nor this article advises on treatment.
As of August 2026. The items and answers are taken as written from the National Cancer Institute page, and sorting the wording by strength is marked as ours. ⚠️⚠️ This is general information and does not replace medical diagnosis or treatment. Decisions about testing and treatment belong with your clinical team.
