A vast amount of information about cancer is available through the Internet and other sources. However, many things you hear from websites, chat rooms, and conversations with friends are inaccurate. Check with your doctor or another credible medical source to verify the accuracy of the claims you hear or read. Common cancer myths—some of which have existed for years—include the following:

General cancer myths

The number of people diagnosed with and dying from cancer is increasing.

Actually, the number of new diagnoses of all cancers combined decreased steadily between 1999 and 2006, and the number of deaths from all cancers combined decreased steadily between 2001 and 2006, according to the most recent study by the National Cancer Institute, the National Institutes of Health, the Centers for Disease Control and Prevention, the American Cancer Society, and the North American Association of Central Cancer Registries. More people with cancer are now living longer lives with a better quality of life due to early diagnosis, lifestyle changes, and better treatment options.

If you are diagnosed with cancer, you will probably die.

Cancer is not a death sentence. There are many effective treatments. In fact, more than 60% of people with cancer survive five years or more after the initial diagnosis. Learn more about survival statistics.

Myths about developing cancer

Cancer is contagious.

No cancer is contagious (capable of spreading from person to person through contact). However, some cancers may be caused by viruses. The human papillomavirus (HPV) is a sexually transmitted disease that can increase the risk of cervical, anal, and some types of head and neck cancers. Meanwhile, hepatitis B and hepatitis C—viruses transmitted by infected intravenous needles and sexual activity—can increase the chance of liver cancer.

If a parent has cancer, then his or her child will develop cancer.

All cancer is due to genetic changes, but not all the genetic changes come from a family member. In fact, only 5% to 10% of cancers are hereditary (from a family member). Most cancers happen after a person acquires multiple mutations (changes in the genetic code, or DNA) from tobacco, sunlight, radiation, or other factors, some of which probably have not been identified yet. And having an inherited gene mutation does not mean you will definitely develop cancer, it just means you have an increased risk of cancer. Another common myth suggests that hereditary gene mutations responsible for breast or ovarian cancer in some women can only be inherited from the mother’s side. However, the most common gene mutations, BRCA1 or BRCA2, can be passed down from either the father or mother. Learn more about cancer genetics and hereditary cancer-related syndromes.

Hair dyes and antiperspirants can cause cancer.

To date, there is no conclusive scientific evidence that these items increase the risk of developing cancer. Some studies have suggested that hair dyes used before 1980 could be linked to an increased risk of non-Hodgkin lymphoma, but the unsafe chemicals have since been removed from hair dye products. There is limited and inconsistent evidence that hair dye can increase the risk of other cancers. Meanwhile, some research suggests skin may absorb aluminum-based compounds—the active ingredient in antiperspirants—and cause hormonal effects, which has led some to believe that antiperspirants could contribute to the development of breast cancer. However, there is no good evidence to support that claim.

A person develops cancer because they have a weakened immune system.

Although this is partially true among certain people—such as those with AIDS or those who take immune-suppressing drugs following an organ transplant—the “strength” of someone’s immune system does not affect the chance of developing cancer. Most common cancers do not occur in people with immune system problems. That also means that attempting to “strengthen the immune system,” which is actually not possible for most people, is not an effective treatment for cancer.

Myths about coping with cancer

It is sometimes easier to remain unaware that you have cancer.

You should not ignore the symptoms or signs of cancer, such as a breast lump. Knowledge of the issue gives you the power to make informed choices and seek the best possible treatment. Since treatment is typically more effective in the early stages of cancer, early diagnosis improves the likelihood of survival.

Positive thinking will cure cancer.

Although a positive attitude can improve your quality of life during cancer treatment, there is no scientific evidence that it can cure cancer. Placing such importance on attitude can lead to unnecessary guilt and disappointment if—for reasons beyond your control—your health does not improve.

Myths about cancer treatments

One clue that a supposed cancer treatment may not be valid is if the evidence for it largely comes from testimonials or anecdotes, where one person says something is true because they claim it worked for them as an individual or they heard about it working for someone else. Scientists almost never rely on testimonial evidence; rather, they determine if a treatment is effective by testing it very precisely on a group of similar patients, called a clinical trial. Learn more about clinical trials and ways to protect yourself from cancer treatment fraud.

The medical establishment is hiding a cure for cancer.

The medical community is not withholding a miracle treatment. There is no one single cure for cancer. More than 100 types of cancer exist, and they respond differently to various methods of treatment. Those who work in the medical field have the same likelihood of developing cancer as the general population, and they are eager for new and better treatments to emerge.

Some people are too old for cancer treatment.

There is no age limitation for cancer treatment, which can be just as helpful for older adults as for younger adults. People with cancer should receive the treatment that is best suited to their condition, regardless of age. Some older adults may have other illnesses that limit the use of specific treatments, so older adults with cancer are encouraged to talk with their doctor about the best approach to their disease. Read more about cancer treatment in older adults.

Cancer treatment is usually worse than the disease.

Although cancer treatments such as chemotherapy and radiation are known to have some side effects that can be unpleasant and sometimes dangerous, recent advances have resulted in many chemotherapy drugs and radiation treatments that are much better tolerated than past treatments. Symptoms like severe nausea and vomiting, hair loss, and tissue damage are much less common these days. For each patient, oncologists always try to balance the known risks and side effects of the treatment with the expected benefits.

Myths about living with cancer

People with cancer remain must remain confined in a hospital bed.

Most people living with cancer are treated on an outpatient basis (with periodic appointments, rather than an overnight stay at a hospital) in their home community and can continue with some or all of their day-to-day activities. For example, many people can work part-time or full-time, care for children, and attend social activities, despite undergoing cancer treatment.

Sugar causes cancer to grow faster.

Although all cells, including cancer cells, use glucose (blood sugar) for energy, sugar does not speed tumor growth. In turn, removing sugar from your diet will not slow tumor growth.

More Information

Medical News: How to Know If It's Accurate

Additional resources

National Cancer Institute: Annual Report to the Nation on the Status of Cancer, 1975-2006

MayoClinic.com: Debunking cancer myths: An interview with a Mayo Clinic specialist

Dana-Farber Cancer Institute: Dispelling Cancer Myths

Last Updated: March 26, 2010