Common Cancer Myths and Misconceptions

Some popular ideas about how cancer starts and spreads seem to make sense, especially when they come from old theories passed down over the years. But wrong ideas about cancer can lead to needless worry and can even get in the way of good prevention and treatment decisions. Below are some of the most common myths, and what the latest science actually shows.

If you have heard one of these ideas from family or friends, know that they usually share it because they care. Understanding the facts can help everyone worry a little less.

Not the way many people fear. In the United States, the chance of dying from cancer has dropped steadily since the 1990s. Five-year survival rates for some cancers—such as breast, prostate, and thyroid cancers—are now 90 percent or better. For all cancers combined, the 5-year survival rate is currently about 69 percent.

These numbers come from large groups of people. How long any one person lives, and whether they will die from the disease, depends on many things—including whether the cancer is slow or fast growing, how far it has spread, whether effective treatments are available, and the person's overall health.

No. Research has shown that cancer cells use more sugar (glucose) than normal cells do. But no studies have shown that eating sugar makes cancer worse, or that stopping sugar makes cancer shrink or disappear.

There is a helpful nuance here: a high-sugar diet can add to excess weight gain, and obesity is linked to a higher risk of developing several types of cancer. So while sugar does not directly feed a tumor, a balanced diet still matters for overall health.

The bottom line: cutting sugar will not treat cancer, but keeping a healthy weight is worthwhile.

In general, no. Cancer is not a contagious disease that easily spreads from person to person. You cannot "catch" cancer from someone who has it.

There is one narrow exception: organ or tissue transplantation. A person who receives an organ or tissue from a donor who had cancer in the past may have a higher risk of a transplant-related cancer later. But that risk is extremely low—about two cases of cancer per 10,000 organ transplants—and doctors avoid using organs or tissue from donors with a history of cancer.

Some cancers can be caused by certain viruses (such as some types of human papillomavirus, or HPV) and bacteria (such as Helicobacter pylori). A virus or bacterium can spread from person to person, but the cancers they sometimes cause cannot spread that way.

The chance that surgery will cause cancer to spread to other parts of the body is extremely low. Surgeons follow standard procedures and take many steps to keep cancer cells from spreading during a biopsy or during surgery to remove a tumor. For example, if they must remove tissue from more than one area of the body, they use different surgical tools for each area.

No. Exposure to air will not make tumors grow faster or cause cancer to spread to other parts of the body.

To date, there is no convincing scientific evidence that links a person's attitude to their risk of developing or dying from cancer. If you have cancer, it is normal to feel sad, angry, or discouraged sometimes, and positive or upbeat at other times. There is no "wrong" way to feel.

People with a positive attitude may be more likely to stay socially connected and active. Physical activity and emotional support may help you cope with cancer—but feeling down does not cause cancer, and staying cheerful is not a cure.

No, not according to the best studies completed so far. Cancer is caused by genetic mutations, and cell phones give off a type of low-frequency energy that does not damage genes.

Power lines give off both electric and magnetic energy. The electric energy is easily blocked or weakened by walls and other objects. The magnetic energy is a low-frequency form of radiation that does not damage genes.

No. Some studies suggest that alternative or complementary therapies, including some herbs, may help patients cope with the side effects of cancer treatment. But no herbal product has been shown to be effective for treating cancer itself.

In fact, some herbal products may be harmful when taken during chemotherapy or radiation therapy, because they can interfere with how those treatments work. If you use any complementary or alternative products—including vitamins and herbal supplements—tell your doctor.

The bottom line: be cautious about "miracle" cures, and always check with your care team first.

Not necessarily. Cancer is caused by harmful changes (mutations) in genes. Only about 5 to 10 percent of cancers are caused by mutations inherited from a parent. In families with an inherited cancer-causing mutation, several family members often develop the same type of cancer. These are called "familial" or "hereditary" cancers.

The other 90 to 95 percent of cancers come from mutations that happen over a person's lifetime, as a natural result of aging and exposure to things in the environment, such as tobacco smoke and radiation.

And if no one in your family has had cancer, that does not make you risk-free. Based on recent data, about 39 percent of men and women will be diagnosed with cancer at some point in their lives. What you eat, how much you eat, and whether you exercise may also affect your risk.

No. The best studies so far have found no evidence linking the chemicals typically found in antiperspirants and deodorants with changes in breast tissue.