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Massachusetts Medical Society's Physician Focus

April 2015

The Causes of Cancer


  • Cancer is the second-leading cause of death in the U.S., surpassed only by heart disease, and claims nearly 600,000 lives each year.
  • Genetic mutations of cells in the human body, poor lifestyle choices, and environmental issues all play roles in causing cancers.
  • Many cancers can be prevented through healthy lifestyle choices, vaccines, and screenings such as colonoscopies and mammograms.
  • Despite continued educational efforts, recent surveys indicate a wide misunderstanding and many misconceptions about the causes of cancers.

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It is the diagnosis that patients perhaps fear the most. Treatments can be long and exhausting, the future seems so uncertain, and the prospect of a life ending far too soon is always present for the patient and his or her family.

Cancer is a common condition, one that can affect just about any part of the body, from the skin to the head and neck to multiple internal organs. More than 1.6 million new cases are expected to be diagnosed in 2015, according to the American Cancer Society, and nearly 600,000 die annually from all types of cancers.

The American public, however, as indicated by recent surveys, reveals a troubling lack of knowledge and many misconceptions about the causes of cancer and steps that can be taken to reduce its risk and even prevent it.

To raise public awareness about the disease, the April edition of Physician Focus with the Massachusetts Medical Society features Robb Friedman, M.D., Medical Director of The Cancer Center at Beth Israel Deaconess Medical Center in Needham, Massachusetts, who joins program host Dale Magee, M.D. to discuss the causes of cancer, how it develops, and what can be done to prevent it.

“I like to describe cancer as the abnormal growth of cells in the body,” says Dr. Friedman, who is board certified in oncology (the study of cancer) and hematology (the study of diseases of the blood). “There are lots of different kinds of cells in the human body, and every single one has the potential to start functioning abnormally, to grow out of control, and start spreading and causing disease. That’s what we call cancer.”

Dr. Friedman reminds us that the human body is “composed of trillions of cells, all working together to make a living organism, and each one of those cells is growing and replicating itself and constantly repairing damage. The DNA inside the cells is replicated thousands of times over the life of a cell.”

In reality, Dr. Friedman explains, cancer is hundreds of different diseases, but because they all share that common abnormal growth and the potential to cause harm, cancer is the name we call it.

“It’s an uncomfortable thought,” Dr. Friedman adds, “but we probably have cancer cells in our body every day.” But he also notes that we have some built-in protection against the disease: “The immune system plays a really important role in protecting us from those cancer cells by eradicating them.”

Cancer can develop at any age, but the disease is more common in older people. The Cancer Society, in fact, notes that 78 percent of all cancer diagnoses occur in people 55 years of age and older. One reason: our immune system weakens as we get older.

Besides the abnormal growth and genetic mutations of cells, the causes of cancer include such factors as environmental exposures to toxic materials and unhealthy lifestyle choices, such as smoking, poor diet, and inactivity. The National Cancer Institute, for example, has estimated that up to one-third of cancers are linked to obesity and lack of physical activity.

While the inner workings of the human body may be beyond the control of individuals, the doctors note that individuals can take specific steps to reduce their risks for cancer – and even prevent some types of the disease.

Healthy lifestyle choices – avoiding tobacco, a good diet with lots of fruits and vegetables and limited amounts of red meat, regular physical activity, and maintaining a healthy weight – can dramatically reduce the risks of cancer. Vaccines are available to prevent cervical and liver cancers, and screenings can prevent colorectal and cervical cancer and detect other cancers early, when treatments are most effective.

While a cancer diagnosis may strike anxiety and fear, the doctors are quick to remind us that all cancers are not the same, that survival rates have improved dramatically in recent years, and that prevention is possible.

Watch the above video for additional discussion, including conversation about how cancer is caused by the “bad luck” of rapid and multiple cell divisions within the body, how obesity and inactivity raise the risk for cancer, and how oncologists face the challenges of what to do with the detection of cancers that are slow growing.

MMS/Richard Gulla

American Cancer Society

National Cancer Institute

American Society of Clinical Oncology

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"Cancer" PSA

From left, Dale Magee, M.D., Robb Friedman, M.D.
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