General questions and answers
What is cancer?
The body is made up of trillions of living cells. Normal body cells grow, divide into new cells, and die in an orderly way. During the early years of a person’s life, normal cells divide faster to allow the person to grow. After the person becomes an adult, most cells divide only to replace worn-out or dying cells or to repair injuries.
Cancer begins when cells in a part of the body start to grow out of control. There are many kinds of cancer, but they all start because of out-of-control growth of abnormal cells.
Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. Cancer cells can also invade (grow into) other tissues, something that normal cells cannot do. Growing out of control and invading other tissues are what makes a cell a cancer cell.
Cells become cancer cells because of damage to DNA. DNA is in every cell and directs all its actions. In a normal cell, when DNA gets damaged the cell either repairs the damage or the cell dies. In cancer cells, the damaged DNA is not repaired, but the cell doesn’t die like it should. Instead, this cell goes on making new cells that the body does not need. These new cells will all have the same damaged DNA as the first cell does.
People can inherit damaged DNA, but most DNA damage is caused by mistakes that happen while the normal cell is reproducing or by something in our environment. Sometimes the cause of the DNA damage is something obvious, like cigarette smoking. But often no clear cause is found.
In most cases the cancer cells form a tumor. Some cancers, like leukemia, rarely form tumors. Instead, these cancer cells involve the blood and blood-forming organs and circulate through other tissues where they grow.
Cancer cells often travel to other parts of the body, where they begin to grow and form new tumors that replace normal tissue. This process is called metastasis. It happens when the cancer cells get into the bloodstream or lymph vessels of our body.
No matter where a cancer may spread, it’s always named for the place where it started. For example, breast cancer that has spread to the liver is still called breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is metastatic prostate cancer, not bone cancer.
Different types of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That’s why people with cancer need treatment that is aimed at their particular kind of cancer.
Not all tumors are cancer. Tumors that aren’t cancer are called benign. Benign tumors can cause problems—they can grow very large and press on healthy organs and tissues. But they cannot grow into (invade) other tissues. Because they can’t invade, they also can’t spread to other parts of the body (metastasize). These tumors are almost never life threatening.
Is cancer contagious?
No, cancer is not contagious. In the past, people often avoided those who had cancer. They were afraid of all kinds of diseases and didn’t know enough about illness to understand that they were in no danger. Even today, families, friends, and co-workers of people with cancer sometimes shy away from them when they learn about the disease. As a result, people with cancer often say they feel isolated and alone. You don’t have to stay away from someone with cancer—you cannot catch it from them. In fact, that person could probably use your company more than ever.
Is cancer caused by stress?
Researchers have done many studies to see if there is a link between personality, stress, and cancer. Careful reviews of scientific evidence do not show that someone’s personality can increase their cancer risk. Study findings do not always agree, but the feeling of being stressed does not appear to be a strong predictor of cancer. Major life stressors, such as divorce or the death of a loved one, may raise cancer risk slightly. Also, poverty is linked to higher cancer risk, but this may be more related to health behaviors and poor access to medical care more than to poverty itself. Of interest, many studies have shown that people who are socially isolated are more likely to die of all causes, including cancer.
We do know that social support and practical help improve the quality of life of people with cancer, and in some cases prolong survival. These things also help people with cancer cope better with their diagnosis, treatment, and recovery. If someone you know has cancer, offering your help and emotional support is a key step toward helping that person manage the effects of their cancer.
Does cancer always cause pain?
Pain is one of the main reasons people fear cancer. If someone you know has cancer, it’s normal to be worried about seeing him or her in pain. But there are some cancers which cause no physical pain at all. When a person with cancer does have pain it can be caused by a number of things. Some people have pain because of the growth of a tumor or as a result of advanced cancer, while others may have pain from surgery or the side effects of treatment.
You should also know that the cancer care team can treat and manage almost any kind of pain. A great deal of progress has been made in pain control, so pain can be reduced or relieved in almost all cases. Even patients with advanced disease can be kept comfortable.
You may also be concerned that someone taking pain medicine for cancer will become addicted to it. But the evidence shows that, in general, people who take prescribed drugs for cancer pain according to the doctor’s directions do not become addicted. For more on this, please see Pain Control: A Guide for Those With Cancer and Their Loved Ones.
Do you always die if you have cancer?
No, but this idea is the major reason people fear cancer. The most recent available data shows that about 68% of people diagnosed with cancer are still alive 5 years later. Among those who are not cured of cancer, many can go on living for some years, even though there will be changes in their lives. For these people, cancer can be a lot like diabetes or heart disease—a chronic illness that is mostly controlled with treatment.
If someone you know has cancer, it’s important for you to know that cancer is not a death sentence. If you believe they are beyond hope or help, you might not offer them your support. The truth is they may be living with a disease that can be treated or controlled. Keep in mind that cancer is often treatable, and even curable. This will help you focus on supporting the person as they learn to live with cancer. So remember the good news: there are nearly 14 million Americans alive today have had cancer, and the survival rate is improving all the time.
Last Medical Review: 05/21/2012
Last Revised: 03/03/2014