What happens when someone has cancer?

Each person’s illness and situation is unique, and so the person’s health care team is in the best position to provide specific information about what each person can expect. Some of the symptoms result from the type of cancer and where it’s located. Medications may also cause some side effects. As well, there are some general effects of cancer, which lead to some common symptoms as cancer progresses.

As cancer progresses it usually affects the whole body. These indicators mark the change in someone’s condition and the progression of the disease:

  • energy and strength;
  • eating;
  • breathing;
  • responsiveness;
  • pain.

The rate at which these indicators change is called the momentum of change, and can give a sense of what to expect.

Energy and strength

Each of us has reserves of energy that we use every day. People with progressive illnesses use more of their energy stores to get through each day, and their illness prevents them from being able to top up their reserves, which healthy people can do. So people who are ill are constantly spending their "energy savings."

There’s no way of directly measuring the “account balance” of reserve energy. One sign of diminishing energy reserves is decreased physical capacity, particularly in the range of activities. Physical tasks become increasingly challenging, and daily activities gradually become limited. When the illness is far advanced, it’s common that someone is in bed all day.

The "energy savings account" has another very important role. These reserves are what we draw from when an unexpected complication comes up, which could include an infection, such as a cold, the flu or pneumonia. When someone doesn’t have enough energy reserves she or he can deteriorate suddenly when faced with an unexpected complication, sometimes to the point of struggling to survive. Such times are uncertain and frightening, and must be taken day by day or even hour by hour.


Most people with cancer lose a lot of weight, even if they’re eating fairly well. This is because the cancer changes the way the body processes nutrients. The body can’t use calories in the usual way, and strength and weight don’t increase with increased food. As cancers progress, people lose their appetite and many find that food isn’t appealing. If they can communicate, they almost always say they aren’t hungry. If they’re being fed through a tube, families usually notice that it may produce uncomfortable effects. Feeding someone who is ill and has no appetite may result in nausea, bloating and heartburn.

Unfortunately, there’s no good remedy for a decreased appetite. When the goal of care is comfort, it’s usually recommended that people eat what they enjoy and realize that they will still lose weight. In advanced stages of illness food is cut back if someone isn’t hungry. This can be upsetting for family and friends. A common worry is that the person is being allowed to starve to death. Yet it’s important to accept that this as an unavoidable part of the illness. If people aren’t enjoying eating, and it isn’t helping them, then forcing food is not serving any purpose and may in fact cause discomfort.


In advanced stages of illness breathing can become irregular and produce a rattling sound. The sounds develop when someone is too weak to cough and clear the secretions that are normally produced in the respiratory system. The secretions then gradually build up in the lungs. With some cancers people may have trouble swallowing, and small amounts of what they’re trying to swallow may go into the lungs and contribute to the secretions. The rattling sound may be frightening, and you may worry that the person is drowning or choking. In fact, a build-up of secretions is generally not distressing for the person who is ill. As breathing becomes more irregular, some people also develop long pauses in their breathing known as apnea.


Generally as people come closer to the end of life they spend most of the time sleeping. This is a sign that the body systems are gradually shutting down. People often become quiet. Some people don’t have the energy to talk, and others become reflective as death approaches. Eventually people may become unconscious, or confused and restless. These are signs of changing brain function. Hearing is thought to be the last sense to fade, so it’s important to continue to talk to the person who is dying, even if he or she doesn’t respond.


Many people with cancer experience some pain. It tends to occur in the areas where the cancer is located. The sensation can vary, depending on what’s causing the pain. For example, pain caused by pressure on a nerve is different from the pain produced by general swelling in an area. There are a number of medications and techniques to treat pain. The health care team will plan treatment depending on the type of pain the person is experiencing. Medications can be adjusted so that the pain will not generally interfere with activities, and is kept under control throughout the day or night.

Momentum of change

Because each person’s situation is different it’s hard to predict how long someone will live as cancer progresses. The most useful guideline is referred to as the momentum of change: if someone’s condition changes significantly from month to month, it’s a strong indication that the person has months left to live. If such changes happen from one week to another, it often means there are only weeks of life left. If there are changes from one day to another or from hour to hour, then there are usually days or hours left.

Those who spend a lot of time with someone in advanced stages of illness usually have a good sense of when things are changing, even when the changes are subtle. These are usually accurate instincts. The momentum of change is a general guideline only. Sometimes a complication or health crisis develops, which may bring a rapid decline. Whether changes are happening slowly or quickly, it’s important for patients and families to recognize this and prepare for the unexpected. It’s helpful to discuss this and address goals or tasks that must be accomplished while the patient is still able to do so.

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