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Cancer

Overview

More than one million people are diagnosed each year with cancer. It strikes half of all men and one out of three women in the United States, and there are currently more than 12 million cancer survivors living in this country. Cancer doesn't discriminate by gender, color, or ethnicity. To help demystify cancer, start by learning basic facts about it.

The Root of Cancer

Cells, which make up human tissue, form the basis of our organs. On the most basic level, cancer is the abnormal growth of some of our cells.

"Our bodies are constantly renewing themselves. What that means is that we have cells that grow and divide. Cells usually have a finite life span,” explains Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society. “Cancer as a disease process really represents cells in our body that no longer respond to the usual growth and death signals. A cancer cell no longer responds to those signals and becomes immortal — it doesn’t die."

When that happens, the cell has "the power to spread elsewhere in the body and grow in areas where that particular type of cell would not normally grow," says Dr. Lichtenfeld.

Types of Cancer

Specific cancers are frequently named for the organ experiencing the abnormal growth of cells, as with breast cancer and prostate cancer. Leukemia, a group of blood cancers, starts with the leukocytes, the type of white blood cells affected, and gets its name from them.

For men, the most common type of cancer is prostate cancer, says Lichtenfeld. For women, it is breast cancer. After those gender-specific cancers, lung cancer and colorectal cancers are the next most common types for both men and women. Following these, the most prevalent types of cancer are split by sex again: bladder cancer and melanoma for men, and uterine cancer and non-Hodgkin lymphoma for women.

Cancer Treatments

The three major types of cancer treatment most often used today are:

  • Surgery to remove the cancer
  • Radiation therapy, which uses energy to kill cancer cells
  • Chemotherapy, which uses drugs to kill cancer cells

Researchers are constantly working to find new and more effective cancer treatment options. Cancer treatment is moving away from simply killing cancer cells and toward targeted therapies for cancer patients. This is "a form of chemotherapy that interferes with the underlying mechanisms that make a cancer cell a cancer cell," says Lichtenfeld.

Cancer Risk Factors

Certain lifestyle behaviors, like smoking, a poor diet leading to overweight or obesity, and being sedentary are all cancer risk factors. Other risk factors are:

  • Other tobacco use, such as chewing tobacco
  • Too much sun exposure
  • Excessive alcohol consumption

It's estimated that 50 percent of cancer deaths could be prevented by some simple lifestyle changes, says Lichtenfeld. These include quitting smoking, eating a healthy diet that includes lots of plant-based foods, maintaining a healthy body weight, and getting regular exercise.

Vaccines, antibiotics, and changing certain sexual behaviors could also prevent cancers that are linked to infectious diseases, like the human papillomavirus, hepatitis B virus, and HIV.

Cancer will probably always sound frightening at first, but understanding what it represents, how it can be treated, and what you can do to help reduce your risk of developing cancer can help put it in perspective.

Complications

Being diagnosed with cancer, particularly if it is incurable, can be very distressing. For many, the news is difficult to take in and comprehend. Many people who are diagnosed with cancer experience the classic stages of the grieving process. These are outlined below.

  • Denial - you may initially disbelieve the diagnosis and think that there is nothing wrong with you.
  • Anger - you may lash out at friends, family, or medical staff.
  • Bargaining - sometimes, people with terminal conditions will try to 'bargain' with their doctors, asking for any sort of treatment that can prolong their life.
  • Depression - you may lose all interest in life and feel that your situation is hopeless.
  • Acceptance - in time, most people will eventually accept the diagnosis.


If you have been diagnosed with cancer, talking to a counsellor, or psychiatrist, may help you combat feelings of depression and anxiety. Taking anti-depressants, or medicines that help reduce feelings of anxiety, may also help as you move through the grieving process. Your GP, or the doctor who is treating you, will be able to advise you about this.

Causes

Cancer begins with an alteration to the structure of DNA that is found in all human cells. This is known as a genetic mutation. The DNA provides the cells with a basic set of instructions, such as when to grow and reproduce.

The mutation in the DNA changes these instructions, so that the cells carry on growing. This causes the cells to reproduce in an uncontrollable manner producing a lump of tissue, known as a tumour.

How does cancer spread?

Cancer is known to affect two specific genes known as the:

  • oncogene, and
  • tumour suppresser gene.


The oncogene is responsible for encouraging cell growth. Cancer seems to cause the oncogene to go into 'overdrive' so that the cells grow and multiply at a faster rate.

Cancer also deactivates the tumour suppresser gene. This gene is designed to regulate cell growth by making sure that cells only reproduce when needed.

The combination of the overactive onocgene, and the deactivated tumour suppressor gene means that the cancer can quickly grow and spread to the other parts of the body, usually via the lymphatic system.

The lymphatic system is a series of glands (or nodes) that are spread throughout your body, much like your blood circulation system. These glands produce many of the specialised cells needed by your immune system.

Once the cancer reaches the lymphatic system it is capable of spreading to any other part of your body, including your bones, blood, and organs.

What causes cancer?

Cancer can be caused by:

  • carcinogens - chemicals that are known to cause the mutations associated with cancer, including alcohol and tobacco,
  • exposure to a significant amount of radiation,
  • infectious diseases such as the human papillomavirus (HPV),
  • hormonal imbalance which can occur during the menopause, and
  • conditions that affect the immune system, such as HIV.


Some types of cancer can run in families. For example, your risks of developing certain types of breast, or ovarian, cancer are higher if you have a close relative who developed the condition.

Diet and lifestyle are also important factors in the development of cancer. People who take regular exercise, eat a healthy, balanced diet, and are a healthy weight, have a lower risk of developing cancer. However, not taking exercise, eating a high fat diet, and being obese increases your chances of developing cancer.

Specific causes of cancer are discussed below.

Carcinogens

It is known that exposure to certain chemicals can cause the mutations that lead to cancer. The most common carcinogen is tobacco smoke, which can cause lung and bladder cancer. Excessive alcohol consumption can also cause cancer, as can exposure to asbestos fibres.

Radiation

Exposure to significant levels of radiation can cause cancer. This includes over-exposure to sunlight, or over-use of tanning beds, or lamps; all of which can cause skin cancer.

However, not all forms of radiation are dangerous. For example, the amount of radiation that is used by X-rays, or radiography machines, is small and will not cause you any harm.

Infectious diseases

Many viral infections can damage cells and cause cancer. The most common infectious conditions known to cause cancer are outlined below.

  • Human Papilloma Virus (HPV), which is responsible for 95% of all cases of cervical cancer.
  • hepatitis B and hepatitis C, both of which can cause liver cancer.
  • Epstien-Barr virus, which is responsible for glandular fever, and has been linked to an increased risk of developing Hodgkin's lymphoma, which is a cancer of the lymphatic system.
  • Human T-lymphotropic virus, which is blood-borne virus that is rare in the UK but common in other parts of the world, such as Japan and Africa and is known to cause leukaemia.


Hormonal imbalance

It is thought that changes in hormone levels can trigger cancerous cell growth in a similar way to exposure to carcinogens. This is why breast cancer is more common in post-menopausal women, as the menopause causes a change of the levels of the hormone, oestrogen, in the body.

Conditions that affect the immune system

Certain cancers, such as Karposi's sarcoma, and lymphoma, are common in people whose immune system is not functioning properly due to a medical condition, such as HIV.

Diagnosis

There are a number of tests that can be used to detect the presence of cancer. These include:

  • blood tests - some forms of cancers release proteins into the blood,
  • X-rays,
  • a magnetic resonance (MRI) scan,
  • a computerised tomography (CT) scan, and
  • an endoscopy - where a flexible tube with a camera on the end is used to look inside your body.


Biopsy

If the presence of cancer is suspected, a diagnosis can normally be confirmed by carrying out a biopsy. This is a procedure that involves surgically removing a small piece of affected tissue and then testing it for the presence of cancerous cells.

Biopsies are very useful for diagnosing cancer, and they can often be used to determine whether the cancer has spread to other parts of the body, or the likelihood that it will spread.

Additional biopsies may also be carried out on the nearest lymph nodes to the site of the cancer in order to check that the cancer has not started spreading through the lymphatic system.

Treatment

In treating cancer, the aim is to remove the cancerous cells while making sure that the cancer does not reoccur. This can be challenging because even if only one cancerous cell remains after treatment, it has the potential to cause a new tumour.

Different techniques are often used in combination as this can increase the chances of all the cancerous cells being removed. The main techniques are outlined below.

Surgery

If the cancer is detected in its early stages, it may be possible to surgically remove the affected tissue. In some cases, it may be necessary to remove the entire organ, such as the prostate gland (prostatectomy), or breast (mastectomy).

Chemotherapy and radiotherapy may also be used before and after surgery to increase the chances of success.

Chemotherapy

Chemotherapy involves the use of powerful cancer-killing medicines. These medicines damage the DNA of the cancerous cells, interrupting their ability to reproduce.

A combination of different medicines is normally used. Chemotherapy is normally used in combination with radiotherapy and surgery.

The medicines that are used in chemotherapy can sometimes damage healthy tissue, as well as the cancerous tissue and, unfortunately, adverse side effects are common.

Side effects of chemotherapy can include:

  • nausea,
  • vomiting,
  • hair loss, and
  • fatigue.

However, the side effects should stop once the treatment has finished. Chemotherapy can also weaken your immune system, making you more vulnerable to infection.

While the medicines used in chemotherapy can have a toxic effect on the body, there is no risk in coming into close physical contact with somebody who is undergoing chemotherapy.

For more information about chemotherapy, see the 'related articles' section.

Radiotherapy

Radiotherapy involves using pulses of radiation to damage cancerous cells. As with chemotherapy, the process also damages healthy cells but, unlike the cancerous cells, the healthy cells have the ability to repair themselves.

However, if you have radiotherapy, you may experience side effects while you are waiting for the healthy cells to repair themselves. These include:

  • tiredness,
  • nausea,
  • loss of appetite,
  • hair loss,
  • sore skin, and
  • a lack of interest in sex.

The side effects of radiotherapy can persist for several weeks, or months, after treatment has finished. See the 'related articles' section for further information about radiotherapy.

Hormonal therapy

The growths of some cancers, such as breast, or prostate cancer, can be slowed by blocking the effects of certain hormones, such as testosterone, or oestrogen.

However, blocking the effects of certain hormones can cause related side effects. In women, the possible side effects of blocking the hormone oestrogen may include:

  • hot flushes and sweats,
  • loss of interest in sex,
  • nausea and vomiting,
  • tiredness,
  • aching joints,
  • headaches, and
  • skin rashes.

In men, the possible side effects of blocking the hormone testosterone may include:

  • hot flushes,
  • sweating
  • tiredness,
  • weight gain,
  • loss of interest in sex,
  • an inability to obtain an erection, and
  • swelling of the breasts.

Monoclonal antibody therapy

Monoclonal antibody therapy is a relatively new kind of treatment that was first introduced in the late 1990s. Monoclonal antibodies are antibodies that are genetically engineered in a laboratory. They are designed to directly target and attack cancer cells. This is why monoclonal antibody therapy is sometimes referred to as targeted therapy.

There are several ways that monoclonal antibodies can attack cancerous cells. They can:

  • kill the cancerous cells by delivering tiny pellets of radioactive material to them,
  • deliver a small amount of chemotherapy medicine directly into the cancerous cells, and
  • block the signals in the cancerous cells that cause them to grow and reproduce.

Some types of monoclonal antibody therapy are still considered to be experimental, and will only be used when other treatments have failed. However, some forms of the therapy are now commonly used, such as the medicine trastuzumab, which is sometimes used in the treatment of breast cancer.

The medicines that are used in monoclonal antibody therapy are administered directly into the vein (intravenously). Side effects of monoclonal antibody therapy may include:

  • nausea,
  • skin rashes,
  • flu-like symptoms, such as chills, fever, and muscle aches,
  • itchy skin, and
  • diarrhoea.

Monoclonal antibody therapy has been known to cause heart problems in some people, such as heart disease, or heart attack. Therefore, it is likely that you will not be able to receive monoclonal antibody therapy if you have a history of heart disease.

If you do have monoclonal antibody therapy, your heart function will be regularly monitored during your treatment. If monitoring reveals that your heart function is being adversely affected, treatment will have to be stopped.

Rarely, monoclonal antibody therapy can cause severe allergic reactions in some people. This is known as an infusion reaction and can be potentially fatal if left untreated.

Most infusion reactions happen within 24 hours of the first time somebody begins treatment, so it is likely that you will be closely monitored once your treatment begins. If you begin experiencing the symptoms of an infusion reaction, anti-allergy medicines, such as corticosteroids, can be used to relieve symptoms.

Immunotherapy

Immunotherapy is a form of monoclonal antibody therapy that uses the body's immune system to attack the cancerous cells.

Normally, the body does not regard the cancerous cells as a foreign object, so the immune system does not attack them.

However, in immunotherapy, the monoclonal antibodies change the composition of the cancerous cells in such a way that the immune system regards them as a foreign object. It then starts attacking the cells, in the same way that it would normally attack an infection.

The side effects of immunotherapy are the same as the other types of monoclonal antibody therapy (see above).

Angiogenesis inhibitor therapy

Another new type of cancer treatment is angiogenesis inhibitor therapy. In order to grow, tumours need to create new blood vessels - a process known as angiogenesis.

Angiogenesis inhibitors are medicines that block the creation of new blood vessels, slowing the growth of the tumour.

The medicines cannot kill tumours, but have been shown to be effective in treating some forms of cancer when used in combination with chemotherapy and radiotherapy.

Alternative and complementary therapies

A large number of alternative therapies have been suggested for the treatment of cancer, such as homeopathy, vitamin supplements, or special diets. However, there is no clinical evidence that these alternative therapies are effective.

Complementary therapies are designed to complement conventional treatment, but not replace it. A number of complementary therapies have been shown to be of some use in coping with the symptoms and psychological effects of cancer.

Examples of complementary therapies include:

  • yoga,
  • relaxation techniques, such as mediation,
  • hypnotherapy, and
  • acupuncture.

A reputable complementary therapist will never make claims that their therapy alone can cure cancer, or try and persuade you to abandon your conventional treatment. The British Complementary Medical Association provides contact details of complementary therapists who have met their professional and ethical standards. See the 'selected links' section for more details.

On-going research

Much of the current research into cancer is focused on understanding more about the genetics of cancer. By finding out more about the specific genetic changes that occur when a cell becomes cancerous, it is then possible to develop new tests to detect cancer in its early stages.

An increased understanding in the genetics of cancer will also allow more effective types of monoclonal antibodies to be developed.

British researchers are also attempting to develop a new method of magnetic resonance imaging (MRI) which, if successful, promises to be 10,000 times more accurate than the current generation of MRI technology. This should allow tumours to be detected while they are in their early stages.

Another avenue of research is to identify people who are most at risk of developing certain types of cancer due to their genes. This will allow more efficient and effective screening programmes to be created, and it may be possible to then use medicines that prevent these types of cancer from occurring.

Symptoms
 

The symptoms of cancer vary depending on what part of your body is affected. However, cancer symptoms can be broadly grouped into three categories. These are:

  • local symptoms - these occur when the cancer is contained in one part of your body,
  • symptoms of metastasis - these are symptoms caused by the cancer beginning to spread to other parts of your body, and
  • systemic symptoms - these are symptoms that are caused by the cancer having spread throughout your body.


Common local symptoms include:

  • unusual swelling, or lumps,
  • pain,
  • jaundice, and
  • ulcers.

Common metastasis symptoms include:

  • swollen glands,
  • coughing blood, and
  • bone pain.

Common systemic symptoms include:

  • weight loss,
  • loss of appetite,
  • tiredness, and
  • night sweats.


Many of the above symptoms can be caused by conditions other than cancer. Therefore, if you have any of the above symptoms, you should not assume that you have cancer. Your GP will be able to advise you.

Types of Cancer

It's estimated that more than 11 million people in the United States have some form of cancer. There are more than 200 different types of cancer, although many are quite rare. The following are the 10 most commonly diagnosed cancer types in 2009 and the estimated number of cancer patients affected by each:

  1. Non-melanoma skin cancer. Affecting more than 1 million people a year, skin cancer can form in the skin cells on any part of the body, though most commonly on skin that’s been exposed to the sun. There are several types of skin cancers, including squamous cell skin cancer, found in the flat cells on the top of the skin, and basal cell skin cancer, found in the round cells deeper inside skin's outer layer. Most commonly, skin cancer affects older people or people who have a compromised immune system.
  2. Lung cancer. Roughly 219,440 cases of this deadly cancer were diagnosed in 2009. Lung cancer strikes the cells inside the lining of the lungs. There are two primary types of lung cancer — small cell and non-small cell lung cancer. Lung cancer claims nearly 160,000 lives annually.
  3. Breast cancer. This type of cancer will affect 194,280 people in 2009. This is by far the most common cancer in women, says Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society. While the overwhelming majority of breast cancer patients are women, about 1,900 cases are diagnosed in men each year.
  4. Prostate cancer. Just over 192,200 cases of prostate cancer are diagnosed annually. Dr. Lichtenfeld says that this is the most common cancer to affect men, most often men over age 50. The prostate gland is a part of the reproductive system in men and is found at the base of the bladder, near the rectum. This type of cancer develops in the tissues inside the prostate gland.
  5. Colorectal cancer. There will be about 146,970 new cases of colon and rectal cancers combined in 2010. The colon is part of the large intestine, which helps to break down and digest food, and the rectum is the end of the large intestine that is nearest the anus.
  6. Bladder cancer. Nearly 71,000 people will receive this diagnosis in 2010. The bladder can be affected by cancer cells that develop within its tissues. The most common type is transitional cell carcinoma, but others, such as adenocarcinomas and squamous cell carcinomas, may also occur, depending on which bladder cells are involved.
  7. Melanoma. Predicted to strike close to 68,720 people, melanoma is another type of skin cancer. It forms in the skin's melanocyte cells, which produce the brown pigment melanin. Because melanoma occurs in skin that contains a lot of pigment, it frequently begins in moles. Melanoma may also be found in other pigmented parts of the body, like the intestines or even the eyes.
  8. Non-Hodgkin lymphoma. Affecting 65,980 people, this is the term for a number of different but related cancers involving white blood cells, or lymphocytes. This type of cancer is frequently characterized by swollen lymph nodes, fevers, and weight loss. People of any age can develop non-Hodgkin lymphoma. There are many different types of non-Hodgkin lymphoma that affect different cells and parts of the body, with varying prognoses and treatment.
  9. Kidney cancer. Kidney cancer is diagnosed in more than 49,000 people each year. The kidneys are the organs that help to excrete waste from the body in the form of urine. Cancer can form inside the tissues or ducts of the kidneys. Although kidney cancer develops mainly in people over 40, one type of kidney tumor usually affects young children.
  10. Leukemia. Approximately 44,790 cases of leukemia were predicted for 2009. The four main types of leukemia are acute myeloid leukemia, acute lymphocytic leukemia, chronic lymphocytic leukemia, and chronic myeloid leukemia. These types of cancer often form inside the bone marrow or other cells and tissues that form blood cells, and are known as blood cancers. Leukemia results in overproduction of certain kinds of white blood cells, which then circulate in the bloodstream. Leukemia can be chronic — a slow-growing type of cancer that begins without symptoms — or acute, meaning the cells can't function normally and symptoms progress rapidly. It affects both adults and children, and kills more children under age 20 than any other cancer.

Other types of cancer that are important to mention include pancreatic, endometrial (uterine), thyroid, and sarcomas, each of which affects fewer than 43,000 people annually.