Medically Reviewed By William C. Lloyd III, MD, FACS

What is cancer?

Cancer is a general term for a group of diseases that occur when there is an uncontrolled growth of abnormal cells in one or more organs or tissues of the body. Cancer is a serious disease and is one of the leading causes of death globally, according to the World Health Organization (Source: WHO Trusted Source World Health Organization Highly respected international organization Go to source ).

Common types of cancer include:

Normally, cells in the body that are old or damaged stop dividing and die. These cells are replaced by healthy young cells. Cancer occurs when old or damaged cells continue to divide and multiply uncontrollably. This results in the development of a malignant tumor or other abnormalities that interfere with the functioning of the affected organ or tissue.

Cancer cells crowd out or destroy healthy cells and, if left untreated, can continue to multiply and spread to other tissues and organs of the body—a process called metastasis. As cancer progresses, it interferes with vital processes and functions of the organ where it began, and of the organs where it has spread, such as the brain, lungs, bones and liver.

There are two main types of cancer:

  • Primary cancer refers to a malignant tumor that originates within a specific body tissue, such as primary lung cancer or primary breast cancer.

  • Secondary cancer (metastatic cancer) is caused by a primary cancer that has begun in one tissue or organ of the body and spread to another site. For example, primary lung cancer or breast cancer can spread to the brain, causing secondary brain cancer. Cancer can metastasize by growing directly into nearby tissues and organs or by spreading through the circulatory system or lymphatic system to other areas of the body.

Cancer can lead to life-threatening complications and be fatal, especially if it goes undetected and untreated. Prognosis of cancer varies depending on the type of cancer and the stage of advancement; your age, medical history, and coexisting conditions or diseases; and other factors. Seeking regular medical care offers the best chances of discovering cancer in its earliest, most curable stage. If you have cancer, following your treatment plan may help reduce your risk of serious complications.

What are the symptoms of cancer?

Symptoms of cancer vary depending on the specific type of cancer, its location, its stage of advancement, and other factors. For many cancers, there are no early symptoms. In some cases, symptoms do not appear until cancer has grown to an advanced stage and spread (metastasized) to other organs and tissues.

Cancer symptoms are caused by pressure from the enlarging tumor mass, either in the primary site or in a secondary (metastatic) location, or by the abnormal cancer cells that may affect organ function or produce abnormal substances. For example:

What causes cancer?

Cancer occurs when a genetic mutation causes old or damaged cells to continue to divide and multiply uncontrollably. The underlying cause of this varies depending on the specific type of cancer. In many cases, the underlying cause of cancer is not known.

Some causes of cancer include:

  • Inherited genes that increase susceptibility to cancer

  • Environmental factors, including exposure to certain chemicals, such as those found in pollution and tobacco. Other environmental factors include specific viruses and bacteria, such as human papillomavirus (HPV) infection, and/or exposure to excessive radiation, such as from the sun.

What are the risk factors for cancer?

Risk factors for cancer vary depending on the specific type of cancer. Not all people with risk factors will develop cancer, and some people who have no risk factors will develop cancer.

Common risk factors for cancer include:

  • Advancing age

  • Alcoholism or heavy alcohol ingestion

  • Chronic hepatitis B or C infection

  • Eating a high-fat, low-fiber diet or a diet that is high in salty and smoked foods

  • Engaging in unsafe sexual practices

  • Excessive sun exposure

  • Infection with Epstein-Barr Virus (the virus that causes monomucleosis)

  • Obesity

  • Personal or family history of cancer

  • Smoking

  • Toxic environmental exposure (arsenic, asbestos, PCBs, certain pesticides, etc.)

    Reducing your risk of cancer

    You may be able to lower your risk of developing some forms of cancer by:

    • Eating a diet that is low in fat and salty and smoked foods, and high in fiber and fruits and vegetables

    • Maintaining a healthy weight

    • Not drinking alcohol or limiting alcohol intake to one drink per day for women and two drinks per day for men

    • Participating in a regular exercise program

    • Quitting smoking

    • Wearing sunscreen and avoiding excessive exposure to the sun

    How is cancer treated?

    Treatment of cancer begins with seeking regular medical care throughout your life. Regular medical care allows a health care professional to best provide early screening tests, such as mammography, Pap smears, digital rectal exams, and fecal occult blood tests. Regular medical care also provides an opportunity for your health care professional to evaluate symptoms and your risks of developing cancer, and promptly order diagnostic testing. These measures may increase the chances of detecting cancer in its earliest, most curable stage.

    The goal of treatment of cancer is to permanently cure the cancer or to bring about a complete remission of the disease. Remission means that there is no longer any sign of the disease in the body, although it may recur or relapse later.

    Cancer treatment plans use a multifaceted approach that is individualized to the type of cancer and stage of advancement; your age, medical history, and coexisting diseases or conditions; and other factors.

    Treatment for cancer is often best planned and delivered by a team of specialists in cancer care. These specialists generally include medical oncologists, radiation oncologists, surgical oncologists, and registered nurses who specialize in cancer care.

    Cancer treatment may include some combination of the following:

    • Chemotherapy

    • Dietary counseling to help people with cancer maintain their strength and nutritional status

    • Pain medications

    • Palliative care to improve the overall quality of life for families and patients with serious diseases

    • Participation in a clinical trial to test promising new therapies and treatments for cancer

    • Physical therapy to help strengthen the body, increase alertness, reduce fatigue, and improve functional ability during and after cancer treatment

    • Radiation therapy

    • Regular follow-up care to monitor your treatment and progress and to address any problems or complications promptly

    • Surgery to remove a cancerous tumor or to treat complications of cancer, such as an intestinal obstruction

    • Targeted therapy with drugs to inhibit or block specific proteins associated with cancer cell growth

    Complementary treatments

    Some complementary treatments may help some people to better deal with cancer and its treatments. These treatments, sometimes referred to as alternative therapies, are used in conjunction with traditional medical treatments. Complementary treatments are not meant to substitute for traditional medical care. Be sure to notify your doctor if you are consuming nutritional supplements or homeopathic (nonprescription) remedies as they may interact with the prescribed medical therapy.

    Complementary treatments may include:

    • Acupuncture

    • Massage therapy

    • Nutritional dietary supplements, herbal remedies, tea beverages, and similar products

    • Yoga

    Hospice care

    In cases in which cancer has progressed to an advanced stage and has become unresponsive to treatment, the goal of treatment shifts away from curing the disease and focuses on treating the person. The goal of hospice care is to help people in their last phases of an incurable disease to live as fully and comfortably as possible. Hospice care involves medically controlling pain and other symptoms while providing psychological and spiritual support as well as services to support the patient’s family.

    What are the potential complications of cancer?

    Complications of cancer are serious and life threatening. They include:

    • Complications from treatment, such as serious infections and suppression of the immune system

    • Metastasis (spread) of a primary cancer to another tissue or organ in the body

    • Organ failure

    • Recurrence of cancer after treatment

    • Severe pain

    You can best treat cancer and lower your risk of complications by following the treatment plan that you and your health care team design specifically for you.

    Was this helpful?
    1. The goals of chemotherapy. American Cancer Society.
    2. Kushi LH, Doyle C, McCullough M, et al. American Cancer Society Guidelines on nutrition and physical activity for cancer prevention: reducing the risk of cancer with healthy food choices and physical activity. CA Cancer J Clin 2012; 62:30.
    Medical Reviewer: William C. Lloyd III, MD, FACS
    Last Review Date: 2020 Nov 18
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