viernes, 25 de mayo de 2012

Understanding Cancer Prognosis - National Cancer Institute

Understanding Cancer Prognosis - National Cancer Institute

National Cancer Institute at the National Institutes of Health

Understanding Cancer Prognosis

Key Points

  • A prognosis is an estimate of the likely course and outcome of a disease.
  • Many factors affect the prognosis of a person with cancer, including the type, location, and stage of the cancer.
  • When estimating a patient’s prognosis, doctors usually use statistics based on data from groups of people whose situations are most similar to that of the patient.
  • Doctors cannot estimate with certainty what the outcome will be for an individual cancer patient.
  1. What is a prognosis?

    A prognosis is an estimate of the likely course and outcome of a disease. The prognosis of a patient diagnosed with cancer is often viewed as the chance that the disease will be treated successfully and that the patient will recover.
  2. What factors affect a patient’s prognosis?

    Many factors can influence the prognosis of a person with cancer. Among the most important are the type and location of the cancer, the stage of the disease (the extent to which the cancer has spread in the body), and the cancer’s grade (how abnormal the cancer cells look under a microscope—an indicator of how quickly the cancer is likely to grow and spread).
    Other factors that affect prognosis include the biological and genetic properties of the cancer cells (these properties, which are sometimes called biomarkers, can be determined by specific lab and imaging tests), the patient’s age and overall general health, and the extent to which the patient’s cancer responds to treatment.
  3. How do statistics contribute to predicting a patient’s prognosis?

    In estimating a cancer patient’s prognosis, doctors consider the characteristics of the patient’s disease, the available treatment options, and any health problems the patient may have that could affect the course of the disease or its ability to be treated successfully.
    The doctor bases the prognosis, in large part, on information researchers have collected over many years about hundreds or even thousands of people with the same type of cancer. When possible, doctors use statistics based on groups of people whose situations are most similar to that of the patient.
    Several types of statistics may be used to estimate a cancer patient’s prognosis. The most commonly used statistics are listed below.
    • Cancer-specific survival: This statistic calculates the percentage of patients with a specific type and stage of cancer who have survived—that is, not died from—their cancer during a certain period of time (1 year, 2 years, 5 years, etc.) after diagnosis. Cancer-specific survival is also called disease-specific survival. In most cases, cancer-specific survival is based on causes of death in medical records, which may not be accurate. To avoid this inaccuracy, another method used to estimate cancer-specific survival that does not rely on information about the cause of death is relative survival.
    • Relative survival: This statistic compares the survival of patients diagnosed with cancer (for example, breast cancer) with the survival of people in the general population who are the same age, race, and sex and who have not been diagnosed with that cancer. It is the percentage of cancer patients who have survived for a certain period of time after diagnosis relative to people without cancer.
    • Overall survival: This statistic is the percentage of patients with a specific type and stage of cancer who are still alive—that is, have not died from any cause—during a certain period of time after diagnosis.
    • Disease-free survival: This statistic is the percentage of patients who have no evidence of cancer during a certain period of time after treatment. Other similar terms are recurrence-free or progression-free survival.
    Cancer survival statistics are frequently given in terms of 5-year survival relative to the general population (that is, as 5-year relative survival percentages or “rates”). For example, according to NCI’s Surveillance, Epidemiology, and End Results program, the 5-year relative survival rate for all women diagnosed with breast cancer during the period from 2001 through 2007 was 89 percent and the 5-year relative survival rate for all patients diagnosed with lung cancer during the same period was 16 percent.
    Because survival statistics are based on large groups of people, they cannot be used to predict exactly what will happen to an individual patient. No two patients are entirely alike, and their treatment and responses to treatment can vary greatly. Also, because it takes years to see the impact of new treatments and diagnostic tests, the statistics a doctor uses to make a prognosis may not reflect the effectiveness of current treatments.
    Nevertheless, the doctor may speak of a favorable prognosis if the information from large groups of people suggests that the cancer is likely to respond well to treatment. A prognosis may be unfavorable if the cancer is likely to be difficult to control. It is important to keep in mind, however, that a prognosis is only an estimate. Again, doctors cannot be absolutely certain about the outcome for an individual patient.
  4. Is it helpful to know the prognosis?

    Cancer patients and their loved ones face many unknowns. Understanding their disease and what to expect can help patients and their loved ones make decisions about treatment, supportive and palliative care, rehabilitation, and personal matters, such as financial matters. Seeking information about prognosis is a personal decision.
    Many people with cancer want to know their prognosis. They find it easier to cope when they know the likely course of their disease. Some patients may ask their doctor about survival statistics or search for this information on their own. Other people find statistical information confusing and frightening, and they think it is too impersonal to be of value to them. It is up to each patient to decide how much information he or she wants.
    A doctor who is most familiar with a patient’s situation is in the best position to discuss his or her prognosis and explain what the statistics may mean.
  5. What is the prognosis if a patient decides not to have treatment?

    Because everyone’s situation is different (see Question 2), this question can be difficult to answer. Also, information used in making a prognosis often comes from studies that have compared new treatments with existing treatments rather than with “no treatment.” Therefore, it is not always easy for doctors to accurately estimate the prognosis of a patient who decides not to have treatment. However, as mentioned above (see Question 4), a doctor who is most familiar with a patient’s situation is in the best position to discuss his or her prognosis.
    There are many reasons why patients may decide not to have treatment. Some patients may be concerned that the benefits of cancer treatments will be outweighed by the side effects. Patients should discuss this concern with their doctor or other health care provider. Many medications are available to prevent or control the side effects caused by cancer treatments.
    Some patients may decide at some point not to have treatment if they know that their type and stage of cancer has a poor prognosis, despite treatment. Patients who choose not to have active cancer treatment should talk with their doctor to ensure that they get palliative treatment to help with the symptoms caused by their disease.
    In these cases, patients may want to think about clinical trials. Clinical trials are research studies that involve people. They test new ways to prevent, detect, diagnose, or treat diseases. People who take part in cancer clinical trials have an opportunity to contribute to scientists’ knowledge about cancer and to help in the development of improved cancer therapies. They also receive state-of-the-art care from cancer experts.
    People interested in taking part in a clinical trial should talk with their doctor. Information about clinical trials is available from NCI’s Cancer Information Service at 1–800–4–CANCER (1–800–422–6237) and in the NCI booklet Taking Part in Cancer Treatment Research Studies. This booklet describes how research studies are carried out and explains their possible benefits and risks.
    Additional information about clinical trials is available on NCI's Clinical Trials page. This page contains a link to NCI’s clinical trials search form, which can be used to find clinical trials that are currently accepting patients.
  6. What is the difference between a cure and a remission?

    A cure means that treatment has successfully eradicated all traces of a person’s cancer, and the cancer will never recur (return). A cure does not mean, however, that the person will never have cancer again. It is possible that another cancer, even the same type of cancer, will develop in the person’s body at some point in the future.
    A remission means that the signs and symptoms of a person’s cancer are reduced. Remissions can be partial or complete. In a complete remission, all signs and symptoms of cancer have disappeared.
    If a patient remains in complete remission for 5 years or more, some doctors may say that the patient is cured. However, some cancer cells can remain undetected in a person’s body for years or even decades after apparently successful treatment, and these cells may eventually cause a recurrence. Although most types of cancer usually recur within the first 5 years after diagnosis and treatment, later recurrences always remain a possibility. Therefore, doctors cannot say with any certainty that an individual cancer patient is cured. The most they can say is that there are no signs of cancer at this time.
    Because of the possibility of recurrence, doctors continue to monitor patients for many years and do tests to look for signs of cancer’s return. They will also look for signs of delayed adverse effects from the cancer treatments received.
This text may be reproduced or reused freely. Please credit the National Cancer Institute as the source. Any graphics may be owned by the artist or publisher who created them, and permission may be needed for their reuse.

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