Treatment of cancer
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Cancer can be treated by surgery, chemotherapy, radiation therapy, immunotherapy, monoclonal antibody therapy or other methods. The choice of therapy depends upon the location and grade of the tumor and the stage of the disease, as well as the general state of the patient (performance status). A number of experimental cancer treatments are also under development. |
Complete removal of
the cancer without damage to the rest of the
body is the goal of treatment. Sometimes this
can be accomplished by surgery, but the
propensity of cancers to invade adjacent tissue
or to spread to distant sites by microscopic
metastasis often limits its effectiveness. The
effectiveness of chemotherapy is often limited
by toxicity to other tissues in the body.
Radiation can also cause damage to normal
tissue.
Because "cancer" refers to a class of diseases,
it is unlikely that there will ever be a single
"cure for cancer" any more than there will be a
single treatment for all infectious diseases.
Surgery
In theory,
cancers can be cured if entirely removed by
surgery, but this is not always possible. When
the cancer has metastasized to other sites in
the body prior to surgery, complete surgical
excision is usually impossible.
Examples of surgical procedures for cancer
include mastectomy for breast cancer and
prostatectomy for prostate cancer. The goal of
the surgery can be either the removal of only
the tumor, or the entire organ. A single cancer
cell is invisible to the naked eye but can
regrow into a new tumor, a process called
recurrence. For this reason, the pathologist
will examine the surgical specimen to determine
if a margin of healthy tissue is present, thus
decreasing the chance that microscopic cancer
cells are left in the patient.
In addition to removal of the primary tumor,
surgery is often necessary for staging, e.g.
determining the extent of the disease and
whether it has metastasized to regional lymph
nodes. Staging is a major determinant of
prognosis and of the need for adjuvant therapy.
Occasionally, surgery is necessary to control
symptoms, such as spinal cord compression or
bowel obstruction. This is referred to as
palliative treatment.
Chemotherapy
Chemotherapy is
the treatment of cancer with drugs
("anticancer drugs") that can destroy cancer
cells. It interferes with cell division in
various possible ways, e.g. with the
duplication of DNA or the separation of
newly formed chromosomes. Most forms of
chemotherapy target all rapidly dividing
cells and are not specific for cancer cells.
Hence, chemotherapy has the potential to
harm healthy tissue, especially those
tissues that have a high replacement rate
(e.g. intestinal lining). These cells
usually repair themselves after
chemotherapy.
Because some drugs work better together than
alone, two or more drugs are often given at
the same time. This is called "combination
chemotherapy"; most chemotherapy regimens
are given in a combination.
The treatment of some leukaemias and lymphomas requires the use of high-dose chemotherapy, and total body irradiation (TBI). This treatment ablates the bone marrow, and hence the body's ability to recover and repopulate the blood. For this reason, bone marrow, or peripheral blood stem cell harvesting is carried out before the ablative part of the therapy, to enable "rescue" after the treatment has been given. This is known as autologous transplantation. Alternatively, bone marrow may be transplanted from a matched unrelated donor (MUD). More about Chemotherapy.
Monoclonal antibody therapy
Immunotherapy is the use of immune mechanisms against tumors. These are used in various forms of cancer, such as breast cancer (trastuzumab/Herceptin®) and leukemia (gemtuzumab ozogamicin/Mylotarg®). The agents are monoclonal antibodies directed against proteins that are characteristic to the cells of the cancer in question, or cytokines that modulate the immune system's response.
Immunotherapy
Other, more contemporary methods for generating non-specific immune response against tumours include intravesical BCG immunotherapy for superficial bladder cancer, and use of interferon and interleukin. Vaccines to generate non-specific immune responses are the subject of intensive research for a number of tumours, notably malignant melanoma and renal cell carcinoma.
Radiation therapy
Radiation therapy
(also called radiotherapy, X-ray therapy, or
irradiation) is the use of ionizing
radiation to kill cancer cells and shrink
tumors. Radiation therapy can be
administered externally via external beam
radiotherapy (EBRT) or internally via
brachytherapy. The effects of radiation
therapy are localised and confined to the
region being treated. Radiation therapy
injures or destroys cells in the area being
treated (the "target tissue") by damaging
their genetic material, making it impossible
for these cells to continue to grow and
divide. Although radiation damages both
cancer cells and normal cells, most normal
cells can recover from the effects of
radiation and function properly. The goal of
radiation therapy is to damage as many
cancer cells as possible, while limiting
harm to nearby healthy tissue. Hence, it is
given in many fractions, allowing healthy
tissue to recover between fractions.
Radiation therapy may be used to treat
almost every type of solid tumor, including
cancers of the brain, breast, cervix,
larynx, lung, pancreas, prostate, skin,
stomach, uterus, or soft tissue sarcomas.
Radiation is also used to treat leukemia and
lymphoma. Radiation dose to each site
depends on a number of factors, including
the radiosensitivity of each cancer type and
whether there are tissues and organs nearby
that may be damaged by radiation. Thus, as
with every form of treatment, radiation
therapy is not without its side effects. More about
Radiation
Therapy.
Hormonal suppression
The growth of some cancers can be inhibited by providing or blocking certain hormones. Common examples of hormone-sensitive tumors include certain types of breast and prostate cancers. Removing or blocking estrogen or testosterone is often an important additional treatment.
Symptom control
Although the
control of the symptoms of cancer is not
typically thought of as a treatment directed
at the cancer, it is an important
determinant of the quality of life of cancer
patients, and plays an important role in the
decision whether the patient is able to
undergo other treatments. Although all
practicing doctors have the therapeutic
skills to control pain, nausea, vomiting,
diarrhea, hemorrhage and other common
problems in cancer patients, the
multidisciplinary specialty of palliative
care has arisen specifically in response to
the symptom control needs of this group of
patients.
Pain medication, such as morphine and
oxycodone, and antiemetics, drugs to
suppress nausea and vomiting, are very
commonly used in patients with
cancer-related symptoms.
Chronic pain due to cancer is almost always
associated with continuing tissue damage due
to the disease process or the treatment
(i.e. surgery, radiation, chemotherapy).
Although there is always a role for
environmental factors and affective
disturbances in the genesis of pain
behaviors, these are not usually the
predominant etiologic factors in patients
with cancer pain. Furthermore, many patients
with severe pain associated with cancer are
nearing the end of their lives and
palliative therapies are required. Issues
such as social stigma of using opioids, work
and functional status, and health care
consumption are not likely to be important
in the overall case management. Hence, the
typical strategy for cancer pain management
is to get the patient as comfortable as
possible using opioids and other
medications, surgery, and physical measures.
Treatment trials
Clinical
trials, also called research studies,
test new treatments in people with
cancer. The goal of this research is to
find better ways to treat cancer and
help cancer patients. Clinical trials
test many types of treatment such as new
drugs, new approaches to surgery or
radiation therapy, new combinations of
treatments, or new methods such as gene
therapy.
A clinical trial is one of the final
stages of a long and careful cancer
research process. The search for new
treatments begins in the laboratory,
where scientists first develop and test
new ideas. If an approach seems
promising, the next step may be testing
a treatment in animals to see how it
affects cancer in a living being and
whether it has harmful effects. Of
course, treatments that work well in the
lab or in animals do not always work
well in people. Studies are done with
cancer patients to find out whether
promising treatments are safe and
effective.
Patients who take part may be helped personally by the treatment(s) they receive. They get up-to-date care from cancer experts, and they receive either a new treatment being tested or the best available standard treatment for their cancer. Of course, there is no guarantee that a new treatment being tested or a standard treatment will produce good results. New treatments also may have unknown risks, but if a new treatment proves effective or more effective than standard treatment, study patients who receive it may be among the first to benefit.
Cancer vaccines
Considerable
research effort is now devoted to the
development of vaccines (to prevent
infection by oncogenic infectious agents, as
well as to mount an immune response against
cancer-specific epitopes) and to potential
venues for gene therapy for individuals with
genetic mutations or polymorphisms that put
them at high risk of cancer.
As of October 2005, researchers found that
an experimental vaccine for HPV types 16 and
18 was 100% successful at preventing
infection with these types of HPV and, thus,
are able to prevent the majority of cervical
cancer cases.
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