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.
Angiogenesis inhibitors were once thought to have potential as a "
silver bullet" treatment applicable to many types of cancer, but this has not been the case in practice.
Surgery
In theory, non-
hematological cancers can be cured if entirely removed by
surgery,
[citation needed] 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. In the
Halstedian model of cancer progression, tumors grow locally, then spread to the lymph nodes, then to the rest of the body. This has given rise to the popularity of local-only treatments such as surgery for small cancers. Even small localized tumors are increasingly recognized as possessing metastatic potential.
Examples of surgical procedures for cancer include
mastectomy for breast cancer,
prostatectomy for prostate cancer, and
lung cancer surgery for non-small cell lung 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.
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.
Chemotherapy
Main article:
Chemotherapy is the treatment of cancer with
drugs ("anticancer drugs") that can destroy cancer cells. In current usage, the term "chemotherapy" usually refers to
cytotoxic drugs which affect rapidly dividing cells in general, in contrast with
targeted therapy (see below). Chemotherapy drugs interfere 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 to cancer cells, although some degree of specificity may come from the inability of many cancer cells to repair
DNA damage, while normal cells generally can. 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
stem cell transplantation. Alternatively,
hematopoietic stem cells may be transplanted from a matched unrelated donor (MUD).
Targeted therapies
Targeted therapy, which first became available in the late 1990s, has had a significant impact in the treatment of some types of cancer, and is currently a very active research area. This constitutes the use of agents specific for the deregulated proteins of cancer cells.
Small molecule targeted therapy drugs are generally inhibitors of
enzymatic domains on mutated, overexpressed, or otherwise critical proteins within the cancer cell. Prominent examples are the tyrosine kinase inhibitors
imatinib (Gleevec/Glivec) and
gefitinib (Iressa).
Monoclonal antibody therapy is another strategy in which the therapeutic agent is an
antibody which specifically binds to a protein on the surface of the cancer cells. Examples include the anti-
HER2/neu antibody
trastuzumab (Herceptin) used in breast cancer, and the anti-CD20 antibody
rituximab, used in a variety of
B-cell malignancies.
Targeted therapy can also involve small
peptides as "homing devices" which can bind to cell surface receptors or affected
extracellular matrix surrounding the tumor. Radionuclides which are attached to these peptides (e.g. RGDs) eventually kill the cancer cell if the nuclide decays in the vicinity of the cell. Especially oligo- or multimers of these binding motifs are of great interest, since this can lead to enhanced tumor specificity and avidity.
Photodynamic therapy (PDT) is a ternary treatment for cancer involving a photosensitizer, tissue oxygen, and light (often using
lasers). PDT can be used as treatment for
basal cell carcinoma (BCC) or
lung cancer; PDT can also be useful in removing traces of malignant tissue after surgical removal of large tumors
.
Immunotherapy
A renal cell carcinoma (lower left) in a
kidney specimen.
Cancer immunotherapy refers to a diverse set of therapeutic strategies designed to induce the patient's own
immune system to fight the tumor. Contemporary methods for generating an immune response against tumours include intravesical
BCG immunotherapy for superficial bladder cancer, and use of
interferons and other
cytokines to induce an immune response in
renal cell carcinoma and
melanoma patients.
Vaccines to generate specific
immune responses are the subject of intensive research for a number of tumours, notably
malignant melanoma and
renal cell carcinoma.
Sipuleucel-T is a vaccine-like strategy in late clinical trials for
prostate cancer in which
dendritic cells from the patient are loaded with
prostatic acid phosphatase peptides to induce a specific immune response against prostate-derived cells.
Allogeneic
hematopoietic stem cell transplantation ("bone marrow transplantation" from a genetically non-identical donor) can be considered a form of immunotherapy, since the donor's immune cells will often attack the tumor in a phenomenon known as
graft-versus-tumor effect. For this reason, allogeneic HSCT leads to a higher cure rate than autologous transplantation for several cancer types, although the side effects are also more severe.
The cell based immunotherapy in which the patients own Natural Killer cells(NK) and Cytotoxic T-Lymphocytes(CTL) are used has been in practice in Japan since 1990. NK cells and CTLs primarily kill the cancer cells when they are developed. This treatment is given together with the other modes of treatment such as Surgery, radiotherapy or Chemotherapy and called as
Autologous Immune Enhancement Therapy (AIET)
Hormonal therapy
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. In certain cancers, administration of hormone agonists, such as
progestogens may be therapeutically beneficial.
Angiogenesis inhibitors
Angiogenesis inhibitors prevent the extensive growth of blood vessels (
angiogenesis) that tumors require to survive. Some, such as
bevacizumab, have been approved and are in clinical use. One of the main problems with anti-angiogenesis drugs is that many factors stimulate blood vessel growth in cells normal or cancerous. Anti-angiogenesis drugs only target one factor, so the other factors continue to stimulate blood vessel growth. Other problems include
route of administration, maintenance of stability and activity and targeting at the tumor vasculature.
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 doctors generally have the therapeutic skills to reduce 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. This is an especially important aspect of care for those patients whose disease is not a good candidate for other forms of treatment. As most treatments for cancer involve significantly unpleasant side effects, a patient with little realistic hope of a cure may choose to seek palliative care only, eschewing more radical therapies in exchange for a prolonged period of normal living.
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. Improved
antiemetics such as
ondansetron and analogues, as well as
aprepitant have made aggressive treatments much more feasible in cancer patients.
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. Doctors have been reluctant to prescribe narcotics for pain in terminal cancer patients, for fear of contributing to addiction or suppressing respiratory function. The
palliative care movement, a more recent offshoot of the
hospice movement, has engendered more widespread support for preemptive pain treatment for cancer patients.
Fatigue is a very common problem for cancer patients, and has only recently become important enough for oncologists to suggest treatment, even though it plays a significant role in many patients' quality of life.
Research
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 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. At the same time, 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. There is no guarantee that a new treatment being tested or a standard treatment will produce good results. In children with cancer, a survey of trials found that those enrolled in trials were on average not more likely to do better or worse than those on standard treatment; this confirms that success or failure of an experimental treatment cannot be predicted.
Complementary and alternative
Complementary and alternative medicine (CAM) treatments are the diverse group of medical and health care systems, practices, and products that are not part of conventional medicine.
"Complementary medicine" refers to methods and substances used along with conventional medicine, while "alternative medicine" refers to compounds used instead of conventional medicine.
CAM use is common among people with cancer; a 2000 study found that 69% of cancer patients had used at least one CAM therapy as part of their cancer treatment.
Most complementary and alternative medicines for cancer have not been rigorously studied or tested. Some alternative treatments which have been investigated and shown to be ineffective continue to be marketed and promoted.
In pregnancy
The incidence of concurrent cancer during
pregnancy has risen due to the increasing age of pregnant mothers
and due to the incidental discovery of maternal tumors during prenatal ultrasound examinations.
Cancer treatment needs to be selected to do least harm to both the woman and her embryo/fetus. In some cases a
therapeutic abortion may be recommended.
Radiation therapy is generally out of the question, and chemotherapy always poses the risk of miscarriage and congenital malformations
.Little is known about the effects of medications on the child.
Even if a drug has been tested as not crossing the placenta to reach the child, some cancer forms can harm the placenta and make the drug pass over it anyway.
Some forms of skin cancer may even metastasize to the child's body.
Diagnosis is also made more difficult, since
computed tomography is infeasible because of its high radiation dose. Still,
magnetic resonance imaging works normally.
However,
contrast media cannot be used, since they cross the placenta.
As a consequence of the difficulties to properly diagnose and treat cancer during pregnancy, the alternative methods are either to perform a
Cesarean section when the child is viable in order to begin a more aggressive cancer treatment, or, if the cancer is malignant enough that the mother is unlikely to be able to wait that long, to perform an abortion in order to treat the cancer.
