Five major therapies

Cancer treatments include surgery, radiation, chemotherapy, biotherapy (also called immunotherapy), and hormonal therapy. Therapies may be used alone or in combination, depending on the type, stage, localization, and responsiveness of the tumor and on limitations imposed by the patient's clinical status.

Surgery, once the mainstay of cancer treatment, is usually combined with other therapies. Surgery may be performed as a biopsy to obtain tissue for study; as continued surgery to remove the bulk of the tumor; or before chemotherapy or radiation to debulk the tumor in hope of a better outcome.

Radiation therapy aims to destroy the dividing cancer cells while damaging non malignant cells as little as possible. Therapeutic radiation is either particulate or electromagnetic. Both types ionize matter and have cellular DNA as their target.

Radiation treatment approaches include external beam radiation and intracavitary and interstitial implants. The latter therapy requires personal radiation protection for all staff members who come in contact with the patient.

Normal and malignant cells respond to radiation differently, depending on blood supply, oxygen saturation, previous irradiation, and immune status. Generally, normal cells recover from radiation faster than malignant cells.

Radiation may be used palliatively to relieve pain, obstruction, malignant effusions, cough, dyspnea, ulcerations, and hemorrhage; it can also promote the repair of pathologic fractures after surgical stabilization and delay tumor spread.

Combining radiation and surgery can minimize radical surgery, prolong survival, and preserve anatomic function. For example, preoperative doses of radiation shrink a tumor, making it operable, while preventing further spread of the disease during surgery. After the wound heals, postoperative doses prevent residual cancer cells from multiplying or metastasizing.

Systemic adverse effects, such as weakness, fatigue, anorexia, nausea, vomiting, and anemia, may subside with antiemetics, steroids, frequent small meals, fluid maintenance, and rest. They are seldom severe enough to require discontinuing radiation but may require a dosage adjustment.

Chemotherapy includes a wide array of drugs, which may induce regression of a tumor and its metastasis. It's particularly useful in controlling residual disease and, as an adjunct to surgery or radiation therapy, it can induce long remissions and sometimes effect cures, especially in patients with childhood leukemia, Hodgkin's disease, choriocarcinoma, or testicular cancer. As a palliative treatment, chemotherapy aims to improve the patient's quality of life by temporarily relieving pain and other symptoms.

Some major chemotherapeutic agents include:

· alkylating agents and nitrosoureas, which inhibit cell growth and division by reacting with DNA

· antimetabolites, which prevent cell growth by competing with metabolites in the production of nucleic acid

· antitumor antibiotics, which block cell growth by binding with DNA and interfering with DNA-dependent ribonucleic acid synthesis

· plant alkaloids, which prevent cellular reproduction by disrupting cell mitosis

· steroid hormones, which inhibit the growth of hormone-susceptible tumors by changing their chemical environment.

The adverse effects of chemotherapy vary. Antineoplastic agents, toxic to cancer cells, can also cause transient changes in normal tissues, especially among proliferating body cells. For example, antineoplastic agents typically suppress bone marrow, causing anemia, leukopenia, and thrombocytopenia; irritate GI epithelial cells, causing nausea and vomiting; and destroy the cells of the hair follicles and skin, causing alopecia and dermatitis. Some chemotherapy drugs can also have permanent effects such as peripheral neuropathy.

The side effects of chemotherapy depend on the type and dose of drugs given and the length of time they are taken.

General side effects:

§ Hair loss

§ Mouth sores

§ Loss of appetite

§ Nausea and vomiting

§ Diarrhea

§ Increased chance of infections (from having too few white blood cells)

§ Easy bruising or bleeding (from having too few blood platelets)

§ Fatigue (from having too few red blood cells)

Long-term or late side effects: Some side effects may not go away or may not happen until years after treatment is finished. Examples include:

§ Infertility (being unable to have children)

§ Heart damage

§ Developing a second cancer

Chemotherapeutic drugs can be given orally, subcutaneously, intramuscularly, intravenously, intracavitarily, intrathecally, intraperitoneally, topically, intralesionally, and by arterial infusion, depending on the drug and its pharmacologic action; usually, administration is intermittent to allow for bone marrow recovery between doses. Dosages are calculated according to the patient's body surface area, with adjustments for general condition, degree of myelosuppression, and weight changes.

Biotherapy (also known as immunotherapy) relies on treatment agents known as biological response modifiers. Biological agents are usually combined with chemotherapeutic drugs or radiation therapy.

The main biotherapy agent classifications include interferons, interleukins, hematopoietic growth factors, and monoclonal antibodies. Interferons have antiviral, antiproliferative, and immunomodulary effects. The interleukins exert their effects on the T-lymphocytes. Monoclonal antibodies such as rituximab provide the most tumor-specific therapy for cancer by selectively binding to tumor cell surfaces.

Hormonal therapy is based on studies showing that certain hormones affect the growth of certain cancer types. For example, the gonadotropin-releasing hormone analogue leuprolide is used to treat prostate cancer.

Hormone-receptive tumors may be treated with aromatase inhibitors (anastrozole, exemestane, letrozole, testolactone), which inhibit the conversion of adrenal androgens to estrogens, thereby inhibiting the growth of hormone-dependent tumors.

Some adverse effects of these hormonal agents include hot flashes, sweating, impotence, decreased libido, nausea and vomiting, and blood dyscrasias.

Дата добавления: 2014-10-15