Text A. Response to Treatment.

 

While being treated for cancer, people are assed to see how the cancer is responding to therapy. The most successful treatment produces a cure. A cure is defined as a complete remission in which all evidence of cancer disappears (complete response). Researchers sometimes estimate cures in terms of the 5-year or 10-year disease-free survival rates, in which the cancer completely disappears and doesn't recur within a defined period, often 5 or 10 years. With a partial response, the size of one or more tumors is reduced by more than half; this response can reduce symptoms and may prolong life, although a cancer eventually grows back. The least successful treatment produces no response.

Sometimes a cancer completely disappears but returns later; the interval between these two events is called the disease-free survival time. The interval from complete response to the time of death is the total survival time. In people who have a partial response, the duration of response is measured from the time of the partial response to the time when the cancer begins to enlarge or spread again.

Some cancers respond well to chemotherapy. Others improve but aren't cured. Some cancers (melanoma, kidney cell cancer, pancreatic cancer, brain cancer) respond poorly to chemotherapy and are termed resistant. Other cancers (breast cancer, small-cell lung cancer, leukemia) may have excellent initial responses to chemotherapy but after repeated treatment may develop resis­tance to the drugs. Because multidrug-resistant genes are found in both normal cells and cancer cells, exposure to one drug can make a tumor resistant to unrelated cancer drugs. Presumably these genes exist to provide cells with the means to escape destruction by a noxious material. As a result, the cell may pump out the drug in self-defense, making the therapy ineffective. Re­searchers are trying to determine how to sup­press the activity of these genes.

Acute lymphoblastic leukemia and acute myelogenous leukemia are two potentially curable cancers. Hodgkin's disease and many of the non-Hodgkin's lymphomas (diffuse large-cell lymphoma, Burkitt's lymphoma, and lymphoblastic lymphoma) are cured in about 80 percent of chil­dren and adults. Chemotherapy cures more than 90 percent of men who have advanced testicular cancer, and about 98 percent of women with choriocarcinoma (a cancer of the uterus).

Surgery. Surgery is one of the oldest forms of cancer therapy. Of the 1 million Americans who devel­oped cancer in 1988, 64 percent had surgery and 62 percent of that group were cured. Treatment and outlook (prognosis) are determined largely by judging the severity and spread of the cancer through a process called staging. Since some cancers can often be cured with surgery alone when treated in their early stages, seeing a doctor as soon as possible is vitally important.

Notes:

the cancer begins to enlarge or spread again рак начинает увеличиваться в размере или распространяться вновь

advanced testicular cancer распространенный рак яичек

Text B. Radiation Therapy.

 

Radiation preferentially destroys cells that divide rapidly. Usually this means cancer, but radiation can also damage normal tissues, especially tissues in which cells normally reproduce rapidly such as skin; hair follicles; the lining of the intestines, ovary, or testis; and the bone marrow. Accurately targeting the radiation therapy protects normal cells as much as possible.

Cells that have an adequate oxygen supply are more susceptible to the damaging effects of radiation. Cells closer to the center of a large tumor often have a poor blood supply and low oxygen levels. As the tumor shrinks, the surviving cells appear to obtain an improved blood supply, which may make them more vulnerable to the next dose of radiation. Dividing the radiation into a series of doses over a prolonged period increases the lethal effects on tumor cells and decreases the toxic effects on normal cells. Cells have the capacity to repair themselves after being exposed to radiation; the treatment plan aims for maximum repairs of normal cells and tissues.

Radiation therapy is usually performed with equipment called a linear accelerator. The rays are directed very closely to the tumor. How the rays will adversely affect normal tissues depends on how large an area is being irradiated and its proximity to the tissues. For example, radiation to tumors of the head and neck often causes inflammation of the mucous membranes in the nose and mouth, resulting in soreness and ulcerations. Radiation to the stomach or abdomen often uses inflammation of the stomach (gastritis) and of the lower intestine (enteritis), resulting in diarrhea.

Radiation therapy plays a key role in curing many cancers, including Hodgkin's disease, early-stage non-Hodgkin's lymphoma, squamous cell cancer of the head and neck, seminoma (a testicular cancer), prostate cancer, early-stage breast cancer, early-stage non-small-cell lung cancer, and medulloblastoma (a brain or spinal cord tu­mor). For early cancers of the larynx and prostate, the rate of cure is essentially the same with radi­ation therapy as with surgery.

Radiation therapy can reduce symptoms when a cure isn't possible, as in multiple myeloma and advanced lung, esophageal, head and neck, and stomach cancers. Radiation therapy can also re­lieve symptoms caused by metastases to the bones or brain.

Note:

divide rapidly делиться быстро (о клетке)

Text C. Chemotherapy.

Although an ideal anticancer drug would de­stroy cancer cells without harming normal cells, no such drug exists. Despite the narrow margin between benefit and harm, however, many people with cancer can be treated with anticancer drugs (chemotherapy) and some can be cured. Today the side effects of chemotherapy can be mini­mized.

Anticancer drugs are grouped into several cat­egories: alkylating agents, antimetabolites, plant alkaloids, antitumor antibiotics, enzymes, hor­mones, and biologic response modifiers. Often, two or more drugs are used in combination. The rationale to combination chemotherapy is to use drugs that work at different parts of the cell's metabolic processes, thereby increasing the likelihood that more cancer cells will be killed. In addition, the toxic side effects of chemotherapy may be reduced when drugs with different toxicities are combined, each at a lower dose than would be needed if one drug were used alone. Finally, drugs with very different properties are sometimes combined. For example, drugs that kill tumor cells may be combined with drugs that stimulate the body's immune system against cancer (biologic response modifiers).

Mustard gas, used as a weapon in World War I is an example of an alkylating agent. Alkylating agents interfere with the DNA molecule, altering its structure or function so that it can't replicate, which then prevents the cell from multiplying. The difference between a beneficial dose and harmful dose, however, is small. Side effects include nausea; vomiting; hair loss; bladder irritation (cystitis) with blood in the urine; low white blood cell, red blood cell, and platelet counts; low sperm count in men (and possible permanent sterility); and an increased risk of leukemia.

Antimetabolites are a broad group of drugs that interfere with steps in the synthesis of DNA or RNA, preventing cell replication. Besides causing the same side effects as alkylating agents, certain antimetabolites cause a skin rash, darkening the skin (increased pigmentation), or kidney failure.

Plant alkaloids are drugs that can stop cell division as it happens, preventing the formation of new cells. Side effects are similar to those of the alkylating agents.

Antitumor antibiotics also injure DNA, preventing cell replication. Side effects are similar to those of the alkylating agents.

A person with acute lymphoblastic leukemia may be given asparaginase, an enzyme that depletes the blood of the amino acid asparagines, which the leukemia needs for continued growth. Side effects include life-threatening allergic re actions, loss of appetite, nausea, vomiting, fever and high blood sugar levels.

Hormone therapies raise or lower levels of certain hormones to limit the growth of cancers that either depend on those hormones or are inhibited by them. For instance, some breast cancers need estrogen to grow. The antiestrogen drug tamoxifen blocks the effects of estrogen and may shrink the cancer. Similarly, prostate cancer may be inhibited by estrogen or antitestosterone drugs.

Side effects vary, depending on the hormone taken. Giving estrogen to a man may have femi­nizing effects, such as breast enlargement. Giving antiestrogen drugs to a woman may cause hot flashes and irregular menstrual periods.

Interferon, the first effective biologic response modifier, is now commonly used to treat Kaposi's sarcoma and multiple myeloma. Another type of immunotherapy uses immune-stimulated cells (lymphokine-activated killer cells) to specifically attack tumors, such as melanoma and kidney cell cancer. A treatment that uses antibodies to tumor cells, which are labeled with either a radioactive material or a toxin, has demonstrated effective­ness in treating some lymphomas.

Notes:

mustard gas горчичный газ

certain antimetabolites cause a некоторые антиметаболиты skin rash, darkening the skin являются причиной сыпи,

(increased pigmentation), пигментации на коже или

or kidney failure почечной недостаточности

 

Text D. Combination Therapy.

 

For some cancers, the best therapy is a com­bination of surgery, radiation, and chemotherapy. Surgery or radiation therapy treats cancer that is confined locally, while chemotherapy kills cancer cells that have escaped beyond the local region. Sometimes radiation or chemotherapy is given, before surgery to shrink a tumor, or after surgery to destroy any remaining cancer cells. Chemo­therapy combined with surgery improves the chances of survival for people with colon cancer, breast cancer, or bladder cancer that has spread to regional lymph nodes. Surgery and chemother­apy can sometimes cure advanced ovarian can­cer.

Cancer of the rectum has been successfully treated with chemotherapy and radiation ther­apy. In advanced colon cancer, chemotherapy ad­ministered after surgery can prolong the disease-free survival. About 20 to 40 percent of head and neck cancers are cured with chemotherapy fol­lowed by radiation therapy or surgery. For those who aren't cured, these treatments can relieve symptoms (palliative therapy).

Surgery, radiation therapy, and chemotherapy play definite roles in treating Wilms' tumor and embryonal rhabdomyosarcomas. In Wilms' tu­mor, a childhood kidney cancer, the goal of sur­gery is to remove the primary cancer, even if tu­mor cells have spread to places in the body far from the kidney. Chemotherapy is started at the time of surgery, and radiation therapy is given later to treat local areas of residual disease.

Unfortunately, some tumors (such as those in the stomach, pancreas, or kidney) respond only partially to radiation therapy, chemotherapy, or a combination of the two. Nevertheless, these therapies can relieve pain from pressure or symp­toms that result when the tumor infiltrates the surrounding tissues. Some resistant tumors (for example, non-small-cell lung cancer, esophageal cancer, pancreatic cancer, kidney cancer) can be treated to increase survival time. Progress in can­cer therapy has come with better combinations of drugs, altered dosages, and better coordina­tion with radiation therapy.

Notes:

shrink a tumor уменьшать, удалять опухоль

surrounding tissues окружающие ткани

respond only partially to therapy отвечать частично на лечение