Environmental pollution can be difficult to pinpoint as a source of cancer because cancer often develops years after exposure. However, there is a well-established link between asbestos and cancer. Researchers estimate that about 1% of cancer deaths are due to air, land, and water pollution.
Cancer progression
Cancer is a progressive disease that
goes through several stages. Each stage may produce a variety of
symptoms. Some symptoms are produced early and may occur due to a tumor
that is growing within an organ or a gland. As the tumor grows, it may
press on the nearby nerves, organs, and blood vessels. This causes pain
and some pressure, which may be the earliest warning signs of cancer. Other cancers cause general symptoms such as fatigue or loss of appetite.
Despite the fact that there are many kinds of cancers producing very different symptoms, the American Cancer Society (ACS) has established the following seven symptoms as possible warning signals of cancer.
changes in the size, color, or shape of a wart or a mole
a sore that does not heal
persistent cough, hoarseness or sore throat
a lump or thickening in the breast or elsewhere
unusual bleeding or discharge
chronic indigestion or difficulty in swallowing
any change in bowel or bladder habits
Many other diseases can produce the same symptoms. However, individuals
with these symptoms should be checked promptly especially if the
symptoms have lingered for some time. For all types of cancer, the earlier a cancer is diagnosed and treated, the better the chance of surviving it. Many cancers, such as breast cancer,
may not have any early symptoms. Therefore, it is important to undergo
routine screening tests such as breast self-exams and mammograms as
well as being alert to the above mentioned symptoms.
Diagnosis
Diagnosis begins with a thorough physical examination and a complete
medical history. The doctor will observe and palpate (apply pressure by
touch) different parts of the body in order to identify any variations
from the normal size, feel, or texture of the organ or tissue. As part
of the physical examination, the doctor will inspect the oral cavity.
By focusing a light into the mouth, he will look for abnormalities in
color, moisture, surface texture, or presence of any thickening or sore
in the lips, tongue, gums, the hard palate on the roof of the mouth,
and the throat. To detect thyroid cancer,
the doctor will observe the front of the neck for swelling. He may
gently manipulate the neck and palpate the front and side surfaces of
the thyroid gland (located at the base of the neck) to detect any
nodules or tenderness. The doctor will also palpate the lymph nodes in
the neck, under the arms, and in the groin. Many illnesses and cancers
cause a swelling of the lymph nodes.
A thorough examination of the skin will detect sores that have been
present for more than three weeks and that bleed, ooze, or crust;
irritated patches that may itch or hurt, and any change in the size of
a wart or a mole.
Examination of the female pelvis is used to detect cancers of the
ovaries, uterus, cervix, and vagina. In the visual examination, the
doctor looks for abnormal discharges or the presence of sores. Then,
using gloved hands the physician palpates the internal pelvic organs
such as the uterus and ovaries to detect any abnormal masses. Breast
examination includes visual observation where the doctor looks for any
discharge, unevenness, discoloration, or scaling. The doctor palpates
both breasts to feel for masses or lumps.
For males, inspection of the rectum and the prostate is part of the
physical examination. The doctor inserts a gloved finger into the
rectum and rotates it slowly to feel for any growths, tumors, or other
abnormalities. The doctor also conducts an examination of the testes,
where he observes the genital area and looks for swelling or other
abnormalities. The testicles are palpated to identify any lumps,
thickening or differences in the size, weight and firmness.
If the doctor detects an abnormality on physical examination or the patient has some symptom that could be indicative of cancer,
the doctor will order diagnostic tests. Laboratory studies of sputum
(sputum cytology), blood, urine, and stool can detect abnormalities
that may indicate cancer. Sputum
cytology is a test where the phlegm that is coughed up from the lungs
is microscopically examined. It is often used to detect lung cancer. A blood test that indicates certain cancers (e.g., prostate cancer)
is easy to perform, relatively inexpensive, and practically risk-free.
Blood tests can be either specific or non-specific. In certain cancers,
the cancer cells release specific
proteins (called tumor markers), and blood tests can be used to detect
the presence of these markers, which indicate the presence of cancer.
However, with a few exceptions, tumor markers are not used for routine
screening of cancers because several non-cancerous conditions also
produce positive results. Blood tests tend to be more useful in
monitoring the effectiveness of the treatment or in following the
course of the disease and detecting recurrent disease.
Imaging tests such as computed tomography scans (CT scans), magnetic
resonance imaging (MRI), ultrasound, and fiber optic scope examinations
help the doctors determine the location of tumors. Conventional x rays
are often used for initial evaluation because they are relatively
cheap, painless, and easily accessible. In order to increase the
information obtained from a conventional x ray, air or a dye may be
used as a contrast medium to outline or highlight parts of the body.
The most definitive diagnostic test for cancer is the biopsy, wherein a piece of tissue is surgically removed for microscope examination. Besides confirming a cancer, the biopsy provides information about the type of cancer, the stage it has reached, the aggressiveness of the cancer,
and the extent of its spread. Since a biopsy provides the most accurate
information, it is considered the definitive diagnostic test.
Screening examinations conducted regularly by healthcare
professionals can result in the detection of cancers of the breast,
colon, rectum, cervix, prostate, testis, tongue, mouth, and skin at
early stages. It cannot be emphasized too much that the earlier a cancer
is detected, the higher the rate of successful treatment. Some routine
screening tests recommended by the ACS are sigmoidoscopy for colorectal
cancer, mammography for breast cancer, pap smear for cervical cancer, and the PSA blood test for prostate cancer. Self-examinations for cancers of the breast, testes, mouth, and skin can also help in detecting the tumors early.
Recent advances in molecular biology and cancer
genetics have contributed to the development of several tests designed
to assess one's risk of getting cancers. These new techniques include
genetic testing to identify mutations in certain genes that have been
linked to particular cancers. As of 2007, however, there are
limitations to genetic testing and its utility and ethical use appear
ambiguous.
Treatment
The aim of cancer treatment is to remove all or as much of the tumor as possible, kill all lingering cancer cells, and prevent the spread or recurrence of malignant cells. While devising a treatment plan for cancer, the likelihood of curing the cancer has to be weighed against the side effects of the treatment. If the cancer is very aggressive and a cure is not possible, treatment is aimed at relieving the symptoms and controlling the cancer for as long as possible (palliative treatment). Cancer
treatment can take many different forms, and it is always tailored to
the individual patient. Decisions about appropriate treatment depend on
the type and location of cancer, the
extent to which it has already spread, the patient's age, sex, general
health status, personal treatment preferences, and access to
specialized health care facilities when certain treatments are
desirable. The major types of treatment are: surgery, radiation,
chemotherapy, immunotherapy, hormone therapy, and bone-marrow
transplantation.
Surgery Surgery is the removal of a visible tumor and some
surrounding tissue under general, regional, or local anesthesia. It is
the most frequently used cancer treatment. During the course of a cancer, surgery can be used for many purposes.
Treatment. Treatment of cancer by
surgery involves removal of the tumor to cure the disease. Surgery is
most effective when a tumor is small and confined to one area of the
body (a condition called "cancer in situ"). Along with the tumor, some of the normal surrounding tissue is also removed to help ensure that no cancer
cells remain in the area. The lymphatic system carries lymph throughout
the body through. Lymph is a clear fluid that contains immune system
cells that fight infection. Since cancer usually spreads via the lymphatic system, adjoining lymph nodes may be examined for cancer cells and sometimes are removed as well.
Preventive surgery. Preventive or prophylactic surgery involves removal
of an abnormal looking area that is likely to become malignant over
time. For example, polyps are removed from the colon in people at high
risk of developing colon cancer before they can become malignant as are certain skin growths. Very high-risk women with a family history of breast cancer
who carry the BRCA1 and BRCA2 genes may want to discuss preventative
mastectomy (breast removal) with their physician. As of 2007,
preventive breast surgery remained controversial.
Diagnostic purposes. The most definitive tool for diagnosing cancer
is a biopsy. Sometimes a biopsy can be performed by inserting a needle
through the skin and drawing out a sample of cells. At other times, the
only way to obtain a tissue sample for biopsy is by performing an open
surgical operation.
Cytoreductive surgery. This is a procedure where the doctor removes as much of the cancer
as possible, and then treats the remaining area with radiation therapy
or chemotherapy or both. It is often done to relieve painful symptoms.
Palliative surgery. The goal of this surgery is to prolong life and to improve the quality of life rather than cure the cancer. It is done when the tumor is so large or has spread so much that removing all the cancer
is not an option. For example, a tumor in the abdomen may be so large
that it may press on and block a portion of the intestine interfering
with digestion and causing pain and vomiting. Debulking surgery may
remove a part of the blockage and relieve the symptoms. In tumors that
are dependent on hormones, removal of the organs that secrete the
hormones is an option. For example, in prostate cancer,
the release of testosterone by the testes stimulates the growth of
cancerous prostate cells. A man may choose to undergo an orchiectomy
(removal of testicles) to slow progress of the disease. Similarly, in a
subtype of aggressive breast cancer, removal of the ovaries (oophorectomy) will stop the synthesis of hormones by the ovaries and may slow the progression of the cancer.
Radiation therapy Radiation kills both malignant and
normal cells. Radiation, sometimes with other non-surgical treatments,
is used when surgery is not possible or desirable. More often,
radiation is used in conjunction with surgery and chemotherapy,
immunotherapy, and/or hormone therapy. Radiation can be used either
before or after surgery and be either external or internal. In the
external form, the radiation is aimed at the tumor from outside the
body. In internal radiation (brachytherapy), a radioactive substance in
the form of pellets or liquid is placed at the cancerous site by means
of a pill, injection, or insertion in a sealed container. This helps
target the radiation directly to the tumor and spare healthy cells.
Chemotherapy: Chemotherapy is the use of drugs to kill cancer
cells; unfortunately chemotherapy drugs often kill or damage healthy
cells too. Chemotherapy destroys the small clusters of hard-to-detect cancer cells that have spread beyond the primary tumor or loose cancer
cells circulating in the body. Chemotherapeutic drugs can be taken
either orally (by mouth) or intravenously, and may be given alone or in
conjunction with surgery, radiation, and hormone therapy. They often
have side effects that range from uncomfortable to serious. When
chemotherapy is used before surgery or radiation, it is known as
primary or neoadjuvant chemotherapy. Neoadjuvant chemotherapy can be
used effectively to reduce the size of a tumor before surgery .
However, the toxic effects of neoadjuvant chemotherapy are severe. In
addition, it may make the body less tolerant to the side effects of
other treatments, such as radiation therapy, that follow the surgery.
The more common use of chemotherapy is as an adjuvant therapy that is
used to supplement and enhance the effectiveness of other treatments.
For example, after surgery, adjuvant chemotherapy can be given to
destroy cancerous cells that still remain in the body. Chemotherapy
drugs kill both healthy and cancer cells. Researchers are working on finding new drugs that are more toxic to cancer cells and less toxic to healthy cells in order to increase the effectiveness of chemotherapy and reduce the side effects.
Immunotherapy Immunotherapy, also called biologic
therapy or biotherapy, uses substances that either stimulate the body's
own immune system to destroy cancer
cells or provides large quantities manmade antibodies (disease fighting
proteins). This is a type of targeted therapy. Large amounts of
antibodies of a single type (called monoclonal antibodies) that react
with specific receptors on cancer
cells are made in the laboratory. When given to the patient, they
inactivate or destroy those cells containing that specific receptor but
do not react with or damage other cells. Successful immunotherapy drugs
have been developed that target two types of breast cancer
cells and one that inhibits the growth of blood vessels into tumors.
Without a blood supply, tumors cannot increase in size. Immunotherapy
is an area of active research.
Hormone therapy: Hormone therapy is standard treatment
for cancers that are hormone-dependent and grow faster in the presence
of particular hormones. These include cancer
of the prostate, breast, and uterus. Hormone therapy involves blocking
the production or action of these hormones. Tamoxifen, an anti-estrogen
breast cancer drug, is the best known of several successful hormone therapy drugs.
Bone marrow transplantation
Bone marrow is the tissue within the bone cavities that contains
blood-forming cells. Healthy bone marrow tissue constantly replenishes
the supply of blood cells. Sometimes, cancer
develops in the bone marrow, resulting in the production of malformed,
nonfunctional blood cells. Other times, the drugs or radiation needed
to destroy cancer cells also destroys
bone marrow cells, reducing the supply of new blood cells to
dangerously low levels. Replacing the bone marrow with healthy cells
counteracts these effect. A bone marrow transplant is the
removal of marrow from one person and the insertion of the
blood-forming cells in someone else. When bone-marrow transplantation
is used to cure certain blood marrow cancers (leukemias), chemotherapy
and radiation must be used to kill all the cancer patient's bone marrow cells. After these cells die, healthy donor bone marrow cells are injected into the cancer
patient. In a successful transplant, these cells take up residence in
the bones and begin producing healthy blood cells. Bone-marrow
transplantation is a complex, often risky, process that involves
finding a donor whose cell surface proteins match as closely as
possible that of the recipient. Matching is necessary so that the
recipient's immune system does not attack and destroy the donor cells
as foreign invaders.
Treatment and prevention of cancers continues to be the focus of a great deal of research. Research into new cancer therapies includes cancer-targeting gene therapy, virus therapy, and the development of drugs that stimulate destruction of cancer
cells but not healthy cells. However, all new therapies take years of
clinical testing and research before becoming widely available.
Individuals interested in volunteering for a clinical trial of a new
drug or cancer therapy can find a list of current clinical trials accepting patients at http://www.clinicaltrials.gov . There is not cost to the patient for participating in a clinical trial. Many different specialists work together as a team to treat cancer patients. An oncologist is a physician who specializes in cancer
care. The oncologist provides chemotherapy, hormone therapy, and any
other non-surgical treatment that does not involve radiation. The
oncologist often serves as the primary physician and coordinates the
patient's treatment plan.
The radiation oncologist specializes in using radiation to treat cancer, while the surgical oncologist performs the operations needed to diagnose or treat cancer.
Gynecologist-oncologists and pediatric-oncologists, as their titles
suggest, are physicians involved with treating women's and children's
cancers respectively. Many other specialists also may be involved in
the care of a cancer patient. For
example, hematologists specialize in disorders of the blood and are
consulted in case of blood cancers and bone marrow cancers or when the
patient's blood count becomes seriously abnormal during treatment. Tissue samples that are removed for biopsy are sent to a laboratory,
where a pathologist examines them to determine the type of cancer
and extent of the disease. Hospice nurses tend the terminally ill in
their homes or hospice settings. Only some of the specialists who are
involved with cancer care have been
mentioned above. There are many other specialties, and virtually any
type of medical or surgical specialist may become involved with care of
the cancer patient should it become necessary.
Complementary and alternative treatment
Many complementary and alternative medicine (CAM) treatments claim
to help prevent or cure various cancers. Complementary therapies are
those used in addition to traditional Western medicine, while
alternative therapies are used in place of conventional Western
medicine. Many of these therapies are successfully used to treat
symptoms caused by cancer or cancer treatment, rather than as a way of curing cancer. Complementary and alternative treatment of cancer
is a complicated arena. CAM treatments may interact with each other and
with conventional treatments in ways that are not always well
understood but that may alter the expected treatment results.
Individuals should discuss all CAM therapies with their physician
before beginning a treatment. In some cases CAM is effective in relieving or reducing the symptoms associated with cancer and cancer treatment. For example, acupuncture has been beneficial in relieving pain in some cancer
patients. Bodywork therapies such as massage and reflexology ease
muscle tension and may alleviate side effects such as nausea and
vomiting. Homeopathy and herbal remedies used in Traditional Chinese
Medicine may alleviate some of the side effects of radiation and
chemotherapy. In the United States, the National Center for
Complementary and Alternative Medicine (NCCAM) within the National
Institutes of Health supervises clinical trials of many CAM cancer therapies.
Certain foods, mainly vegetables, fruits, and grains, are believed by
many people to offer protection against various cancers. However,
isolation of an individual constituents with anti-cancer
activity has proven difficult. In some laboratory studies, vitamins
such as A, C, and E, as well as compounds such as isothiocyanates and
dithiolthiones found in broccoli, cauliflower, and cabbage, and
beta-carotene found in carrots have been shown to protect against cancer
or slow its growth. Other studies, however, have shown that large doses
of some of these substances can also cause serious side effects. As of
2007, the ACS recommended a diet high in fruits, vegetables, and whole
grains and low in calories and fats as the best way to maintain health.
The ACS does not recommend taking mega-doses of any dietary supplements
to cure or reduce the risk any cancer.
Prognosis: A cancer patient's prognosis is affected by many factors, particularly the type of cancer the patient has, the stage of the cancer, the extent to which it has metastasized, and the aggressiveness of the cancer.
In addition, the patient's age, general health status and the
effectiveness of the treatment being pursued also are important
factors. Many cancers are completely curable if detected and treated at
their early stages.
To help put into perspective the future course and outcome of a cancer
and the likelihood of recovery from it, doctors often use statistics.
Five- or ten-year survival rates are the most common measures used. The
number refers to the proportion of people with the cancer who are expected to be alive, five or ten years after initial diagnosis, compared with a similar population that is free of cancer. It is important to note that while statistics can give information about the average survival experience of cancer
patients in a given population, they cannot be used to indicate
individual prognosis, because no two patients are exactly alike.
Prevention According to nutritionists and epidemiologists
from leading universities in the United States, a person can reduce the
risk of developing cancer by following these guidelines.:
Eat a diet high in fruits and vegetables and low in animal fats.
Having regular screenings for common cancers such as those of the breast, colon, and prostate.
Exercise vigorously for at least 20 minutes every day or walk moderately for 10 hours a week.
Keep weight within normal limits; avoid excessive weight gain.
Avoid tobacco use (including exposure to second hand smoke).
Decrease or avoid consumption of animal fats and red meats.
Avoid excessive alcohol use (more than 2 drinks per day).
Avoid exposure to the sun during the midday hours when the sun's rays are the strongest.
Avoid risky sexual practices such as sex with multiple partners and sex without using a condom.
Avoid known carcinogens in the environment or work place.
In addition, following the advice of physicians in refraining from
certain activities or drugs that are proven as risk factors for certain
cancers can help lower one's cancer risk. For instance, while physicians have long known a small increased risk for breast cancer
was linked to use of HRT, the long-term The Women's Health Initiative
study released finding in 2003 found even relatively short-term use of
estrogen plus progestin hormone replacement therapy (HRT) is associated
with increased risk of breast cancer,
diagnosis at a more advanced stage of the disease, and a higher number
of abnormal mammograms. The longer a woman used HRT, the more her risk
increased.
Although embryonic stem cell research is in its infancy it is a fact that researchers have demonstrated that rogue stem cells often play a role in creating cancers. Theories persist that environmental causes are at work causing these rogue cells to develop into cancerous tumors etc.... However stem cell researchers are busy studying how this occurs and may soon offer help in alleviating these effects.
