Chapter 10 Behavioral Factors in Cancer
cancer - A group of diseases characterized by the presence of new cells that
grow and spread beyond control. Humans, all animals, and even plants develop
cancers.
mutation theory - During the 19th century, a parasite or other infectious
organism was thought to be the cause. No such organism was ever found so the
idea that cancer comes about as the result of a "mutation" or change in the
structure of previously normal cells became accepted.
neoplastic - refers to tissue that is "new" and grows at abnormally rapid rates.
These cells rob the host of nutrients, oxygen, etc. and return nothing.
benign - As related to cancer, the cell growth is confined to a single tumor or
limited area.
malignant - tumors have the ability not only to grow but also to spread to other
parts of the body.
metastasize - To undergo metastasis, cells from the malignant tumor spread to
previously unaffected parts of the body by way of the cardiovascular or lymph
systems and start new colonies.
three types of cancers - make up "95%" of malignancies: (1) carcinomas, (2)
sarcomas, and (3) leukemia.
carcinomas - are cancers of the epithelial tissues that line the inner and outer
surfaces of the body (skin, stomach lining, mucous membranes).
sarcomas - are cancers of the "connective" tissues (bone, muscle, cartilage).
leukemia - Cancer that originates in the blood or blood-producing cells (such as
in the bone marrow or stem cells).
lymphomas - are a rare type of cancer which develops in the lymphoid tissues,
including the lymph nodes.
behavior and lifestyle - are the primary contributors to cancer development.
carcinogenic - Cancer-inducing.
overall death rates - from cancer climbed steadily in the U.S. from 1900 until the
mid 1990s when it began to decline (see Fig 10.1). While better treatments may
have helped, this decline was "primarily" due to lifestyle changes such as lower
smoking rates and better diet. Rates fell for men more than for women.
lung cancer - Has the highest "death rate" of all the cancers in the U. S. It
shows an interesting gender difference based in culture. Smoking became more
popular among women during the 1970s and 80s. This is reflected in death rates
that were still on the rise in 2001 (see Fig. 10.2). In contrast, the death rate for
men had begun a downward trend by the mid 90s. Women's death rates will
likely show a similar change in the coming years.
breast cancer - is "almost" exclusively a female problem (99.2%) but there are a
tiny number of cases that occur in males. It is the cancer with the highest
incidence and fastest increasing incidence (but not death rate).
Two suspected
causes for the increasing incidence are: (1) early diagnosis via the use of
"mamographies," and (2) increases in obesity which is a risk factor. It is
important to remember that with cancers, incidence, prevalence, and death rates
are VERY different things.
prostate cancer - is the cancer with the "highest incidence" among men.
Incidence increased in the 1980s with earlier and better diagnosis when the
"Prostate-Specific Antigen" (PSA) blood test was introduced.
colorectal cancer - has the "second highest death rate" (after lung cancer) in
the U. S.
Stomach cancer - death rates have dropped very dramatically (see Figs. 10.1
and 2). This is most likely a "technology related change." As modern
refrigeration improved, fewer and fewer foods were "cured" or preserved with
salts and other chemicals.
testicular cancer - is unusual that it almost always strikes young men in their
twenties. It rarely strikes older men as is the case with most cancers.
cancers on the increase - include Non-Hodgkin’s lymphoma, liver cancer, and
melanoma (a very deadly form of skin cancer).
inherent risk factors - include advancing age, family history (genetics) and
ethnic background.
advancing age - is the single "strongest" cancer risk factor as was the case with
cardiovascular disease. The singular and notable exception to this is testicular
cancer which strikes most frequently in young adulthood (as in the case of world
class cyclist Lance Armstrong).
the BRCA 1 and BRCA2 genes - normally provide the code for production of a
specific protein which protects against breast cancer. When these genes are
mutated, the protein is not produced and risk of breast cancer is greatly
increased.
ethnicity - African Americans have higher cancer rates than European
Americans who, in turn, have higher rates than Hispanic or Asian Americans. As
with cardiovascular disease, the causes for these differences are thought to be
primarily behavioral and psychosocial.
environmental risk factors - Prolonged and/or high level exposure to a number
of environmental risks such as radiation, asbestos, and petroleum products do
increase cancer risk. However, brief and/or low level exposure does NOT carry
the same risks (e.g., working in a nuclear plant is a risk factor but merely living
near one is not). Living near high voltage electrical power lines was long thought
to be a cancer risk but it actually is NOT.
behavioral risk factors - cigarette smoking is the primary cause of preventable
deaths in the U. S with a "risk ratio of apx. 23." The "dose-response"
relationship between cigarette smoking and cancer offer strong support for a
causal relationship. Smoking increases risk for several types of cancers, not just
lung cancer. When combined with other risk factors (e.g., exposure to
environmental pollutants, toxins, sedentary lifestyle, smoking has a "synergistic
effect").
synergistic effect - The effect of two or more risk factors is "greater than the
sum of each alone." In other words, the risk resulting from smoking and
excessive sun exposure is greater than we would expect from simply adding the
risk for each of the two.
diet and cancer - Although some research suggests a high fat diet as a risk
factor, the idea that the "Western Diet" (high in fats and processed foods) causes
colorectal cancer is NOT supported.
Some foods may help prevent cancer (thought the effects are weak ones) by
acting as "antioxidants." These work by preventing ingested (food) carcinogens
from being converted to the form in which they can damage cell DNA. Two of the
best candidates are lycopene (from cooked tomato products like in pizza) and
"flavonols" found in many fruits and vegetables. Vitamin C may offer some
protection against lung cancer.
water - is the most inexpensive food that may help prevent cancer. By diluting
the urine in the bladder, it may lower the concentration of carcinogens.
beta-carotene - A form of vitamin A found in abundance in vegetables such as
carrots and sweet potatoes may help fight breast cancer.
selenium - A trace element found in grain products and in meat from grain-fed
animals which may help in the prevention of colon and prostate cancer.
prudent diet - A dietary pattern high in fruits, vegetables, whole grains, low-fat
dairy products, fish, and poultry and low in red meat and refined grains (basically
a common sense diet with "MODERATION" being the key). Such a diet may
reduce one's overall risk.
Western diet - An eating pattern high in fatty and processed meats, refined
grains, sweets, and high-fat dairy products.
alcohol - is a considerably "weaker" risk factor than smoking or poor diet. It
may, however, play a particular role in liver cancer because: (1) the liver is
responsible for metabolizing alcohol, (2) high alcohol intake may cause
"cirrhosis" of the liver, and (3) cirrhotic livers are more likely to develop cancer.
Also, alcohol has a synergistic effect when combined with smoking.
sun exposure - Some exposure is necessary for vitamin D and other reasons.
However, excessive exposure has been clearly linked to skin cancer (there is
also a genetic component). Light skinned, blue eyed, fair haired people are at
higher risk for exposure-related skin cancer.
Kaposi’s sarcoma - A sexual (AIDS) related malignancy characterized by
multiple soft, dark blue or purple nodules on the skin, with hemorrhages.
non-Hodgkin’s lymphoma - A malignancy characterized by rapidly growing
tumors that are spread through the circulatory or lymphatic systems. It is related
to sexual activity (though NOT particularly to AIDS).
psychosocial risk factors - The accumulated evidence suggests that neither
neuroticism nor extraversion nor any other major component of personality poses
a significant cancer risk. Though Lance Armstrong might disagree, a strong
"fighting spirit" has NOT been proven to significantly impact cancer outcomes. At
present, the role of psychosocial factors in cancer incidence and outcome is
"UNCLEAR."
oncologist - A physician who specializes in the treatment of cancer.