Most are chemicals or sources of radiation, both of
which alter the molecular structure of cells in
ways that change their functions. The most com-
mon natural CARCINOGENis the ultraviolet radia-
tion of sunlight, which is responsible for nearly all
SKIN CANCER. Other carcinogens are manmade,
notably industrial chemicals such as formaldehyde
and vinyl chloride. Many manufacturing processes
use these and other carcinogenic chemicals; it is
nearly impossible to avoid exposure to them.
Aging and cancer Genetic damage to cells may
also occur as a consequence of natural deteriora-
tion within cells that takes place with aging. Cells
become less able to repair themselves and expo-
sure to carcinogens leaves them more vulnerable,
allowing errant growth and division. Some can-
cers that are more common in advanced age are
also less harmful to health overall. For example,
researchers estimate that 90 percent of men over
age 85 have prostate cancer, yet in most of them
the cancer is so slow growing that it does not
require treatment.
Traditions in Medical HistorySurgery was the first treatment for cancer. Even
ancient documents record procedures for removal
of tumors. However, the development of ANESTHE-
SIAgave surgery its big boost as treatment for can-
cer, allowing surgeons to more selectively remove
cancerous tumors. Though the operations were
often extensive and traumatic, they were able to
save lives.
RADIATION THERAPY was the next treatment
developed for cancer. Though doctors began using
X-rays on tumors shortly after the discovery of X-
rays in the late 19th century, the treatment was
often more dangerous than the cancer. Radiation
BURNS and radiation sickness were common as
doctors struggled to find a balance between
enough radiation to kill the tumor and not
enough radiation to kill the patient. Finally, in the
middle of the 20th century advances in technol-
ogy and understanding made it possible for radia-
tion to achieve this balance.
For centuries folk medicine contained various
substances purported to treat cancer, some of
which have become the basis for contemporary
CHEMOTHERAPY(such as the camptothecins, vinca
alkyloids, and taxanes). During the first half of the
20th century doctors realized that one SIDE EFFECT
of poisonous mustard gas, used as a weapon of
war, was that it eradicated certain types of cancer.
Further exploration resulted in the first class of
therapeutic chemotherapy agents, the alkylating
agents.
In the later decades of the 20th century,
researchers made significant breakthroughs in
understanding the functions of the immune sys-
tem and were able to develop methods to take
advantage of the body’s own mechanisms for
fighting cancer. IMMUNOTHERAPYis now at the fore-
front of cancer research.Breakthrough Research and Treatment Advances
Cancer treatment focuses on removing or dis-
abling cancer cells so they can no longer grow and
divide. Though cancer remains the second-leading
cause of death in the United States, successes in
treatments since the 1990s have improved the
outlook significantly. Nearly 10 million Americans
live with their cancer under control, in REMISSION,
or cured. Treatment is so often curative for basal
cell carcinoma (BCC) and squamous cell carci-
noma (SCC), the two most common types of SKIN
cancer, that cancer statistics do not include these
cancers among them.
As researchers learn more about cancer, they
are discovering ways to bolster the immune sys-
tem’s ability to detect and eradicate cancer cells
before they gain enough momentum to establish
themselves as tumors. Cancer vaccines currently
in investigational trials show great promise for
preventing the development of CERVICAL CANCER,
prostate cancer, and lymphoma, and for prevent-
ing the RECURRENCE of other types cancer. New
treatments specifically target molecular functions,
either in cancer cells or within the immune
response. These therapies reduce the unpleasant
side effects traditionally characteristic of cancer
treatment as well as improve the ability to eradi-
cate the cancer. Other therapies establish bound-
aries around the cancer, containing it so it cannot
spread and interfere with structures and functions.
Many types of cancer may soon be as manageable
(and perhaps preventable) through therapeutic
interventions and lifestyle modifications as other
chronic health conditions such as CARDIOVASCULAR
DISEASE(CVD) and DIABETES.Cancer 365