865
CHAPTER TWENTY-TWO
Reproductive System
lower doses can temper some of the side effects
of these powerful drugs.
Newer treatments developed specifically
for breast cancer are easier to tolerate and can
be extremely effective. They are usually given
after the standard therapies, but in the future
may become a first line of attack. Three types
of drugs keep signals (estrogen and growth fac-
tors) from stimulating cancer cells to divide:
1. Selective estrogen receptor modulators
(SERMs), such as tamoxifen and raloxifene,
block estrogen receptors. About half of
people with breast cancer have receptors
for estrogen on their cancer cells.
2. Aromatase inhibitors block an enzyme
required for tissues other than those
of the ovaries to synthesize estrogens.
These drugs are used in women past
menopause, whose ovaries no longer
synthesize estrogen. They are prescribed
after a five-year course of a SERM.
3. Trastuzumab can help people whose
cancer cells bear too many receptors
that bind a particular growth factor. It
is a monoclonal antibody, based on an
immune system protein. Trastuzumab
blocks the growth factor from signaling
cell division. Marketed as Herceptin,
this drug treats a particularly aggressive
Eighty percent of the time, a breast lump
is a sign of fibrocystic breast disease, which is
benign (noncancerous). The lump may be a cyst
or a solid, F
brous mass of connective tissue called
a F
broadenoma. Treatment for F
brocystic breast
disease includes vitamin E, synthetic androgens,
and lowering ca±
eine intake.
Surgery, Radiation, and
Chemotherapies
If biopsied breast cells are cancerous, treatment
usually begins with surgery. A lumpectomy
removes a small tumor and some surrounding tis-
sue; a simple mastectomy removes a breast; and a
modiF
ed radical mastectomy removes the breast
and surrounding lymph nodes but preserves the
pectoral muscles. Radical mastectomies, which
remove the muscles too, are rarely done any-
more. In addition, a few lymph nodes are typically
examined, which allows a physician to identify
the ones that are a±
ected and must be removed.
Most breast cancers are then treated with
radiation and combinations of chemotherapeutic
drugs, plus sometimes newer drugs targeted to
certain types of breast cancer. Standard chemo-
therapies kill all rapidly dividing cells, and those
used for breast cancer include ²
uorouracil, doxo-
rubicin, cyclophosphamide, methotrexate, and
paclitaxol. Protocols that provide more frequent,
form of the disease that strikes younger
women.
Prevention Strategies
Health-care providers advise women to have
baseline mammograms by the age of forty, and
yearly mammograms after that, or beginning at
age fifty, depending upon medical and family
histories. Although a mammogram can detect a
tumor up to two years before it can be felt, it can
also miss some tumors. Thus, breast self-exam is
also important in early detection.
Genetic tests can identify women who have
inherited certain variants of genes—such as
BRCA1, BRCA2, p53,
and
HER-2/neu
—that place
them at high risk for developing breast can-
cer. Some of these women have their breasts
removed to prevent the disease. Only 5% to 10%
of all breast cancers arise from an inherited ten-
dency. Much research seeks to identify the envi-
ronmental triggers that contribute to causing
the majority of cases. Gene expression proF
ling
is beginning to be used to identify which drugs
are most likely to help particular patients, such
as those with leukemia, as described in Clinical
Application 14.2 (pp. 536–537). Gene expression
proF
ling for breast cancer can also predict risk of
recurrence after surgery. This type of information
is important in choosing follow-up treatment.
effectiveness. It is slightly less effective than combined hor-
mone contraceptives.
Injectable Contraception
An intramuscular injection of Depo-Provera (medroxy-
progesterone acetate) protects against pregnancy for three
months by preventing maturation and release of a secondary
oocyte. It also alters the uterine lining, making it less hospi-
table for a developing embryo. Depo-Provera is long-acting;
it takes ten to eighteen months after the last injection for the
effects to wear off.
Use of Depo-Provera requires a doctor’s care, because
of potential side effects and risks. The most common side
effect is weight gain. Women with a history of breast cancer,
depression, kidney disease, high blood pressure, migraine
headaches, asthma, epilepsy, or diabetes, or strong family
histories of these conditions, should probably not use this
form of birth control.
A large dose of high-potency estrogens can prevent implantation of
a developing embryo in the uterus. Such a “morning-after pill,” taken
shortly after unprotected intercourse, promotes powerful contrac-
tions of smooth muscle in a woman’s reproductive tract. This may
dislodge and expel a fertilized egg or early embryo. However, if the
embryo has already implanted, this treatment may harm it.
PRACTICE
60
Describe two methods of contraception that use mechanical
barriers.
61
What action can increase the e±
ectiveness of chemical
contraceptives?
62
What substances are contained in oral contraceptives?
63
How do combined hormone contraceptives, including oral
contraceptives, and injectable contraceptives prevent pregnancy?
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