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P A R T 2
Chemotherapeutic agents
the cell cycle include those in the breasts, testicles and
ovaries. Some cells take weeks, months or even years to
complete the cycle.
Cancer cells tend to move through the cell cycle at
about the same rate as their cells of origin. Malignant
cells that remain in a dormant phase for long periods
are difficult to destroy. These cells can emerge long after
cancer treatment has finished—after weeks, months or
years—to begin their division and growth cycle all over
again. For this reason, antineoplastic agents are often
given in sequence over periods of time, in the hope that
the drugs will affect the cancer cells as they emerge from
dormancy or move into a new phase of the cell cycle.
A combination of antineoplastic agents targeting differ
ent phases of the cell cycle is frequently most effective in
treating many cancers.
Oncology:
Cell cycle
The goal of cancer therapy, much like that of
anti-infective therapy, is to limit the offending cells to
the degree that the immune system can then respond
without causing too much toxicity to the host. However,
this is a particularly difficult task when using antineo
plastic drugs because, for the most part, these agents are
not specific to mutant cells, and affect normal human
cells as well. In most cases, antineoplastic drugs primar
ily affect human cells that are rapidly multiplying with
many cells in many phases of the cell cycle (e.g. those
in the hair follicles, GI tract and bone marrow). Much
research is being done to develop drugs that will affect
only the abnormal cells.
Imatinib
, released in 2001,
was the first of a growing number of drugs to target
the enzymes used by very specific abnormal cells. Other
agents that affect only the mechanisms of cancer cells
have been marketed. It is anticipated that many more
such drugs will be released in the near future.
Antineoplastic drugs are associated with many
adverse effects, with specific adverse effects occurring
with particular drugs. These effects are often unpleas
ant and debilitating. Some antineoplastic drugs exert
toxic effects on ova and sperm production, affecting
the person’s fertility. These agents are also usually selec
tive for rapidly growing cells, posing a danger to the
developing fetus during pregnancy. Consequently, preg
nancy is a contraindication to the use of antineoplastic
BOX 14.1
Drug therapy across the lifespan
Antineoplastic agents
CHILDREN
Antineoplastic protocols have been developed for the
treatment of most paediatric cancers. Combination therapy
is stressed to eliminate as many of the mutant cells as
possible. Dose and timing of these combinations is crucial.
Double checking of dose, including recalculating
desired dose and verifying the drug amount with another
nurse, is good practice when giving these toxic drugs to
children.
Children need to be monitored closely for hydration
and nutritional status.The nutritional needs of a child
are greater than those of an adult, and this needs to be
considered when formulating a care plan.
These children need support and comfort.They also
need to be allowed to explore and learn like any other
children. Body image problems, lack of energy and the
need to protect the child from exposure to infection can
isolate a child receiving antineoplastic agents.The total
care plan of the child needs to include social, emotional
and intellectual stimulation.
Monitor bone marrow activity very carefully and adjust
the dose accordingly.
ADULTS
The adult receiving antineoplastic drugs is confronted with
many dilemmas that the care provider needs to address.
Changes in body image are common, with loss of hair,
skin changes, gastrointestinal complaints and weight loss.
Fear of the diagnosis and the treatment is also common
with these individuals. Networking support systems and
providing teaching, reassurance and comfort can have a
tremendous impact on the success of the drug therapy.
PREGNANCY AND BREASTFEEDING
Pregnant and breastfeeding women should not receive
these drugs, which are toxic to the developing cells of
the fetus. Pregnant women who are diagnosed with
cancer are in a difficult situation.The drug therapy can
have serious adverse effects on the fetus, and not using
the drug therapy can be detrimental to the mother.
Education, support and referrals to appropriate specialists
are important. Breastfeeding women should find another
method of feeding the baby to prevent the adverse effects
to the fetus that occur when these drugs cross into breast
milk. Use of barrier contraceptives is urged when these
drugs are being used by women of childbearing age.
OLDER ADULTS
Older adults may be more susceptible to the CNS and
gastrointestinal effects of some of these drugs. Older
people should be monitored for hydration and nutritional
status regularly. Safety precautions should be instituted if
CNS effects occur, including increased lighting, assistance
with ambulation and use of supports.
Many older people have decreased renal and/or
hepatic function. Many of these drugs depend on the
liver and kidney for metabolism and excretion. Renal
and liver function tests should be done before (baseline)
and periodically during the use of these drugs, and dose
should be adjusted accordingly.
Protecting these people from exposure to infection and
injury is a very important aspect of their care. Older people
are naturally somewhat immunosuppressed because of
age, and giving drugs that further depress the immune
system can lead to infections that are serious and difficult
to treat. Monitor blood counts carefully, and arrange for
rest or reduced dose as indicated.
