Chemotherapy: It's becoming tougher on cancer, less tough on you

Chemotherapy refers to drugs used to fight cancer that has already spread or is likely to. It’s known as a systemic treatment because the drugs typically travel in the bloodstream to tissues throughout the body. Chemotherapy is designed to kill cells that are growing rapidly—a hallmark of cancer.

Usually, chemotherapy is given following surgery or radiation therapy to destroy any lingering cancer cells. This is called adjuvant (add-on) therapy. Sometimes, however, doctors give chemotherapy first, to shrink a large tumor and make surgery possible. This approach is known as neoadjuvant chemotherapy.

How drugs are delivered

Which drugs are used and how they are administered depends primarily on the type of cancer a
person has. Often drugs are given in combination to increase their effectiveness and deter drug resistance. Chemotherapy cycles usually continue for up to several months.

The following are the main methods used to deliver drugs in chemotherapy.

• Intravenous (by vein). This method, which is the most common, provides rapid distribution of medication throughout the body. A small pump implanted under the skin may deliver the infusion over a period of hours or days.
• Injection. The drug may be injected under the skin, into a muscle, or directly into a skin cancer.
• Oral (by mouth). The drug is taken as a pill.
• Topical (on the skin). This approach works best for small skin cancers.
• Intra-arterial (into an artery). One example is delivering a drug into the liver through the hepatic artery. This floods the liver with the drug while minimizing the exposure of other tissues in the body.
• Intra-peritoneal. This approach involves delivery of a drug directly into the abdominal cavity. To achieve this, a catheter is usually inserted following the surgery to remove the tumor. One example of intra-peritoneal chemotherapy is that used to treat advanced ovarian cancer.

Side effects

Most people are familiar with the well-known side effects of chemotherapy. Cancer drugs usually target rapidly dividing cells, but cancer cells aren’t tthe only ones that fit that profile. Other rapidly growing cells are located in the hair follicles, digestive tract, reproductive system, and bone marrow. That’s why chemotherapy as it moves through the body may cause, for example, hair loss, nausea and vomiting, or anemia and fatigue. And, a woman’s menstrual cycle may be interrupted. But today medications are available that minimize certain chemotherapy side effects—notably nausea as well as anemia and low white blood cell counts, which result from the drugs’ effect on bone marrow.

Choosing a treatment

No two cancers are alike, which is why doctors are increasingly tailoring chemotherapy regimens to suit individuals. A person’s age, other medical problems, levels of certain hormones or other proteins, and genetic makeup—as well as personal preferences—can all influence the choice of
treatment.

The relatively new field of pharmacogenomics is helping doctors make better treatment choices. By identifying a person’s particular variant genes, doctors can predict, for example, how an individual’s body will process certain drugs. With this knowledge, they can then select the best drug and
dosage.

Taking better aim

Another new development is targeted therapy. While traditional chemotherapy takes a “shotgun” approach—for example, killing all fast-dividing cells it encounters—newer drugs, sometimes referred to as “designer drugs” or biologicals, are more selective. Researchers, using their knowledge of the key role of a particular gene or protein in a cancer, are designing drugs that act on that specific molecule. This makes it possible to kill cancer cells while sparing healthy ones. Other new drugs are aimed at factors that aid the growth of cancer cells, such as the formation of new blood vessels that feed the tumor. In the future, still other targets may be identified.

From Cancer Advances, the Mayo Clinic Women’s HealthSource, and the Johns Hopkins Medical Letter