For decades, the most common treatment plan for a woman with early stage breast cancer included surgery to remove the tumor, followed by chemotherapy to eliminate any potential stray cancer cells circulating in the system. But a landmark study now concludes most women with early breast cancer can safety forego chemotherapy. This shift in thinking about when—or whether—to prescribe chemotherapy applies to other types of cancer too. Thanks to genetic research on cancer, the cancer treatment model is shifting away from chemotherapy to targeted therapies—and, in some cases, no drug treatment at all.
Doctors have used medications to treat illness for thousands of years. As cancer became more prevalent throughout the 19th century, researchers developed powerful new medications, oftentimes given in a mixture or “cocktail” to treat cancer. Chemotherapy drugs interfere with a cancer cell’s ability to multiply, which can significantly reduce the number of cancer cells circulating in the body or eliminate them altogether. Doctors traditionally have used chemotherapy in combination with other cancer treatments, like radiation therapy or surgery.
Chemotherapy can be very effective at eliminating or suppressing cancer in the body, but because chemotherapy is delivered through the bloodstream the treatment also can cause several serious side effects involving other healthy parts of the body. Many people who receive chemotherapy report severe nausea, vomiting, hair loss, and memory problems that can occur after chemotherapy treatment. Chemotherapy also can suppress the immune system, which makes the body more susceptible to infection. A desire to eliminate these side effects coupled with an increasing understanding of cancer genetics has led researchers to develop new cancer therapies tailored to how certain cancers cells grow and the specific characteristics of a person’s tumor.
As researchers continue to study the role of genes and proteins in cancer, their discoveries are paving the way toward a more personalized approach to cancer treatment. Chemotherapy employs a nonselective approach to cancer treatment: the drugs are toxic to healthy cells along with the malignant ones. On the other hand, scientists design targeted therapies to focus in on cancer cells and other targets in the body that cancer cells need to grow and spread. Targeted therapies also affect healthy cells, but to a much lesser degree than do chemotherapy drugs. Targeting the tumor instead of taking a broad-spectrum approach confers several benefits to the patient, including potentially fewer side effects and more effective cancer destruction.
Not all types of cancer can currently be treated using targeted therapies. Although targeted therapy for cancer may seem logical, the process of designing and creating a targeted therapy and using it safely in people is a long process. Many targeted therapies are being developed for a variety of cancers. However, the most common cancers currently treated by targeted therapy include breast cancer, colorectal cancer, lung cancer, blood cancer, and melanoma.
Targeted therapy works by taking advantage of the specific characteristics of cancer cells—such as the particular proteins (or amounts of protein) it makes or a defect in its genetic code—and then focusing treatment on those factors. To determine if you would benefit from a targeted therapy, your doctor first needs to analyze your cancer’s genetic makeup.
Types of targeted cancer therapies include:
Monoclonal antibodies. Also known as mAbs, these proteins are made by cells in a laboratory. When administered to the cancer patient, the antibodies attach to the surface of cancer cells and either deliver toxins into the cell or disrupt their function, destroying the cancer cells and tumor. Monoclonal antibodies also can serve as a “flag” to identify cancer cells more clearly to the immune system.
Small-molecule drugs. Taken by mouth, these pills contain tiny molecules that can enter a cell and alter its behavior. One type of small-molecule therapy, for example, stops the production of blood vessels in tissue surrounding a tumor. Without a blood supply, the tumor cannot survive.
Hormone therapy. Hormones that stimulate cancer cell growth make good anticancer targets. Drugs that reduce hormone production or block its function also inhibit cancer cell growth.
Examples of targeted therapies include:
Checkpoint inhibitors.These drugs boost the body’s immune system to respond to a tumor and, at the same time, make it more difficult for cancer cells to resist the immune system attack. Checkpoint inhibitors are usually monoclonal antibodies.
Epidermal growth factor receptor (EGFR) inhibitors. Many tumors produce excessive amounts of a protein called EGFR, which makes it a good target. An EGFR inhibitor stops or disrupts production of this protein, which slows or halts cancer growth. EGFR inhibitors are either monoclonal antibodies or small molecules.
Human epidermal growth factor (HER2) therapy. HER2 is another growth factor receptor that stimulates cell growth. Patients with breast and other cancers that overproduce HER2 protein may be candidates for monoclonal antibodies and small molecules that block HER2 function.
While it used to be commonplace for everyone diagnosed with cancer to receive chemotherapy, doctors can now use genetic testing to determine whether or not a person is likely to benefit from this treatment. A recent, large study confirmed that the vast majority of women with a particular type of hormone receptor-positive, early breast cancer do not benefit from receiving treatment beyond surgery to remove the tumor and hormone therapy.
This ability of doctors to discover if chemotherapy would be beneficial or not for an individual patient likely means far fewer people will undergo chemotherapy in the future, at least for breast cancer. Moving away from chemotherapy and harnessing the power of more targeted therapies will spare many people from the unpleasant side effects it can cause.
