UNDERSTANDING CANCER

Various Types of Cancer Treatment

Different types of cancer behave very differently — growing at different rates and responding to different treatments in a variety of ways. Many factors, including cancer type, genetic makeup of the cancer, and stage of disease, as well as a person’s age, overall health and family history, determine which treatment or combination of treatments is best for an individual’s unique cancer.

Oncologists and cancer researchers worldwide continue to discover, refine and improve the therapeutic weapons used to fight cancer. Today, new types of therapy are being used alone or in combination with traditional cancer treatments — surgery, chemotherapy and radiation therapy — offering more treatment options for many patients. The expansion of treatment options and the use of combinations of treatments mean that you will most likely be treated by a team of doctors, each with a different expertise, who will work together to coordinate a treatment plan that is best for you and your particular cancer.

The treatment of cancer can be defined in several ways, and it may be helpful to clarify some points before describing the specific types of treatment. First, primary treatment is the definitive treatment, or the treatment that is designed to potentially eliminate the disease. Surgery is often the primary treatment, but radiation therapy or chemotherapy may also be primary treatment approaches.

In some cases, treatment is given after primary treatment to destroy any microscopic deposits of cancer cells that may remain or that may be too small to be detected with laboratory testing or imaging studies. This treatment, known as adjuvant therapy, decreases the risk of recurrence, which can help extend survival. Treatment may also be given before primary treatment to help shrink a tumor, for example, to make it easier to surgically remove. This treatment is called neoadjuvant therapy.

Another point to clarify is that there is overlap in how many types of treatment are defined. For example, chemotherapy is defined as the use of drugs to kill cancer cells. This definition actually applies to any treatment involving drugs, including hormone therapy and targeted therapy, which you will learn about. However, chemotherapy usually means treatment with conventional anticancer drugs that have been used for years. Always ask your doctor for clarification if you do not understand the discussion of your treatment options.

Types of Treatment

To help you understand the various types of cancer treatments, here is a description of each:

Surgery

Most people with a solid cancerous tumor are treated with some type of surgical procedure. Surgical removal of a tumor offers the best chance for cure, especially if cancer cells have not spread beyond the original site to other parts of the body.

Many advances have been made in the techniques used for removing cancerous tumors, and less invasive approaches, such as laparoscopy or robotic surgery, can sometimes be used. These new techniques increase the likelihood of a shorter recovery time, with fewer side effects.

Chemotherapy

Chemotherapy is a cancer treatment that uses drugs to kill cancer cells. It is also popularly known as chemo for short. Chemotherapy may be given alone or in conjunction with surgery or radiation therapy to treat most types of cancer.

Chemo kills cells that divide rapidly. Rapid cell division is a main property of cancer cells. However, chemotherapy can also kill other types of cells that divide rapidly, including cells in hair follicles, bone marrow and the digestive tract, leading to some common side effects of chemo: hair loss (alopecia), a reduction in red and white blood cells and blood platelets (myelosuppression) that can cause anemia and a risk of infection, and inflammation of the lining of the mouth and digestive tract (mucositis) that can cause ulceration in the mouth, vomiting and diarrhea.

Chemotherapy may be given to cure cancer, prolong the patient’s life or lessen symptoms. Many cancer patients receive combination chemotherapy, which involves treating patients with a number of drugs at the same time. Combination chemotherapy is used because some cancer drugs are more effective when combined with other drugs.

Cancer patients may be given chemotherapy before surgery or radiation therapy to shrink the primary tumor — a therapy known as neo-adjuvant therapy. Patients may also be given chemotherapy after surgery or radiation therapy to help destroy any remaining cancer cells — a therapy known as adjuvant chemotherapy. So-called palliative chemotherapy is used to decrease the number of cancer cells, the size of a tumor, or the amount of cancer in the body and to increase life expectancy.

While some cancer cells grow rapidly, others grow slowly. Consequently, different cancer drugs are used to target the growth patterns of specific cancer cells. If you are diagnosed with cancer, your doctor will develop a treatment plan for you and determine the chemotherapy drug or drugs right for you. It’s important for you to discuss the plan with your doctor as well as the risks and benefits of the treatment he or she recommends to help your doctor decide what’s best for you.

Your doctor will determine the dosage and frequency of the chemotherapy you receive, depending on the type of cancer you have and the type of chemo you are taking.

Chemo may be given in the form of a pill or liquid that you may take at home; as a shot given in your doctor’s office, a hospital, cancer center, clinic or at home; intravenously with a needle or through a tiny tube (a catheter) in a hospital, cancer center or clinic; or as a cream rubbed onto your skin. Intravenous chemo is the most common form.

Some chemotherapy drugs may affect a woman’s ability to become pregnant while she is under treatment and in the future. If you are a woman who may want to have children in the future, tell your doctor before you begin treatment. Chemo can also decrease sexual desire in both women and men. However, the desire usually returns when treatment stops.

Conventional Chemotherapy

Conventional chemotherapy is referred to as systemic therapy because the drugs travel through the bloodstream to all parts of the body. Chemotherapy may be given intravenously (through a small tube inserted into a vein) or orally (by mouth).

Conventional chemotherapy is usually delivered in cycles, with treatment periods usually followed by recovery (rest) periods in an on-again, off-again manner. Treatment often consists of combinations of drugs, sometimes given together and sometimes given after each other (sequentially). A combination of chemotherapy drugs is known as a regimen.

Hormone Therapy

The growth of some cancers is driven by hormones that occur naturally in the body. For example, estrogen fuels the growth of some breast cancers, and testosterone plays an important role in the growth of prostate cancer. Hormone therapy acts to block the development of hormones, which in turn, slows or stops the progression of cancer.

Hormone therapy for breast cancer, also known as endocrine therapy, includes tamoxifen and aromatase inhibitors. These drugs are called antiestrogen agents because they inhibit the production of estrogen or interfere with its action.

Hormone therapy for prostate cancer involves either surgery or drugs. Surgical removal of the testicles eliminates the source of about 90% of testosterone in a man. Alternatively, several drugs are available to interfere with the production of testosterone. Hormone therapy in men is often referred to as androgen-deprivation therapy.

Radiation Therapy

Radiation therapy is the use of high-energy x-rays to destroy or damage cancer cells. Radiation treatments are given either externally, with use of a radiation machine known as a linear accelerator, or internally through radioactive material that is implanted in the body.

External-beam radiation therapy is the most common type of radiation therapy and is used for a wide variety of cancers. This type of treatment is similar to a conventional x-ray except that the radiation beams are strong enough to kill cancer cells. New techniques, such as intensity-modulated radiation therapy, enable doctors to target the radiation dose to the tumor better so that radiation beams can be delivered more precisely, causing less damage to healthy cells in the pathway of the radiation beam.

Radiation therapy can also be delivered directly through radioactive seeds that are implanted in or near a tumor. This type of radiation therapy is known as brachytherapy. The radioactive seeds used in brachytherapy may be temporary or may stay in place permanently. Temporary radioactive seeds are implanted and removed with the use of a catheter inserted into the part of the body with the tumor. Permanent seeds are inserted into tissues and will stop giving off radiation after a few weeks to months. Brachytherapy is done most often for prostate, gynecologic, head and neck, lung cancers and, most recently, for some cases of early stage breast cancer.

Radiopharmaceuticals are another type of internal radiation therapy. These agents are substances that include a radioactive component that destroys cancer cells. Radiopharmaceuticals are most often used for bone and thyroid cancers and lymphomas.

Biologic Therapy

This type of cancer treatment uses biological substances that work to stimulate your immune system or your bone marrow to help fight cancer or control the side effects of other treatments, such as chemotherapy. Biological therapy may be used to boost specific aspects of your immune system so it can better destroy cancer cells and prevent cancer from spreading to other parts of your body.

Laser Therapy

This form of cancer treatment uses a laser — a highly focused and powerful beam of light energy — to shrink or destroy tumors. Laser therapy is most often used to treat cancers that are superficial, that is, cancers on the surface of the body such as skin cancer, and some cancers in the early stages of development

Targeted Therapies

Targeted therapy is treatment with agents that were developed to inhibit or modify specific molecules that send signals along signaling pathways, complex systems that direct basic cell functions, such as cell division and cell death. Targeted therapy drugs block these signals.

Targeted therapy is used for a wide variety of cancer types, and many types of targeted therapy drugs can be taken by mouth. These drugs are usually given in combination with another type of therapy, especially chemotherapy.

Most targeted therapy drugs are either small-molecule drugs or monoclonal antibodies. Both types are made in a laboratory and are designed to locate and bind to specific substances on the surface of or inside the cancer cells.

Small-molecule drugs can pass through the cell membrane and act on a target inside the cell. Many small-molecule drugs are tyrosine kinase inhibitors (TKIs), which act against specific cell signaling pathways involved in tumor growth. Some examples of TKIs are imatinib (Gleevec), sunitinib (Sutent), gefitinib (Iressa), erlotinib (Tarceva) and dasatinib (Sprycel).

Monoclonal antibodies cannot pass through the cell membrane and instead are used against targets found on the cell surface. These targeted therapy drugs include trastuzumab (Herceptin), rituximab (Rituxan), cetuximab (Erbitux), panitumumab (Vectibix) and alemtuzumab (Campath-1H).

Some monoclonal antibodies target proteins involved in the development of blood vessels within a tumor. Targeting these proteins blocks the growth of new blood vessels, which cuts off the blood supply to the tumor; without a blood supply, the tumor cannot grow. The formation of new blood vessels is known as angiogenesis, and these drugs are known as antiangiogenic agents. Bevacizumab (Avastin) is an antiangiogenic agent.

Monoclonal Antibodies

Monoclonal antibodies (MAbs) are antibodies produced in a laboratory instead of by the body’s immune system. They can be designed to attack cancer cells. When injected into the body, MAbs attach themselves to receptors on the surface of cancer cells and may prevent the cells from growing, serve as markers so the immune system can find and attack the cells, or make the cells more sensitive to chemotherapy. Sometimes MAbs are attached to drugs, radioactive material, or toxins because MAbs can deliver those agents to cancer cells, reducing damage to normal cells.

MAbs have been approved to treat many types of cancer, including lymphomas and lung, colorectal, and breast cancer, and MAbs are increasingly being studied and approved as first-line treatments. For example, trastuzumab (Herceptin) was approved in 2006 for patients with early-stage breast cancers that make too much of a protein called HER-2. Trastuzumab already had been approved for treating advanced (metastatic) HER-2-positive breast cancer. HER-2-positive tumors tend to grow more aggressively and are more likely to recur than tumors that don’t overproduce HER-2. Another MAb, rituximab (Rituxan), was approved in 2006 for the first-line treatment of certain types of non-Hodgkin’s lymphoma.

Clinical trials may lead to more approvals of MAbs as first-line treatments. For example, in 2007 a phase III clinical trial with patients who have advanced colorectal cancer found that the addition of the MAb cetuximab (Erbitux) to a standard first-line chemotherapy combination cut the risk of further cancer growth or spread by 15 percent. It also increased the number of patients able to undergo surgery to remove their tumors.

Angiogenesis Inhibitors

By interfering with angiogenesis — the formation and development of new blood vessels — these targeted treatments make it difficult for cancer tumors to grow and spread. Two angiogenesis inhibitors added recently to the cancer treatment arsenal are sunitinib (Sutent), approved in 2006 for kidney cancer and gastrointestinal stromal tumors (GIST), and sorafenib (Nexavar), approved in 2005 for kidney cancer. In 2007, an additional study of sorafenib in a phase III clinical trial involving patients with hepatocellular carcinoma, the most common liver cancer, yielded encouraging results: Those who received sorafenib lived about 44 percent longer than patients who didn’t receive the drug, and time to cancer progression also improved.

Another major advance in 2007 was a phase III clinical study involving the angiogenesis inhibitor bevacizumab (Avastin), which also is a monoclonal antibody. The trial showed that adding bevacizumab to an older kidney cancer drug as a first-line treatment for advanced kidney cancer almost doubled progression-free survival, which is the length of time during and after treatment in which the cancer does not grow. Bevacizumab also is used to treat metastatic colorectal cancer and non-small cell lung cancers.

Growth-factor Inhibitors

These therapies work by hindering the action of enzymes, which play a role in the chemical messages necessary for the cell to grow and develop. An example is erlotinib (Tarceva), approved in 2004, for patients with non-small cell lung cancer who have been treated with another chemotherapy medication and not gotten better. In 2005, it was approved for patients with pancreatic cancer.

Immunotherapy

Immunotherapy helps repair or stimulate a person’s own immune system, the body’s defense against harmful organisms or substances such as bacteria, viruses, and cancer cells. Immunotherapy is either active or passive; active immunotherapy stimulates a person’s own immune system to fight cancer, and passive immunotherapy involves the use of parts of the immune system, such as antibodies, that are made in a lab. The most common type of passive immunotherapy is treatment with a monoclonal antibody, which is more often considered a targeted therapy drug.

Some antibodies used for immunotherapy are radiolabeled, which means that they contain a radioactive substance. These antibodies attach to cancer cells, and the radioactive substance kills them. This treatment, also known as radioimmunotherapy, has been used primarily for some types of non-Hodgkin lymphoma.

Another form of immunotherapy is treatment with cytokines, which are special proteins on white blood cells that help stimulate an immune response. Interleukin-2 (IL-2) and interferon-alpha are two cytokines that have been approved for treatment of metastatic melanoma and kidney cancer.

Cancer vaccines are also a form of immunotherapy. Although cancer vaccines have been studied for years, progress has been slow and most cancer vaccines are still in experimental stages. The most recently developed vaccine is sipuleucel-T (Provenge), which is approved for the treatment of advanced prostate cancer.

Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation is done to help the body produce new blood cells. Stem cells are found in the bone marrow, and they have a special feature that enables them to develop into any one of the three types of blood cells (red blood cells, white blood cells, and platelets [clotting cells]). There are two types of stem cell transplantation: autologous and allogeneic.

With autologous stem cell transplantation, a person’s own stem cells are removed and preserved so that very high doses of chemotherapy and/or radiation therapy can be given to attack cancer cells without destroying the stem cells. The person’s stem cells are infused back into the body once the intensive radiation therapy or chemotherapy has been completed. An allogeneic stem cell transplantation is the use of stem cells obtained from a donor with healthy bone marrow whose stem cells are a close match to the those of the person to be treated. Allogeneic stem cell transplantation is also considered to be a form of immunotherapy because it establishes a new immune system for a person.

Stem cell transplantation and high-dose chemotherapy and/or radiation therapy is used most often for leukemias, lymphomas, multiple myeloma, germ-cell tumors, and pediatric tumors.