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November 2002 CE.
This second article in a three-part series provides healthcare representatives with an understanding of the treatment of cancer.
Judy Chase, Pharm.D., Division of Pharmacy, University of Texas, M.D. Anderson Cancer Center, Houston, TX; John J. Kavanagh, M.D., chief professor, section of gynecologic medical oncology, department of clinical investigation, University of Texas, M.D. Anderson Cancer Center; and Patton B. Saul, M.D., medical director and director of gynecologic oncology, Lewis-Gale Cancer Center, Salem, VA, clinical associate professor of gynecology and gynecologic oncology, University of Virginia School of Medicine, Charlottesville, VA, served as consultants for this article for the Certified Medical Representatives Institute Inc.
* Describe the major types of cancer and available treatment options.
* Describe the role of surgery in the treatment of cancer.
* Describe the roles of chemotherapy and radiation therapy in the treatment of cancer.
* Describe the roles of biological therapies and bone marrow transplants in the treatment of cancer.
* Define multimodality therapy.
More cancer treatments are available than ever before, and in many cases their efficacy has improved significantly.
This article begins with a discussion of the types of cancer and then describes some of the available treatments for cancer and their specific applications.
Overview of types of cancer
Solid tumors. Many, but not all, of the most common types of cancer develop as solid neoplasms or tumors.
Lung cancer is the second most common cancer and the most common cause of cancer death in both men and women. The major risk factor is tobacco smoking. Lung cancer is usually divided into small cell lung cancer and non-small cell lung cancer. Surgery may cure early non-small cell lung cancer; for more advanced non-small cell lung cancer, surgery plus radiation therapy or chemotherapy may prolong life, but survival is usually less than five years. Small cell lung cancer is more responsive to chemotherapy and radiation therapy, but survival beyond two years is rare.
Breast cancer, the most common malignancy in women, is highly treatable if it is detected in the early stages. Most patients today receive limited surgery combined with radiation therapy, chemotherapy or hormone therapy.
Prostate cancer is the most common cancer in men living in the United States. The growth rate of prostate cancer is highly variable and thus, treatment decisions are usually made on a case-by-case basis. Elderly patients with slow-growing tumors may receive no treatment. Younger patients and those with more aggressive cancers may receive surgery, radiation therapy, hormone therapy or cryosurgery. Prostate cancer responds poorly to conventional chemotherapy.
Cancers of the colon and rectum account for 10% of all cancers in the United States and are generally more common in industrialized countries. Colorectal cancers are often curable by surgery in the early stages. Adjuvant chemotherapy aids survival in patients undergoing surgery. Patients with rectal cancers may also receive radiation therapy.
Hematologic malignancies. Some cancers do not form solid tumors at specific locations, but are disseminated throughout the body from the outset. These include the leukemias, the lymphomas and multiple myeloma.
The most common form of cancer in children is leukemia. Lymphomas, especially Hodgkin's disease, are also seen in young patients. Chemotherapy is the main treatment for childhood leukemia. Some biological agents have also shown promise. For certain types of leukemia, bone marrow transplant offers the only chance of a cure. Childhood lymphomas can usually be cured by radiation therapy or chemotherapy.
The chronic forms of the leukemias and lymphomas, which progress more slowly but are less responsive to therapy, are more common in older patients. Multiple myeloma is most common in older patients and is incurable. Chemotherapy can reduce the number of malignant plasma cells in multiple myeloma patients, leading to temporary remission in some cases. Bone marrow and blood stem cell transplants appear to prolong remission in some patients.
Skin cancers. Among the cancers that are increasing most rapidly in incidence are melanoma and other cancers of the skin. The most important risk factors for melanoma and other skin cancers are light skin color and exposure to ultraviolet light, usually sunlight. The most common types of skin cancer – basal cell and squamous cell – are almost always curable by surgery, radiation therapy or chemotherapy. Melanoma, on the other hand, accounts for only about 5% of all cases of skin cancer but causes three times as many deaths as all other types combined. Surgical excision of the primary growth (and regional nodes if indicated) is the only treatment for melanoma that offers a possibility of cure.
Surgery in cancer treatment
About 90% of cancer patients undergo surgery for diagnosis, treatment, management of complications or some other reason. Only about 13% can be cured by surgery alone, however. In the majority of cases, surgery must be supplemented by some other form of treatment.
Surgery may be used as a preventive measure. If the patient has a benign disease or condition associated with increased risk of cancer, surgery may be performed to remove the affected organs or tissues and thus prevent cancer from developing in them.
Surgery may also aid in the diagnosis and staging of cancer. A minimally invasive technique, such as needle aspiration biopsy, may be used to obtain sample cells for a definitive determination of the type and stage of a cancer. If results from a needle or core biopsy are not definitive, or if the tumor site is unfavorable for a needle biopsy, a surgical biopsy may be performed. Because cancer often recurs if it has spread to the lymph nodes, a number of nodes from the area of the tumor are usually removed and examined at the time of local surgery.
For many types of cancer, the surgical removal of the tumor may be the main form of treatment. Surgical excision may cure cancer in some cases, but only if the cancer is confined to a local area, its position is such that it can be safely removed and a margin of normal tissue from around the tumor can also be removed. Surgery is also frequently combined with other modes of treatment in cancer therapy.
Palliative surgery is any operation performed to ease symptoms without trying to achieve a cure. Palliative surgeries used in cancer include removal of solitary metastases, removal of hormone-producing glands that promote tumor growth, treatment of radiation or chemotherapy complications, and stabilization of brittle bones.
Reconstructive surgery may be necessary if the removal of a large tumor or organ produces a deformity or a functional problem. Surgery may also be used to aid the administration of chemotherapy or radiation therapy. The treatment of complications of cancer and cancer treatment, such as infections or bowel obstructions, may require surgery.
Surgery may be used for a "second look" at a cancer that has already been treated. "Second-look" procedures involve follow-up surgery within a predetermined time frame after the original surgery or adjuvant treatment to check for the presence or absence of disease.
About half of all cancer patients receive radiation therapy as part of their treatment plan. Radiation therapy is a local-regional treatment method that uses high-energy ionizing rays or particles to alter the biology of cancerous tumors. Radiation therapy may be used to cure cancer by eradicating all cancerous cells, to control the growth and spread of cancer, to eliminate microscopic metastasis, or to improve quality of life by easing symptoms associated with advanced cancer.
Radiation is a local therapy, meaning it attacks cancer cells in a specific area only. Because of this, it is often used in combination with chemotherapy, which is systemic. Some cancers are highly responsive to radiation therapies, such as leukemias and lymphomas, and cancers of the skin and epithelial tissues. The vascular and connective tissue elements of almost all tumors show moderate sensitivity. Low sensitivity is characteristic of cancers of the salivary glands, liver, kidney and pancreas, as well as the sarcomas.
Ionizing radiation kills cancer cells or stops their growth. It does this either directly or by producing DNA-damaging oxygen radicals. Normal cells are usually less affected by the damaging radiation. However, tissues such as bone marrow, epithelium and hair follicles may be vulnerable.
Radiation therapy can be delivered in the form of a beam from an external source or by implantation of radioactive material in the body. In external radiation therapy, a machine that usually emits x-rays or gamma rays is placed at some distance from the body. Internal radiation therapy involves inserting radioactive materials into a body cavity or placing them directly into the tumor itself. The implanted materials usually emit beta radiation.
It is estimated that more than half of cancer patients receive systemic chemotherapy as part of their treatment. Chemotherapy may be used to cure the cancer or to control tumor growth when a cure is impossible. Chemotherapy is also used to relieve pain or other symptoms, to shrink tumors prior to surgery or radiation therapy, or to destroy microscopic metastases after surgical removal of the primary tumor.
Chemotherapy agents disrupt mitosis, the process by which cells replicate their DNA and divide into daughter cells. The rapid division of tumor cells makes them more sensitive to chemotherapy agents than most normal cells. Most chemotherapy regimens consist of combinations of several drugs. This practice maximizes the number of tumor cells killed, prevents or delays the development of resistance, and helps keep toxic effects within an acceptable range. Drugs with different mechanisms of action are usually combined to avoid cross-resistance or enhanced adverse effects.
Biotherapy involves the use of biologically derived agents to modify the relationship between tumor and host by altering the host's biologic response to tumor cells, with a resultant therapeutic effect. Most biotherapies are designed to activate the patient's immune system and induce it to attack cancer cells. Biotherapy agents can thus be expected to slow tumor growth or even induce regression.
Some major groups of biotherapy agents are interferons, interleukins and hematopoietic growth factors. The interferon proteins have a variety of biologic functions, including fighting viral infections, controlling cell proliferation and regulating the immune response. The interleukins act as messengers between the white blood cells (leukocytes) of the immune system, prompting them to become active, proliferate and produce other immune-related chemical messengers. Hematopoietic growth factors are a family of protein hormones that control the production and maturation of blood cells of all types.
Monoclonal antibodies, which can be programmed to recognize different proteins on cancer cells, work by locating and binding to the targeted cells wherever they are in the body. Alone (or unlabeled), monoclonal antibodies demonstrate significant activity against certain types of lymphomas. Monoclonal antibodies may also be used to deliver drugs such as radiation or chemotherapy agents.
Some other biotherapies include retinoids, tumor necrosis factors, gene therapy, vaccines and enzyme inhibitors.
Bone marrow transplant
Transplantation of bone marrow or blood stem cells can offer hope of survival to some cancer patients whose prognosis would otherwise be poor. These procedures are relatively new, and their applications are currently somewhat limited because of the risks and expense involved and the frequent lack of a suitable donor. The purpose of a bone marrow transplant is to replenish blood cells (red cells, white cells and platelets) in patients whose blood cell levels have been depleted by cancer or cancer therapy. If the patient's body accepts the graft, precursor stem cells in the donor marrow mature into blood cells of all types. The donor marrow may be harvested in advance from the patient; this procedure is called an autologous bone marrow transplant. In an allogeneic transplant, the marrow comes from another person, usually a close relative, whose blood antigen profile is carefully matched with that of the patient.
Multimodality and other therapies
Most cancer patients today receive a combination of treatments. Each mode of treatment has both advantages and limitations. For example, surgery and radiation therapy may shrink or eliminate tumors but are ineffective against cancer cells that have spread outside the local area. Chemotherapy, by contrast, fights metastasis or micrometastasis but is less effective than surgery or radiation therapy in treating large, bulky tumors. Some advantages of multimodality therapy include spatial cooperation between treatments, toxicity independence, protection of normal tissue and enhanced therapeutic effects. Some disadvantages include exacerbation of adverse effects, increased difficulty in staging the cancer, logistics of obtaining treatments and increased expense.
Pharmacologic and technologic discoveries continue to expand the field of options for cancer treatment. However, a new area known as complementary and alternative medicine is becoming more popular among patients. Complementary and alternative medicine encompasses a wide range of philosophies, approaches and therapies, such as visualization, relaxation, acupressure, massage, homeopathy, nutrition, spiritual practices, psychotherapy, vitamins, herbal products and acupuncture. However, it is associated with risks such as unknown adverse effects, interactions with other treatments, and delay or avoidance of seeking conventional treatment. Despite these risks, certain therapies have been shown to be more effective than conventional therapy alone.
* Types of cancer include:
• Solid tumors (lung, breast, colorectal, prostate).
• Hematological malignancies (leukemia, lymphomas, myeloma).
* Surgery can be used for prevention of cancer, for diagnosis and staging of cancer, to cure some cancers, and as adjuvant therapy for widely spread cancers.
• Surgery is also used to ease symptoms of cancer and treat complications of cancer treatment.
• Radiation therapy is delivered either externally or internally and is considered local therapy.
• Leukemias, lymphomas, and cancers of the skin and epithelium are responsive to radiation therapy.
* Chemotherapy agents preferentially disrupt the division of cancer cells, although normal cells are also affected.
• Chemotherapy regimens often combine several drugs with slightly different effects.
* Biotherapy involves the use of biologically derived agents to either directly attack cancer or stimulate the immune system to attack cancer cells.
• Biotherapies slow tumor growth, boost immune cell production or deliver drugs directly to a tumor.
* Bone marrow transplant is most often used in patients with a poor prognosis, and its goal is to stimulate production of blood cells.
* Multimodality therapy refers to cancer treatment that combines several different types of therapies; this can increase the effectiveness of the treatment, but can also increase the risk of adverse effects and the cost.
* Many complimentary and alternative medicines are being explored by cancer patients; some have been recognized by physicians for relief of symptoms related to cancer treatment.
© 2002 The Certified Medical Representatives Institute Inc., Roanoke, VA 24018. All rights reserved. No part of this article may be reproduced by any method or in any form without written permission from the CMR Institute. Reprints of this article are available from the CMR Institute. Request Continuing Education article OM-2.