Cancer therapy, definitive

Definition

Definitive cancer therapy is a treatment plan designed to control and potentially cure cancer using one or a combination of interventions including surgery, radiation, chemotherapy, biological or targeted therapies.

Purpose

The primary purpose of definitive care is to establish a cure and to destroy and remove all cancer cells from the person diagnosed with cancer.


Surgery

Surgery is not only a diagnostic tool, but is also used for tumor removal. The surgeon usually identifies potential candidates for tumor removal which typically occurs during a surgical procedure. Surgery can be curative for some stomach, genital/urinary, thyroid, breast, skin, and central nervous system cancers. The best chance for a surgical cure is usually with the first operation. It is essential that the cancer surgeon (oncologic surgeon) be experienced in the specific procedure.

Radiation therapy

Radiation therapy is administered to many cancer patients during the course of treatment of cancer. This type of treatment can be used as the sole method of cure for tumors in the mouth and neighboring structures in the oral cavity, vagina, prostate, cervix, esophagus, Hodgkin's disease, and certain types of cancer in the spinal cord and brain. Research and clinical trials have demonstrated that combination treatment is typically more effective than radiation therapy alone.

Chemotherapy

Chemotherapy is curative treatment strategy for some cancers. It is most effective against choriocarcinoma, cancer of the testis, some types of lymphomas, and cancer of skeletal muscles.

Biological and targeted therapies

Biological therapies and targeted therapies offer a newer and promising direction for cancer control and cure. Targeted therapies interfere with the actions of specific molecules involved in the growth and progression of cancerous tumors. One type of targeted therapy is directed toward stopping angiogenesis, which is the development of a blood supply to the tumor. Usually when cancer cells grow they manage to derive a blood supply that allows passage of nutrients promoting continuation of abnormal cancer growth. Treatment that focuses on destroying these blood vessels is called antiangiogenesis therapy. Cutting off the blood supply has been shown to destroy tumors, since this stops the flow of essential nutrients required for cancer growth.

Other examples of targeted therapies include use of certain growth factors which can stimulate selfdestructive pathways in cancer cells (apoptosis) and gene therapy, which is directed toward inhibiting specific cellular signals that promote cancer cell multiplication.



Surgery

Surgical removal of the tumor must be performed with care and accuracy. The surgeon must avoid overmanipulation of the surgical field. Too much movement within the area can cause cancer cell displacement into surrounding tissue. If this occurs and no further treatment is administered, the tumor may grow again. The surgeon also should perform an assessment concerning tissue removal around the cancer site. Tissue around the site may not seem cancerous by visual inspection, but adjacent structures may have cancer cells which can only be detected microscopically. Surrounding tissue removal is usually part of the operative procedure. Pieces of tumor and the surrounding area are analyzed microscopically during the operation for cell type. An adequate resection (removal of tissue)will reveal normal cells in the specimens analyzed fromareas bordering the cancerous growth.

Surgery can also help to decrease the tumor bulk (size) and, along with other treatment measures, may provide a cure for certain cancers. Surgery generally works best on slow-growing cancers.

Not only can surgery be curative for some cancers, but it is an essential diagnostic tool. Examples of diagnostic procedures which can be done in the surgical environment include an aspiration biopsy, in which a needle is inserted to extract (aspirate) fluid contained inside a cancerous growth; a needle biopsy in which the surgeon uses a specialized needle to obtain a core tissue specimen; an incision biopsy which removes a section from a large tumor; and an excision biopsy, a procedure which removes the entire tumor. The surgeon also can take samples of neighboring lymph nodes. Cancer in surrounding lymph nodes is an important mechanism for distant spread of cancer to other areas. If microscopic analysis determines the presence of cancer cells in lymph nodes, the surgeon may decide to perform a more aggressive surgical approach.

Radiation therapy

Similar to surgical intervention, radiation therapy is a localized treatment. It involves the administration of ionizing radiation to a solid tumor location. This generates reactive oxygen molecules, causing the destruction of DNA in local cells. There are three commonly used radiation therapy beams: gamma rays from a linear accelerator machine produce a focused beam; orthovoltage rays are of less energy, thus penetrate less and typically deliver higher doses to superficial tissues (efficient for treating skin cancers); and megavoltage rays are high energy producing beams that can penetrate deeply situated internal organs, while sparing extensive skin damage.

Brachytherapy delivers radiation internally by placing radioactive materials such as radioactive seeds and pellets within close proximity or directly into the cancerous tumor. Teletherapy delivers radiation to a specific area of the body using a machine which delivers a beam of radiation from a source which is external to the body.

Chemotherapy

Chemotherapy drugs work by disrupting cancer cell division which leads to cell death. Combining several different chemotherapy agents with different mechanisms of action and different toxicity profiles often results in more effective therapy and is known as combination chemotherapy. Chemotherapy is considered to be systemic therapy because it is typically administered via the blood and circulates through the entire body. The choice of chemotherapeutic agents depends on the specific type of cancer and the effectiveness of that drug(s) on the specific cancer being treated.

Curative chemotherapy usually requires multiple administrations of the chemotherapy drug over several months. This is referred to as a treatment cycle.

Biologic or targeted therapy

Targeted therapies, as the name implies, are designed to target specific molecular flaws of cancer cells. Some drugs in this classification target specific proteins produced by cancer cells, some target cancer cell communication pathways in an attempt to disrupt the pathways, some work to inhibit new blood vessel growth required to sustain a tumor, while other drugs target the pathways in cancer cells which facilitate the ability of cancer cells to metastasize.

Biologic therapies primarily function to alter the patient's response to cancer. These treatments tend to stimulate specific immune cells or immune chemicals to destroy cancer cells.

Precautions

Surgical resection requires an experienced surgeon and surgical team, preoperative assessment, imaging studies, and delicate operative technique. Care should be taken during the procedure to avoid unnecessary tumor manipulation, which can cause cancer cells to infiltrate adjacent structures. If manipulation is excessive, cells can enter nearby areas for future re-growth. Accurate isolation of the tumor also can help avoid contamination of the surgical area. Early ligation of the blood supply to the tumor is an essential component of a surgical cure.

Radiation therapy requires extensive treatment planning and imaging. Care must be taken to localize the cancer treatment field while attempting to spare normal tissue from the effects of radiation. This requires image monitoring and exact positioning during radiation treatment sessions.

Chemotherapy usually causes destruction of normal cells, and some cancer cells can develop immunity or become refractory to the effects of chemotherapy. These agents must be administered only by clinicians who are experienced and who have been educated specifically in the administration of these very potent drugs. Side effects and patient tolerance issues typically are anticipated and dosages may have to be specifically altered.

Biological or targeted therapies may cause patient toxicity resulting in extensive side effects. The side effect profile of biologic or targeted agents is usually different from the side effect profile of chemotherapy agents. Side effects of biologic or targeted agents are usually specific to the classification of the drug while some drugs have their own unique side effects.

Preparation

For all treatment modalities imaging studies, biopsy, and constant blood analysis is essential before, during, and after treatments. Surgical candidates should undergo extensive pre-operative evaluation with imaging studies, blood chemistry analysis, stabilized health status, and readiness of staff for any potential complications and cell biopsy analysis. Patients with other pre-existing chronic disease may require intensive postoperative monitoring.

Prior to radiotherapy, the patient undergoes extensive imaging studies. Additional planning strategies include beam localization to spare normal tissues, calibration of fractionated doses, and specific positioning during treatment sessions.

Patients who receive curative chemotherapy should be informed of possible side effects associated with the chemotherapeutic agent. Patients should also be informed of temporary lifestyle changes and medications that may offer some symptomatic relief.

Patients undergoing biologic or targeted therapies should be advised of potential side effects, treatment cycles, and specific tests for monitoring progress.

Aftercare

Patients will typically be evaluated by imaging studies, blood analysis, physical examination, and will be observed for response to treatment. These follow-up visits usually occur at specific time intervals during the course of treatment. Surgical patients may require closer observation during the initial post-operative period to avoid potential complications. Reconstructive surgery can be considered to improve appearance and restore function. Certain surgical procedures (such as flaps and microsurgery of blood vessels) can restore new tissues to a previous surgery site.

Surgical risks

Surgical therapy can be both disfiguring and disabling. Any surgical procedure contains a risk for complications during and after the procedure in the post-operative period. Patients are monitored very closely during and after surgery to minimize the risk of complications.

Radiation risks

Many normal tissues can be adversely affected by radiation therapy. Side effects from radiation therapy are dependent on the area being treated. Some of the more common side effects which can occur shortly after a treatment cycle include nausea, vomiting, fatigue, loss of appetite, and bonemarrow suppression (a decrease in the cells that provide defense against infections and those that carry oxygen to cells). Radiation therapy also can cause skin changes in the skin in the treatment field, difficulty swallowing, oral gum disease, and dry mouth. Additionally, radiation therapy can cause damage to local structures within the irradiated field.

Chemotherapy risks

Many commonly utilized chemotherapy agents cause bone marrow suppression as a side effect of treatment. Additionally, cells called platelets-important for normal blood clotting-may be significantly lowered, causing patients to bleed. This may be problematic enough to limit the treatment course. Bone marrow suppression can increase susceptibility to infection. Some chemotherapy agents may also cause infertility. Patients commonly have bouts of nausea and vomiting shortly after a treatment session. Rapidly multiplying normal cells also are affected such as skin cells (causing blistering and ulceration) and hair cells causing loss of hair, a condition called alopecia.

Biologic therapy risks

Biologic therapies can cause patients to develop suppression of cells that help the body fight against infection. As with all other treatment methods for cancer, patients will be screened very carefully to determine if the benefits of the treatment outweigh the potential risks to the patient.