Joel W. Goldwein, MD and Thomas J. Dilling, MD
Ultima Vez Modificado: 28 de mayo del 2002
This article begins with a brief explanation of the medical assessment that newly-diagnosed patients undergo to evaluate their cancer. It also provides information about various treatments that doctors administer to cancer patients. A number of complex scientific terms (identified in bold type) are explained in the text.
Once a diagnosis of cancer is made, it is important that the stage of disease be assessed. Stage generally refers to the degree to which the cancer has spread beyond its original location. Lower stages of cancer (stages I and II) are generally more confined to their site or region of origin than more advanced stages (III or IV).
Different cancer types are staged in different ways, according to a complex series of rules. While there are subtle differences in the staging rules for different cancer types, a physician generally needs to look at three things:
The T, N, and M stages have many nuances within them, and each is subdivided (T1, T2, T3, etc.) Different combinations of T, N, and M combine under the staging rules to determine whether a patient is stage I, II, III, or IV. In some cancers, there are even additional stages to account for unique situations (Stage V, for instance). It should also be noted that some cancers are staged with different staging systems, but the TNM system is the most common.
Ultimately, the goal of staging is threefold:
A patient's cancer stage is evaluated in a variety of ways. These include taking a thorough history of the patient's disease, doing a careful physical examination, and obtaining laboratory and radiographic studies (various blood tests, a chest x-ray, and abdominal CT scan, etc.) In some cases, surgical exploration is required to fully stage a patient's disease. In other cases, surgeons need to extract only a small sample of the cancerous tissue (a biopsy), which is generally a relatively minor procedure.
Staging, while important for most cancers, does not tell the whole story. Other factors such as tumor biology, the patient's overall medical condition, and the skills and resources available to the health care team can all impact on the ultimate outcome.
As mentioned in Part I of this article, cancerous cells can be "graded" according to their degree of "differentiation". Differentiation refers to how closely the cancerous cells resemble their cells of origin. The more differentiated a cancer cell looks, the closer it resembles cells belonging to its organ of origin. The more undifferentiated a cell is, the less "normal" it looks under a microscope. A differentiated colon cancer, for example, is cancerous, but it still looks, under the microscope, like "colon" cells. It may also behave as a colon cell (more or less) in terms of attachment to its neighboring cells. In some cancers, grade can affect the cancer stage and/or impact on treatment decisions (more about this in a moment).
Assessment of tumor type and grade is made by a pathologist. Pathologists are physicians trained in looking at tumor samples both as a whole and under the microscope to assess their type, grade and other features such as invasiveness and lymphatic involvement.
The treatment of cancer is a very complex subject. The following discussion is quite general, and not all parts of it apply to all types of cancer. For that reason, patients are urged to consult OncoLink's Cancer Types section for more specifics as to how the following might apply to them.
Surgery is often the first step in the treatment of cancer. The objective of surgery varies. Sometimes it is used to remove as much of the evident tumor as possible, or at least to "debulk" it (remove the major bulk(s) of tumor so that there is less that needs to be treated by other means). Depending on the cancer type and location, surgery may also provide some symptomatic relief to the patient. For instance, if a surgeon can remove a large portion of an expanding brain tumor, the pressure inside the skull will decrease, leading to improvement in the patient's symptoms.
Not all tumors are amenable to surgery. Some may be located in parts of the body that make them impossible to completely remove. Examples of these would be tumors in the brainstem (a part of the brain that controls breathing) or a tumor which has grown in and around a major blood vessel. In these cases, the role of surgery is limited due to the high risk associated with tumor removal.
In some cases, surgery is not used to debulk tumor because it is simply not necessary. An example is Hodgkin's Lymphoma, a cancer of the lymph nodes that responds very well to combinations of chemotherapy and radiation therapy. In Hodgkin's Lymphoma, surgery is rarely needed to achieve cure, but almost always used to establish a diagnosis.
Chemotherapy is another common form of cancer treatment. Essentially, it involves the use of medications (usually given by mouth or injection) which specifically attack rapidly-dividing cells (such as those found in a tumor) throughout the body. This makes chemotherapy useful in treating cancers that have already metastasized, as well as tumors that have a high chance of spreading through the blood system but are not evident beyond the primary tumor. Chemotherapy may also be used to enhance the response of localized tumors to surgery and radiation therapy. This is the case, for example, for some cancers of the head and neck.
Unfortunately, other cells in the human body which also normally divide rapidly (such as the lining of the stomach and hair) are also affected by chemotherapy. For this reason, some (though not all) chemotherapy agents induce nausea or hair loss. These side effects are temporary, and doctors have medications they can provide to help alleviate many of these side effects. So, in general, chemotherapy treatments are well tolerated by patients. As our knowledge of science has continued to grow, researchers have devised newer chemotherapeutic agents that are not only better at killing cancer cells, but that also have fewer side effects for the patient. Often, a patient's fear of chemotherapy treatment is worse than the reality. For more information about the side effects of cancer treatment, see OncoLink's Coping with Side Effects section.
Chemotherapy is administered to patients in a variety of ways. Some are pills that are taken daily or once a week or some other schedule. Some are administered by an intravenous injection. For those, a patient goes to the doctor's office and spends several hours there while the medication is administered, or perhaps spends a day or night in the hospital. Some other chemotherapeutic agents require continuous infusion into the bloodstream, 24 hours a day. For those, a minor surgical procedure is performed to implant a small pump that the patient wears. This pump then slowly administers the medication. In many cases, a permanent port is placed in a patient's vein so that they do not have to have repeated needle sticks.
Chemotherapy treatment often involves the use of more than one medicine at a time. There are many different chemotherapy combinations, each used for different types and stages of cancers. These combinations often have acronyms which are derived from the first letter of each of the chemotherapy agents in the combination. For this reason, a patient may hear a physician refer to "MOPP chemotherapy" (nitrogen Mustard, Oncovin, Procarbazine and Prednisone) or some other acronym. Depending on the combination of agents in the therapy, a patient may have some combination of pills or intravenous injections to undergo, administered according to a particular schedule.
Chemotherapy schedules also involve a "break" or "vacation" to allow the body to recuperate. The exact timing of this break depends on the type of cancer and the chemotherapy combination being used, as well as a patient's response and tolerance. But, a hypothetical example might include receiving chemotherapy for three weeks in a row and then having a week off, then restarting again for three weeks, then a week off, and so on. A patient might undergo these "cycles" four or six times. (The exact number of cycles, too, depends on the regimen, the cancer type, and sometimes the patients response and tolerance).
For more specific information about chemotherapy, see OncoLink's Chemotherapy Menu.
Radiation therapy is another commonly-used weapon in the fight against cancer. Radiation kills cancer by damaging the DNA within the tumor cells. The radiation is "applied" two possible ways. The first, and most common, involves pointing a beam of radiation at the patient in a highly precise manner, focusing on the tumor. To do this, a patient lies on a table and the beam moves around him/her. This only takes a couple minutes, but is done five days per week for 3-6 weeks (depending on the type of tumor), to achieve a particular total prescribed "dose."
Another radiation method sometimes employed, called brachytherapy, involves taking radioactive pellets ("seeds") or wires and implanting them in the body in the area of the tumor. Sometimes these implants are temporary, and sometimes they are permanent. In the case of permanent implants, the radiation in the seeds "decay" or fade away over a period of days or weeks so that the patient is not radioactive. For temporary implants, the entire dose of radiation is usually delivered in about two days, and the patient must remain in the hospital during that time. After the seeds or wires have been in place for the prescribed number of hours, the radiation oncologist removes them and the patient can go home.
In either case, radiation is generally delivered to a very targeted area, to gain local control over a cancer (as opposed to treating the whole body, as chemotherapy does.)
Bone Marrow Transplantation
Some highly selected patients may be referred for bone marrow transplants. This procedure is usually performed either because a patient has a cancer that is particularly aggressive or because they have a cancer that has relapsed after being treated with conventional therapy. Bone marrow transplantation is a complicated procedure. There there are many types, and they vary in their potential for causing side effects and cure. Most transplants are performed at special centers, and in many cases their use is considered investigational.
In preparation for a transplant, a patient is treated with high doses of chemotherapy and/or radiation (usually to the whole body). This preparatory therapy is designed to destroy cancerous cells in the bone marrow and other areas of the body. In some cases, it is also designed to suppress the body's immune system so that the new donated marrow is less likely to be "rejected" [Some transplants use marrow that is collected in advance from the actual cancer patient. These transplants are not associated with the rejection risk.]. After preparation is complete, the patient receives a transplant of donated bone marrow infused by vein. The marrow may come from a specially-matched donor (allogeneic transplant) or may be the marrow the patient previously donated (an autologous transplant). As a side effect, the preparatory regimen may also injure healthy constituents of a patient's marrow and other tissues such as the gut. Throughout this process, the patient remains in the hospital in an "isolation" room, this because the patient's immune system is severely compromised until the transplanted bone marrow "takes" and the patient's blood counts rise to a sufficient level. Other organs that are injured during the transplant recover in much the same way that the marrow does. The patient is discharged when after sufficient marrow and organ recovery.
Because this topic is so complex, we urge you to read OncoLink's Bone Marrow Transplant section.
Other Therapies There are a number of other therapies, though most of them are still being explored in clinical trials and have not yet become standard of care. Examples include:
For more information about all these types of therapies, as well as others, consult OncoLink's Treatment Section. Readers should also understand that not every experimental treatment modality is applicable to one particular kind of cancer. Patients should therefore read the relevant Cancer Type about their cancer.
In addition, patients should look at various clinical trials that are currently available. A clinical trial is a study designed to analyze the utility of a new treatment. There are several types of clinical trials including ones which study cancer treatment, cancer screening and prevention, quality of life and others. Cancer treatment clinical trials are categorized by Phases outlined below.
|Phase I||Identifies safe dose level of a new drug or treatment.|
|Phase II||Identifies the degree of response a particular cancer shows to a new therapy.|
|Phase III||Compares the new treatment with standard therapy.|
A Phase III clinical trial is one of the most commonly offered to cancer patients. In this type of clinical trial, patients may be randomly assigned to a particular therapeutic regimen that is among two or more possible treatments for a particular disease. One of the possible treatments includes the "standard" or "traditional" therapy, and the other treatment regimens are considered "experimental". Sometimes these studies are double-blinded, which means that neither the patients nor the physicians know which particular treatment is being administered. There are two reasons for blinding a study. First, it is well known that patients who are aware they are receiving an experimental therapy have a tendency to claim improvement in symptoms (the "placebo effect") whether they are really improving or not. Secondly, researchers who may be biased about a new therapy one way or another, may unconsciously apply this bias to observed results and thereby tarnish the outcome of the experiment. Double-blinding a study controls for both of these possibilities.
Participation in clinical trials may be offered at no additional cost to the patient compared to receiving standard treatments. Some insurance companies reimburse for these experimental treatments. By participating in the clinical trial process, patients themselves may receive cutting-edge care and also contribute to medical knowledge, thereby helping to improve treatment for future patients. The University of Pennsylvania has many open Clinical Trials.Imprima English
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