Radiation Therapy
Radiation therapy has become the mainstay of treatment of anal cancer. The radiation comes in the form of high energy x-rays that are delivered to the patient only in the areas at highest risk for cancer. These x-rays are similar to those used for diagnostic x-rays, but they are of a much high energy. The high energy of x-rays in radiation therapy results in damage to the DNA of cells. Cancer cells divide faster than healthy cells, and so their DNA is more likely to be damaged than that of normal cells. Additionally, cancer cells are generally less able to repair damaged DNA than normal cells are, so cancer cells are killed more easily by radiation than normal cells are. Radiation therapy exploits this difference to treat cancers by killing cancer cells, while killing fewer cells in normal, healthy tissue. Typically, radiation for anal cancer is given daily, Monday through Friday, for 5 to 6 weeks. The radiation treatments themselves are short, lasting only a few minutes. Like diagnostic x-rays, radiation treatments cannot be felt and do not hurt. Radiation is delivered like a beam of light, only affecting areas where it is aimed. In treatment of anal cancer, the radiation is usually aimed at the entire pelvis for the first 2-3 weeks so that any cells in the lymph nodes surrounding the anus are treated with radiation. After this, the radiation is aimed more specifically at the anus in the lower part of the pelvis. Most commonly, radiation treatment for anal cancer can result in irritation to the skin. This reaction can be quite severe with redness, dryness, and breakdown of the skin. Often, patients will require a break during radiation treatment to allow the skin to heal prior to resuming treatment. Other side effects of radiation can include fatigue, diarrhea, and lowering of blood counts.
Chemotherapy
Chemotherapy refers to medications that are usually given intravenously or in pill form. Chemotherapy travels throughout the bloodstream and throughout the body to kill cancer cells. This is one of the big advantages of chemotherapy. If cancer cells have broken off from the tumor and are somewhere else inside the body, chemotherapy has the chance killing them, while radiation does not. In the setting of anal cancer, chemotherapy is most commonly given at the same time as radiation. This will be discussed further below under the section entitled "Combined Modality (Chemoradiotherapy)."
A number of different chemotherapeutic agents exist, each with their own side effects. The most common chemotherapies used in anal cancer are 5 flourouracil (5FU) and mitomycin C. Sometimes, mitomycin C may be replaced with cisplatin in order to reduce toxicities from chemotherapy. Exactly which chemotherapeutic agents are given for anal cancer varies according to the physician giving them. It is important to discuss the risk of each of these medications with your medical oncologist. Based on your own health status and the risks of side effects that you are willing to accept, the choice of chemotherapy can vary.
Chemotherapy is used in different situations to treat anal cancer. If the cancer is localized to the anus and pelvic lymph nodes, it may be used in combination with radiation therapy to achieve the best chance of killing all of the cancer cells (see “Combined Modality (Chemoradiotherapy).” If the cancer has spread to distant parts of the body, chemotherapy drugs such as cisplatin, carboplatin, and 5FU may be used without radiation to reduce the number of tumor cells and prevent or minimize symptoms all over the body. This is the case because chemotherapy is able to travel throughout the bloodstream, while radiation is not. In this setting, radiation may be used separately to relieve certain symptoms, such as pain, from cancer in other parts of the body. Unfortunately, if cancer is present in organs distant from the anus, chemotherapy is generally not very successful at controlling it.
Combined Modality (Chemoradiotherapy)
Chemotherapy has been shown to be radiosensitizing when given at the same time as radiation therapy. This means that the effect of the radiation is increased when given together with chemotherapy. Several large trials have shown that local control of the tumor is significantly improved when 5FU and mitomycin with chemotherapy are used, as compared to radiation alone. Using chemotherapy and radiation together has not been shown to change the rate of survival of patients when compared to radiation alone; however, using chemotherapy and radiation together has been shown to reduce the risk of cancer recurring (coming back) in the anus. For this reason, combined modality treatment is recommended for most patients with anal cancer, unless a certain patient is unable to tolerate chemotherapy and radiation together. If this is the case, the patient may have radiation with or without chemotherapy given at a separate time.
Surgery
Although surgery was the primary treatment for anal cancer 20 years ago, its role has greatly diminished since then. When performed, surgical resection usually is an abdominal perineal resection (APR), which consists of a wide excision of the anus, including the anal muscles, with placement of a permanent colostomy. A colostomy is performed by connecting the bowel to a hole in the abdominal wall (called a stoma). The stool that passes through the stoma is collected in a bag that is attached to the outside of the abdominal wall with adhesive. This bag can then be emptied by the patient as needed. Because the combination of chemotherapy and radiation therapy result in similar rates of local control and survival when compared to surgery, chemoradiation has been favored over surgery because it offers patients a good chance at preserving anal sphincter function, avoiding the need for permanent colostomy.
There are several situations in which surgery should be considered for anal cancer. Patients with carcinoma in situ or small, well-differentiated anal cancers that have not invaded into the anal sphincter can sometimes undergo a surgical excision without removing the anal muscles. In these early cases, the results of surgical excision can be quite good, and the patient can avoid the potential side effects of chemoradiotherapy. Alternatively, extensive anal cancers that have destroyed the anal sphincter, such that the patient cannot control bowel movements, are often treated with surgery (an APR). In these cases, patients have already lost their sphincter function, and require a colostomy to handle bowel movements. Because patients in this situation usually have very large tumors, they may require surgical removal of the tumor, which will usually be followed by radiation, with or without chemotherapy, after the operation. Surgery can also be performed in patients who cannot otherwise tolerate radiation therapy, or who do not want radiation therapy Finally, surgery is often performed if cancer recurs in the anus following previous treatment with radiation therapy if additional chemotherapy and radiation cannot be given.
Radiation therapy has become the mainstay of treatment of anal cancer. The radiation comes in the form of high energy x-rays that are delivered to the patient only in the areas at highest risk for cancer. These x-rays are similar to those used for diagnostic x-rays, but they are of a much high energy. The high energy of x-rays in radiation therapy results in damage to the DNA of cells. Cancer cells divide faster than healthy cells, and so their DNA is more likely to be damaged than that of normal cells. Additionally, cancer cells are generally less able to repair damaged DNA than normal cells are, so cancer cells are killed more easily by radiation than normal cells are. Radiation therapy exploits this difference to treat cancers by killing cancer cells, while killing fewer cells in normal, healthy tissue. Typically, radiation for anal cancer is given daily, Monday through Friday, for 5 to 6 weeks. The radiation treatments themselves are short, lasting only a few minutes. Like diagnostic x-rays, radiation treatments cannot be felt and do not hurt. Radiation is delivered like a beam of light, only affecting areas where it is aimed. In treatment of anal cancer, the radiation is usually aimed at the entire pelvis for the first 2-3 weeks so that any cells in the lymph nodes surrounding the anus are treated with radiation. After this, the radiation is aimed more specifically at the anus in the lower part of the pelvis. Most commonly, radiation treatment for anal cancer can result in irritation to the skin. This reaction can be quite severe with redness, dryness, and breakdown of the skin. Often, patients will require a break during radiation treatment to allow the skin to heal prior to resuming treatment. Other side effects of radiation can include fatigue, diarrhea, and lowering of blood counts.
Chemotherapy
Chemotherapy refers to medications that are usually given intravenously or in pill form. Chemotherapy travels throughout the bloodstream and throughout the body to kill cancer cells. This is one of the big advantages of chemotherapy. If cancer cells have broken off from the tumor and are somewhere else inside the body, chemotherapy has the chance killing them, while radiation does not. In the setting of anal cancer, chemotherapy is most commonly given at the same time as radiation. This will be discussed further below under the section entitled "Combined Modality (Chemoradiotherapy)."
A number of different chemotherapeutic agents exist, each with their own side effects. The most common chemotherapies used in anal cancer are 5 flourouracil (5FU) and mitomycin C. Sometimes, mitomycin C may be replaced with cisplatin in order to reduce toxicities from chemotherapy. Exactly which chemotherapeutic agents are given for anal cancer varies according to the physician giving them. It is important to discuss the risk of each of these medications with your medical oncologist. Based on your own health status and the risks of side effects that you are willing to accept, the choice of chemotherapy can vary.
Chemotherapy is used in different situations to treat anal cancer. If the cancer is localized to the anus and pelvic lymph nodes, it may be used in combination with radiation therapy to achieve the best chance of killing all of the cancer cells (see “Combined Modality (Chemoradiotherapy).” If the cancer has spread to distant parts of the body, chemotherapy drugs such as cisplatin, carboplatin, and 5FU may be used without radiation to reduce the number of tumor cells and prevent or minimize symptoms all over the body. This is the case because chemotherapy is able to travel throughout the bloodstream, while radiation is not. In this setting, radiation may be used separately to relieve certain symptoms, such as pain, from cancer in other parts of the body. Unfortunately, if cancer is present in organs distant from the anus, chemotherapy is generally not very successful at controlling it.
Combined Modality (Chemoradiotherapy)
Chemotherapy has been shown to be radiosensitizing when given at the same time as radiation therapy. This means that the effect of the radiation is increased when given together with chemotherapy. Several large trials have shown that local control of the tumor is significantly improved when 5FU and mitomycin with chemotherapy are used, as compared to radiation alone. Using chemotherapy and radiation together has not been shown to change the rate of survival of patients when compared to radiation alone; however, using chemotherapy and radiation together has been shown to reduce the risk of cancer recurring (coming back) in the anus. For this reason, combined modality treatment is recommended for most patients with anal cancer, unless a certain patient is unable to tolerate chemotherapy and radiation together. If this is the case, the patient may have radiation with or without chemotherapy given at a separate time.
Surgery
Although surgery was the primary treatment for anal cancer 20 years ago, its role has greatly diminished since then. When performed, surgical resection usually is an abdominal perineal resection (APR), which consists of a wide excision of the anus, including the anal muscles, with placement of a permanent colostomy. A colostomy is performed by connecting the bowel to a hole in the abdominal wall (called a stoma). The stool that passes through the stoma is collected in a bag that is attached to the outside of the abdominal wall with adhesive. This bag can then be emptied by the patient as needed. Because the combination of chemotherapy and radiation therapy result in similar rates of local control and survival when compared to surgery, chemoradiation has been favored over surgery because it offers patients a good chance at preserving anal sphincter function, avoiding the need for permanent colostomy.
There are several situations in which surgery should be considered for anal cancer. Patients with carcinoma in situ or small, well-differentiated anal cancers that have not invaded into the anal sphincter can sometimes undergo a surgical excision without removing the anal muscles. In these early cases, the results of surgical excision can be quite good, and the patient can avoid the potential side effects of chemoradiotherapy. Alternatively, extensive anal cancers that have destroyed the anal sphincter, such that the patient cannot control bowel movements, are often treated with surgery (an APR). In these cases, patients have already lost their sphincter function, and require a colostomy to handle bowel movements. Because patients in this situation usually have very large tumors, they may require surgical removal of the tumor, which will usually be followed by radiation, with or without chemotherapy, after the operation. Surgery can also be performed in patients who cannot otherwise tolerate radiation therapy, or who do not want radiation therapy Finally, surgery is often performed if cancer recurs in the anus following previous treatment with radiation therapy if additional chemotherapy and radiation cannot be given.
No comments:
Post a Comment