Chemotherapy and Radiation
For colon cancer (those not involving the rectum) the final stage of the cancer is not usually known until surgery is complete. When the pathologist is finished with the specimen, your surgeon will discuss the results with you and help you decide if chemotherapy is worthwhile for you. If so, an oncologist will be consulted to take care of you during the chemotherapy process and beyond. The decision must consider many things, but will largely hinge upon the pathologic stage.
- Stage I: No chemotherapy needed.
- Stage II: Chemotherapy warranted in only select high risk cases, but no for the majority. You may wish to discuss the pros and cons with an oncologist.
- Stage III: Chemotherapy is more clearly beneficial to reduce the risk of recurrent disease.
- Stage IV: Chemotherapy is usually offered either to extend life and protect against rapid tumor growth (palliation) or to pre-operatively treat select cases that are planning to go on eventually to a combined surgery of the main colon cancer and the metastatic tumor in hopes of cure.
The chemotherapy usually starts 4-6 weeks after recovery from surgery. Since 2004, the most common and effective chemotherapy regimen is a combination of 5-Fluorouracil (5-FU) and oxaliplatin. This combination is known as FOLFOX and is given for approximately 6 months. In Stage III patients this has been shown to render 72% of patients disease free at 5 years. This is in comparison to historic controls who did not receive chemotherapy under where the likelihood of recurrent disease over 5 years was 50%. A newer agent called capecitabine (Xeloda) is a pill version of 5-FU, that shows similar results and can be used in combination with oxaliplatin. These chemotherapy medicines (with the exception of Xeloda) are given through the veins and usually require a special indwelling IV line called a Portacath to be placed by your surgeon. Although there are newer agents being constantly investigated, they are primarily used for Stage IV cases.
Radiation is not ordinarily used for colon cancer, but it is used for rectal cancer. That is explained by two important principles: 1. the small intestine is very intolerant of radiation and would be damaged by the treatment if used for colon cancer since the colon resides in the abdominal cavity along with the small bowel. There would be no way to protect the small bowel from the harmful effects of radiation. 2. The rectum resides in the pelvis away from the small intestine, but surrounded by the bony pelvis and in very close proximity to other important structures such as the bladder, gynecologic organs of women or prostate nizagara in men and the nerves affecting the function of those organs.
For colon cancer getting margins around the main tumor is usually not difficult because the colon is prednisone freely mobile within the peritoneal cavity. However, because the rectum is in the pelvis, it is in close proximity to these other genitourinary organs and margins are much more difficult, yet critical, to obtain. For that reason, effort is made to use endorectal ultrasound or MRI to assess the depth of the rectal cancer and to see if lymph nodes are enlarged. If found to be Stage II or III, radiation is given prior to surgical intervention. Since the radiation is more effective when given concurrent with chemotherapy, the two are given over a 6 week course before surgery. This often leads to tumor shrinkage allowing the surgeon to achieve a margin negative resection, meaning that the entire tumor was removed with a rim of normal tissue around it and protecting the surrounding other organs not involved by the cancer. The radiation given before the surgery is found to be more effective in preventing pelvic recurrence of tumor as compared to after surgery and leads to better defecatory function by not radiating the new colon that has been attached to the remaining rectum after surgical removal of the rectal cancer.
