Colon cancer is a type of cancer that originates from the large intestine. In fact, the common name of large bowel cancers is colorectal cancer. If colorectal cancers originate from the lower part of the large intestine, they are called "rectal cancer" and if they originate from other parts of the large intestine they are called "colon cancer".
Colorectal cancers are one of the most common types of cancer; it is estimated that approximately 1,000,000 people in the world get this cancer every year. As of 2012, colorectal cancer is the second most common type of cancer in women and the third most common type of cancer in men.
Excessive meat consumption, especially processed meat, plays an important role in the development of colorectal cancers. In addition, advanced age, alcohol consumption, constipation and inflammatory diseases such as ulcerative colitis or Crohn's disease of the large bowel increase the likelihood of colorectal cancer. If a member of the family has colorectal cancer, the risk is increased in other family members. In about 5% of the cases, genetic transmission may cause colorectal cancer. However, colorectal cancer develops in 75-80% of patients without any risk factors.
How is it diagnosed?
Colorectal cancers sometimes lead to complaints such as constipation, hemorrhoids and thinning of feces. Sometimes bleeding may be seen in the stool, but generally it can only be detected with special test. Chronic bleeding may cause anemia and sometimes, the only symptom of the patient may be unexplained anemia. In such patients, the tumor can be seen with colonoscopy a definitive diagnosis can be made by obtaining biopsy in the same serssion. After diagnosis of colorectal cancer is made, radiological investigations such as CT, PET-CT and MRI are performed. On these films, it is understood whether the tumor is spread to the lymph nodes, the abdominal membrane and organs such as the liver and lung. Based on these findings these findings, it is decided which treatment should be applied in the patient.
Colorectal cancers sometimes cause no complaints and can be detected by chance in colonoscopy performed for screening. Since approximately 80% of colorectal cancers first begin as polyps and then turn into cancer, colonoscopy can detect the tumor at very early stages and sometimes even before it turns into cancer. The polyps detected during colonoscopy can be biopsied and even removed in the same session, thus preventing the cancer from developing. It is recommended that screening colonoscopy be performed in normal individuals every ten years between 50-75 years of age. In addition to screening colonoscopy, it is recommended to carry out a blood test and DNA test in the stool at regular intervals.
How is it treated?
In colorectal cancer, the first choice of treatment is surgery if the patient is eligible. In some cases, the tumor is minimized by prior (neoadjuvant) chemotherapy or radiotherapy, followed by the operation. In some cases, these treatments can be given after the surgical operation (adjuvant). If the patient has a diagnosis of metastasis at distant organs such as the liver and lungs at the time of diagnosis, chemotherapy and sometimes radiotherapy are preferred. In such patients, if the liver and lung metastases are in a small number and in a single site, both the tumor in the bowel and the metastases may be surgically removed, or the metastases are treated with methods such as radiofrequency, microwave, and cryoablation.
Interventional treatments in colorectal cancers
If the colorectal cancer is located near the anus (rectum cancer), it is often necessary to perform chemotherapy before or after surgery. In such patients, the chemotherapy drug can be given directly to the tumor from the feeding artery of the rectum, rather than to the entire body from the veins. Thus, both the chemotherapy drug becomes more effective in the rectum and the systemic side effects can be reduced. In this method, which is called intraarterial chemotherapy, rectal cancer may become smaller and subsequent surgery may be much easier and effective (neoadjuvant intraarterial chemotherapy).
Rectum cancer may relapse in some patients after surgery. In such cases, colonoscopic biopsy cannot be taken from suspicious masses because the rectum is already removed by surgery. In such cases, a computed tomography guided trucut needle biopsy can be performed to determine whether the suspicious mass is cancer or not. In recurrent rectum cancer, the tumor can sometimes not be surgically removed, the patient may not receive radiotherapy because of previous radiotherapy, and even classical chemotherapy may not be very effective. In such cases, intraarterial chemotherapy can be applied and give successful results because of its stronger regional effect.
Our team is one of the pioneers of intraarterial chemotherapy for rectum cancer and received the first prize at an oncology congress. Click this link to see the award.
Interventional treatments in colorectal cancer metastases
A significant proportion of colorectal cancer patients develop distant organ metastases at the time of diagnosis or later. These metastases are mostly seen in the liver and secondly, in the lungs. If the liver and lung metastases are few in number and their diameter is less than 3 cm, they can be treated with methods such as radiofrequency, microwave and cryoablation.
In many patients with colorectal cancer, metastases in the liver numerous and extensive (e.g. in both lobes of the liver); in such cases, percutaneous ablation is not a viable option. In these patients, classical chemotherapy can be tried first. If it is not successful, transarterial therapies such as chemoembolization and radioembolization may be performed. In liver metastases of colorectal cancer, chemoembolization is usually performed with microparticles loaded with chemotherapy drug called irinotecan. With this method, which is also called DEBIRI, these microparticles are given to the tumors directly from the liver artery via angiography performed every 2-3 weeks. In DEBIRI, both the feeding vessels are occluded and the tumors become bloodless and the irinotecan is released into the tumors from these particles for some days or weeks. The DEBIRI method can be used in combination with normal chemotherapy. Studies have shown that when used in this way DEBIRI can extend patient survival by approximately 2 times compared to normal chemotherapy.
Radioembolization is another frequently used interventional treatment in colorectal liver metastases. In this method, a radioactive substance called Yttrium 90 is loaded into microspheres with a diameter of 50 microns and administered directly into the tumors from the liver artery. Thus, an effective treatment is performed by administering radiation at a much higher dose (3-4 times) than conventional radiotherapy, and the surrounding normal tissues are protected from the effects of radiation. Since DEBIRI and radioembolization kill the tumor with different mechanisms, they are not alternative to each other but may complement each other. Therefore, they can be used together at different times in the same patient.
In colorectal cancer patients, metastases may sometimes only be present in the right or left lobe of the liver. However, the diseased lobe cannot be removed by surgery because the remaining lobe is too small to be sufficient for the patient. In such patients, besides the effective treatment of tumors such as DEBIRI and radioembolization, the feeding vessel of the diseased lobe can also be occluded (portal vein embolization or PVE). In this way, while the diseased lobe becomes smaller (atrophy), the healthy lobe grows (hypertrophy). When the volume of the healthy lobe reaches a certain level, the patient can be safely operated and the diseased lobe be removed.
Colorectal cancers can also metastasize to other organs, including the lungs, besides the liver. Lung metastases can be treated or locally controlled by percutaneous ablation methods, such as radiofrequency, microwave, and cryoablation, if their number and size are favorable.
Interventional oncology in cancer management
Prof Saim Yilmaz, MD