Ask the Expert

To provide patients and their families with a more in-depth understanding about colorectal cancer, how it’s treated, and what different options are available, we spoke with Arturo Loaiza-Bonilla, M.D., Chief of Medical Oncology and Medical Director of Research at Cancer Treatment Centers of America® (CTCA) in Philadelphia. Dr. Loaiza-Bonilla focuses on gastrointestinal malignancies. We asked him about the kinds of diagnostics patients may require, the latest approaches in treating colorectal cancer, such as surgery and immunotherapy, and the differences between permanent and temporary ostomies, and when an ostomy may be necessary.

Question: What types of additional diagnostics and imaging tests would a patient need after receiving a colorectal cancer diagnosis?

Dr. Loaiza-Bonilla: The first thing we do after a diagnosis, which is usually done by biopsy, is to learn the stage, how big the tumor is, how developed it is, where exactly it is growing, how it is affecting surrounding tissue. We need to know where this cancer is located and where it came from. We then do blood work to get readings on what’s going inside the body, such as kidney and liver function, and to look for tumor biomarkers, which cancer patients may have in their bloodstream and that we don’t usually see in healthy patients. Those tumor marker levels may be elevated in some cancer patients, and not in others. We specifically look at CEA levels, or carcinoembryonic antigen levels, so we follow those numbers throughout treatment. After that, we do CT (computerized tomography) scans, which take images of the chest, abdomen and pelvis to determine whether the cancer is confined to where the colonoscopy found that cancer, or whether it exists elsewhere.

Question: How is the stage of colorectal cancer determined?

Dr. Loaiza-Bonilla: It’s all based on the stage of the tumor, whether it’s stage I, II, III or IV. Stages I and II are the earliest stages, when the tumor is confined to the colon or rectum; in stage III, it has spread to the lymph nodes; and in stage IV, it has traveled to other organs in the body. For stages I and II, surgeons perform an R0 (R-zero) resection, which is a complete removal of the tumor. They also remove “margins,” or small amounts of surrounding tissue, to ensure they have not left cancerous cells behind.

Question: How is a more advanced colorectal cancer treated?

Dr. Loaiza-Bonilla: It gets more complicated with stage III and IV colorectal cancers, and we need as much information as possible about how the cancer is behaving. Surgeons have to look at removing surrounding lymph nodes for stage III, to see whether the cancer has metastasized further. Also, these patients have a higher risk of recurrence, so after surgery, we often have to add treatments, which may include chemotherapy and/or radiation. For some colorectal cancers, we may give chemotherapy or radiation before surgery to shrink the tumor, which is called neo-adjuvant treatment. This helps produce more positive results from surgery and may help reduce the risk of bowel incontinence, because the surgeon won’t need to go as deep and compromise those sphincter muscles because we’ve shrunk the tumor. We refer to that as “colostomy-free outcomes.” With a stage IV, which is metastatic cancer, we need to look at the genetic blueprints of the tumor, find weaknesses where we can attack, and, based on that information, select particular drugs that can zero in on weak spots. That varies patient by patient.

Question: When would radiation be used instead of chemotherapy?

Dr. Loaiza-Bonilla: Usually, radiation therapy is given in combination with chemotherapy (at a lower dose), and we use it to shrink the tumor before surgery (neoadjuvant), or to remove microscopic cancer cells from the surgical site after we remove the tumor. This mostly depends on the location of the tumor. Rectal cancers are ideal candidates because of the anatomical structure of the rectum, which is confined to the pelvis, making it a fixed portion of the bowel that can be targeted with better precision. The colon is always moving within the abdomen because of peristalsis, which is the medical term for bowel movements. This makes radiation very difficult to administer because we cannot predict where or how the colon will move in that moment in time, making it a moving target. However, the rectum is more fixed, making it a better target for radiation. Patients who have to have part of their rectum removed are more likely to need a colostomy or ileostomy to help them manage waste after surgery. We also use radiation therapy to treat single spots of cancer that has spread or metastasized and causing pain, for example in the bones, etc.

Question: Can you explain the difference between a colostomy and an ilestomy and when they would be recommended?

Dr. Loaiza-Bonilla: “Ostomy” means having a diversion somewhere in the body, so an ilestomy is performed on the ileum, or small bowel, and a colostomy is performed on the colon. These two procedures have the same purpose, but the location of the tumor determines which ostomy you need to use. As you know, the digestive tract is quite long. The small bowel can be 20 feet long, and consists of the duodenum, jejunum and ileum. The small bowel is connected to the large intestines, or colon, which is about five feet long. We have several sections of colon, which is very large. The colon consists of the cecum, the ascending colon on the right side, the transverse colon, the descending colon on the left side, and the sigmoid colon, which connects to the rectum and anus. If the tumor is close to the ascending colon or if it’s causing obstruction and you need to bypass the whole colon, that’s when you use an ileostomy. If the tumor is located more toward the end of the colon, and you just need to bypass part of the colon to pass waste, then this is when you might need a colostomy.

Question: When would a patient need a permanent versus a temporary ostomy?

Dr. Loaiza-Bonilla: Temporary ostomies are recommended when we anticipate that the reasons for the obstruction are something we can reverse, such as when a bypass in the colon is no longer needed. Temporary ostomies depend on the treatment, such as a complete resection of the tumor, so it could take several months. If a patient has cancer in the lymph nodes after the tumor is removed, we have a window of a few weeks after the surgery when chemotherapy is more likely to have positive results. In those cases, we advise patients to have their ostomy reversed after they’ve finished the chemotherapy. After an ostomy is reversed, the healing process takes time before the patient can return to normal bowel function, usually several weeks to a few months. Permanent ostomies are for when we know bowel function will never be restored. For example, if the patient has a low-lying tumor in the rectum, and we have to remove the sphincter to remove the cancer, then we know the patient will need a permanent ostomy.

Question: What are the differences between chemotherapy and radiation?

Dr. Loaiza-Bonilla: Radiation, either with protons or photons, is limited by the dose and the area. It’s a singular treatment limited by the beam of radiation that’s being delivered, so it’s quite targeted to one area. You could not treat colorectal cancer with radiation therapy if it has spread to other areas of the body or into a number of lymph nodes because you would have to pinpoint all of these individual areas with beams of radiation, and that’s not only ineffective but quite toxic. You could use radiation on a patient with metastatic cancer, but you are only delivering radiation to a single site that is symptomatic. You’re not going to radiate multiple sites at multiple times because that would be too much for any one person to endure. With chemotherapy, the goal is to reach multiple sites with a single drug. Not all drugs are the same; they have different features to attack particular weaknesses of a colorectal tumor and have targeting abilities. With chemotherapy, targeted therapy and immunotherapy, we look for the molecular underpinnings of the tumor so we can destroy the tumor’s DNA and stop it from growing.

Question: Can you talk about some of the advances in colorectal cancer treatment?

Dr. Loaiza-Bonilla: The most recent development in colorectal cancer involves exploring micro-satellite instability (MSI) within the tumor, to determine whether the tumors struggle with DNA repair. We use immunotherapy or drugs called immune checkpoint inhibitors for tumors that are MSI-high or mismatch repair deficient, removing the blindfold of the immune system so it can fight cancer on its own. A tumor that is MSI-high has a broken DNA repair system, and produces several abnormal proteins that the immune system can recognize and then attack, so MSI-high tumors tend to be sensitive to immunotherapy. Two immune checkpoint inhibitors approved by the Food and Drug Administration for MSI-tumors are pembrolizumab and nivolumab. They’re very new. We are seeing quite promising results with these agents, which we are combining with chemotherapy and targeted therapies in some cases, leveraging the immune system to attack tumors. It is a very exciting time to be an oncologist and being able to help many patients with these novel therapies.