Aki Ohinata, MSPA-C
Physician Assistant
Department of Gastrointestinal Medical Oncology
The University of Texas MD Anderson Cancer Center
Hello. My name is Aki Ohinata. I'm a Physician Assistant at Department of GI Medical Oncology at University of Texas MD Anderson Cancer Center. Today, I'll be discussing overview of the colorectal cancer as part of the Colorectal Survivorship Program.
At the conclusion of this lesson, the participants will be able to discuss the epidemiology and etiology of colorectal cancer; identify those at increased risk of the disease; list advantages and disadvantages of various screening tests; define the stage of disease using American Joint Committee on Cancer Staging System; and order appropriate testing for newly diagnosed patients.
Colorectal cancer is the second leading cause of cancer-related deaths in the United States when both sexes are combined. Expected death in 2010 is roughly a little over 51,000, with lifetime risk of men developing colon cancer slightly higher than women.
Colorectal cancer is thought to result from sequential accumulation over the years of genetic and molecular alterations that ultimately lead to transformation of normal epithelium into intraepithelial neoplasia/dysplasia, then malignant epithelium.
Seventy-five percent of all colorectal cancer patients have sporadic disease. The remaining 25 percent of the patients have a family history of colorectal cancer. Genetic mutations have been identified as the cause of inherited cancer risk in some colon cancer-prone families, but these mutations are estimated to only account for five to six percent of colorectal cancer cases overall.
This chart describes the rel --- relative and absolute risk of developing colorectal cancer, based upon the patient's family history, mainly looking into the involvement of first-degree relatives with colorectal cancer. And, as you could tell, the more patients with first-degree --- more than one first-degree relative with colorectal cancer diagnosis have the higher risk of developing cancer themselves. And, the close second will be one affected first-degree relative diagnosed with colorectal cancer before the age of 45.
As mentioned on the previous slide, inherited gene mutations being the cause of colorectal cancer is a small percentage in overall cases. However, these patients do have higher increased risk of developing the cancer compared to the general sporadic colon cancer patients. Mutation in the APC gene, which is a tumor suppressor gene, is shown in familial adenomatous polyposis and Gardner syndrome. Mutation in DNA repair gene is seen in hereditary nonpolyposis colon cancer, or HNPCC, also known as the Lynch syndrome. Peutz-Jeghers syndrome is known to have a mutation in STK11 gene, which is also thought to be a tumor suppressor gene. A mutation in MADH4 gene is associated with the juvenile polyposis.
This chart describes as --- absolute risk factors for colorectal cancer for mutation care --- carriers in hereditary colorectal cancer syndromes. In this chart, it shows that FAP does have the highest absolute risk in mutation carriers where there is a 90 percent risk by age 45 years old. Lynch syndrome also has a higher absolute risk of 40 percent to 80 percent by the age 75.
Other risk factors for colorectal cancer includes diet high in total fat and meat, including both red and white meat, cigarette smoking, sedentary lifestyle, inflammatory bowel disease, older age, low fiber diet, and obesity.
Patients without increased risk of colorectal cancer should undergo screening at age 50. Patients with increased risk of colorectal cancer, for example, personal family history of colorectal cancer, adenomatous polyp, or IBD, should undergo screening before age 50.
This chart explains available test types for screening methods and other pros and cons. Fecal occult blood test is a very simple test that could be completed at home by the patient, but it does fail to detect most polyps and/or cancer, and also could show puls ---false positive results. Sigmoidoscopy is a common test that could be done in the physician's office, and it is also helpful to obtain tissue biopsy. The limitation is that this study can only examine the lower half of the colon and the rectum. Colonoscopy is the most sensitive test currently available to diagnose or screen for colorectal cancer. And, this can obtain tissue biopsies and remove polyps, if needed. The thorough bowel preparation is required to undergo this test. Virtual colonoscopy is a noninvasive procedure. However, this also requires a thorough bowel prep. If abnormality is found, patient is required to have a colonoscopy done, and this also accounts for its limitations. Double bari --- or double contrast barium enema is a test where complications are very rare. However, this also cannot remove polyps or obtain biopsy, if needed. A digital rectal exam is the most simple test usually done by the --- in the physician's office. However, it can only detect abnormality in the lower rectum.
This chart describes --- I'm sorry--- this chart shows the frequency of the testing required for colorectal cancer screening. For general population with average risk, recommendation is for colonoscopy every 10 years or fecal occult blood test annually and flexible sigmoidoscopy every five years beginning at age 50. Depending on the patient's risk factors or family history, the frequency of these screenings are shortened and most of the time the testing are started at a younger age than 50 years old.
Colonoscopy currently is the most sensitive test available for detection of colorectal cancer.
Okay. I'll be discussing some histologies.
Immunohistochemical markers: These are the typical colorectal cancer staining when seen under the microscope. These are po --- negative for CK7, positive for CK20, positive for CEA, positive for CDX2, and negative: TTF1. Microsatellite instability test is performed mainly for screening inherited cancer risk factors. MSI-low are stable, shows no absent immunostains of mismatch repair proteins. MSI-high suggests absence of staining in one or more of the mismatch repair proteins and for these MSI-high patients he or she should consider genetic testing to rule out or further evaluate possibility of inherited cancer genes, such as the Lynch syndrome.
The AJCC staging system is utilized for appropriate staging of colorectal cancer. T stands for the tumor, N for the node, and M for metastatic disease. This chart is actually the Sixth Edition of the AJCC Cancer Staging Guidelines.
This is an illustration of difference between Stage I through IV of the colon cancer.
We do have the AJCC Seventh Edition available which can be obtained through this website listed.
This chart describes the survivor rate based upon the staging. Traditionally, the earlier the staging the better the five-year survival rate. And, as higher end staging or increased lymph node involvement decreases the overall five-year survival rate.
Once the diagnosis of colorectal cancer has been made, patients should have a baseline tumor marker, the CEA, drawn along with standard lab work including CBCs and chemistries. Staging workup via imaging studies such as CT scan, MRI or PET-CT scan should be completed. CT scan is ideal for baseline and restaging workup. For rectal cancer, flexible sigmoidoscopy with EUS or MRI of the pelvis can be used to evaluate the T and the N staging preoperatively. Refer patients to oncologists for evaluation and management.
This chart shows an algorithm on referral process for patients newly diagnosed with colon cancer. Once the diagnosis of colon cancer has been made, it is recommended to obtain baseline CEA and CT including the chest, abdomen and, pelvis. If the patient is found not to have metastatic disease, then they should be referred to a colorectal surgeon for resection. Based upon the staging, the patient will then receive appropriate treatment, if necessary. For patients with metastatic disease at the time of presentation, it is recommended for them to be referred to a medical oncologist to initiate systemic therapy. If the patient presents with obstructive symptoms, they could be considered to be referred to a surgeon for possible diverting surgery or stent placement.
For patients with newly diagnosed rectal cancer, the initial workup is similar, including the baseline CEA and CT of the chest, abdomen, and pelvis. But, in addition to this, we rec --- rec --- recommend obtaining a flexible sigmoidoscopy with EUS or MRI of the pelvis for the preoperative T and N staging. Patients without metastatic disease and was found to have Stage I rectal cancer, they should be referred to the colorectal surgeon for resection followed by surveillance. For patients with Stage II or III rectal cancer, he or she should be referred to the radiation oncologist and medical oncologist for neoadjuvant chemoradiation therapy followed by resection by the colorectal surgeon. These patients will then go on to receive the adjuvant therapy as needed. A patient who is found to have metastatic disease at time of presentation should be referred to the medical oncologist for initiation of systemic therapy. Again, if the patient presents with obstructive symptoms, bleeding, or severe rectal pain, they sh --- may benefit from evaluation by the colorectal surgeon for diverting surgery or stent placement as well.
In summary, colorectal cancer is the second leading cause of cancer-related death in the United States when both sexes are combined. It is a preventable disease in many cases with routine screening. It is important to identify a patient population at increased risk of colorectal cancer early on to start the screening, and once the col --- diagnosis of cancer has been made, to efficiently refer these patients to an oncologist. Thank you very much for your time. We appreciate any feedback. Thank you.
Review of Colorectal Cancer video
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