Washington University Colorectal Surgeons answer patient questions regarding colorectal cancer. As internationally recognized leaders in the field, Washington University surgeons partner with Siteman Cancer Center to treat about 350 new colorectal cancer patients a year.
Colorectal cancer refers to cancers that develop from the lining or mucosa of colon and rectum or large intestine. Cancers of the colon and rectum are typically called adenocarcinomas, and are the third most common cancer in men (lung, prostate, colorectal) and in women (lung, breast, colorectal).
Colorectal cancer refers to cancers that occur anywhere within the colon or rectum. The type of cells that make up the line of the large intestine are the same so the difference between the colon and rectum is based on 2 things – anatomy and treatment.
The rectum is the last 6-8 inches of the colon and is located in the pelvis. Within the abdominal cavity the colon is covered by peritoneum, but as it moves into the pelvis to “exit the body” it loses this peritoneal lining and is surrounded by the fat, organs and bony structures of the pelvic bones.
As a result of these anatomical differences, the initial treatment of rectal cancer often differs from colon cancer. Colon cancers are treated with surgery first and the need for further treatments such as chemotherapy are based on the pathologic stage determined from surgery. On the other hand, rectal cancers may be treated with chemotherapy and radiation therapy before surgery. Therefore evaluation prior to determining treatment is important. The first exams are a digital rectal exam and proctoscopy, which allow the surgeon to look inside the rectum to determine the exact location of the rectal cancer. The second exam is a rectal cancer-specific pelvic MRI to determine how far through the wall of the rectum the cancer has grown, if there are lymph nodes involved, and the relation of the tumor to the margins and other structures of the pelvis.
There are no symptoms specific for colorectal cancer, as over 75% of people have no symptoms or family history of colorectal cancer at the time of diagnosis. Therefore, risk appropriate screening for colorectal cancer is extremely important. Common symptoms associated with colorectal cancer include blood associated with bowel movements, blood in the stool, change in bowel habits, new or changing abdominal pain, and unexplained weight loss. The blood may be bright red, occur as clots or appear as black stools. Persistent bleeding does need to be evaluated. The change in bowel habits can range from thin stools to constipation to frequent loose stools. If none of these changes resolve by improving your bowel regimen, a colonoscopy in the next step. Abdominal pain associated with a change in bowel habits should prompt a call to your physician for evaluation.
The major risk factors for the development of colorectal cancer are age, genetics and diet.
By age 50, the risk of developing colorectal polyps or cancer begins to increase, which is why it is recommended to begin screening at age 50.
Genetics plays a significant role in the development of colorectal cancers. There are 2 well-defined genetic cancer syndromes that are associated with colorectal cancer: Familial Adenomatous Polyposis (FAP) and Hereditary Nonpolyposis Colorectal Cancer (HNPCC) or Lynch’s disease. These syndromes account for only 5-10% of all cases of colorectal cancer. A family history of colorectal cancer impacts your risk of developing colorectal cancer based on the number of family members affected and their degree of relation to you. For example, a patient’s risk is increased 2-3 fold if they have one first degree relative (mom, dad, bother, sister or children) with a history of colorectal and the risk increases to 3-4 fold if they have 2 first degree relatives affected. The risk is increased 1.5 times if there is a second degree relative (grandparents, aunts and uncles). Understanding your family history can help assess your risk for developing colorectal cancer.
Diet clearly impacts your risk of developing colorectal cancer, but the data is sometimes difficult to understand. We do know that there is a direct correlation between the amount of animal fat consumed and the risk of developing colorectal cancer. Also, westernized countries with diets with a high degree of processed foods also have a higher incidence of colorectal cancer than countries with a lower rate of processing food.
Colorectal cancer screening is any test that is able to examine the colon for the presence of colorectal polyps or cancers. There are many tests available to help detect colorectal cancer, and they all have their advantages and disadvantages. Colorectal cancer is extremely preventable and any form of colorectal cancer screening has been shown to be beneficial at improving the detection and survival for colorectal cancer. Screening tests include stool based tests, x-ray based tests, and colonoscopy.
Stool based tests include:
- Highly sensitive fecal immunochemical test (FIT) – annual
- Highly sensitive guaiac-based fecal occult blood test (gFOBT) – annual
- Multi-targeted stool DNA test (example: Cologard) – every 3 years
The most effective X-ray base study used today is the virtal colonoscopy or CT colonography. This test is a specialized CT scan able to examine the colon. A prep or colon cleanse is still required and at the time of the exam air is instilled into the colon so that it is distended for the exam.
The gold standard for colorectal cancer screening is the colonoscopy, because it is the best test available to detect small and large polyps and cancers. In addition to being diagnostic, it can also be therapeutic. If a polyp is detected, it can be removed and biopsied, and once removed, a cancer is prevented. The major drawback of colonoscopy is the prep. It can be challenging but there are several 2 dose low volume preps that make it more tolerable.
There are no blood tests that can be used to diagnose colorectal cancer. There are 2 tests that are used in surveillance or follow-up for patients who have been treated for colorectal cancer. The first is a tumor marker or protein called carcinoembryonic antigen or CEA. This is part of routine follow-up for patients with a history of colorectal cancer. Gardant360 test for the presence of genes in the blood stream associated with colorectal cancer. This test is also used for surveillance in patients with a history of colorectal cancer. It is used when there is an elevated CEA level but all imaging (CT scan, MRI or PET scan) are negative.
There are 2 types of staging for colorectal cancer.
Prior to treatment, imaging with a CT scan or MRI can provide clinical staging. The goal of this is to determine if there is concern that the tumor has spread beyond the original site in the colon.
The pathologic staging is the most accurate and cannot be determined until after surgery. The pathologic stage is determined once a pathologist is able to examine the tumor and lymph nodes under a microscope, and it is based on the TNM system. The T is how far into or through the wall of the colon the tumor has grown. The N stage examines the lymph nodes and the M stage examines the presence of tumor in sites other than the colon or lymph nodes. The final stage is then a combination of three components.
Stage I cancers are those where the tumor is confined to the muscle layer of the colon wall and all lymph nodes are negative. Stage II tumors have grown through muscle layer and have negative lymph nodes. Stage III tumors can invade any layer of the colon wall but have one or more positive lymph node. A tumor is stage IV once it has grown in any site distant from the colon and its lymph nodes such as the liver or lung.
Colorectal cancer is very curable, but most importantly it is preventable.
Risk appropriate screening is the best tool to prevent or cure colorectal cancer. However, once a colorectal cancer develops there is a good chance that it is curable. For colon cancer, the primary treatment is surgery, which entails removal of the tumor and the lymph nodes associated with that segment of the colon. This allows the pathologist to examine the tumor and the lymph nodes to determine the stage of the tumor. The stage then helps to determine the need for further treatment and gives us an idea of cure rate for that tumor.
Stage I tumors require no further treatment and the curability is around 95%.
Stage II tumors typically do not require any further treatment but there are certain situations where chemotherapy might be discussed. Survival at 5 years after surgery is around 90%.
Stage III is when the tumor has been found in the lymph nodes that were removed at the time of surgery. Patients with stage III colon cancer are treated with chemotherapy. First line chemotherapy includes 3 drugs – 5-FU or capcitabine, leucovorin, oxaliplatin, and lasts for 8-12 cycles. Each cycle lasts 2 weeks and consists of one week where the chemotherapy is given and then a rest week. Five-year survival for stage III colorectal cancer is greater than 70%.
The treatment for stage IV colorectal cancer includes chemotherapy and may include surgery or radiation dependent upon the individual situation. There are several other chemotherapy options available that included targeted therapy and immunotherapy. Survival for stage IV colorectal cancer is around 15% and is dependent upon the number of tumor deposits and the number of sites involved.
Washington University Colon and Rectal can provide screening, care options and treatments for colorectal cancer. Meet our specialists below.