Colorectal cancer: diagnosis, treatment options, and more
Understanding Colorectal Cancer
Colorectal cancer can be found in a few different ways. Few patients will present with symptoms like bleeding from the rectum, blood in the toilet bowl, changes in stool shape, belly cramps, or a sudden urge to go to the bathroom. Sometimes, it's spotted during a scan, like a CT scan, or through a screening colonoscopy or sigmoidoscopy, which involves taking a camera to look inside the colon or rectum. Some patients, particularly those who choose to forego a colonoscopy, may have a stool test that shows that there is blood or cancer DNA. It may also be better imaged through tests like CT colonography or a barium enema. To make the diagnosis, doctors typically take a small piece of tissue in a procedure called a biopsy.
Staging Colorectal Cancer
Once colorectal cancer is found, doctors figure out the extent of its spread through a process called "staging." They look at things like the size of the tumor and if it's grown through the colon wall (T), if cancer cells are in the lymph nodes (N), and if cancer cells have spread to other parts of the body (M). They use tests like CT scans, MRIs, PET/CT scans, and blood tests to check for tumor markers like CEA and CA 19-9. The stage can be from 1 to 4, with 4 representing metastatic disease, or when cancer has left the colon or rectum and gone to other places. The stage and type of colorectal cancer help your doctor decide the best treatment.
Different Types of Colorectal Cancer
Doctors look at two main things to determine the type of colorectal cancer. First, they look at the kind of cells the cancer is made of. For example, the most common type is called "adenocarcinoma," which means it starts in cells that form glands. There are also other types like carcinoid tumors, which start in hormone-producing cells, and gastrointestinal stromal tumors (GIST), which begin in muscle tissue.
Second, doctors study the genetics of the tumor. This helps them choose the right treatments. Some gene mutations run in families, like familial adenomatous polyposis (FAP) and hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome).
Difference Between Colon and Rectal Cancer
The colon is the first 5 feet of the large intestine, and the rectum is the last 6 inches. Surgery is often used more for colon cancer because it's easier to reach. Rectal cancer is in a tighter space and often requires different types of care, including surgery, radiation, and systemic therapy. There are an increasing number of novel treatment approaches being tested that are aimed at sparing a patient surgery or radiation, but so far, only select patients are eligible based on their biomarkers.
Systemic Therapy
Colorectal cancer is tested for specific markers like "microsatellite instability" or MSI-high and "microsatellite stable" or MSS. They also check for genetic changes like KRAS, BRAF V600E, HER2, and markers for Lynch syndrome (MLH1, MSH2, MSH6, PMS2, and EPCAM). These tests help doctors choose the right therapy.
For early stages (1-2), surgery is often enough if the cancer hasn't spread to lymph nodes. Some high-risk stage 2 cases may need a short course of chemotherapy.
In stage 3, the cancer has spread to nearby lymph nodes but not to other organs. Treatment usually starts with surgery to remove the part of the colon or rectum with cancer. Then, patients get a short course of chemotherapy, generally either FOLFOX or CapeOx. If surgery isn't possible, some patients may have radiation therapy before surgery to shrink the tumor.
For advanced colorectal cancer (stage IV or it comes back), different treatments are considered. Some people with only a few metastases (oligometastases) might have them surgically removed, and then treated with an aim of cure. This is different from many other stage IV cancers where a cure is unlikely.
Remember to discuss your specific diagnosis and treatment options with your doctor.
