Colon cancer – also known as colorectal cancer – is one of the deadliest forms of cancer, responsible for the second-most cancer mortalities in the U.S. among men and women combined. Nevertheless, it’s a hopeful time for patients with colon cancer and their clinicians. The disease’s death rate has been trending downward for years. Earlier detection via colonoscopy and other forms of screening has played an important role in this decline.
The same is true for improvements in treatment.
Advances in colon cancer treatment take many forms, from innovative uses of targeted therapy to treat metastatic disease to immunotherapy to treat patients with colon cancer caused by a hereditary condition known as Lynch syndrome. These advancements give clinicians more tools with which to combat colon cancer.
Signs of Colon Cancer
“Importantly, patients should know that the absence of colon cancer symptoms doesn’t mean an absence of disease – a fact that underscores the importance of screening to catch asymptomatic precancerous polyps or early cancer,” said Dr. Gregory Britt, medical oncologist and hematologist at Rocky Mountain Cancer Centers (RMCC). “In many cases, colon cancer is, initially, a silent disease. Symptoms may not appear until the disease is advanced, by which time treating it is usually more complex.”
When colon cancer symptoms occur, patients may overlook them or assume another condition is responsible. Signs of colon cancer include:
- Blood in the stool
- Constipation or diarrhea
- Persistent abdominal pain
- Unexplained weight loss, which may be the result of a diminished appetite or a bowel obstruction
Tools for Early Detection
Some patients may be unaware of the various colon cancer screening options now available. For many patients and clinicians, colonoscopy remains the screening method of choice. Colonoscopy is unique among colon cancer screening tools in that it allows for the detection and removal of precancerous polyps and certain early cancers during the same procedure.
In 2021, the U.S. Preventive Services Task Force changed its colorectal cancer screening guidelines to recommend screening begins at age 45 instead of 50, and continues until 75, for people of average risk for the disease. When possible, primary care providers should identify high-risk patients and counsel them about starting screenings earlier.
Colonoscopy, of course, is the best-known visual colon cancer screening. Others in this category, in which a clinician uses an endoscope or CT imaging to look for abnormal growths in the colon and rectum, include flexible sigmoidoscopy and CT colonography. Importantly, a colonoscopy is necessary to investigate suspicious results from a flexible sigmoidoscopy or CT colonography.
Stool-based colon cancer screenings have gained prominence in recent years due in part to their noninvasive nature and convenience for patients. Capable of detecting potential indicators of colon cancer in stool samples, these tests may need to be repeated more frequently than visual screenings. In addition, as with non-colonoscopy visual screenings, stool tests that indicate the presence of colon cancer require a follow-up colonoscopy.
An important point to emphasize to patients is that colonoscopy is a common colon cancer screening tool, but it can also play a role in the diagnostic process and even prevent some potential cancers from developing. During a colonoscopy, a clinician may perform a biopsy or remove polyps altogether so pathology analysis can determine if cancer is present.
Colon Cancer Diagnosis
“A complete blood count may point to the possibility of colon cancer if it indicates that bleeding is occurring, potentially setting the stage for anemia,” Dr. Britt said. “However, a biopsy is necessary to definitively diagnose colon cancer. Common imaging tests, including CT, MRI, ultrasound, and X-ray, can help clinicians gauge the tumor’s size and whether it has spread to other organs.”
Molecular testing can help clinicians characterize the tumor for the purposes of treatment planning. The American Society of Clinical Oncology (ASCO) recommends all patients with colorectal cancers undergo testing for mismatch repair defects to check for Lynch syndrome, which causes colon cancer in certain patients. In addition, mismatch repair defect testing can help determine candidacy for immunotherapy in patients with metastatic disease caused by Lynch syndrome.
Improving diagnosis is a key area of focus in colon cancer research. Researchers are studying the efficacy of genetic tests at predicting the risk of colon cancer recurrence, as well as liquid biopsies, which use blood samples instead of tumor samples.
The Present and Future of Colon Cancer Treatment
A variety of colorectal cancer treatment options are available, including surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy. The type(s) of treatment – some patients require multiple modalities – depend on the cancer’s stage and whether it arose in the colon or rectum.
Researchers are studying new treatments for colorectal cancer, including advanced forms of the disease. One promising area of investigation is immunotherapy. Lynch syndrome causes around 5% of colorectal cancer cases, according to the National Cancer Institute, which reports that this group of colon cancer tumors has a potential weakness – their large numbers of mutations can leave them open to attack by immunotherapies.
Oncologists use some immune checkpoint inhibitors, a type of immunotherapy, to treat metastatic colorectal cancer due to Lynch syndrome, as well as microsatellite instability-high colorectal cancer – a form of cancer characterized by numerous mutations. Now, researchers are studying the potential of immunotherapies – often in combination with chemotherapy and other modalities – to treat a wider range of patients with colorectal cancer. This includes patients with deficient DNA mismatch repair metastatic disease, a form of metastatic cancer in which cells cannot repair themselves during the division process. A monoclonal antibody immunotherapy is now the first-line standard treatment for one type of metastatic colorectal cancer.
“This is an exciting time for colorectal cancer care, as innovations in early detection and diagnosis, as well as treatment, help us improve outcomes and quality of life for patients,” Dr. Britt said. “Primary care providers and other referring clinicians play a key role in these efforts by educating patients about colon care and referring them for evaluation when necessary.”
At RMCC, our specialists offer the latest forms of colorectal cancer treatment, and we participate in clinical trials that are helping to determine the therapies of the future. Visit our website to refer a patient.