What is Colorectal Cancer?


March is National Colorectal Cancer Awareness Month. According to the American Cancer Society’s 2021 report, colorectal cancer affects approximately 4.1% of men and women combined over the course of their lifetime in the United States. National Colorectal Cancer Awareness Month is an opportunity to raise awareness about this deadly disease and the importance of early detection.
Colorectal cancer is a type of cancer that affects the colon (large intestine) or rectum.1 This cancer develops when abnormal cells in the lining of the colon or rectum begin to grow and divide uncontrollably, forming a tumor. Over time, the tumor can invade and damage nearby tissues and organs or spread to other parts of the body, such as the liver or lungs.
Colorectal cancer is the third most common cancer worldwide, accounting for approximately 10% of all cancer cases. In 2020, an estimated 1.9 million new cases of colorectal cancer were diagnosed globally, and approximately 935,000 deaths were attributed to the disease.2 According to the American Cancer Society, as of 2023, there are 106,970 new cases of colon cancer and 46,050 new cases of rectal cancer in the US annually. It is estimated that the worldwide number of new diagnoses each year will increase to 3.2 million by 2040.2 The risk of developing colorectal cancer increases with age, with more than 90% of cases occurring in people aged 50 and older.3
For patients experiencing colorectal cancer, there are many medical and emotional challenges they may encounter.4 As we continue to work with healthcare providers, Baylor Genetics’ goal is to provide both patients and providers resources to help both better navigate this disease. For National Colorectal Cancer Awareness Month, we would like to share educational information about colorectal cancer, including its cause, symptoms, testing, and treatment options that will benefit healthcare providers and their patients.


Colorectal cancer can be influenced by both genetic and environmental factors. In some cases, the disease can be inherited through a family’s genetic makeup. Changes within certain genes are associated with a high-risk (predisposition) for developing cancer. People with a family history of colorectal cancer, especially those with a first-degree relative (e.g., parent, sibling, or child) who has had the disease, have a higher risk of developing the disease themselves.
“With colorectal cancer, about 70% of individuals will have what’s called ‘sporadic cancer,’ which is to say that there are no inherited genetic or familial factors that are contributing to it,” said Robert Rigobello, Senior Genetic Counselor at Baylor Genetics. “On the other hand, about 5-10% of patients with colorectal cancer have inherited genetic changes which directly lead to them developing that cancer.”
The most well-known hereditary colorectal cancer syndromes are Lynch syndrome and familial adenomatous polyposis (FAP).
Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is the most common inherited colorectal cancer syndrome and accounts for approximately 3% of all newly diagnosed cases of colorectal cancer. Lynch syndrome is caused by changes in the mismatch repair genes (MLH1, MSH2, MSH6, and PMS2) and epithelial cellular adhesion molecule (EPCAM).6 Lynch syndrome causes about 4,200 colorectal cancers per year.7 People with Lynch syndrome have a 50-80% lifetime risk of developing colorectal cancer, and their risk of other cancers, such as uterine (endometrial) and ovarian cancer, is also increased.
FAP, on the other hand, is a less common cancer syndrome, accounting for less than 1% of cases.7 FAP is caused by changes in the adenomatous polyposis coli (APC) gene which leads to the formation of numerous polyps in the colon and the rectum. Both Lynch syndrome and FAP are inherited in an autosomal dominant pattern, which means that a person only needs to inherit one copy of the mutated gene from a parent in order to develop the condition.
Regular screening for colorectal cancer, as well as making healthy lifestyle choices, can help reduce the risk of developing the disease. If detected early, colorectal cancer is often treatable, which is why it’s important to be aware of the signs and symptoms of the disease and to undergo regular screening. Screening recommendations might be different for patients that have been previously diagnosed with colorectal cancer or have a genetic change associated with a predisposition to developing colorectal cancer.


Colorectal cancer may not cause any symptoms in the early stages, which is why screening is important for early detection.5 However, as the cancer grows and spreads, it can cause a range of signs and symptoms, including changes in bowel habits, such as persistent diarrhea or constipation, blood in the stool or rectal bleeding.
Other symptoms include:

  • Abdominal pain
  • Cramping
  • Unexplained weight loss
  • Weakness
  • Feeling that the bowel is not empty even after a bowel movement
  • Anemia

By educating your patients about the signs and symptoms of cancer, you can help them recognize when they may need to seek medical attention. There is also an opportunity for them to share this knowledge with their friends and family, which can help raise awareness and promote early detection for these groups.
While diagnosis may be made based on clinical symptoms or invasive procedures, such as a colonoscopy, there are other preventative and early testing options which may be best for your patient.


Approximately 1 in 3 people in the US will be affected by cancer during their lifetimes and 5 – 10% of colorectal cancers are believed to be due to hereditary predisposition.8 At Baylor Genetics, our Hereditary High-Risk Colorectal Cancer Panel analyzes 22 genes associated with an increased risk for colorectal cancer.
Genes in the panel:

  • APC
  • AXIN2
  • BMPR1A
  • GALNT12
  • GREM1
  • MLH1
  • MLH3
  • MSH2
  • MSH3
  • MSH6
  • NTHL1
  • PMS2
  • POLD1
  • POLE
  • PTEN
  • RNF43
  • RPS20
  • SMAD4
  • STK11
  • TP53

It’s important to note that while Baylor Genetics Hereditary High-Risk Colorectal Cancer Panel is a powerful tool for identifying inherited cancer risk, it’s not appropriate for everyone. The decision to undergo genetic testing should be made in consultation with a healthcare provider or a genetic counselor who can help determine whether testing is appropriate based on individual circumstances and risk factors.


There are several methods for detecting and identifying colorectal cancer, including both invasive and non-invasive tests. Invasive tests, such as colonoscopies, are typically recommended for individuals with an increased risk of colorectal cancer or those with abnormal results on non-invasive tests, such as fecal occult blood tests or stool DNA tests. The American Cancer Society and many healthcare providers recommend colonoscopies as one of the appropriate methods of screening for individuals between ages 45 –75 years.
Non-invasive tests may be recommended for individuals at average risk of colorectal cancer as they are less invasive. These include tests such as fecal immunochemical tests (FIT), which detect blood in stool samples, or virtual colonoscopies, which use CT scans to produce detailed images of the colon.
It is important for healthcare providers to take a personalized approach when assessing their patient’s risk of hereditary cancer and determining appropriate screening or testing options. This may involve a comprehensive evaluation of personal and family medical history, as well as consideration of other factors such as age, sex, and lifestyle.


There are several treatment options available for colorectal cancer, depending on the stage and location of the cancer. Some of the most common treatment options include: 10

  • Surgery for colon and rectal cancer involves removing the cancerous tumor and surrounding tissue.
  • Radiation therapy uses high-energy rays or particles to destroy cancer cells.
  • Chemotherapy uses anticancer drugs that maybe be taken orally or injected intravenously.
  • Targeted therapy uses drugs that target specific proteins that aid in the growth of cancer cells.
  • Immunotherapy uses drugs to help the body’s immune system recognize and attack cancer cells.

The choice of treatment may vary based on several factors including location of the tumor, the patient’s health and medical history, and other personal factors.


Raising awareness about colorectal cancer can play a vital role in enhancing the early detection rates and improving access to screening and treatment options, particularly for underserved populations. Educating patients about the risk factors, signs, symptoms, and screening options is an effective way to spread awareness about colorectal cancer.
Nearly one-third of the eligible population in the United States remains unscreened for colorectal cancer, despite the availability of multiple screening modalities and various public health programs aimed at increasing screening rates.11 Some reasons individuals may not be getting screened include lack of awareness or education about the importance of screening 12, fear or discomfort with the screening process 13, and limited access to screening options.13
By prioritizing preventive care and leveraging the latest advancements in genetic testing, Baylor Genetics can identify potential health risks earlier and help improve patient health outcomes. By working collaboratively, we can help individuals and families affected by cancer make informed decisions about their healthcare and improve their overall quality of life.
If you have questions or would like to discuss whether Baylor Genetics’ Hereditary High-Risk Colorectal Cancer Panel is the right test for your patient, our genetic counselors are available to speak with you.

  1. American Cancer Society. (2020, June) https://www.cancer.org/cancer/colon-rectal-cancer/about
  2. Yue Xi, Pengfei Xu, Global colorectal cancer burden in 2020 and projections to 2040, Translational Oncology, Volume 14, Issue 10, 101174, 2021.
  3. American Cancer Society (2023, January) https://www.cancer.org/cancer/colon-rectal-cancer/about
  4. National Cancer Institute. (2023. March) https://www.cancer.gov/about
  5. Centers for Disease Control and Prevention. (February 2023) https://www.cdc.gov/cancer/colorectal/about
  6. National Cancer Institute. (2023, February) https://www.cancer.gov/types/colorectalgeneticspdq/about
  7. Centers for Disease Control and Prevention. (2022, March) https://www.cdc.gov/genomics/disease/colorectal_cancer/lynch/about
  8. Baylor Genetics. Hereditary Cancer (2023, January) https://www.baylorgenetics.com/hereditary-cancer/
  9. Preisler, L., Habib, A., Shapira, G. et al. Heterozygous APC germline mutations impart predisposition to colorectal cancer. Sci Rep 11, 5113, 2021.
  10. American Cancer Society. ((2020, June) https://www.cancer.org/cancer/colon-rectal-cancer/treating/about
  11. Shaukat, Aasma, Kahi, Charles J. Burke, Carol A.; Rabeneck, Linda; Sauer, Bryan G.; Rex, Douglas K. ACG Clinical Guidelines: Colorectal Cancer Screening 2021. The American Journal of Gastroenterology 116(3): p 458-479, 2021.
  12. Harmy MY, Norwati D, Noor NM, Amry AR. Knowledge and attitude of colorectal cancer screening among moderate risk patients in West Malaysia. Asian Pac J Cancer Prev.,12(8):1957-60, 2011
  13. American Cancer Society. (2020, June) https://www.cancer.org/cancer/colon-rectal-cancer/detection-diagnosis-staging/screening-tests/about

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