Polygenic score
Influential genes: SMAD7
Mutations or alterations in the SMAD7 gene can contribute to the development of various types of cancer, including colorectal cancer.
Colorectal cancer (CRC) is a type of cancer that begins in the colon or the rectum. Afterward, it can spread to other organs, most commonly to the regional lymph nodes, liver, lungs, and peritoneum. It has a high prevalence and unfortunately also high mortality. There is a strong genetic linkage - genetic mutations can be inherited or arise de novo. Other risk factors include race, age, family history, diet, smoking, alcohol, obesity, diabetes, IBD, etc. People can be asymptomatic or present with symptoms like a change in their bowel habits, blood on or in the stool, unexplained anemia, abdominal or pelvic pain, bloating, unexplained weight loss, or vomiting. It is recommended to undergo a screening examination (after the age of 50) to diagnose CRC in the early stages (colonoscopy or occult fecal blood test). Other examinations like CT, blood tests, etc. can be done to determine the stage of CRC. The treatment options are surgery, chemotherapy, radiotherapy, immunotherapy, targeted biological therapy, or a combination of those.
CRC is the third most commonly diagnosed cancer in males and the second in females, according to the World Health Organization. The prevalence is estimated to be 0,7% (5,253,335 people) worldwide and 0,2% (1,536,168 people) in Europe. [1]
A lot of various modifiable and non-modifiable risk factors are associated with the development of colorectal cancer. There is a strong genetic linkage, as different mutations can make an individual highly predisposed to this cancer. Ethnicity is another risk factor - African Americans have the highest CRC rates of all ethnic groups and a 20% higher mortality. Lifestyle also plays an important role in CRC development. An unhealthy diet, high in processed meat, red meat, food cooked using high cooking temperatures, and low in fiber can lead to CRC. Other risk factors include age (higher risk after the age of 50), smoking, family history of CRC, colonic polyps, obesity, Diabetes, Inflammatory bowel disease, cystic fibrosis, acromegaly, androgen deprivation therapy, abdominopelvic irradiation, and renal transplantation.
Colorectal carcinoma (CRC) is a heterogeneous disease. It is estimated that less than 10% of patients are affected due to an inherited predisposition to CRC. Hereditary syndromes are divided according to the occurrence of polyposis. The most common syndromes include familial adenomatous polyposis (FAP), MUTYH-associated polyposis (MAP), or those without polyposis such as Lynch syndrome. These syndromes are associated with an elevated risk of developing CRC. Another 25 % of cases are referred to as familial CRC, but unfortunately, it is the least researched area of CRC, however, genomic and transcriptomic research has revealed possibly associated mutations in APC, TP53, and KRAS genes. The majority of cases are thought to develop sporadically.[2,3]
Genetic testing allows us to detect whether you have the predisposition to develop this disease. In Macromo, we use polygenic risk scores and causative evidence-based genetic variants for evaluation. The polygenic risk score (PRS) represents the total number of genetic variants that increase an individual's risk of developing a particular disease. All variants across their genome are summed and ranked according to their effect on disease development.
Common signs of colorectal cancer include the following: change in bowel habits (constipation, diarrhea, narrowing of stools, incomplete evacuation, and bowel incontinence), blood on or in the stool, unexplained anemia, abdominal or pelvic pain, bloating, unexplained weight loss and vomiting. Some patients can be asymptomatic, leading to a delayed diagnosis and a worse prognosis. Around 20% of patients have distant metastases at the time of presentation at the doctor’s. The most common metastatic sites are the regional lymph nodes, liver, lungs, and peritoneum.
It is recommended to undergo a screening examination regularly, even if there are no symptoms, after the age of 50. In case some risk factors are present (family history of CRC, genetic mutations, etc) it can be recommended to undergo screening earlier. The best screening method is colonoscopy (to visualize the colon). Detecting a small amount of blood in the stool can be also used as a screening examination - the so-called “occult blood” in the stool. During the diagnostic process, your doctor may perform the following tests: blood tests (complete blood count, tumor markers, and liver enzymes), imaging tests (X-rays, CT scan, MRI scan, PET scan, ultrasound, angiography), biopsy, diagnostic colonoscopy (done after you show symptoms, not as a routine screening test) or a proctoscopy.
Depending on the stage of CRC, different treatment options or a combination of them can be used. These include surgery, chemotherapy, radiation therapy, targeted drug therapy, and immunotherapy.
There are several steps you can take to lower the chance of getting CRC. The protective factors are physical activity, diet, and certain drugs (like aspirin or other NSAIDs), although the use of these in the context of prevention is not recommended due to their own adverse effects outweighing any potential benefits.[4] It can be beneficial to consume high amounts of fruit and vegetables, resistant starch, fiber, fish, garlic, coffee, and various vitamins and minerals (Vit B6, Vit D, folic acid, magnesium, and calcium). You should also limit the consumption of red and processed meat. Diagnosing CRC at early stages can give a much better prognosis, so screening is an important secondary prevention method.
The survival rate for people with colorectal cancer depends on the stage of cancer at the time of diagnosis and the individual’s response to treatment.
CRC has a high mortality rate, in 2020 it was the second most common cause of cancer-related deaths. The mortality is 25% higher in males than females and 20% higher in African Americans than in other ethnic groups.
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