Cancer prevention awareness
By: Dr. James Aw, Chief Medical Officer, OMERS
July 7, 2025
Cancer affects us all. We all know someone who’s lived with it. Perhaps you’ve been a caregiver for a loved one with cancer. You may even be a survivor yourself. It can be a scary and stressful journey.
It is estimated that the human body has over 30 trillion cells. Cancer occurs when normal cells turn into cancer cells (carcinogenesis) which have a predisposition for uncontrolled growth and the ability to invade other tissues. Genetic and environmental factors can drive mutations in genes (oncogenes, tumour suppressing genes) that lead to cancer growth. Some cancers are “benign” and stay local, not easily spreading to other organs. However, they can cause some local mechanical pressure effects depending on their location (i.e. skin masses, nervous system growths like meningiomas, nerve sheath, etc.). “Malignant” cancers are more aggressive and unstable. Malignant cancers spread to other organs (metastasis) and can be lethal. There are over 100 different types of cancers.
What are the common cancers?
Globally – the most common cancers are lung, colorectal, breast (women), prostate (men) and stomach cancer. Men tend to have higher rates of bladder, stomach, larynx and esophageal cancer, where women tend to have higher rates for thyroid and gallbladder cancers. Estrogen (higher levels in women) is linked to breast, endometrial and ovarian cancers. Young people (children, young adults) have higher rates of blood cancers (leukemia), lymphoma, thyroid, testicular (male), melanoma (skin), sarcomas (bone and soft tissue) and brain tumours (gliomas). Could this be the next epidemic for young people?
Does race influence the types of cancer?
Black individuals have a higher incidence of prostate cancer, myeloma, stomach, colorectal and pancreatic cancer. Black women have higher mortality rates from breast cancer than white women. Asian and Hispanic individuals have higher rates of liver (hepatitis B) and stomach cancers. Indigenous persons have higher mortality rates with kidney, liver, stomach and cervical cancer. White persons have higher lung cancer detection rates. Incidence and mortality rates may be affected by socioeconomic and cultural factors which limit access to care and screening.
Are infectious diseases linked to cancer?
Hepatitis B and C virus infections are linked to liver cancer. Human papilloma virus (HPV), which is sexually transmitted, is linked to cervical, anorectal and oropharangeal cancers, and HIV to Kaposi’s sarcoma. Helicobacter pylori bacteria are associated with stomach cancers, and Epstein Barr virus with lymphoma. Not all chronic infections lead to cancer, but prevention is key (i.e. vaccines for hepatitis and HPV, safe sex practices and H pylori treatment).
What is the role of genetic screening?
Around 10% of all cancers are inherited. There are specific hereditary cancer syndromes that are linked to early onset cancers. Examples include Lynch syndrome (colorectal, endometrial), Familial Adenomatous Polyposis (colorectal cancer) and BRCA1/2 mutations (breast, ovarian cancer). Polygenic risk scoring (aggregate of multiple genetic variants) is another tool to assess cancer risk. It is best to consult with a genetic counsellor to have a proper family history assessment and review the pros/cons of testing.
What is the role of lifestyle?
Around a third of cancer deaths are attributable to tobacco use, obesity, alcohol, poor diet (low in fruits, vegetables, high intake of processed foods/saturated fats) and lack of physical activity. Cancer cells thrive if the body is subject to chronic inflammation, weakened immunity and epigenetics (environmental toxins that can lead to genetic instability).
Obesity is linked to chronic inflammation (increased risk of colorectal, liver, endometrial, esophageal, pancreatic, breast cancer) and alcohol may facilitate the movement of carcinogens within cells. Alcohol is linked to liver (cirrhosis), colorectal, breast and cancers of the mouth, throat and esophagus.
A healthy diet should include fruits, vegetables, whole grains, legumes, and minimize red meat. A healthy gut microbiome can reduce inflammation and may suppress cancer growth (colorectal cancer). High fibre, Mediterranean diet and probiotic type foods (i.e. yogurt, kefir, sauerkraut, kimchi) can produce short chain fatty acids which suppress cancer growth.
What is the role of the environment?
UV radiation (sun burn) can cause skin cancer. Air pollution is a risk factor for lung cancer. Excessive ionizing radiation (medical xrays, CT, etc.) and radon (older homes) can cause certain cancers (leukemia, thyroid, breast, lung, stomach, colon, esophageal, bladder and ovarian). Medical treatments that weaken the immune system (i.e. organ transplants, immunosuppressive medication) can also make it more difficult for the body to fend off cancer cells and may increase risk. Pesticides and chemicals affecting hormones in younger people may be linked to cancer. Certain occupations involve exposures to chemicals that need to be monitored (asbestos, arsenic, diesel, etc.).
What is the role of screening?
Population based screening guidelines (when to start, end, how frequent) are often debated between cancer advocacy groups, statisticians and payors. Screening protocols vary depending on your level of risk. Routine and advanced modalities may be included for breast (mammogram, ultrasound, MRI), colorectal (Fecal immunochemical testing, colonoscopy, CT colonography, stool DNA), cervical (HPV swab, PAP smear), lung (low dose lung CT) and prostate (PSA, ultrasound, MRI).
Emerging cancer screening includes liquid biopsy (molecular markers) which is a blood test, but there are ongoing standardization and cost issues that are being sorted out. However, the future of precision cancer screening and early detection may be focused on blood testing (i.e. before cancer cells develop into tumours visible on imaging).
If you are in a high-risk group, review the need for earlier screening with your primary care provider (i.e. shared decision making).
In summary, the most impactful cancer prevention strategies are:
Healthy weight
Healthy diet
Physical activity
Don’t smoke
Alcohol moderation
Sun protection
Vaccination for Hepatitis and HPV