Understanding the Causes of Cancer

Cancer remains a leading cause of death worldwide. In 2023, there were an estimated 19 million new cancer cases and approximately 10 million cancer-related deaths globally. These numbers are projected to rise, with predictions indicating that by 2040, there could be nearly 30 million new cancer cases and 16 million cancer-related deaths annually.

Understanding the causes of cancer is crucial for prevention and treatment. This article explores the genetic, environmental, and lifestyle factors contributing to cancer and offers insights on how to mitigate these risks.

When does cancer occur?

Cancer begins at the cellular level when cells grow uncontrollably and invade normal tissue. This progression happens in multiple stages, starting from precancerous changes to the development of malignant tumors. Some cancers can spread to other parts of the body through the bloodstream or lymphatic system through a process known as metastasis.

Where does cancer occur?

Cancer can affect various body parts, including the skin, bones, blood vessels, muscles, lungs, kidneys, and more. It can also impact the immune system, which plays a key role in both the development and progression of cancer.

Can you inherit cancer?

Cancer can be inherited when certain gene mutations are passed down through families.

Genes, which are segments of DNA located on chromosomes, can mutate over time due to factors such as diet, lifestyle choices, and environmental exposures. This is known as the genetic cause of cancer. While only 5-10% of all cancers are genetically inherited, these tend to occur earlier in life.

Examples include Lynch syndrome, which increases the risk of colon and uterine cancers, and mutations in the BRCA gene family, which are linked to breast and ovarian cancers.

Today, biomarker tests are available to assess individual risks and guide appropriate treatment options based on a person’s genetic profile.

What are the behavioral and lifestyle factors that cause cancer?

A handful of behavioral factors may lead to genetic mutations and cancer development.

According to Dr. Harold Varmus, Nobel laureate and former director of the National Institutes of Health, “The prevention of cancer requires us to look not just at genetic predisposition but at how our lifestyle choices and environmental exposures interact with our biology to affect cancer risk.”

Smoking tobacco: Smoking can lead to lung cancer, as well as cancers of the mouth, throat, esophagus, pancreas, bladder, cervix, and kidneys. The carcinogens in tobacco smoke damage the DNA in cells, which can lead to mutations and uncontrolled cell growth.
Excessive UV exposure (tanning or sunbathing): UV exposure causes skin cancer, including melanoma, basal cell carcinoma, and squamous cell carcinoma. UV radiation damages the DNA in skin cells, which can trigger mutations that result in cancerous growths.
Unhealthy dietary choices and obesity: Consuming red and processed meats can increase cancer risk, particularly colorectal cancer. Diets high in red and processed meats are linked to higher levels of carcinogenic compounds like nitrates and nitrites, which can damage the lining of the bowel. Additionally, the microbiome, consisting of all the microscopic organisms in our bodies, supports the immune system’s ability to protect against harmful pathogens. Diets and behaviors directly impact the microbiome and the immune system’s response to cancer. Obesity is likely to surpass smoking as the leading preventable cause of cancer. Consuming animal fat aids tumor growth and reduces anti-tumor immune cells. Researchers continue to explore the link between obesity and cancer development, emphasizing the importance of maintaining a healthy diet and weight.
High alcohol consumption: High alcohol consumption is linked to various cancers, including those of the mouth, throat, esophagus, liver, breast, colon, stomach, pancreas, head and neck. Alcohol can act as a solvent, making it easier for other carcinogens to enter cells, and it can also be converted into acetaldehyde, a toxic chemical that damages DNA. Recent studies suggest that around 4% of cancers worldwide are caused by alcohol intake, highlighting the significant impact of excessive alcohol consumption on cancer risk.
Unsafe sex: Engaging in unsafe sex can lead to viral infections such as human papillomavirus (HPV) and human immunodeficiency virus (HIV), which increase cancer risk. HPV is a major cause of cervical cancer, as well as cancers of the anus, penis, throat, and mouth. HIV weakens the immune system, making it harder for the body to fight off cancer-causing infections.
Inflammatory conditions (obesity and ulcerative colitis): Conditions like obesity and ulcerative colitis are linked to higher cancer risks. Chronic inflammation can lead to DNA damage over time, increasing the risk of cancer. Obesity is associated with cancers of the breast, colon, rectum, endometrium, esophagus, kidney, and pancreas, while ulcerative colitis increases the risk of colorectal cancer.

Can where you live or work cause cancer?

Exposure to environmental factors, such as certain chemicals and radiation can indeed influence your cancer risk. Let’s explore some of these key factors in more detail:

Air quality: Poor air quality and pollution contribute to lung cancer. Pollutants in the air, such as particulate matter and industrial emissions, can damage lung tissue and lead to cancer over time. This complicates the diagnosis and treatment process, making it crucial to address air quality for cancer prevention.
Sun exposure: Approximately 90% of skin cancers are caused by UV rays from the sun, tanning salons, and sunlamps. UV radiation can damage the DNA in skin cells, leading to mutations that result in skin cancer. One in five Americans will be diagnosed with skin cancer before age 70. Protecting your skin from excessive sun exposure is essential to reduce this risk. Advances in immunotherapy have successfully treated over 99% of skin cancer cases, offering hope and effective treatment options for those affected.
Radiation and chemical exposure: Exposure to high doses of radiation, such as those from chemotherapy and contact with radioactive materials, can increase the risk of developing cancer. Additionally, chemicals like asbestos and benzene are potent carcinogens that can lead to various cancers. Minimizing exposure to these harmful substances is critical for cancer prevention.

Do viruses or bacteria cause cancer?

Yes, bacterial and viral infections can cause genetic mutations and chronic inflammation that contribute to the development of cancer.

Theories surrounding bacterial causes of cancer date back over 100 years, put forth by the Father of Cancer Immunotherapy, Dr. William B. Coley, often referred to as the Father of Cancer Immunotherapy. Dr. Coley observed that bacterial infections could sometimes lead to the regression of cancerous tumors, leading him to develop “Coley’s toxins,” a mixture of killed bacteria used to stimulate the immune system. His pioneering work laid the groundwork for modern cancer immunotherapy by highlighting the potential of the immune system in combating cancer.

Some common viruses speculated to increase cancer risk include:

Human papillomavirus (HPV): This virus is linked to cervical, anal, penile, and several head and neck cancers. HPV is known to cause mutations in the DNA of infected cells, which can lead to the development of cancerous tumors.
Hepatitis B and C: These viruses can lead to liver cancer. Chronic infection with hepatitis B or C can cause long-term liver inflammation and damage, increasing the risk of developing liver cancer over time.
Epstein-Barr virus (EBV): This virus is associated with certain lymphomas and nasopharyngeal cancer. EBV can cause changes in the DNA of infected cells, contributing to the development of these types of cancer.
Helicobacter pylori: This bacterium is linked to stomach cancer. Chronic infection with Helicobacter pylori can cause long-term inflammation of the stomach lining, which can lead to the development of stomach cancer.

Vaccines and treatments to protect against virus-related cancers are crucial in the fight against cancer. For example, a vaccine protecting against hepatitis B has been available since 1982, significantly reducing the incidence of liver cancer caused by this virus. CRI funds research into both preventive and therapeutic cancer vaccines, emphasizing the importance of these advancements in cancer prevention and treatment. This type of research is vital in developing new methods to prevent virus-related cancers and improve the outcomes for those already affected.

How to Reduce Your Cancer Risk

About 4 in 10 cancer cases can be prevented through healthy living and policies that protect the public. Key steps include:

Quitting smoking
Maintaining a healthy weight
Eating a balanced diet
Limiting alcohol intake
Protecting yourself from the sun
Staying physically active
Avoiding exposure to harmful chemicals
Getting vaccinated against cancer-causing viruses

CRI’s Role in Advancing Cancer Research

As a leader in innovative research, CRI supports the development of new immunotherapy treatments and their combination with traditional methods like chemotherapy. Ongoing research and support from institutions like CRI promise more personalized and effective cancer treatments.

Learn more about the latest advancements in cancer treatment and support groundbreaking research. Donate today to help us fund vital research moving us closer to imaging a world immune to cancer.