Why is cancer important?
Cancer is a major global health challenge. It is not one single disease, but a large group of diseases in which abnormal cells grow in ways that can interfere with the normal functioning of the body and may spread to other parts of the body.
According to WHO, cancer caused nearly 10 million deaths worldwide in 2024, making it one of the leading causes of death globally. The most common cancers include cancers of the lung, breast, colon and rectum, and prostate.
But cancer is not simply a matter of individual biology or personal choices. Risk is shaped by tobacco exposure, infections, environmental pollution, occupational exposures, radiation, access to prevention, early detection, diagnosis and treatment, and the social and economic conditions in which people live.
WHO and IARC reported in 2026 that approximately 37% of new cancer cases in 2022—around 7.1 million cases—were linked to causes that can potentially be prevented.
If cancer prevention depends partly on the environments and systems around us, how can individuals, communities, governments and global institutions share responsibility?
Personal hints
Ask yourself
- What do I already know about cancer?
- Which things can increase or decrease cancer risk?
- Why might cancer affect different people differently?
- Where can I find trustworthy cancer information?
- Why is early detection important for some cancers?
Look beyond the individual
Cancer risk is not distributed equally. People may experience different exposures to tobacco smoke, air pollution, occupational hazards, infections, ultraviolet radiation and other risk factors.
Access to vaccination, screening, diagnosis, treatment, medicines and supportive care also varies between communities and countries.
Explore
Let's build a common language for understanding cancer.
Cell
The basic structural and functional unit of the body. Cancer begins when changes within cells disrupt normal control of growth and behaviour.
Tumour
An abnormal mass of tissue. Tumours may be benign or malignant; not every tumour is cancer.
Malignant
Describes a cancerous growth that can invade surrounding tissues and, in some cases, spread to distant organs.
Metastasis
The spread of cancer cells from the original site to another part of the body.
Risk factor
A characteristic, exposure or condition associated with a greater likelihood of developing a disease.
Carcinogen
An agent or exposure that can cause cancer, such as tobacco smoke, certain forms of radiation or some occupational chemicals.
Prevention
Actions and policies that reduce exposure to cancer risks and help prevent cancer from developing.
Early detection
Finding cancer at an earlier stage when treatment may be more effective. Early detection includes awareness, timely diagnosis and, for selected cancers, screening.
Learn
What is cancer?
Cancer develops when abnormal cells grow and divide in an uncontrolled way. These cells can sometimes invade nearby tissues and spread to distant parts of the body.
Cancer develops through a complex interaction between genetic changes and environmental, behavioural and biological factors. There is therefore no single explanation for all cancers.
Can cancer be prevented?
Many cancers can be prevented or their risk reduced. WHO and IARC estimate that around four in ten cancer cases globally could potentially be prevented by addressing known preventable causes.
Important prevention strategies include reducing tobacco exposure, limiting harmful alcohol exposure, preventing certain infections through vaccination, reducing exposure to carcinogens, protecting against excessive ultraviolet radiation, and supporting healthier environments.
Prevention is therefore both a personal and a population-level responsibility.
Tobacco and cancer
Tobacco is one of the most important preventable causes of cancer. Tobacco exposure is associated with many cancers, including lung, oral, throat, oesophageal, stomach, bladder, pancreatic and several other cancers.
Protecting people from tobacco therefore requires more than asking individuals to make different choices. Smoke-free environments, regulation, taxation, health information and support for cessation are examples of population-level approaches.
Infections and cancer
Some infections can contribute to cancer. Important examples include human papillomavirus (HPV), hepatitis B virus and hepatitis C virus, as well as certain other infectious agents.
Vaccination, infection prevention, testing and appropriate treatment can therefore contribute to cancer prevention. HPV vaccination is particularly important because persistent infection with high-risk HPV types can cause cervical cancer and several other cancers.
Screening and early detection
Screening means testing people who do not necessarily have symptoms to identify disease or precancerous changes at an earlier stage.
Screening is not appropriate for every cancer or for every person at every age. Effective screening programmes require evidence, quality assurance, follow-up and access to diagnosis and treatment.
This is an important health-systems lesson: finding a possible cancer is only useful if people can receive appropriate follow-up and care.
Treatment and survivorship
Cancer treatment may include surgery, radiation therapy, medicines such as chemotherapy or targeted treatments, immunotherapy, hormone therapy, or combinations of different approaches.
Advances in diagnosis and treatment have improved outcomes for many cancers. However, access to high-quality treatment remains unequal between and within countries.
People who survive cancer may also need long-term follow-up, rehabilitation, psychological support and help returning to school, work and everyday life.
Palliative care
Palliative care aims to improve quality of life and relieve suffering for people with serious illness and their families.
It can be provided alongside cancer treatment and is not limited to the final days of life. Access to appropriate palliative care is an important part of compassionate and equitable cancer systems.
Young people and cancer
Cancer is much less common in children and adolescents than in adults, but young people can develop cancer and families can be profoundly affected by it.
Young people can also become important health advocates: learning about prevention, challenging misinformation, supporting inclusive communities and understanding how science and public policy influence cancer outcomes.
Think
Critical-thinking questions
- Why would it be misleading to say that cancer is simply caused by unhealthy personal choices?
- Why might two people with similar genetic risk experience different cancer outcomes?
- Why is vaccination relevant to cancer prevention?
- Why might screening without access to diagnosis and treatment fail to improve health outcomes?
- How might poverty influence both cancer risk and cancer survival?
- Should governments regulate cancer-causing exposures even when individuals can theoretically avoid them? Why?
- Why might a cancer treatment that exists scientifically still be unavailable to some patients?
Connect: from Self to World
My health
Learn what cancer is, how risk factors work, and how reliable evidence differs from myths.
Our support
Understand how cancer can affect families, friendships, emotions, education and everyday life.
Healthy environments
Explore tobacco control, air quality, vaccination, occupational safety, healthy food environments and access to cancer services.
Health systems
Ask how governments organize cancer prevention, screening, cancer registries, diagnosis, treatment, medicines and palliative care.
Global cancer equity
Compare how cancer risks, prevention opportunities, treatment access and survival differ across countries.
Social Determinants of Health
Cancer risk and outcomes are shaped by the conditions in which people are born, grow, learn, work, live and age.
- Income and poverty: can influence housing, food environments, environmental exposures, transportation and access to healthcare.
- Education: can influence access to health information, prevention opportunities and the ability to navigate health systems.
- Housing and environment: can influence exposure to air pollution, indoor pollutants and other environmental risks.
- Work: some occupations involve exposure to carcinogens, radiation, dusts, chemicals or other hazards.
- Healthcare access: affects vaccination, screening, timely diagnosis, treatment, medicines, rehabilitation and palliative care.
- Geography: people living in rural, remote or underserved areas may face additional barriers to specialized services.
- Commercial determinants: industries and markets can influence exposure to products and environments associated with cancer risk.
If some communities face greater exposure to cancer risks and have less access to prevention and treatment, is giving everyone exactly the same resources enough to achieve health equity?
Sustainable Development Goals
Cancer connects directly to SDG 3 and especially Target 3.4, which includes reducing premature mortality from cancer and other major noncommunicable diseases.
But cancer prevention and care also depend on inequality, environmental conditions, gender, sustainable communities and responsible production.
Global Leadership & Evidence
Who leads cancer action?
- World Health Organization (WHO) — develops global guidance and supports countries in cancer prevention, early detection, treatment and palliative care.
- International Agency for Research on Cancer (IARC) — generates international evidence on cancer causes, prevention, surveillance and burden.
- WHO/IARC Global Cancer Observatory — provides global cancer incidence, mortality and prevalence data.
- UNICEF and other UN agencies — contribute to vaccination, child and adolescent health, equity and health-system strengthening relevant to cancer prevention and care.
- National and provincial health authorities — organize cancer prevention, screening, diagnosis, treatment, surveillance and public-health programmes.
- Cancer registries and research institutions — generate data that help countries understand where cancer occurs, who is affected and how outcomes change.
Global Evidence Date
Global evidence: WHO & IARC, 2026
GHE last reviewed: August 2026
Next scheduled review: August 2027
WHO reported in July 2026 that cancer caused nearly 10 million deaths globally in 2024. WHO and IARC also reported in February 2026 that approximately 37% of new cancer cases in 2022—around 7.1 million cases— were linked to preventable causes.
GHE treats this module as living evidence. New evidence, recommendations and global cancer data should therefore be incorporated during scheduled reviews.
Core evidence sources: WHO • International Agency for Research on Cancer (IARC) • Global Cancer Observatory • United Nations
Reflect
My reflection
What changed in your understanding of cancer after completing this module?
Which cancer-related question would you like to investigate further?
How can you distinguish evidence from misinformation about cancer?
Equity reflection
Which groups might have fewer opportunities for cancer prevention or early diagnosis?
What barriers could prevent someone from receiving timely cancer treatment?
What could governments and communities do to reduce these inequalities?
Act
- Learn to recognize reliable sources of cancer information.
- Challenge cancer myths and misinformation when you encounter them.
- Support environments that protect people from tobacco smoke.
- Learn why vaccination against cancer-causing infections can be important.
- Learn about environmental and occupational factors that can contribute to cancer risk.
- Support respectful, stigma-free communities for people living with or recovering from cancer.
- Explore how governments can make prevention, diagnosis and treatment more accessible.
- Ask how cancer research and health systems can better serve underserved populations.
Test Your Thinking: 10 MCQs
These questions test knowledge, interpretation, application, social determinants of health, SDGs, health-system responsibility and global-health thinking.
1. Which statement best describes cancer?
Answer: B
2. Which statement best explains why cancer prevention is a public-health issue?
Answer: B
3. Which is an example of a cancer-causing infection?
Answer: A
4. Why can HPV vaccination contribute to cancer prevention?
Answer: B
5. Which example best illustrates a social determinant of cancer?
Answer: A
6. Why is early detection alone not enough to guarantee better cancer outcomes?
Answer: B
7. Which SDG is most directly connected with cancer prevention and treatment?
Answer: A
8. Which situation best demonstrates health inequity?
Answer: B
9. Which statement best reflects population-health thinking?
Answer: C
10. Which action best represents the GHE approach to cancer?
Answer: B