Cancer Explained: Symptoms, Tests, Treatment and How to Lower Your Risk Reading time: 16 minutes | Last updated: September 2026 It feels...
Cancer Explained: Symptoms, Tests, Treatment and How to Lower Your Risk
Reading time: 16 minutes | Last updated: September 2026
It feels like cancer is everywhere now. Fifteen or twenty years ago, most of us knew only a few people who had it. Today we hear about men and women in their 30s and 40s being diagnosed. So is cancer really becoming more common, or does it just feel that way?
The honest answer is: a bit of both. This guide explains in simple words what cancer is, what causes it, which warning signs to watch for, which tests are recommended, how it is treated, and which healthy habits can lower your risk. It uses recent data from the World Health Organization (WHO), the American Cancer Society (ACS) and leading cancer research groups, as of September 2026.
Quick answers
- Worldwide, about 20.6 million people were diagnosed with cancer in 2024, and nearly 10 million die from it each year (WHO Global Status Report on Cancer 2026).
- In the US, five-year survival for all cancers combined reached a record 70%, and cancer death rates are down 34% since 1991 (American Cancer Society (ACS) Cancer Statistics, 2026).
- But cancers in people under 50 are rising, especially colorectal (bowel) and breast cancer.
- Nearly 4 in 10 cancer cases are linked to risks we can reduce, such as tobacco, alcohol, excess weight, inactivity and some infections.
- Screening and paying attention to symptoms can catch cancer early, when it is much easier to treat.
In this article
- Is cancer really becoming more common?
- What is cancer?
- What causes cancer?
- Why are more young people getting cancer?
- Common warning signs and symptoms
- How is cancer tested and diagnosed?
- Recommended screening tests
- How to lower your risk: a healthy lifestyle
- How is cancer treated?
- Latest research and trends in 2026
- Conclusion and your simple action plan
- Sources and further reading
Is Cancer Really Becoming More Common?
Two things are true at the same time. Fewer people are dying of cancer in some countries, but the total number of cases and the number of young patients are going up.
| The good news | The worrying news |
|---|---|
| US cancer death rates have fallen 34% since 1991. About 4.8 million deaths have been avoided. | Worldwide, cancer cases could rise from about 20.6 million a year to nearly 35 million by 2050 if nothing changes. |
| Five-year survival for all cancers combined hit 70% for people diagnosed in 2015–2021. In the mid-1970s it was about 50%. | Cancers in adults under 50 are rising. The American Association for Cancer Research (AACR) reports that early-onset cancers are up more than 15% since 2000. |
| Survival has jumped for some of the hardest cancers since the mid-1990s: myeloma (32% to 62%) and liver cancer (7% to 22%). | Breast cancer is rising, especially in women under 50. Colorectal cancer is also rising in adults under 50. |
| The main reasons are less smoking, earlier detection and better treatment. | Access is unequal. Fewer than one in three countries include cancer care in their universal health coverage packages. |
Sources for the US figures: ACS Cancer Statistics 2026, published in CA: A Cancer Journal for Clinicians. Global figures: WHO 2026 report linked above.
Why do total cases keep rising even when death rates fall?
- People are living longer. Cancer risk goes up with age, so an older population means more cases.
- Populations are growing. More people means more diagnoses in total.
- Better testing. Screening finds some cancers earlier, and some that might once have been missed.
- Lifestyle and environment. WHO’s cancer agency (IARC) says the cancer picture is increasingly driven by obesity, physical inactivity, unhealthy diets and air pollution.
A note about the numbers
Most detailed statistics in this article come from the United States, because it publishes the most complete yearly data. Rates differ from country to country. Forecasts such as the 2050 figure are projections, not certainties. Ask your local health authority about numbers and screening programs in your own country.
What Is Cancer?
Your body is made of trillions of tiny cells. Healthy cells grow, divide and die in an orderly way, and old cells are replaced by new ones.
Cancer starts when the DNA inside a cell is damaged. The damaged cell stops following the rules. It keeps dividing and does not die when it should. Over time, the extra cells can form a lump called a tumor. Cancer cells can also break away and spread to other parts of the body. This spreading is called metastasis.
- Cancer is not one disease. There are more than 100 types. Most are named after the body part where they start, such as breast, lung or colon cancer.
- Some cancers do not form a lump. Blood cancers such as leukemia are examples.
- Doctors use “stages” (0 to IV) to describe how far a cancer has grown or spread. An earlier stage usually means easier treatment and better survival.
For a basic definition from a trusted source, see this National Cancer Institute training page.
| Benign tumor | Malignant tumor (cancer) | |
|---|---|---|
| Spreads to other body parts? | No | Can spread |
| Invades nearby tissue? | Usually not | Often yes |
| Danger to life | Usually low, but it can press on organs | Can be serious without treatment |
| Comes back after removal? | Rarely | May come back |
What Causes Cancer?
Cancer rarely has one single cause. It usually develops when several things add up over many years. Some risks you can change, and some you cannot.
| Risk factor | Why it matters | Can you change it? |
|---|---|---|
| Tobacco | Smoking causes lung cancer and many other cancers. Lung cancer is still the leading cause of cancer death worldwide. | Yes |
| Alcohol | WHO lists alcohol as a preventable cause of cancer. For cancer prevention, not drinking is the safest choice. | Yes |
| Excess weight and low activity | High body weight and too little exercise are both linked to higher cancer risk. | Yes |
| Unhealthy diet | Lots of processed meat, red meat, sugary drinks and highly processed food raises risk. Whole plant foods help lower it. | Yes |
| Infections | HPV, hepatitis B and C, and the stomach bacterium H. pylori can lead to cancer. Vaccines and treatment help. | Often |
| Air pollution | WHO’s cancer agency names air pollution as a growing driver of cancer. | Partly |
| Age | The longer we live, the more DNA damage builds up. | No |
| Family history and inherited genes | Some gene changes (for example BRCA) raise risk. People with a strong family history may need earlier or extra tests. | No, but you can screen earlier |
| Random DNA errors | Every time a cell divides there is a small chance of a mistake. Sometimes cancer is simply bad luck. | No |
The encouraging part
Nearly four in ten cancer cases worldwide are linked to preventable risk factors, including infections (HPV, hepatitis B and C, H. pylori), alcohol, tobacco, high body weight and too little physical activity, according to WHO. That means healthy choices and vaccines really do matter.
Why Are More Young People Getting Cancer?
You are not imagining it. Doctors and researchers see the same pattern. Here is what the data shows:
- ACS researchers say colorectal cancer is now the top cause of cancer death in adults under 50 (ACS colorectal screening update (May 2026)).
- Colorectal cancer in adults under 50 has been rising by about 1% to 2% a year since the mid-1990s. People born in 1990 are about twice as likely to get colon cancer and four times as likely to get rectal cancer as people born in 1950 (The ASCO Post).
- Breast cancer is rising faster in women under 50 (about 1.1% a year) than in older women (0.5% a year), according to a 2000–2021 global review of early-onset cancer.
- A 2024 ACS study found 17 types of cancer becoming more common in younger generations, including breast, pancreatic, stomach, uterine and colorectal cancers (mentioned in a September 2026 news report).
What might be causing it?
Scientists do not have a final answer yet. At an AACR conference on this topic, the rough agreement was that several factors probably interact and that much more research is needed. These are the main ideas being studied. None of them is proven as the single cause:
- Obesity, diet, inactivity and alcohol. These matter, but doctors say obesity does not fully explain the rise in aggressive breast cancers in women under 50.
- Changes in gut bacteria (the microbiome). Researchers are studying how gut bacteria may affect inflammation and cancer, but there are still big knowledge gaps.
- The “exposome”. This means everything a person is exposed to during life, such as chemicals, pollution and modern city living.
- Faster biological ageing. New research on biological ageing suggests younger generations appear biologically older than earlier ones did at the same age, and that faster biological ageing is linked to a higher risk of early-onset lung, digestive, uterine and colorectal cancers. This shows a link, not proof of cause.
- More screening. When the recommended start age for bowel screening dropped to 45, screening in people aged 45–50 rose sharply and more cancers were found. That explains part of the rise, but doctors at Memorial Sloan Kettering Cancer Center stress the overall increase is real and not just a blip.
Two important reminders
- Be careful with online posts that blame one food, one chemical or one habit. Current science points to many small factors working together.
- Young adults are often diagnosed late because doctors and patients think “too young for cancer”, and because people under 45 are outside regular screening programs. If a symptom does not go away, push for answers.
Common Warning Signs and Symptoms
Some cancers cause no symptoms in the early stage, which is why screening is so important. When symptoms do appear, they depend on where the cancer is. The American Cancer Society lists these common warning signs:
| Warning sign | What to look for |
|---|---|
| Unexplained weight change | Losing or gaining 10 pounds (about 4.5 kg) or more for no known reason. |
| Extreme tiredness | Fatigue that does not improve with rest. |
| A new lump or swelling | In the breast, testicle, neck or anywhere else, and it does not go away. |
| Bowel changes | Constipation or diarrhea that will not settle, blood in the stool, narrower stools. |
| Bladder changes | Pain when passing urine, blood in the urine, or needing to go much more or less often. |
| Skin changes | A new mole, a mole that changes size, shape or color, or a sore that does not heal. |
| Cough, voice or swallowing problems | A cough that will not go away, hoarseness, coughing up blood, or trouble swallowing. |
| Unusual bleeding | Bleeding between periods or after menopause, or blood from the nipple. |
| Ongoing pain | New pain with no clear reason that does not go away or keeps getting worse. |
| Fever or night sweats | Repeated fever or drenching sweats with no clear cause. |
A simple rule to follow
- A symptom with no clear reason that lasts more than two to three weeks should be checked by a doctor.
- Blood in the stool or urine should always be checked, even if it happens only once.
- Most of these signs are caused by common, harmless problems such as infections, piles or irritable bowel syndrome. But you cannot tell by guessing. See the colorectal cancer symptoms guide for an example of how symptoms overlap.
How Is Cancer Tested and Diagnosed?
There are two different situations. Screening means testing people who feel well (covered in the next section). Diagnosis means finding out what is wrong when you have symptoms or a screening test looks unusual. Doctors usually work through these steps:
| Test or step | What it does |
|---|---|
| Medical history and physical exam | Your doctor asks about symptoms and family history and examines you. |
| Blood and urine tests | Can give clues, such as a low red blood cell count, but blood tests alone rarely confirm cancer. |
| Imaging: X-ray, ultrasound, CT, MRI, PET | Takes pictures inside the body to find and measure tumors. |
| Endoscopy or colonoscopy | A thin tube with a camera looks inside the gut, airways or other organs. |
| Biopsy | A small piece of tissue is removed and examined under a microscope. This is the test that confirms cancer. |
| Genetic (molecular) tests on the tumor | Show gene changes in the cancer that help choose targeted treatments. |
| Staging | Combines the results to describe how far the cancer has spread. |
Recommended Screening Tests
Screening finds cancer early, or even before it starts. For example, a colonoscopy can remove growths called polyps before they turn into cancer. The table below shows the ACS screening guidelines by age for people at average risk. Other expert groups, such as the US Preventive Services Task Force, differ slightly on some ages, and each country has its own program. Ask your doctor what applies to you.
| Cancer | Main test | When to start | How often |
|---|---|---|---|
| Breast | Mammogram | Option to start at 40; recommended by 45 | Yearly from 45 to 54; every 1–2 years from 55 |
| Cervical | HPV test (preferred) or Pap test | 25 | HPV test every 5 years; a self-collected HPV test every 3 years; up to at least age 65 |
| Colorectal (bowel) | Stool tests, colonoscopy or CT colonography | 45, continuing to 75 | Colonoscopy usually every 10 years; stool tests every 1–3 years depending on the test |
| Lung | Low-dose CT scan | 50 to 80, only for people with a heavy smoking history (about 20 pack-years or more) | Yearly |
| Prostate | PSA blood test, after talking to a doctor | 50 (45 for higher-risk men) | Decided together with your doctor |
A “pack-year” is packs smoked per day multiplied by the number of years smoked. For example, one pack a day for 20 years equals 20 pack-years.
What changed for bowel cancer screening in 2026
- The ACS kept the start age at 45 and added a new preferred at-home stool RNA test. It also added blood-based tests, but only for people who refuse or do not finish the preferred tests (ASCO Post).
- Any abnormal result from a test other than colonoscopy must be followed by a colonoscopy, ideally within 6 months.
- The ACS says more than 20 million eligible Americans, about 1 in 3, have not been screened as recommended. When bowel cancer is found at an early stage, five-year survival is above 90%.
Do you need earlier or extra tests?
- You may need to start earlier if a close relative had cancer, especially at a young age, or if you carry an inherited gene change such as BRCA.
- No screening test is perfect. Some tests give false alarms, so ask your doctor about both benefits and downsides.
- Screening is for people without symptoms. If you have symptoms, do not wait for your screening date. See a doctor now.
How to Lower Your Risk: A Healthy Lifestyle
No habit can guarantee you will never get cancer. But the science is clear that healthy choices lower the odds. These targets follow the ACS Diet and Physical Activity Guideline and WHO advice:
| Habit | Simple target |
|---|---|
| Avoid tobacco | Do not smoke or vape, and stay away from second-hand smoke. |
| Stop alcohol | The safest amount for cancer prevention is none. Stop It.. |
| Stay active | 150–300 minutes of moderate activity (such as brisk walking) or 75–150 minutes of vigorous activity each week. Add strength exercises on 2 or more days and sit less. |
| Keep a healthy weight | Avoid gaining weight in adult life. |
| Eat a plant-rich diet | Plenty of vegetables, fruit, whole grains and beans. Limit red and processed meat, sugary drinks and highly processed foods. |
| Protect your skin | Use shade and sunscreen, and avoid tanning beds. |
| Get vaccinated and treated | Ask about the HPV and hepatitis B vaccines. Get tested and treated for hepatitis C and H. pylori if advised. |
| Know your family history | Tell your doctor about cancers in close relatives so you can plan screening. |
Where do stress and sleep fit in?
Many people ask whether stress causes cancer. The National Cancer Institute (NCI) says there is no solid evidence that stress alone directly causes cancer. But stress can push people toward smoking, overeating, drinking and being less active, and those habits do raise risk. Calming your mind is still a smart part of a healthy life. For simple daily techniques, read The Ultimate Stress Management Guide.
Sleep is similar. The international cancer agency IARC classifies night-shift work as “probably carcinogenic” (Group 2A), but human evidence is described as limited and studies do not all agree. Poor sleep also makes it harder to eat well, exercise and keep a healthy weight. For practical tips, see The Ultimate Guide to Better Sleep.
Please remember
Some people who do everything right still get cancer. That is never their fault. Healthy habits and regular screening simply give you the best chance of prevention or early detection.
How Is Cancer Treated?
Treatment depends on the type of cancer, how advanced it is and your general health. According to the National Cancer Institute, some people have only one treatment, but most have a combination, such as surgery with chemotherapy and radiation.
| Treatment | What it does |
|---|---|
| Surgery | A surgeon removes the tumor and sometimes nearby tissue. |
| Radiation therapy | High doses of radiation kill cancer cells and shrink tumors. |
| Chemotherapy | Drugs kill or stop the growth of fast-growing cells. It can also affect some healthy cells, which causes side effects. |
| Targeted therapy | Drugs aimed at specific changes inside cancer cells that help them grow and spread. It needs tumor testing first. |
| Immunotherapy | Helps your own immune system find and fight cancer. |
| Hormone therapy | Slows or stops the growth of some breast and prostate cancers that use hormones to grow. |
| Blood stem cell transplant | Restores blood-forming stem cells after high-dose chemotherapy or radiation, mostly used for blood cancers. |
Practical tips if you or a loved one is diagnosed
- Ask your doctor to explain the goal of treatment: cure, control, or comfort.
- Ask whether genetic testing of the tumor is needed to find targeted options.
- Consider a second opinion, especially for rare or complex cancers.
- Ask about support services, such as nutrition advice, mental health support and help with side effects.
- Bring a family member or friend to appointments and write questions down beforehand.
Latest Research and Trends in 2026
- Living longer with cancer. A Columbia University cancer expert describes how cancer is becoming a long-term, manageable condition for many people, rather than the death sentence it was once often seen as.
- Smarter drugs. The ASCO 2026 meeting highlighted immunotherapies, antibody-drug conjugates, T-cell engagers and targeted drugs moving into earlier stages of treatment. Antibody-drug conjugates work a bit like guided missiles: an antibody carries a strong drug straight to the cancer cell.
- Blood tests to track cancer after treatment. Some experts expect tests that detect tumor DNA in the blood to become routine for follow-up. This is still developing and is an expert prediction, not standard care everywhere.
- More screening choices. Bowel screening now includes newer stool and blood tests (see above), and US cervical screening guidelines now allow a self-collected HPV test using approved devices.
- Multi-cancer blood tests. Tests such as Galleri look for signals from many cancers in one blood sample. An FDA advisory panel meeting to review it is scheduled for September 23, 2026. A large UK trial reported in early 2026 that it did not meet its main goal, although follow-up continues. Right now no trial has yet shown that these tests save lives. These tests are meant to add to, not replace, standard screening.
Reality check
Many new advances are recent, expensive or available only in some countries. Exciting research is not the same as proven benefit for every patient, so ask your doctor what is right for your situation.
Conclusion and Your Simple Action Plan
Cancer is more common in total, and it is showing up more often in younger adults. That is worrying, but it is not hopeless. More people than ever survive cancer, and many cancers can be prevented or caught early. The best response is not fear. It is small, steady actions.
- Know your family history and share it with your doctor.
- Book the screening tests that match your age and risk.
- Do not ignore a symptom that lasts more than two to three weeks, even if you are young.
- Build healthy habits: stay active, eat mostly plants, keep a healthy weight, avoid tobacco and stop alcohol.
- Protect your sleep and manage stress. Start with The Ultimate Guide to Better Sleep and The Ultimate Stress Management Guide.
- Ask about vaccines such as HPV and hepatitis B.
This article is for education. If you are worried about a symptom or your risk, please talk to a doctor.
Sources and Further Reading
- WHO Global Status Report on Cancer 2026: global cases, deaths, 2050 projection and preventable causes.
- American Cancer Society (ACS) Cancer Statistics, 2026: US cases, deaths and survival.
- American Association for Cancer Research (AACR) on early-onset cancer, and The ASCO Post on early-onset digestive cancers.
- ACS screening guidelines by age and the ACS colorectal screening update (May 2026).
- ACS Diet and Physical Activity Guideline and the National Cancer Institute (NCI) fact sheet on stress.
- National Cancer Institute overview of cancer treatment types.
This article is general information, not medical advice. Statistics and guidelines were checked in September 2026 and can change, so please confirm with your doctor or local health authority.
