What We Mean When We Talk About Cancer
Cancer is not one disease. It is, in fact, a collection of more than 200 related conditions that share a common characteristic: the uncontrolled growth and spread of abnormal cells. Normally, the cells in your body grow, divide, and die in an orderly fashion. This cycle is tightly regulated by your DNA, which acts like an instruction manual for each cell. Cancer begins when something damages or alters this instruction manual, causing cells to grow and multiply when they should not. These abnormal cells can form masses called tumours, invade nearby tissues, and, in some cases, spread to distant parts of the body through the bloodstream or lymphatic system, a process known as metastasis.
It is important to say this clearly at the outset: a cancer diagnosis, while serious, is not what it was even twenty years ago. Survival rates for many cancers have improved dramatically thanks to advances in early detection, surgical techniques, targeted therapies, immunotherapy, and supportive care. More people are living with, and beyond, cancer than ever before. Understanding the disease, knowing your risk factors, and being attentive to your body's signals are among the most meaningful things you can do for your long-term health.
What Causes Cancer? The Interplay of Factors
Genetics and Family History
About 5 to 10 percent of all cancers are driven primarily by inherited genetic mutations passed down from parent to child. The most well-known examples include mutations in the BRCA1 and BRCA2 genes, which significantly increase the risk of breast and ovarian cancer, and Lynch syndrome, which raises the risk of colorectal and several other cancers. If you have a strong family history of cancer, particularly if multiple close relatives were diagnosed at young ages, genetic counselling can help you understand your personal risk and explore proactive steps such as enhanced screening or preventive measures.
However, it is essential to keep this in perspective. The vast majority of cancers are not directly inherited. Having a family member with cancer increases your statistical risk to some degree, but it does not make cancer inevitable. Many people with genetic risk factors never develop the disease, while some people with no family history do. Cancer is almost always the result of a complex interplay between genetics, lifestyle, environment, and sometimes, plain chance.
Lifestyle Factors
This is where your choices carry genuine power. Research consistently shows that a significant proportion of cancers are linked to modifiable lifestyle factors, meaning behaviours and exposures that you can change.
Tobacco use remains the single largest preventable cause of cancer worldwide. It is linked not only to lung cancer but also to cancers of the mouth, throat, oesophagus, stomach, pancreas, kidney, bladder, and cervix, among others. Quitting tobacco at any age reduces cancer risk, and the benefits grow with each smoke-free year. If you currently use tobacco in any form, speaking with your doctor about cessation support is one of the most impactful health decisions you can make.
Alcohol consumption is another established risk factor. Even moderate drinking has been linked to increased risk of cancers of the breast, liver, mouth, throat, oesophagus, and colon. The risk increases with the amount consumed. If you choose to drink, limiting intake to no more than one drink per day for women and two for men aligns with current health guidelines, though from a cancer perspective alone, less is better.
Diet and body weight play a meaningful role as well. Excess body fat, particularly around the abdomen, is associated with increased risk for at least 13 types of cancer. A diet rich in processed meats, refined sugars, and low in fruits and vegetables has been linked to higher cancer rates, while diets emphasising whole foods, fibre, and plant-based nutrients appear to be protective. This does not mean any single food causes or prevents cancer, but the overall pattern of your eating habits matters over time.
Physical inactivity independently raises cancer risk. Regular exercise helps regulate hormones, supports immune function, aids in maintaining a healthy weight, and reduces chronic inflammation, all factors that influence cancer development.
Environmental and Occupational Exposures
Certain environmental exposures contribute to cancer risk, though for most people, lifestyle factors carry greater weight. Ultraviolet (UV) radiation from the sun and tanning beds is the primary cause of skin cancers, including melanoma. Protecting your skin with sunscreen, protective clothing, and shade is straightforward and effective. Occupational exposures to substances like asbestos, benzene, formaldehyde, and certain industrial chemicals have been linked to specific cancers, and workplace safety regulations exist to minimise these risks. Additionally, radon, a naturally occurring radioactive gas that can accumulate in homes, is the second leading cause of lung cancer after smoking.
Infections
Some cancers are associated with chronic infections. Human papillomavirus (HPV) is linked to cervical, throat, and several other cancers, and vaccination against HPV has proven remarkably effective at prevention. Hepatitis B and C viruses increase the risk of liver cancer, and Helicobacter pylori (H. pylori), a bacterium that infects the stomach lining, is associated with stomach cancer. The good news is that vaccinations, antiviral treatments, and antibiotic therapy can address these infections and reduce associated cancer risks.
Prevention: What You Can Actually Do
Cancer prevention is not about achieving perfection or living in a state of constant vigilance. It is about making informed, consistent choices that collectively reduce your risk over time. Here are the strategies that the evidence supports most strongly.
Do not use tobacco. If you already do, seek help to quit. The health benefits begin almost immediately and continue to accumulate for years. Limit alcohol or avoid it altogether. Maintain a healthy weight through a balanced diet and regular physical activity. Protect your skin from excessive sun exposure. Get vaccinated against HPV and hepatitis B where recommended. And perhaps most importantly, participate in recommended cancer screenings.
Screening tests can detect cancer or precancerous changes before symptoms develop, when treatment is most effective. Current guidelines recommend regular screening for breast cancer (mammography), cervical cancer (Pap smear and HPV testing), colorectal cancer (colonoscopy or stool-based tests), and lung cancer (low-dose CT scan for high-risk individuals, such as long-term smokers). Prostate cancer screening (PSA test) is recommended on an individual basis after discussion with a doctor. These screenings are not about looking for trouble; they are about giving yourself the earliest possible advantage if something is found.
Early Warning Signs: What Your Body May Be Telling You
Cancer symptoms vary enormously depending on the type, location, and stage of the disease. Many early cancers cause no symptoms at all, which is precisely why screening is so important. However, there are certain changes in your body that warrant attention and a conversation with your doctor.
Unexplained weight loss of 10 pounds or more without changes in diet or exercise can sometimes be an early sign of cancer, particularly cancers of the pancreas, stomach, oesophagus, or lung. Persistent fatigue that does not improve with rest may occur with many cancers as the disease affects how your body uses energy or causes subtle blood loss.
Changes in the skin deserve attention: a new mole or a change in an existing mole's size, shape, or colour; a sore that does not heal; yellowing of the skin or eyes (jaundice); or unusual darkening or redness. Persistent pain without a clear cause, particularly headaches, back pain, or bone pain, should be evaluated. Changes in bowel or bladder habits, such as persistent constipation, diarrhoea, blood in the stool, or blood in the urine, can be associated with colorectal, bladder, or kidney cancers.
A persistent cough or hoarseness lasting more than three weeks, particularly in smokers or former smokers, warrants investigation. Difficulty swallowing that worsens over time can be a sign of oesophageal or throat cancer. Unusual bleeding or discharge, including blood in the sputum, vaginal bleeding between periods or after menopause, or nipple discharge, should always be evaluated. Lumps or thickening anywhere in the body, particularly in the breast, testicles, lymph nodes (neck, armpits, groin), or soft tissues, should be examined by a doctor even if they are painless.
It is worth emphasising that every single one of these symptoms can be caused by conditions other than cancer, and most of the time, they are. A persistent cough is far more likely to be a respiratory infection than lung cancer. A new mole is usually just a new mole. The point is not to panic over every change in your body, but to pay attention, recognise what is not normal for you, and seek medical evaluation when something persists or seems unusual. Early detection saves lives, and the vast majority of the time, getting checked provides reassurance rather than bad news.
The Importance of Early Detection
The statistics on early detection are striking. When breast cancer is detected at stage 1, the five-year survival rate is nearly 100 percent. For colorectal cancer caught early, survival rates exceed 90 percent. Even lung cancer, which historically has had poorer outcomes, shows dramatically improved survival when caught before it has spread. These numbers illustrate a simple but powerful truth: the earlier cancer is found, the more treatable it tends to be.
Early detection works through two channels: screening (testing before symptoms appear) and prompt evaluation of symptoms when they do arise. Both require you to be an active participant in your own health. Keep up with recommended screening schedules, know your family history, and do not delay seeing a doctor when something concerns you. Many people put off medical visits out of fear of what might be found, but delay rarely makes outcomes better, while early action very often does.
When to Seek Medical Advice
See your doctor if you experience any persistent, unexplained symptom that lasts more than two to three weeks, particularly if it is worsening. Seek prompt evaluation for any new lump or mass, unexplained bleeding, significant unintentional weight loss, or a change in a mole. If cancer runs in your family, discuss your risk with your doctor and ask whether genetic counselling or enhanced screening would be appropriate for you.
Cancer is a word that carries enormous emotional weight, and that is understandable. But fear serves us best when it motivates action rather than avoidance. The tools for prevention, early detection, and treatment have never been better, and the most important tool of all is your willingness to stay informed, stay attentive, and stay engaged with your health.