Most cancers originate from environmental and lifestyle factors (like smoking, diet, alcohol, sun exposure, infections) that cause genetic mutations in cells over time, rather than inherited genes, with only 5-10% being directly hereditary. These acquired genetic changes disrupt normal cell growth, leading to uncontrolled division, with carcinomas (from skin/lining cells) being the most common type, affecting organs like breast, lung, colon, and prostate.
Cancer cells have gene mutations that turn the cell from a normal cell into a cancer cell. These gene mutations may be inherited, develop over time as we get older and genes wear out, or develop if we are around something that damages our genes, like cigarette smoke, alcohol or ultraviolet (UV) radiation from the sun.
About 90% of cancers are caused by environmental and lifestyle factors, not genetics, including smoking, poor diet (red meat, fried foods), alcohol, sun exposure, pollutants, infections, obesity, and inactivity; only 5–10% are due to inherited genetic defects, with most cancers arising from lifestyle-induced genetic mutations. Tobacco alone accounts for about a third of cancer deaths, while diet, obesity, and inactivity contribute significantly, with controllable factors being key to prevention.
Cancer Genes
The discovery of certain types of genes that contribute to cancer has been an extremely important development for cancer research. Over 90% of cancers are observed to have some type of genetic alteration.
Which cancers are hereditary?
At a Glance. Breast, lung and bronchus, prostate, and colorectal cancers account for almost 50% of all new cancer cases in the United States. Lung and bronchus, colorectal, pancreatic, and breast cancers are responsible for nearly 50% of all deaths.
For example, the risk of breast cancer and ovarian cancer is increased (as well as some other cancers) in families with inherited breast and ovarian cancer syndrome. Colon and endometrial cancer risk are increased in Lynch syndrome (also known as hereditary non-polyposis colorectal cancer, or HNPCC).
Solid cancers: This is the most common type of cancer, making up about 80% to 90% of all cases. This includes carcinoma that forms in epithelial tissue (like your skin, breast, colon and lungs) and sarcoma that forms in bone and connective tissues.
Mutations can happen by chance when a cell is dividing. They can also be caused by the processes of life inside the cell. Or by things coming from outside the body, such as the chemicals in tobacco smoke. And some people can inherit faults in particular genes that make them more likely to develop a cancer.
Incurable cancers are those that current treatments cannot completely eliminate, often because they are advanced (spread) or have returned after initial treatment, but they are not necessarily untreatable; treatments like chemo, radiation, and new targeted therapies aim to control the disease, slow growth, relieve symptoms, and improve quality of life. Common examples of cancers often considered incurable include pancreatic, liver, brain, esophageal, and certain advanced lung cancers, but research continuously offers new hope, with many patients living longer with ongoing management.
Cervical cancer is one of the most preventable cancers thanks to the HPV vaccine. HPV, or the human papillomavirus, causes 99% of all cervical cancers. The HPV vaccine, which is given in 2 doses, targets 9 different types of the virus.
The important lifestyle factors that affect the incidence and mortality of cancer include tobacco, alcohol, diet, obesity, infectious agents, environmental pollutants, and radiation.
According to the American Cancer Society, lung cancer and especially lung cancer caused by asbestos is the deadliest form of cancer. It has killed an estimated 142,600 to over 148,000 individuals between 2019 and the beginning of 2021, making it three times deadlier than breast cancer.
The 7 key warning signs of cancer often include changes in bowel/bladder habits, a sore that won't heal, unusual bleeding/discharge, a lump or thickening, persistent indigestion/difficulty swallowing, changes in moles, and a nagging cough or hoarseness, though many symptoms can overlap, so persistent changes warrant a doctor visit. These signs, especially when lasting over a couple of weeks, suggest a need for medical evaluation to rule out serious conditions, notes the American Cancer Society and Mayo Clinic.
Cancer is caused by changes to DNA. Most cancer-causing DNA changes occur in sections of DNA called genes. These changes are also called genetic changes. Genetic changes that cause cancer can be inherited or arise from certain environmental exposures.
Top 10 Causes of Cancer
The older we are, the more likely we are to develop cancer. Many people are surprised by this, which could be because there are often stories in the media about younger people with cancer. Anyone can get cancer, but cancer at a young age is rare. Most cases of cancer are in people aged 50 and over.
An obvious focus for rising cancer rates is the vicious circle of obesity, highly processed foods, and sedentary lifestyles, which are an epidemic in America and growing in many countries. “We know obesity causes inflammation, which can lead to cancer,” explains Dr. Goldfarb.
While increases and decreases in specific cancer deaths vary compared to last year, overall, this number is substantially larger than what was reported in 2024.
What cancers have the highest survival rates?
Around 40% of cancers could be prevented through lifestyle changes such as eating healthily, being active, maintaining a healthy weight and not smoking.
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Overall, though, diagnosis of multiple cancers at once can occur in up to 17% of patients. Sometimes, people can have more than one cancer because a given risk factor — such as tobacco use, alcohol use or a genetic mutation — can cause more than one type of cancer.
Genetic disorders