Leading risk factors for preventable cancers are smoking, getting too much ultraviolet (UV) radiation from the sun or tanning beds, being overweight or having obesity, and drinking too much alcohol.

• Genetics: Cancer syndromes (Ataxia–telangiectasia, Bloom syndrome, BRCA1 & BRCA2, Fanconi anemia, Familial adenomatous polyposis, Hereditary breast and ovarian cancer, Hereditary nonpolyposis colorectal cancer, Li–Fraumeni syndrome, Nevoid basal-cell carcinoma syndrome, Von Hippel–Lindau disease, Werner syndrome, Xeroderma pigmentosum).
• Physical and chemical agents: Smoking, materials like arsenic, asbestos, benzene, beryllium, cadmium, chromium, ethylene oxide, nickel, plutonium.
• Lifestyle: Alcohol, diet, obesity.
• Hormones:
• Infection and inflammation: viruses, bacteria and parasites, inflammation.
• Radiation: non-ionizing radiation, ionizing radiation.
• Rare causes: organ transplantation, trauma, maternal-fetal transmission.