Cancer is a complex group of diseases with multiple potential causes. While the exact cause of many cancers remains unknown, there are established risk factors that have been shown to increase a person's chances of developing cancer. Here are some of the top causes and risk factors:

1. Tobacco Use: Smoking is linked to various types of cancer, including lung, throat, mouth, pancreatic, bladder, and kidney cancer. Chewing tobacco has been linked to cancer of the oral cavity and pancreas.

2. Alcohol Consumption: Excessive alcohol use can lead to cancers of the mouth, throat, esophagus, liver, breast, and colon.

3. Poor Diet and Physical Inactivity: A diet low in fruits and vegetables and high in processed and red meats can increase risk.

Obesity increases the risk of several types of cancer, including breast, colon, prostate, uterus, kidney, and rectum.

Physical inactivity may increase the risk of certain cancers.

4. Exposure to Sun and Ultraviolet (UV) Radiation: UV radiation from the sun or from tanning beds can lead to skin cancers, including melanoma.

5. Exposure to Environmental Toxins: Prolonged exposure to certain chemicals and toxins, such as asbestos, benzene, aromatic amines, and polychlorinated biphenyls (PCBs), can lead to increased cancer risk.

6. Infections: Some infections, particularly viral, can increase cancer risk. Examples include Human papillomavirus (HPV), Hepatitis B and C, and Epstein-Barr virus.

7. Radiation Exposure: Exposure to high levels of radiation, like that from nuclear plant accidents or atomic bombs.

8. Genetics and Family History: Frequent exposure to medical imaging radiation (when not properly regulated) can also pose a risk.

Certain genetic mutations can increase the risk for specific types of cancer. For example, BRCA1 and BRCA2 mutations are associated with a higher risk of breast and ovarian cancer.

9. Hormone Replacement Therapy (HRT): Some forms of HRT have been associated with increased risk of certain cancers, particularly breast cancer.

10. Certain Chemicals and Other Substances: Long-term exposure to carcinogens, whether in the workplace or in the environment, can increase the risk of cancer.

11. Chronic Inflammation: Conditions causing chronic inflammation, such as ulcerative colitis, can increase the risk of developing cancer.

12. Immunosuppression: Being immunocompromised or taking immunosuppressive drugs can elevate the risk of certain cancers.

13. Age: Simply getting older is a significant risk factor for the development of many types of cancer.

While some of these risk factors are beyond individual control, many are modifiable through lifestyle choices. Adopting a healthy lifestyle that includes regular exercise, a balanced diet, avoiding tobacco and excessive alcohol, and protecting oneself from excessive sun exposure can significantly reduce the risk of many types of cancer. Regular medical check-ups and screenings can also play a crucial role in early detection.