Claim: Cancer can be prevented by maintaining a healthy weight.

Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body . Not all tumors are cancerous ; benign tumors do not spread to other parts of the body . Possible signs and symptoms include a lump , abnormal bleeding , prolonged cough , unexplained weight loss and a change in bowel movements . While these symptoms may indicate cancer , they may have other causes . Over 100 types of cancers affect humans .   Tobacco use is the cause of about 22 % of cancer deaths . Another 10 % is due to obesity , poor diet , lack of physical activity , and excessive drinking of alcohol . Other factors include certain infections , exposure to ionizing radiation and environmental pollutants . In the developing world nearly 20 % of cancers are due to infections such as hepatitis B , hepatitis C and human papillomavirus -LRB- HPV -RRB- . These factors act , at least partly , by changing the genes of a cell . Typically many genetic changes are required before cancer develops . Approximately 5 -- 10 % of cancers are due to inherited genetic defects from a person 's parents . Cancer can be detected by certain signs and symptoms or screening tests . It is then typically further investigated by medical imaging and confirmed by biopsy .   Many cancers can be prevented by not smoking , maintaining a healthy weight , not drinking too much alcohol , eating plenty of vegetables , fruits and whole grains , vaccination against certain infectious diseases , not eating too much processed and red meat , and avoiding too much sunlight exposure . Early detection through screening is useful for cervical and colorectal cancer . The benefits of screening in breast cancer are controversial . Cancer is often treated with some combination of radiation therapy , surgery , chemotherapy , and targeted therapy . Pain and symptom management are an important part of care . Palliative care is particularly important in people with advanced disease . The chance of survival depends on the type of cancer and extent of disease at the start of treatment . In children under 15 at diagnosis the five-year survival rate in the developed world is on average 80 % . For cancer in the United States the average five-year survival rate is 66 % .   In 2015 about 90.5 million people had cancer . About 14.1 million new cases occur a year -LRB- not including skin cancer other than melanoma -RRB- . It caused about 8.8 million deaths -LRB- 15.7 % -RRB- of human deaths . The most common types of cancer in males are lung cancer , prostate cancer , colorectal cancer and stomach cancer . In females , the most common types are breast cancer , colorectal cancer , lung cancer and cervical cancer . If skin cancer other than melanoma were included in total new cancers each year it would account for around 40 % of cases . In children , acute lymphoblastic leukaemia and brain tumors are most common except in Africa where non-Hodgkin lymphoma occurs more often . In 2012 , about 165,000 children under 15 years of age were diagnosed with cancer . The risk of cancer increases significantly with age and many cancers occur more commonly in developed countries . Rates are increasing as more people live to an old age and as lifestyle changes occur in the developing world . The financial costs of cancer were estimated at $ 1.16 trillion US dollars per year as of 2010 .