Cancer is a group of diseases characterized by the uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death.
Although the reason why the disease develops remains unknown for many cancers, particularly those that occur during childhood, there are many known cancer causes, including lifestyle factors, such as tobacco use and excess body weight, and non-modifiable factors, such as inherited genetic mutations, hormones, and immune conditions.
These risk factors may act simultaneously or in sequence to initiate and/or promote cancer growth.
Can Cancer Be Prevented?
A substantial proportion of cancers could be prevented, including all cancers caused by tobacco use and other unhealthy behaviors.
According to a recent study by American Cancer Society epidemiologists, at least 42% of newly diagnosed cancers in the US – about 729,000 cases in 2018 – are potentially avoidable, including 19% that are caused by smoking and 18% that are caused by a combination of excess body weight, physical inactivity, excess alcohol consumption, and poor nutrition.
Certain cancers caused by infectious agents, such as human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), and Helicobacter pylori (H. pylori), could be prevented through behavioral changes, vaccination, or treatment of the infection.
Many of the more than 5 million skin cancer cases that are diagnosed annually could be prevented by protecting skin from excessive sun exposure and not using indoor tanning devices.
Screening can help prevent colorectal and cervical cancers by allowing for the detection and removal of precancerous lesions. Screening also offers the opportunity to detect some cancers early, when treatment is more likely to be successful.
Screening is known to help reduce mortality for cancers of the breast, colon, rectum, cervix, and lung (among long-term current or former heavy smokers). In addition, a heightened awareness of changes in certain parts of the body, such as the breast, skin, mouth, eyes, or genitalia, may also result in the early detection of cancer.
How Many People Alive Today Have Ever Had Cancer?
More than 15.5 million Americans with a history of cancer were alive on January 1, 2016. Some of these individuals were diagnosed recently and are still undergoing treatment, while most were diagnosed many years ago and have no current evidence of cancer.
How Many New Cases and Deaths Are Expected to Occur in 2018?
About 1.7 million new cancer cases are expected to be diagnosed in 2018. This estimate does not include carcinoma in situ (noninvasive cancer) of any site except urinary bladder, nor does it include basal cell or squamous cell skin cancers because these are not required to be reported to cancer registries.
About 609,640 Americans are expected to die of cancer in 2018, which translates to about 1,670 deaths per day. Cancer is the second most common cause of death in the US, exceeded only by heart disease.
How Much Progress Has Been Made against Cancer?
Cancer death rates are the best measure of progress against cancer because they are less affected by detection practices than incidence and survival. The overall age adjusted cancer death rate rose during most of the 20th century mainly because of the tobacco epidemic, peaking in 1991 at 215 cancer deaths per 100,000 people.
As of 2015, the rate had dropped to 159 per 100,000 (a decline of 26%) because of reductions in smoking, as well as improvements in early detection and treatment.
This decline translates into more than 2.3 million fewer cancer deaths from 1991 to 2015, progress that has been driven by rapid declines in death rates for the four most common cancer types – lung, colorectal, breast, and prostate.
