Worldwide, cancer is among the leading causes of morbidity and mortality; cancer contributed to approximately 8.2 million deaths in 2012, or an estimated 13% of overall deaths.[1]WHO expects a 70% increase in the number of new cancer cases over the next two decades.[2] The burden of cancer is substantial and increasing worldwide.[3] The incidence, prevalence, and mortality of specific cancers vary widely across countries as a result of variations in lifestyle risk factors (such as tobacco use, physical inactivity, excess body weight, reproductive patterns), the prevalence of carcinogenic infections (e.g., Hepatitis B, Hepatitis C, HPV), genetics, and the availability of health care resources.[3] In 2012, lung, prostate, colorectal, gastric, and liver carcinomas were the most common cancers among men, while breast, colorectal, lung, cervical, and gastric carcinomas were most common among women.[4] In 2014, the Agency for Healthcare Research and Quality estimated the direct medical costs associated with cancer in United States at $87.7 billion dollars.[5] It is estimated that HBV/HCV and HPV are responsible for up to 20% of cancer deaths in low- and middle-income countries.[6] It is also estimated that more than 30% of these cases are preventable.[6] Measures to prevent some types of cancer include effective screening, vaccination, and lifestyle modifications. This page provides information about the epidemiology and primary care aspects of preventing cancer.
Epidemiology
Worldwide, cancer is among the leading causes of morbidity and mortality; cancer contributed to approximately 8.2 million deaths in 2012, or an estimated 13% of overall deaths.[1] The most common type of cancer (excluding non-melanoma skin cancers) is breast cancer; it is estimated that there were more than 249,000 new cases in the United States in 2016. The next most common cancers are lung cancer and prostate cancer. In the United States, to qualify as a common cancer, the estimated annual incidence for 2016 had to be 40,000 cases or more.
The following table presents official estimates of new cases and deaths in the United States for each common cancer type:[7]
American Cancer Society: Cancer Facts & Figures 2016
In 2013, the most commonly diagnosed cancers and leading causes of cancer-related death in children aged 0 to 19 years were leukemia and central nervous system cancers.[9]
The USPSTF concludes that the current evidence is insufficient to assess the additional benefits and harms of clinical breast examination (CBE) beyond screening mammography in women 40 years or older.
The decision to start regular, biennial screening mammography before the age of 50 years should be an individual one and take patient context into account, including the patient's values regarding specific benefits and harms.
Studies have reported that, for women of all age groups with an average risk, breast cancer screening was associated with a reduction in breast cancer mortality of approximately 20%, although there was an uncertainty in the quantitative estimates of outcomes for different breast cancer screening strategies in the United States.[11]
The decision to screen for colorectal cancer in adults aged 76 to 85 years should be an individual one, taking into account the patient’s overall health and prior screening history.
Adults in this age group who have never been screened for colorectal cancer are more likely to benefit from screenings.
Screening would be most appropriate among adults who 1) are healthy enough to undergo treatment if colorectal cancer is detected and 2) do not have co-morbid conditions that would significantly limit their life expectancy.
Women aged 21 to 65 (Pap Smear) or 30-65 (in combo with HPV testing)
The USPSTF recommends screening for cervical cancer in women age 21 to 65 years with cytology (Pap smear) every 3 years or, for women age 30 to 65 years who want to lengthen the screening interval, screening with a combination of cytology and human papillomavirus (HPV) testing every 5 years.
Studies have shown that, in patients undergoing regular cervical cancer screenings, approximately 70%-80% of cervical cancer deaths can be prevented.[13]
The USPSTF recommends annual screening for lung cancer with low-dose computed tomography (LDCT) in adults aged 55 to 80 years who have a 30 pack-year smoking history and currently smoke or have quit within the past 15 years. Screening should be discontinued once a person has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability/willingness to have curative lung surgery.
The National Lung Screen Trial (NLST), a randomized controlled trial involving 50,000 participants, demonstrated a 20% relative lung cancer mortality benefit for screening.[14]
Two doses of HPV vaccine at least six months apart.
Age >15 years
Three doses of HPV vaccine over a span of 24 weeks, with a minimum of 4 weeks interval between the first two doses, and 12 weeks between second and third doses.
Young women can get the HPV vaccine until they are 27 years old and young men can get the HPV vaccine until they are 22 years old.[15]
All infants should receive their first dose of hepatitis B vaccine as soon as possible after birth, preferably within 24 hours, followed by two or three additional doses.
The vaccination schedule for children and adults involves 3 intramuscular injections, the second and third doses administered 1 and 6 months after the first.[15]
HPV vaccine relevance in cancer prevention
Studies have reported, that introduction of the 4vHPV vaccine, has decreased the prevalence of HPV 6/11/16/18 cervical/vaginal infections, genital warts, low- and high-grade cytological abnormalities, CIN2, CIN3, and AIS among females in their teens and 20s.[16]
Adults who are exposed to secondhand smoke at home or at work increase their risk of developing lung cancer by 20% to 30%. Concentrations of many cancer-causing and toxic chemicals are higher in secondhand smoke than in the smoke inhaled by smokers.
Skin cancer is the most common kind of cancer in the United States. Exposure to ultraviolet (UV) rays from the sun and tanning beds appears to be the most important environmental factor involved with developing skin cancer. To help prevent skin cancer while still having fun outdoors, protect yourself by seeking shade, applying sunscreen, and wearing sun-protective clothing, a hat, and sunglasses.
Studies around the world have shown that drinking alcohol regularly increases the risk of getting mouth, voice box, and throat cancers.
A large number of studies provide strong evidence that drinking alcohol is a risk factor for primary liver cancer, and more than 100 studies have found an increased risk of breast cancer with increasing alcohol intake. The link between alcohol consumption and colorectal (colon) cancer has been reported in more than 50 studies.[20]
Hepatitis is inflammation of the liver, which is most often caused by a virus. In the United States, the most common type of viral hepatitis is Hepatitis C. Over time, chronic Hepatitis C can lead to serious liver problems including liver damage, cirrhosis, liver failure, or liver cancer. CDC recommends that anyone who was born between 1945 and 1965 get tested for Hepatitis C.
↑[www.cdc.gov/uscs. "U.S. Cancer Statistics Working Group. United States Cancer Statistics: 1999–2013 Incidence and Mortality Web-based Report. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention and National Cancer Institute; 2016"] Check |url= value (help).
↑Baan R, Straif K, Grosse Y, Secretan B, El Ghissassi F, Bouvard V; et al. (2007). "Carcinogenicity of alcoholic beverages". Lancet Oncol. 8 (4): 292–3. PMID17431955.CS1 maint: Explicit use of et al. (link) CS1 maint: Multiple names: authors list (link)