Page 13 Complete Your CE Test Online - Click Here prevention/risk/substances/carcinogens. The NCI has links to the specialty groups like the U.S. National Toxicology Program (NTP) and the International Agency for Research on Cancer (IARC), which is part of the World Health Organization. There is also access to good research in websites like PubMed,, (see section “Resources for Nurses” or “Disproven Carcinogens and Other Cancer Myths”). Age Advancing age is the most important risk factor for cancer overall, and for many individual cancer types (Figure 1). According to the most recent statistical data, the median age of a cancer diagnosis is 66 years. This means that half of cancer cases occur in people below this age and half in people above this age. One-quarter of new cancer cases are diagnosed in people aged 65 to 74 [137]. A similar pattern is seen for many common types of cancer. For example, the median age at diagnosis is 61 years for breast cancer, 68 years for colorectal cancer, 70 years for lung cancer, and 66 years for prostate cancer [137]. Of course, cancer can occur at any age. For example, bone cancer is most frequently diagnosed among people under age 20, with more than 25% of cases occurring in this age group. And 10% of leukemias are diagnosed in children and adolescents under 20 years of age, whereas only 1% of cancer overall is diagnosed in that age group. Some types of cancer, such as neuroblastoma, are more common in children or adolescents than in adults [137]. Inherited genetic changes There are a number of genetic syndromes which increase cancer risk that can be inherited. A few of the more common ones are discussed here. BRCA1, BRCA2, and breast cancer BRCA1 and BRCA2 are human genes that produce tumor suppressor proteins. When either of these genes is mutated, DNA damage may not be repaired properly. Given that inherited mutations are present in every cell of the body, there are many cells available that will be more likely to develop additional genetic alterations that can lead to cancer. Certain inherited mutations in BRCA1 and/or BRCA2 increase the risk of breast and ovarian cancers, and they are linked to increased risks of some other types of cancer. Figure 1. Percent of New Cancers by Age Group: All Cancer Sites. SEER 18 2007-2011, adapted from NCI. All Races, Both Sexes [137]. Breast and ovarian cancers in women with BRCA1 and BRCA2 mutations tend to develop at younger ages than in those without these mutations [140]. A woman’s lifetime risk of developing breast and/or ovarian cancer is greatly increased if she inherits a harmful mutation in BRCA1 or BRCA2 [140]: ● ● Breast cancer: About 12% of women in the general population will develop breast cancer sometime during their lives [103]. By contrast, 55-65% of women with a harmful BRCA1 mutation and around 45% of women with a harmful BRCA2 mutation will develop breast cancer by age 70 [43,75]. ● ● Ovarian cancer: About 1.3% of women in the general population will develop ovarian cancer sometime during their lives [103]. In contrast, 39% of women who inherit a harmful BRCA1 mutation and 11-17% of women who inherit a harmful BRCA2 mutation will develop ovarian cancer by age 70 [43,75]. Mutations in BRCA1 and BRCA2 account for around 15% of all ovarian cancers [235]. Harmful mutations in BRCA1 and BRCA2 increase the risk of several cancers in addition to breast and ovarian cancer. BRCA1 mutations may increase a woman’s risk of developing fallopian tube and peritoneal cancer [52,91]. Men with BRCA2 mutations, and to a lesser extent BRCA1 mutations, are also at increased risk of breast cancer [267]. Men with harmful BRCA1 or BRCA2 mutations have a higher risk of prostate cancer, and men and women with BRCA1 or BRCA2 mutations may be at increased risk of pancreatic cancer [120,90]. Who should be tested for BRCA mutations? Because harmful BRCA1 or BRCA2 gene mutations are relatively rare in the general population, mutation testing of individuals who do not have cancer should be performed only when the person’s individual or family history suggests the possible presence of a harmful mutation in BRCA1 and/or BRCA2 [140]. In December 2013, the U.S. Preventive Services Task Force recommended that women who have family members with breast, ovarian, fallopian tube, or peritoneal cancer be evaluated to see if they have a family history that is associated with an increased risk of a harmful mutation in one of these genes [296]. Family history factors that are linked with an increased likelihood of having a harmful mutation in BRCA1 or BRCA2 include [140]: ● ● Breast cancer diagnosed before age 50. ● ● Cancer in both breasts in the same woman. ● ● Both breast and ovarian cancers in either the same woman or the same family. ● ● Multiple breast cancers. ● ● Two or more primary types of BRCA1- or BRCA2-related cancers in a single family member. ● ● Men with breast cancer. ● ● Ashkenazi Jewish ethnicity (i.e. ethnic Jews whose families came from Eastern Europe, which constitute the majority of ethnic Jews in the U.S.).