___________________________________________________________________________ Colorectal Cancer
Native Hawaiian people have a higher incidence of colorectal cancer than White people, and Alaska Native individuals have a two-fold higher incidence (88.5 per 100,000) and mortality (35.9 per 100,000) than American Indian individuals (46 and 17.5, respectively) [10]. The risk of colorectal cancer increases after 44 years of age. The incidence rates increase by about 80% to 100% with each five-year age group until 50 years of age and then by 20% to 30% from ages 55 to 59 years and older. From 2015 to 2019, the age-specific incidence of colorectal cancer in the United States ranged from 60.6 per 100,000 population in individuals 55 to 59 years of age to 234.7 in individuals 85 years of age and older [10]. Most cases (90%) of colorectal cancer are diagnosed after 50 years of age; only 6% are diagnosed in persons younger than 55 years of age [1; 11; 12]. Although colorectal cancer remains more common in older individuals, the incidence is increasing among younger adults. Between 2004 and 2013, the number of young-onset (before 50 years of age) cases increased 11.4% [13]. In that same period, the number of cases in adults 50 years of age or older decreased 2.5%. Figures for rectal cancer alone are more difficult to ascertain because epidemiologic studies usually report colon and rectal cancer together as colorectal cancer. However, 2024 projections estimate 46,220 new rectal cancer diagnoses [8]. Approximately 4.2% of Americans will be diagnosed with colorectal cancer at some point in their lifetime. Of those diagnosed, 50% will die from the disease. The overall five-year survival rate is 65.7% [11]. Cancer stage at diagnosis strongly influences duration of survival. With colon and rectum can- cer, the five-year survival is approximately 91% in patients diagnosed with localized cancer, 73% with limited regional extension, and 13% with distant metastases [14]. Despite advances in surgical techniques and adjuvant therapy, the mod- est survival improvements in patients with advanced neoplasm provide the rationale for implementing primary and secondary preventive approaches to reduce morbidity and mortality from colorectal cancer [1; 2; 3]. COLORECTAL CANCER RISK FACTORS For most people, the dominant risk factor for colorectal cancer is increasing age. As noted, risk increases dramatically after 50 years of age. Other nonmodifiable factors, such as family his- tory of colorectal cancer, personal history of colorectal cancer or high-risk adenomas, genetic predisposition, and inflamma- tory bowel disease, also elevate the risk of colorectal cancer [15]. There are also modifiable factors that increase (or decrease) an individual’s risk of colorectal cancer, including alcohol use, cigarette smoking, diet, and physical activity.
INTRODUCTION Colorectal cancer is the third leading cause of cancer death in the United States, and roughly 35% of those who develop colorectal cancer die from the disease [1; 2; 3]. Improved thera- pies and widespread primary prevention through screening have resulted in the United States being the only developed country with declining colorectal cancer incidence and mortal- ity [4]. However, there is substantial room for improvement, and primary care provider knowledge of colorectal cancer is essential to continue reducing cases through screening and early detection. While this course addresses important content domains related to colorectal cancer, a few related areas are not addressed: management of cancer-related pain and cancer of the anus. With 90% of anal cancer cases associated with the human papillomavirus (HPV), this malignancy is considered distinct from rectal cancer [5]. In contrast, rectal cancer bears such similarity to colon cancer that both cancers are frequently combined in epidemiologic and clinical reports. EPIDEMIOLOGY Worldwide, colorectal cancer is the second leading cause of cancer-related death among both sexes [6]. The incidence varies geographically, with the highest estimated rates per 100,000 population in Australia/New Zealand (34.9 in men, 27.7 in women) and lowest in Africa (9.1 in men, 7.5 in women). The highest estimated mortality rates per 100,000 population are in Europe (12.1 in both sexes) and the lowest are in Africa (5.6 in both sexes) [6]. In the United States, colorectal cancer is the third leading cause of cancer death, with 107,320 new diagnoses of colon cancer, 46,950 new diagnoses of rectal cancer, and 52,900 deaths projected for 2025 [7]. From 2011 to 2019, rates decreased by about 1% per year overall, although declining incidence was confined to individuals 65 years of age and older. Rates have increased by 1% to 2% per year since the mid-1990s in adults younger than 55 years of age and have stabilized in adults 55 to 64 years of age [8]. The death rate has decreased by 56%, from 29.2 per 100,000 in 1970 to 12.8 in 2021, primarily due to earlier detection and improvements in treatment [8]. During 2016 to 2020, the overall mortality rate from colorectal cancer in the United States was 13.1 per 100,000 population and was 43% higher in men (15.7) than in women (11.0). From 2015 to 2019, the incidence of colorectal cancer was highest in American Indian/Alaska Native individuals (48.6 per 100,000), followed by non-Hispanic Black individuals (41.7), and lowest in Asian American/Pacific Islander individu- als (28.6) [9]. However, there are striking differences within these heterogeneous populations. For example, Japanese and
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