The incidence of colorectal cancer (CRC) in the US has been decreasing for the past two decades, with decreases of 2.8% in men and 2.2% in women noted since 1998.1 This decrease has been attributed to increased CRC screening among individuals ages 50 years and older. Routine screening is not recommended for adults younger than 50 years who do not have increased risk for CRC, e.g. family history or personal/family history of polyps.2 Siegel, Jemal & Ward, well known for their annual articles on cancer statistics, noted an unexpected increase in the diagnosis of invasive CRC among men and women under age 50 in the US.3 The researchers analyzed Surveillance, Epidemiology, and End Results (SEER) data for invasive CRC cases diagnosed between 1992-2005 in major racial/ethnic populations: non-Hispanic White, non-Hispanic Black, Hispanic and Asian American/Pacific Islander. The SEER database reflects approximately 14% of the US population.1

Results
  • Overall, incidence rates of colorectal cancer per 100,000 young individuals (ages 20-49 years) increased 1.5% per year in men and 1.6% per year in women from 1992 to 2005.
  • Among non-Hispanic Whites, rates increased for both men and women in each 10-year age grouping (20-29, 30-39, and 40-49 years) and for every stage of diagnosis.
  • The largest annual percent increase in CRC incidence was in the youngest age group (20-29 years), by 5.2% per year in men and 5.6% per year in women
  • The increase in incidence among non-Hispanic Whites was predominantly driven by rectal cancer, for which there was an average increase of 3.5% per year in men and 2.9% per year in women over the 13-year study interval
  • In non-Hispanic Whites <age 50, there was an increase in left-sided CRC, particular in the distal colon and rectum
  • Although the incidence of rectal cancer seems to have leveled off in women since 1999 to 2001, rates in men continued to increase through 2002 to 2005

Discussion
Although the purpose of this study was not to determine cause, Siegel, Jemal & Ward comment on the following CRC risk factors with respect to the increase in diagnoses in young adults in the US:
Obesity is a known risk factor for men and, to a lesser extent, postmenopausal women. They also note that evidence is beginning to emerge that obesity may be a stronger risk in premenopausal compared with postmenopausal women. It is unknown if obesity has a stronger effect on specific tumor sites, such as left-sided or rectal cancers.
Dietary patterns, particularly increased consumption of red and processed meat, decreased consumption of milk and calcium-containing foods and increased intake of fast-food items, which are usually higher in fat, processed meats and low in calcium content.
Type 2 diabetes is an established risk factor for CRC
Behavioral/lifestyle factors such as alcohol intake and smoking are discussed but not directly attributed to this increase due to declines in alcohol consumption and the length of the induction period for smoking to cause cellular changes leading to cancer.

Nursing Implications
Oncology and primary care healthcare professionals have assumed that CRC is primarily a disease of people over age 50. Clearly, this is no longer the case. CRC incidence is increasing among young adults in the US. Obesity, poor eating habits and type 2 diabetes are all on the increase in the US, beginning with school-age children and continuing through adulthood. Counseling patients and the public on reduction of these contributing factors and the importance of beginning screening promptly at age 50 will raise awareness of the risks of CRC. More research is needed to determine the ongoing prevalence of CRC among racial and ethnic, age, gender and other subgroups and how risk factors affect each of those groups in adults under age 50. Young adults who present with symptoms of CRC such as rectal bleeding, abdominal pain, alteration in bowel pattern, weight loss or unexplained anemia should be evaluated for CRC with standard screening tools.

References 

  1. Horner MJ, Ries LAG, Krapcho M, Neyman N, Aminou R, Howlader N, Altekruse SF, Feuer EJ, Huang L, Mariotto A, Miller BA, Lewis DR, Eisner MP, Stinchcomb DG, Edwards BK (eds). SEER Cancer Statistics Review, 1975-2006, National Cancer Institute. Bethesda, MD, http://seer.cancer.gov/csr/1975_2006/, based on November 2008 SEER data submission, posted to the SEER web site, 2009.
  2. Smith RA, Cokkinides V, Brawley OW. Cancer Screening in the United States, 2009: A Review of Current American Cancer Society Guidelines and Issues in Cancer Screening. CA Cancer J Clin. 2009;59:27-41. Free full text available here:
  3. Siegel RL, Jemal A, Ward EM. Increase in Incidence of Colorectal Cancer Among Young Men and Women in the United States. Cancer Epidemiol Biomarkers Prev. 2009;18:1695-1698. Link to abstract http://cebp.aacrjournals.org/content/18/6/1695.abstract