See ColonCancerCheck at http://health.gov.on.ca/en/ms/coloncancercheck Colorectal cancer subsite distribution differs by sex (Apr. 2010) Proximal colon cancers are most common in females, while rectal cancers are most common among males. Differences in risk factors may explain the variation in subsite proportions between sexes. The distribution of cancers occurring along subsites of the colon and rectum differs between sexes. Among females, proximal colon cancers are most common, accounting for approximately 42% of all colorectal cancers. Rectal cancers and distal colon cancers account for the second (28%) and third (22%) largest proportion of female cases, respectively. In contrast, rectal cancers are most common among males (38% of all cases), followed by cancers of the proximal (31%) and distal (25%) colon. The predominance of proximal colon cancers among females and rectal cancers among males in Ontario is consistent with patterns in other developed countries (1,2). The reasons for this sex difference, however, remain unclear. Risk factors for colorectal cancer include genetic and environmental factors such as obesity, insufficient physical activity, alcohol consumption, and red meat consumption. Hormone replacement therapy and non-steroidal anti-inflammatory drug use have a protective effect (3). Increasingly, it is being recognized that colorectal cancer risk factors, tumour characteristics, and response to treatment may vary across anatomic subsites (3,4). Differences in exposure and response to risk factors between males and females may therefore explain the varying subsite distribution of colorectal cancers observed between sexes.   Ontario’s colorectal cancer screening program, ColonCancerCheck, recommends screening Ontarians at average risk of colorectal cancer with the fecal occult blood test (FOBT) beginning at age 50. For those at increased risk (defined as a family history of one or more first degree relatives with colorectal cancer), it recommends colonoscopy for screening beginning at age 50 or 10 years younger than the age at which the relative was diagnosed, whichever occurs earlier. Screening for colorectal cancer can reduce the number of deaths from colorectal cancer by facilitating early detection of cancerous tumours and detecting and removing precancerous polyps. For more information: See ColonCancerCheck at http://health.gov.on.ca/en/ms/coloncancercheck See Insight on Colorectal Cancer: News and information on colorectal cancer and screening in Ontario at http://www.cancercare.on.ca/common/pages/UserFile.aspx?fieldID=13734 Talk to your health care provider or call Cancer Information Service (1 888 939-3333) References 1. Bray F and Larsen IK. Trends in colorectal cancer incidence in Norway 1962–2006: an interpretation of the temporal patterns by anatomic subsite. Int J Cancer 2010;126:721–732. 2. Wu XC, Chen VW, Steele B, Ruiz B, Fulton J, Liu L, et al. Subsite-specific incidence rate and stage of disease in colorectal cancer by race, gender, and age group in the United States, 1992–1997. Cancer 2001;92(10):2547–2554. 3. Giovannucci E and Wu K. Cancers of the colon and rectum. In: Schottenfeld D, Fraumeni JF, Jr., editors. Cancer epidemiology and prevention. 3rd ed. New York: Oxford University Press; 2006. p. 809–829. 4. Iacopetta B. Are there two sides to colorectal cancer? Int J Cancer 2002;101:403–408. This Ontario Cancer Fact was prepared by the Colorectal Cancer Network (CRCNet). Production of this Cancer Fact has been made possible through a financial contribution from Health Canada, through the Canadian Partnership Against Cancer. The views expressed herein do not necessarily represent the views of The Canadian Partnership Against Cancer. Citation: Cancer Care Ontario. Colorectal cancer subsite distribution differs by sex. April 2010. Available at http://www.cancercare.on.ca/english/ocs/snapshot/ont-cancer-facts/. Prepared by: The Colorectal Cancer Network (CRCNet).

See ColonCancerCheck at http://health.gov.on.ca/en/ms/coloncancercheck Colorectal cancer subsite distribution differs by sex (Apr. 2010) Proximal colon cancers are most common in females, while rectal cancers are most common among males. Differences in risk factors may explain the variation in subsite proportions between sexes. The distribution of cancers occurring along subsites of the colon and rectum differs between sexes. Among females, proximal colon cancers are most common, accounting for approximately 42% of all colorectal cancers. Rectal cancers and distal colon cancers account for the second (28%) and third (22%) largest proportion of female cases, respectively. In contrast, rectal cancers are most common among males (38% of all cases), followed by cancers of the proximal (31%) and distal (25%) colon. The predominance of proximal colon cancers among females and rectal cancers among males in Ontario is consistent with patterns in other developed countries (1,2). The reasons for this sex difference, however, remain unclear. Risk factors for colorectal cancer include genetic and environmental factors such as obesity, insufficient physical activity, alcohol consumption, and red meat consumption. Hormone replacement therapy and non-steroidal anti-inflammatory drug use have a protective effect (3). Increasingly, it is being recognized that colorectal cancer risk factors, tumour characteristics, and response to treatment may vary across anatomic subsites (3,4). Differences in exposure and response to risk factors between males and females may therefore explain the varying subsite distribution of colorectal cancers observed between sexes.   Ontario’s colorectal cancer screening program, ColonCancerCheck, recommends screening Ontarians at average risk of colorectal cancer with the fecal occult blood test (FOBT) beginning at age 50. For those at increased risk (defined as a family history of one or more first degree relatives with colorectal cancer), it recommends colonoscopy for screening beginning at age 50 or 10 years younger than the age at which the relative was diagnosed, whichever occurs earlier. Screening for colorectal cancer can reduce the number of deaths from colorectal cancer by facilitating early detection of cancerous tumours and detecting and removing precancerous polyps. For more information: See ColonCancerCheck at http://health.gov.on.ca/en/ms/coloncancercheck See Insight on Colorectal Cancer: News and information on colorectal cancer and screening in Ontario at http://www.cancercare.on.ca/common/pages/UserFile.aspx?fieldID=13734 Talk to your health care provider or call Cancer Information Service (1 888 939-3333) References 1. Bray F and Larsen IK. Trends in colorectal cancer incidence in Norway 1962–2006: an interpretation of the temporal patterns by anatomic subsite. Int J Cancer 2010;126:721–732. 2. Wu XC, Chen VW, Steele B, Ruiz B, Fulton J, Liu L, et al. Subsite-specific incidence rate and stage of disease in colorectal cancer by race, gender, and age group in the United States, 1992–1997. Cancer 2001;92(10):2547–2554. 3. Giovannucci E and Wu K. Cancers of the colon and rectum. In: Schottenfeld D, Fraumeni JF, Jr., editors. Cancer epidemiology and prevention. 3rd ed. New York: Oxford University Press; 2006. p. 809–829. 4. Iacopetta B. Are there two sides to colorectal cancer? Int J Cancer 2002;101:403–408. This Ontario Cancer Fact was prepared by the Colorectal Cancer Network (CRCNet). Production of this Cancer Fact has been made possible through a financial contribution from Health Canada, through the Canadian Partnership Against Cancer. The views expressed herein do not necessarily represent the views of The Canadian Partnership Against Cancer. Citation: Cancer Care Ontario. Colorectal cancer subsite distribution differs by sex. April 2010. Available at http://www.cancercare.on.ca/english/ocs/snapshot/ont-cancer-facts/. Prepared by: The Colorectal Cancer Network (CRCNet).