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Does breast cancer increase colon cancer risk?

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Updated: October 5, 2006

Question: Does breast cancer increase colon cancer risk?


That's a good question and one the medical community is still asking itself. Some studies indicate that breast cancer increases colon cancer risk and others say it doesn't.

Answer: It basically boils down to genetics. You may have heard of BRCA 1 and BRCA 2, commonly referred to as the breast cancer genes. Some research has determined that the BRCA genes increase colon cancer risk and other research has shown that they don't. There's also a genetic disorder called Peutz-Jeghers syndrome (PJS) which is known to increase a person's risk of both breast cancer and colon cancer.

BRCA Genes and Colon Cancer

These genes are actually a double whammy for women because they increase the chances of breast cancer and ovarian cancer. Scientists have looked into their triple-whammy potential (colon cancer) with mixed results.

For example, research published in the journal Cancer Genetics and Cytogenetics found that breast cancer plays an important role in colon cancer development. However, research published in the Journal of the National Cancer Institute found no association whatsoever between breast cancer and colon cancer. Then there's another study, published in Diseases of the Colon and Rectum, that determined breast cancer doesn't increase the risk of colon cancer but it changes the way people get it. Sounds a little odd, right?

It's actually pretty interesting. Researchers examined data from about 750 people, a third of whom had the BRCA 1 or BRCA 2 genes. Turns out, women and men with the BRCA genes weren't any more likely to get colon cancer than people without the genes. But, the people with the BRCA genes who did get colon cancer got it about five years earlier (age 62-ish rather than age 67-ish) and had better survival rates.

PJS and Colon Cancer

Unlike the BRCA genes, PJS is pretty straightforward. People with PJS have more than a 90% chance of developing cancer by age 64. They're at increased risk for several types of cancer, but breast and colon cancer top this list. So in this case, does breast cancer increase the risk of colon cancer? Sort of. If you're diagnosed with breast cancer and found to have PJS, then you're at increased risk for colon cancer. But that's pretty unlikely since PJS occurs in about one out of every 120,000 people.

Sources:
  1. Breast Cancer, Colon Cancer and Osteoporosis. The Health Report. 17 May 1999. 28 Aug. 2006 [http://www.abc.net.au/rn/talks/8.30/helthrpt/stories/s25678.htm].
  2. Garcia-Patino, E. and Gomendio, B. "Loss of Heterozygosity in the Region Including the BRCA1 Gene on 17q in Colon Cancer." Cancer Genetics and Cytogenetics 104.2 (Jul. 1998): 119-123. 28 Aug. 2006 [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=98331422&dopt=Abstract].
  3. Genetics of Breast and Ovarian Cancer: Peutz-Jeghers Syndrome. National Cancer Institute. 3 Aug. 2006. 28 Aug. 2006 [http://www.nci.nih.gov/cancertopics/pdq/genetics/breast-and-ovarian/HealthProfessional/Page2#Section_153].
  4. Lin, K. and Ternent, C. "Colorectal Cancer in Hereditary Breast Cancer Kindreds." Diseases of the Colon and Rectum 42.8 (Aug. 1999): 1041-1045. 28 Aug. 2006 [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=99385310&dopt=Abstract].
  5. Medical Encyclopedia: Colon Cancer. Medline Plus. 9 Nov. 2004. 28 Aug. 2006 [http://www.nlm.nih.gov/medlineplus/ency/article/000262.htm].
  6. Marignani, P. "LKB1, the Multitasking Tumour Suppressor Kinase." Journal of Clinical Pathology 58 (2005): 15-19. 28 Aug. 2006 [http://jcp.bmjjournals.com/cgi/content/full/58/1/15].
  7. Niell, B. and Rennert, G. "BRCA1 and BRCA2 Founder Mutations and the Risk of Colorectal Cancer." Journal of the National Cancer Institute 96.1 (Jan. 2004): 15-21. 28 Aug. 2006.

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