Genetic roots of pancreatic cancer

Introduction

• 5-10% of the cases of pancreatic cancer are believed to be caused by genetic factors. The remainder are sporadic.

• The genetic cancer syndromes that can cause pancreatic cancer often do not feature pancreatic cancer as a hallmark cancer. Rather, these syndromes tend to cause other types of cancer primarily, with pancreatic cancer as a possible associated cancer.

• It is important to discuss your family history with your doctor or with a Genetics specialist in order to determine whether genetic testing may be useful to you or your family.

• Genetic testing of any kind has benefits, risks and limitations. We recommend that you seek genetic testing through a facility that is prepared to discuss all of these factors with you before proceeding with genetic testing.

Pancreatic Cancer Genes

• BRCA2: BRCA 2 was the second major breast cancer susceptibility gene discovered. Classically, mutations in the BRCA 2 gene increase an individual's susceptibility to breast and ovarian cancer. A handful of studies have shown that mutations in the BRCA 2 gene may also increase an individual's risk of pancreatic cancer. Genetic testing for mutations in the BRCA 2 gene may be particularly of interest to you if there is a family history of breast or ovarian cancer with or without pancreatic cancer. The lifetime risk to get breast cancer if there is a BRCA 2 mutation is 87%, the lifetime risk of ovarian cancer is 40%, the lifetime risk of pancreatic cancer is still unknown, but is expected to be low (<5%).

• P16 - Familial Melanoma: P16 was discovered as a gene that causes an increased susceptibility to melanoma. Mutations in the p16 gene confer an 80% lifetime risk of melanoma, making regular visits to the dermatologist and skin scanning very important. One study of the p16 gene also found that there is a 17% risk of pancreatic cancer by the age of 75. Two other studies of this gene, however, found no increased risk of pancreatic cancer over the general population. Genetic testing for p16 may be of interest to you or your family if there is a history of melanoma and pancreatic cancer.

• Peutz-Jeghers syndrome: Peutz-Jeghers syndrome (PJS) is characterized by increased freckle-like pigmentation of the lips, inside of the mouth, genitalia, hands and feet. PJS is also associated with multiple hamartogenous polyps (benign tumor-like nodules) of the GI tract. There has been an increased risk of pancreatic, lung, ovarian and breast cancers associated with PJS. It is believed that individuals with PJS have a 36% lifetime risk of pancreatic cancer. Genetic testing for PJS is available. Testing may be of interest to you or your family if there is a history of polyps in the GI tract or increased freckle-like pigmentation and pancreatic cancer.

• Hereditary Nonpolyposis Colon Cancer (HNPCC): HNPCC is a hereditary colon cancer susceptibility syndrome that is primarily associated with colon cancer, endometrial cancer and ovarian cancer. Pancreatic cancer has been found to also be associated with HNPCC, however studies have been unable to prove a statistical significance in the increased risk of pancreatic cancer. Testing for HNPCC may of interest to you or your family if there is a history of colon, endometrial or ovarian cancer with or without pancreatic cancer. The lifetime risk of pancreatic cancer due to HNPCC is expected to be low (<5%).

Hereditary pancreatitis:

• Mutations in a gene known as PRSS1 is known to cause acute attacks of pancreatitis. Typically attacks begin during childhood and can progress to chronic pancreatitis later in life. Mutations in the PRSS1 gene have been associated with a 40% lifetime risk of pancreatic cancer. Testing for PRSS1 may be of interest to you or your family if there is a strong family history of pancreatitis and/or pancreatic cancer.

• Mutations in other genes such as SPINK1 and CFTR (the cystic fibrosis gene) have been known to cause chronic or recurrent pancreatitis. They are not specifically associated with pancreatic cancer. However, damage due to chronic pancreatitis can cause pancreatic cancer. Mutations in the CFTR gene in individuals with pancreatitis may explain some underlying level of pancreatic insufficiency. Individuals who do not have any lung involvement are not given the diagnosis of cystic fibrosis even though the gene is the same. Certain changes in the gene cause chronic pancreatitis without lung problems.

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