The Genetics of Pancreatic Cancer: Part 2
In recognition of Pancreatic Cancer Awareness Month we’ve compiled information about inherited forms of pancreatic cancer. This is the second installment of our series, check out the first installment.
As you may know, pancreatic cancer is relatively uncommon, with a lifetime risk of ~1.5% for individuals in the United States. For the majority of pancreatic cancers the cause is unknown and there is no known family history of the disease. In these circumstances, a cancer is termed “sporadic.” General population risk factors that increase the risks for developing pancreatic cancer include: cigarette smoking, type 2 diabetes, chronic pancreatitis, obesity, cirrhosis of the liver, and family history of pancreatic cancer.
In ~10% of cases, pancreatic cancers are “hereditary.” These cancers are often due to inherited genetic changes and are usually found in families with pancreatic and other cancers. Hereditary pancreatic cancer is due to inherited genetic causes that people are born with (these gene changes do not develop over time).
Hereditary pancreatic cancer can be divided into the three categories below. We covered Category 1 in a previous post. In this post, we will discuss Categories 2 and 3 below:
1. Hereditary Cancer Syndromes that include an increased risk for pancreatic cancer
a. Pancreatic cancers, adenocarcinomas
b. Pancreatic cancers, neuroendocrine tumors
2. Hereditary Disease that causes inflammation of the pancreas leading to an increased risk
3. Unknown Genetic Causes
2. Hereditary Diseases Associated with an Increased Risk of Pancreatic Cancer
i. Hereditary Pancreatitis (HP)
- Primarily due to mutations in the PRSS1 gene that can be inherited from either parent
- Mutations in other genes (SPINK1, CFTR, and CTRC) have also been found in families with HP.
- Pancreatitis is recurring inflammation of the pancreas that can gradually cause damage to the pancreas and surrounding tissue.
- Clinical features of HP include recurrent pancreatitis, often beginning in the teenage years, and leading to chronic pancreatitis in late adolescence to early adulthood
- Lifetime risk of pancreatic cancer 25-40%
- Smoking is associated with a further increase in risk and younger age of onset of PC
- Rare and accounts for a small percentage of pancreatic cancer cases
ii. Cystic Fibrosis (CF)
- Due to mutations in the CFTR gene.
- An individual with CF has 2 mutations, one inherited from each parent.
- CF is characterized by lung disease and the lack of enough pancreatic digestive enzymes (pancreatic insufficiency).
- Patients with CF may have a ~5-7% risk of pancreatic cancer.
3. Unknown Genetic Causes
- While the above genetic syndromes account for ~20% of familial pancreatic cancer, it is clear that there are other, yet undiscovered familial pancreatic cancer genes. For example, relatives of patients with pancreatic cancer have an increased risk for developing pancreas cancer themselves.
Referral for Genetic Counseling:
A referral to genetic counseling for hereditary pancreatic cancer should be considered for individuals with a personal and/or family history that includes any of the following risk factors:
- Multiple cases of pancreatic cancer on the same side of the family.
- A combination of related cancers on the same side of the family (e.g. pancreatic/breast/ovarian, pancreatic/melanoma, or pancreatic/colon/uterine/ovarian).
- Multiple related primary cancers in one individual (e.g. pancreatic/melanoma, pancreatic/breast).
- Ashkenazi Jewish ancestry and pancreatic cancer.
- Pancreatic cancer and multiple and/or early onset gastrointestinal polyps including greater than 15 gastrointestinal polyps or greater than 5 hamartomatous polyps.