Peritoneal cancer (PPC) is a rare malignancy that develops in the peritoneum, the thin layer of tissue lining the inside of the abdomen and covering the organs within it. It is strongly associated with ovarian and fallopian tube cancers because all three conditions arise from the same type of epithelial cell. While most cases occur sporadically, a significant percentage of diagnoses are linked to inherited genetic factors, making the role of hereditary mutations important for assessing personal risk.
Inherited Genetic Mutations and Peritoneal Cancer
Inherited genetic mutations represent a well-defined pathway for increased peritoneal cancer risk. The most recognized genes involved are BRCA1 and BRCA2, which normally repair damaged DNA within cells. Inheriting a non-functional copy of these genes compromises DNA repair, allowing mutations to accumulate and increasing the lifetime risk of several cancers, including PPC.
An inherited BRCA1 or BRCA2 mutation is estimated to be present in 15 to 20% of all ovarian, fallopian tube, and peritoneal cancers collectively. For individuals with a BRCA1 mutation, the lifetime risk of developing one of these cancers can be up to 45%. The risk associated with BRCA2 is slightly lower but remains substantially elevated compared to the general population.
Genetic syndromes other than BRCA mutations also contribute to hereditary risk. Lynch syndrome, for example, is caused by inherited mutations in DNA mismatch repair (MMR) genes. These MMR genes fix errors that occur when DNA is copied, and their malfunction leads to an increased cancer risk, including PPC. While primarily known for increasing the risk of colorectal and endometrial cancers, its connection to PPC is a recognized part of the syndrome’s profile.
Non-Genetic Causes and Risk Factors
Although inherited gene mutations are a major consideration, most cases of peritoneal cancer are not hereditary. The majority of diagnoses are sporadic and linked to a combination of acquired and lifestyle factors.
Increasing age is a primary factor, with most patients diagnosed over the age of 60. This suggests that the accumulation of genetic damage over time contributes to the cancer’s development. Other non-genetic factors include obesity, the use of hormone replacement therapy after menopause, and a history of endometriosis. Additionally, women who have never had children or have experienced infertility appear to have a slightly higher risk.
Assessing Personal Risk Through Genetic Counseling
Individuals concerned about their risk for peritoneal cancer can seek guidance through genetic counseling. A genetic counselor collects a detailed medical and family history, focusing on cancers like ovarian, breast, prostate, and colon, to determine the likelihood of an inherited mutation. This process is crucial because a positive test result informs surveillance and risk-reduction strategies.
Genetic testing is typically recommended for anyone diagnosed with peritoneal cancer, regardless of family history, because the results can influence treatment options. For unaffected individuals, testing is usually considered if they have multiple close relatives with a history of ovarian, fallopian tube, or peritoneal cancer, or if a known BRCA or Lynch syndrome mutation exists in the family.
The genetic test involves analyzing a blood or saliva sample for mutations in a panel of genes associated with hereditary cancer risk. If a pathogenic mutation is identified, the counselor explains the implications, including the increased lifetime risk of PPC and other associated cancers. Understanding a positive result allows individuals to discuss options with their medical team, such as enhanced surveillance or risk-reducing surgeries.