Chapter 12: Hereditary Cancer Syndromes

INTRODUCTION

Screening for familial cancer is an important part of the initial evaluation of a patient, and should be a regular part of each subsequent visit to assess any changes in the family history. Obstetricians and gynecologists have an important role in identifying those women with a potentially hereditary cancer syndrome. Although it is not expected that the practicing OB/GYN would be familiar with all the hereditary cancer syndromes, they should be able to recognize the key features in a family history that suggest the patient may be at risk, and make an appropriate referral for evaluation and counseling. This chapter will outline some common hereditary cancer syndromes likely to be seen by the OB/GYN, and provide a list of key features present in families with hereditary forms of cancer.

HEREDITARY CANCER SYNDROMES

Hereditary Breast and Ovarian Cancer

This is a dominantly inherited syndrome most commonly caused by germline mutations in the genes BRCA1 and 2. In the general population the mutated gene is found in approximately 1 in every 500 persons, but in those of Ashkenazi Jewish ancestry the cancer frequency is 1 in every 40 individuals.¹ However, the majority of breast and ovarian cancers are sporadic, with only 5% to 10% of them being caused by a BRCA1 or 2 mutation.

Key features strongly suggestive of a BRCA1 or 2 mutation would be early onset of breast or ovarian cancer in a patient (prior to age 50), a family history with multiple affected members, or the presence in the family history of both breast and ovarian cancer. It is important to recognize that males who carry one of these mutations may be asymptomatic, but also are at risk for breast, prostate, and pancreatic cancer. Even in women with the mutation, the gene is not completely penetrant. For a female with the mutation there is 40% to 66% lifetime risk of breast cancer, and up to a 46% risk of ovarian cancer. These risks are significantly higher than the US general population risk of 12% for breast cancer and 1.5% for ovarian cancer. In addition, many of these cancers will occur before the age of 50.² Equally of concern is the risk of breast cancer in the contralateral breast which is between 40% and 65% over a lifetime, and up to 30% 10 years postdiagnosis.³

Patients with early onset breast or ovarian cancer, or those with family histories similar to that seen in the case study, should be referred to individuals trained in cancer genetic counseling for evaluation and genetic testing. If the patient is found to carry a pathogenic mutation, an appropriate ...