Familial cancer refers to a pattern where cancer occurs more frequently within certain families. Most cancer cases occur sporadically due to factors like age, lifestyle, and environmental exposures, but 5% to 10% are influenced by inherited factors. Understanding this pattern indicates an increased predisposition to certain cancers, informing screening and prevention strategies for individuals and their families.
What is Familial Cancer?
Familial cancer describes when multiple family members, often on the same side, develop the same or related cancers. This clustering can also involve cancers diagnosed at younger ages or individuals developing more than one primary cancer. Unlike sporadic cancer, which arises from random genetic mutations, familial cancer suggests a shared underlying risk factor.
Familial cancer differs from hereditary cancer. Hereditary cancer is a specific type of familial cancer caused by a single, inherited gene mutation that significantly increases risk. Familial cancer, however, may be due to a combination of genetic factors, shared environmental exposures, or lifestyle choices, without a single identified gene mutation. While both highlight family health history, hereditary cancer has a more predictable inheritance pattern and often involves earlier onset.
How Cancer Can Be Inherited
Cancer development involves mutations in genes that regulate cell growth and division. In familial cancer, particularly hereditary syndromes, individuals inherit a germline mutation, meaning it’s present in every cell of their body. This differs from somatic mutations, which occur in non-reproductive cells and are not passed on to offspring.
Most inherited cancer predispositions follow an autosomal dominant inheritance pattern. This means one copy of a mutated gene, inherited from either parent, is sufficient to increase cancer risk. These inherited mutations often affect tumor suppressor genes, which normally control cell growth. If one copy of a tumor suppressor gene is mutated, the remaining healthy copy can still function, but one additional mutation in that second copy is needed for uncontrolled cell growth. Less common, inherited mutations in oncogenes, which promote cell growth, can also increase cancer risk.
Recognizing Familial Cancer
Identifying patterns within a family’s health history can be a significant step in recognizing a potential familial cancer risk. One key indicator is the presence of multiple close blood relatives on the same side of the family with the same or related types of cancer. For example, a mother, daughter, and sisters all diagnosed with breast cancer could suggest a familial pattern.
Another important “red flag” is cancer diagnosed at an unusually young age, such as breast cancer before age 50 or colorectal cancer before age 50. The occurrence of multiple primary cancers in the same individual, like breast cancer in both breasts or a person developing both breast and ovarian cancer, also warrants attention. Rare cancers, or cancers occurring in a sex not typically affected (such as male breast cancer), can also be signs of an inherited predisposition. Collecting a detailed family health history, spanning at least three generations on both the mother’s and father’s sides, is therefore very important in identifying these patterns.
Genetic Testing and Counseling
Genetic counseling is a process involving a healthcare professional who specializes in genetics. They assess an individual’s personal and family medical history to determine the likelihood of an inherited cancer risk. During this assessment, the counselor discusses the potential benefits and limitations of genetic testing, helping individuals make informed decisions about whether to proceed.
Genetic testing typically involves providing a blood or saliva sample, which is then analyzed to identify specific inherited gene mutations linked to increased cancer risk. A positive test result indicates the presence of a harmful genetic change, which can help explain why cancer developed in an individual and guide future risk management strategies. However, a negative result does not eliminate all cancer risk, as most cancers are sporadic, and a “variant of uncertain significance” means the impact of a genetic change is not yet fully understood. Genetic testing results can also provide valuable information for other family members, allowing them to consider their own risk and testing options.
Managing Inherited Cancer Risk
For individuals identified with an inherited cancer risk, a personalized management plan is developed with healthcare providers. One common strategy is increased surveillance, which involves more frequent and earlier screenings than recommended for the general population. For instance, women with BRCA1/2 mutations might undergo annual mammograms and breast MRIs starting at a younger age.
Risk-reducing medications, known as chemoprevention, may also be considered to lower cancer incidence. For example, certain medications can reduce the risk of breast cancer in high-risk individuals. In some cases, prophylactic surgery, the preventive removal of organs at high risk of developing cancer, can be an option. This might include a prophylactic mastectomy to reduce breast cancer risk by up to 90% or a salpingo-oophorectomy to significantly lower ovarian cancer risk in individuals with BRCA1/2 mutations. Lifestyle factors, such as maintaining a healthy diet and engaging in regular exercise, also contribute to overall cancer prevention, even for those with an inherited predisposition.