Cancer is caused due to both genetic and environmental factors. While environmental factors are controllable such as diet, exercise, exposure to toxins and sunlight, what cannot be changed is your family history. Studies have shown that those who have close relatives who have had some form of cancer are more predisposed to having cancer themselves. Understanding how your family medical history affects cancer risk goes a long way in taking essential steps for early screening and detection to prevent cancer.
Does cancer run in families?
Cancer cannot be passed down from the parents to their offspring. Similarly, genetic changes in tumor cells are also not inheritable. What follows down the generations are any genetic changes that increase the risk of cancer which are mostly present in the parent’s egg or sperm cells. A parent who has mutated BRCA1 and BRCA2 gene can pass it on to their child, thereby increasing the child’s risk of developing breast cancer and many other cancers. This pattern shows that cancer does sometimes run in families. According to research, up to 10% of all cancers are caused due to inherited faulty genes.
Role of genetic changes in causing cancer
A number of cancers are caused due to inherited genes such as breast, ovarian, colorectal, prostate, pancreatic cancer and melanoma. Most DNA changes that cause cancer occur at the gene level. Crucial mechanisms that work at the gene level include:
• Mutations in Proto-oncogenes: Proto-oncogenes are normally responsible for cell growth. However, due to mutations, they can turn cancerous.
• Mutations in Tumor Suppressor genes: These genes are specialized in inhibiting cell growth, repair DNA damage, and trigger programmed cell death (apoptosis). When these undergo mutational changes, cells escape growth restraints and grow uncontrollably leading to cancer.
Higher risk of getting cancer
If you have a family history of cancer, your chances of developing the same increases considerably. You are at higher risk in the following eventualities, if:
• One of your relatives was diagnosed before 50 years with breast, uterine, or colorectal cancer.
• Two or more of your relatives from same side of the family were diagnosed with breast, uterine, or colorectal cancer.
• A male relative was diagnosed with cancer of the breasts.
• A female relative was diagnosed with cancer of the ovaries.
Common hereditary conditions that lead to cancer
There are certain family cancer syndromes (also called hereditary cancer syndromes) which can lead to cancer, if inherited. These are caused by genetic variations in certain cancer-causing genes. The major inherited cancer-leading conditions are:
• Hereditary Breast and Ovarian Cancer (HBOC): This condition occurs due to BRCA1 and BRCA2 gene mutations, often resulting in breast and ovarian cancers.
• Lynch Syndrome: This syndrome is caused by mutations in DNA mismatch repair genes. A person who inherits this genetic condition has an increased risk of developing various types of cancers such as colorectal and endometrial cancer.
• Familial Adenomatous Polyposis (FAP): Certain changes in the APC gene are responsible for this familial syndrome. People who inherit this gene are more susceptible to developing colorectal cancer, due to high chances of forming numerous colon polyps.
Generally, a genetic counsellor can assess your risk of inheriting cancers by taking an extensive medical history of your family. Using risk assessment tools and deciding if genetic testing is right for you, the counsellor can help you make choices that reduce your risk of cancer. By staying proactive through regular check-ups and consulting a genetic counsellor, if needed, you can transform the knowledge of your family history into a practical tool for early detection of cancer and its prevention.