What is hereditary cancer
A cancer is said to be hereditary when it develops due to abnormalities in the genes that have been transferred from the parent to the child.
Each cell in the body contains 23 pairs of chromosomes in the nucleus. These chromosomes contain genes, about 25000 of them. The genes define all our characteristics and how the cells in the body function. Faults appear in the genes over time and increasing age due to external factors such as smoking etc. All the faults may not happen at once and can accumulate over time. A cell that has developed multiple errors in its genes can go on to become a cancer cell and therefore faulty genes play an important part in the development of cancers. Faults that are acquired over time in a person are not transferred to children. Certain faults in the genes can be inherited from the parents. People or families that have inherited genes which could cause cancer, have a higher risk of developing cancer in their lifetime. Faulty genes that are inherited from parents, which can produce cancer are commonly tumour suppressor genes. In a normal situation, these genes function to suppress the formation of a cancer in the body by repairing damaged DNA. But when there is a fault in this gene, the repairing process is impaired leading to the accumulation of more faults which increases the risk of getting a cancer. There are two copies of each gene in the body and if one of them is damaged, there is a 50% chance for the child to inherit the faulty gene from the parent. A small number of cancers happen due to inherited genes in the family. In all, about 5% of all cancers are due to this. The rest of them are due to external environment and lifestyle factors.
How do you know if you have a cancer that is hereditary?
As said above, only about 5% of all cancers are hereditary. Generally, in people with these types of cancers, there is a strong family history of cancer. This means there are many people in the family who have developed a cancer. These can be close relatives such as brother, sister, mother, aunt, uncle, parents or grandparents. Two or three cancers in the family are needed for suspecting a genetic link. Also, in families with a genetic link, the cancers develop in a younger age than expected. Usually, there are specific criteria that a person needs to fit in, to be suspect or to consider testing for a hereditary link in cancer.
What to do if genetic or hereditary cancer is suspected?
If there is a concern or suspicion of hereditary cancer in the family due to the above-mentioned reasons or otherwise, an appointment with an oncologist or a genetics specialist if one is available is appropriate. They will be able to take a detailed history of the cancers and advise whether further tests are needed to look for this link. Following the advice, the person or patient has to decide whether to undergo testing or not for these conditions. They would have to assess the pros and cons of having such tests and the emotional and psychological impact that may have on them and their families. Seeing a counsellor may help with coping with the situation and make an informed choice. Often, these tests do not need to be done urgently and therefore, time can be taken before a decision is made.
Types of Hereditary cancers
Listed here are some of the cancers that are seen. Based on the abnormalities present in the genes, one or many cancers may develop as a result.
Hereditary Breast and Ovarian Cancer
This condition is discussed in detail in a separate section in FAQ’s. See that section for more details.
Familial Adenomatous Polyposis (FAP)
This is an inherited condition which is transmitted in an autosomal dominant fashion (50% risk in children). Patients who have FAP have a high risk of developing colon and rectal cancers mainly, but also other cancers. Patients or close relatives of patients known to have this condition can develop multiple benign polyps in the intestine which can later develop into cancers. Therefore regular screening for these cancers and early preventive surgery of the colon can be considered to reduce the risk of development of a cancer. Screening for those at highest risk is started early, before the age of 15. Screening is done with flexible sigmoidoscopy, colonoscopy.
Neurofibromatosis Type 2
This is inherited in an autosomal dominant pattern and is a syndrome due to which patients are at risk of tumours such as acoustic neuromas, meningiomas, schwannomas of other nerves and spinal tumours.
Lynch syndrome is inherited in an autosomal dominant (50% risk of transmission to child) pattern. The syndrome occurs due to a mutation in DNA repair genes such as MLH1, MSH2, MSH6, PMS2. This syndrome accounts for about 3% of all colorectal and endometrial cancers. People who have Lynch syndrome are at risk of developing, colon, rectal, endometrial(uterus), ovary, stomach, ureter, brain, skin, and stomach cancers. This syndrome should be suspected in individuals who have colorectal cancer at a young age, <50 years, strong family history of above-mentioned cancer or more than one cancer in the same individual.
This is a syndrome that occurs due to a mutation in p53 gene and poses a risk of developing cancers such as breast cancers, sarcomas, brain tumours and adrenocortical tumours. Patients who have a strong family history of above cancers, more than one or two close relatives with cancers, should consider testing for this condition.
Von Hippel-Lindau syndrome (VHL)
This is an inherited condition that leads to the development of benign and malignant tumours or cancers. This condition is inherited in an autosomal dominant pattern, meaning that 50% of children born to an affected parent can get the condition. VHL can lead to the development of tumours such as haemangioblastomas, which occur mainly in the brain. Other cancers include cancer of the kidney, pancreas and pheochromocytoma.