Cancer is notoriously famous as the curse that passes down generations, affecting direct blood descendants of cancer patients with the same ferocity. How true is this? Let’s find out – is cancer hereditary, or not.
Cancer as we know it today can be broadly categorised as ‘Sporadic’ or ‘Hereditary’. Before we begin breaking down the inheritance of cancer, we need a basic understanding of how cancer is developed in the first place.
What Causes Cancer?
“Cancer” is a genetic mutation. All known cancers are caused by changes to the genes in our bodies. When genes get damaged, their changes are termed ‘mutations’.
Consistent mutation can cause these affected cells to grow out of control and cause cancer.
How Does Non-Hereditary (Sporadic) Cancer Develop?
Cancer is not a result of a single genetic mutation; it takes more than one mutation to develop a tumour. It takes more than one gene mutation for cancer to occur. For people with no history of cancer who end up developing cancer, such mutations happen over the course of a lifetime, leading to cancer in later life.
How Is Cancer “Inherited”?
Some people (people with a family history of cancer) are born with a gene mutation that they inherited from their mother/father. This damaged gene creates higher cancer risk, as compared to regular people (people who don’t have a family history of cancer).
When a tumor develops as a result of a hereditary gene mutation, it is called ‘Hereditary Cancer’s. Only about 5% to 10% of all cancers are thought to result directly from gene defects (called mutations) inherited from a parent.
Reference: American Cancer Society
How Is Hereditary Cancer Different From Regular (Sporadic) Cancer?
Sporadic (non-hereditary) Cancers and Hereditary Cancers are different in many aspects that eventually decide the prognosis of each patient and what treatment/procedure is more effective in each case:
- Hereditary cancers are partly caused by genetic mutations passed directly from parents to children. Having said that, we must note that in such families, other blood relatives are likely to share these same gene changes. On the other hand, Sporadic cancers are believed to be a result of gene damage acquired from environmental exposures, dietary factors, hormones, normal aging, and other influences. Most of such “acquired” genetic changes are not shared among relatives or passed on to children.
- Hereditary cancers often develop earlier than the sporadic variety of the same cancer type, which is why more frequent screening is recommended for people with a family history of cancer.
- Hereditary cancers can be much more aggressive than the sporadic variation of the same cancer type. For instance, Hereditary Prostate Cancer is known to be much more aggressive (develops, progresses and metastasizes faster) than Sporadic Prostate Cancer.
- Hereditary cancers respond to different treatments when compared to the sporadic variations of the same cancer type.
How To Recognise A Family Cancer Syndrome?
For families that have had a history of the same type of cancer, the disease is strongly linked to an inherited gene mutation. This inherited gene mutation is a part of a family cancer syndrome.
The following factors hint towards the existence of a Family Cancer Syndrome. Stay on alert for Family Cancer Syndrome:
- If the same type of cancer (especially a rare cancer type) is common in different members of the same family
- If cancer develops in relatively younger ages, such as patients in their early twenties.
- If the same family member develops more than one type of cancer (e.g. a Woman who develops both Breast and Ovarian cancer)
- If cancer occurs in a family member, in an organ pair (such as cancer in both breasts, or both kidneys)
- If siblings develop the same, childhood cancer (such as a brother and a sister developing sarcoma)
- If cancer occurs in a gender that’s usually not the target victim of that cancer type/subtype (e.g. A male family member developing Breast Cancer)
- If cancer has been developing in members of all subsequent generations (Such as the grandfather, father and son all developing cancer in the same bloodline)
Genetic Tests That Can Help In Detecting Hereditary Cancers
Genetic Testing refers to the use of medical tests to identify specific mutations in a person’s genes. There are many genetic tests in use today, and more in development. Out of these, Predictive Genetic Testing is the type of testing that can be used to identify family members who are at higher risk of developing cancer from an inherited gene mutation.
Such tests are advised to patients when:
- A patient has a strong family history of certain types of cancer. In such cases, Predictive Genetic Testing can help establish whether they’re carrying a gene mutation that increases their risk. If they do exhibit an inherited mutation, they can opt for earlier cancer screening and if possible, undertake preventive measures. For instance, changes in BRCA1 and BRCA2 genes are tested in women with known blood relatives (mothers/sisters) who have had Breast Cancer.
- A patient whose cancer diagnosis is confirmed can be tested for inherited gene mutations if there is a family history of cancer. The results of such tests can help other family members decide if they wish to get tested for the same genetic mutations.
- A patient has a close relative who has tested positive for a known gene mutation. This helps the patient decide if they wish to get tested for the same gene mutation or get screened for the known types/subtypes of cancer that can develop from such a mutation. Alternatively, they can take steps to lower their risk of cancer.