Can cancer be genetic?

Cancer is now one of the top causes of deaths in India, after heart attacks, up from seventh position in 2000. What's more alarming is that by 2020, 70% of the world's cancer cases will be found in developing countries, with a fifth in India. Nearly seven lakh Indians die of cancer every year, while over 10 lakh are newly diagnosed with the disease. Some of these cancers are hereditary.

What is hereditary cancer?

All cancers are caused by changes in genes in our bodies. When genes are damaged, they can develop mutations. And when these mutations occur, cells can grow and cause cancer. For most people who develop cancer, the gene mutations happen over the course of a lifetime, leading to cancer later in life. Some people are born with a gene mutation that they inherited from their mother or father. This damaged gene puts them at a higher risk for cancer than most people. When cancer occurs because of an inherited gene mutation, it is referred to as "hereditary cancer."
Let's look at how cancerous genes are carried in family:
* Cancer in a close relative, like a parent or sibling, is more cause for concern than cancer in a distant relative. Even if the cancer was from a gene mutation, the chances of it passing on to you gets lower with more distant relatives.
* The age of the person when the cancer was diagnosed is also important. For example, colon cancer is rare in people under 30. Having two or more cases in close relatives under 30 could be a sign of an inherited cancer syndrome. On the other hand, prostate cancer is common in elderly men, so if both your father and his brother were found to have prostate cancer when they were in their 80s, it is less likely to be due to an inherited gene change.
Here are some types of hereditary cancers:

Breast & ovarian cancers

The main hereditary breast and ovarian cancer (HBOC) syndromes are caused by mutations in one of two genes: BRCA1 or BRCA2. The risk of breast and ovarian cancer is high with mutations in either gene, but tends to be higher with BRCA1 mutations. Along with breast and ovarian cancer, this syndrome can also lead to fallopian tube cancer, primary peritoneal cancer, male breast cancer, pancreatic cancer, prostate cancer, as well as some others.

Non-polyposis colorectal cancer

The most common inherited syndrome that increases a person's risk for colon cancer is called hereditary non-polyposis colorectal cancer (HNPCC), or Lynch syndrome. People with this syndrome have a high risk of colorectal cancer. Most of these cancers occur before age of 50. HNPCC also leads to a high risk of endometrial cancer (cancer in the lining of the uterus) in women. Other cancers linked with HNPCC include cancer of the ovary, stomach, small intestine, pancreas, kidney, brain, ureters and bile duct.

Li-Fraumeni syndrome

This is a rare syndrome that can lead to the development of a number of cancers, including sarcoma (such as osteosarcoma and soft-tissue sarcomas), leukaemia, brain cancers, cancer of the adrenal cortex and breast cancer. This syndrome is most often caused by inherited mutations in the gene for p53 (TP53, a tumour suppressor gene). People with Li-Fraumeni can also be affected by more than one cancer in their lifetime.

Genetic counselling & testing

People with a strong family history of cancer may want to find out about their genetic make-up. This may help the person or other family members in planning health care for the future. The best way to decide if your cancer or the cancer in your family is caused by an inherited mutation is to consult a genetic counsellor. A genetic counsellor can provide you and your family with information about genetic testing and your cancer risk. Genetic counselling and testing may be recommended for some people with a strong family history of cancer. Here are a few advantages of genetic testing:
* It helps understand the cancer risk to guide medical decisions about the best way to manage the risk.
* It provides information to help people who have been diagnosed with cancer make treatment decisions.
* It affects eligibility for some clinical trials and research studies.
* It helps your relatives understand and manage their risk for cancer.

(The author is sr consultant, Medical Oncology & Hemato-Oncology, HCG)