Five out of a hundred people with cancer have inherited a copy of a susceptibility gene. Those people were born with a varyingly increased risk of developing cancer.
Statistically, we all run the risk of developing cancer within the span of our lifetime. In people without an inherited predisposition gene it takes a considerable number of genetic mutations to cause the uncontrolled growth that is cancer. As the genetic changes are accumulated over time, the chances of cancer development increase with age.
When someone has a hereditary cancer the faulty gene is present in each cell of that person’s body, and that includes a woman’s embryo. As each of the carrier’s cells contains the cancer predisposition gene since birth, cancer will develop earlier than in a non-carrier’s body. For example, women with an inherited breast cancer gene have more chances of developing the disease in their late thirties or in their forties, that is, two to three decades earlier than women without the faulty gene.
The breast cancer faulty gene, however, belongs to the low-penentrance type of cancers, where the faulty predisposition gene causes cancer development in a relatively small percentage of carriers. Highly penetrant types of hereditary cancer may affect as many as 100% of the carriers.
Some couples having a hereditary type of cancer that may affect their child’s life at childhood or even at birth, consider preimplantation genetic diagnosis (PGD) with their in-vitro fertilization (IVF).
Dr Paraschos participated in the world's first PGD.