What causes childhood cancer?
Children’s cancers are very different to adult cancers. They occur in different parts of the body, and respond differently to treatment. The most common cancer in children is leukaemia, which accounts for a third of all cases of children’s cancer.

Cancer is not infectious and most are not inherited. It is unlikely that another child in a single family will also develop cancer although brothers and sisters of children with acute lymphoblastic leukaemia are at slightly increased risk of developing it themselves. This risk however is still extremely small. It is not thought to be caused by something a parent has, or has not done.

Generally, the causes of childhood cancer are unknown. It is possible that some cancers actually start inside the womb when the foetus is developing and rapid cell division is occurring, but it is not known why this should happen. 

Similarly, it is thought that some cancers can occur after exposure to a type of virus - such as the virus that causes glandular fever for example.  Again, the process surrounding why this should happen is unknown.  

Some types of cancer treatments, such as radiotherapy and chemotherapy do increase the risk of later developing another type of cancer such as bone cancer. This is a rare occurrence so the risk is small compared to the risk of leaving the original cancer untreated.

Certain genetic conditions such as downs syndrome can increase the risk of getting leukaemia, and retinoblastoma, a rare form of eye cancer is known to be inherited in 40% of cases.  Children with the inherited form of retinoblastoma are at a slightly higher risk of developing other tumours later in life.

Cancers such as bone tumours in teenagers and young people may be related to periods of fast growth when the cells are dividing rapidly, but the exact cause is not known.

Source: www.clicsargent.org.uk