For those types of cancers where it is more common to get the cancer as you get older, sometimes referred to as ‘adult’ cancers, being diagnosed at a younger age means the cancer may be more aggressive. This is not the case for cancers more common in younger people, such as testicular cancer where the most common age group is 20 to 39. It is also not the case for many childhood cancers, which actually may be more easily treated than their adult counterparts, as is the case for example, with many childhood leukaemias. It takes several changes in the genes of a cell to trigger a cancer. Some genetic changes you are born with, while others are from the environment. Often the process takes many decades. However, if an adult cancer appears in younger people it can behave more aggressively. That does not mean, however that it will not respond to treatment.