Leukemia is the most common form of childhood cancer. In the United States, leukemia affects around 3,500 children aged 0-14 each year which represents around 40% of all childhood cancers. In young adults, leukemia rates are somewhat lower but the disease is still one of the 5 most common forms of cancer in the 15-39 age group.
Childhood leukemia rates in the USA have been increasing steadily by around 1% a year for the past half century. The reasons for this increase have not been established although some research has suggested increased exposure to electro-magnetic fields may explain at least part of the rise. Despite the rise in leukemia rates, deaths from the disease have actually fallen by more than 50% since 1975 due to newer chemotherapeutic agents delivering much higher cure rates.
Although leukemia is the most common cause of death by disease in childhood, the chances of a child dying from leukemia are still very low – only about 1 in 10,000.
Leukemia rates peak between the ages of 2 and 5 at around 9 cases per 100,000 per year and fall to a low of around 3 per 100,000 for young adults. To put these rates in perspective: the chances of a teenager being seriously injured or dying in a motor vehicle accident in the United States are around 50 per 100,000 per year – more than 10 times the rate of leukemia in that age group.
There are four major types of leukemia: chronic myeloid (or myelogenous) leukemia (CML), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and acute lymphocytic leukemia (ALL). Although CLL is the most common form of leukemia overall, it is exceedingly rare in individuals aged under 40. ALL is the most common form of leukemia in children, accounting for more than 80% of total cases. Around half of all leukemia cases that occur in young adults are AML, a quarter are CML and the remaining quarter are ALL.
Leukemia survival rates have increased dramatically in recent years, particularly in younger patients. In the under 20 and 20-49 age groups, leukemia survival rates have more than doubled since 1975. In older age groups, survival improvements have been more modest.
The graph to the right shows 5-year survival rates for the under 45 age group across the four sub-types of leukemia. With the exception of AML, survival rates are very high.
Chronic myeloid leukemia has an excellent prognosis in young patients however this hasn’t always been the case. By far the most significant recent advance in leukemia treatment has been the development of Bcr-Abl tyrosine-kinase inhibitors such as imatinib and nilotinib. These drugs have transformed chronic myeloid leukemia from a virtual death sentence to a manageable chronic disease. These treatments work extremely well in younger patients and when CML is still in its chronic (1st) phase. Studies have found 5-year relative survival rates in excess of 95% for chronic phase CML patients who are treated with imatinib. As a result, 5-year survival rates have more than doubled from around 40% to over 80% in less than 20 years.
Acute myeloid leukemia has the lowest survival rate of the leukemia sub-types with 54% of under 45 year olds diagnosed with the disease still alive after 5 years. AML is a very aggressive disease that frequently recurs. Although more than three quarters of young adults achieve complete remission following AML treatment, almost half of these patients will relapse, typically within 2 years of initial treatment. The prognosis for relapsed AML is very poor. The good news is that for younger patients who manage to survive 2 years following AML diagnosis relapse becomes unlikely and most of these patients go on to live normal healthy lives.
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