Childhood deaths from cancer have decreased by nearly 40% in the past 15 years in Australia, our latest figures show. While overall cancer rates have increased during the past 30 years, mortality rates have dropped, both overall and for particular types of childhood cancer.

According to unpublished data from the Australian Paediatric Cancer Registry, childhood cancer death rates decreased by about 3% per year between 1998 and 2013. There have been significant improvements in survival for childhood leukaemias, lymphomas, neuroblastoma and malignant bone tumours.

Today, tumours of the central nervous system (mainly brain tumours) account for 40% of all childhood cancer deaths, the single largest cause of cancer deaths for children in Australia. These are followed by leukaemias (23%) and neuroblastoma (12%), which is the most common solid tumour in childhood, usually found in the abdomen.

Death rates from leukaemia – the most common form of childhood cancer – have dropped from 16.6 deaths per million children in 1998 to 4.4 in 2013. This equates to an overall decrease of 68% over that period.

Five-year survival for all childhood cancers increased from 77% for the period 1994-2003 to 84% for 2004-2013. We know 98% of children who survive the first five years after diagnosis will survive a further five years.

However, there was little or no survival change for several types of childhood cancers over recent years. These included brain, kidney and liver cancers.

Childhood cancer in Australia

Australia has the lowest childhood cancer death rate of all G20 countries. And Australia’s five-year survival rates for childhood cancer are among the best in the world.

The key reason for the downward trends of death rates is improved treatment, particularly the introduction of more effective chemotherapy protocols and adjunct therapies such as radiotherapy. Cancer research, especially clinical trials, has contributed to improved treatments and better survival rates.

However, our figures also show Australia has one of the highest childhood cancer rates in the world. Incidence of childhood cancer increased significantly from 1983 until the mid-1990s, but has remained fairly constant since.

Cancer is the second leading cause of death in Australian children, behind injury and poisoning. Around 710 children aged under 15 are diagnosed with cancer each year and about 100 die from the disease.

The causes of most childhood cancers and factors driving changes in incidence over time are largely unknown. Unlike cancer in adults, where behavioural factors such as smoking, alcohol consumption, diet and exercise play an important role, almost nothing is known about what may increase cancer risk in children.

A possible exception to this is melanoma. Our figures show a 38% decrease in the incidence of melanoma among children in Australia between 1993 and 2013. This is most likely the result of long-running public health campaigns such as Slip, Slop, Slap that promote improved sun protection, particularly among children.

Tough cancers in children

In the most recent period, almost all children (98%) diagnosed with the rare eye-cancer retinoblastoma survived for at least five years. Five-year survival rates also exceeded 90% for lymphomas (cancers of the lymphatic system), germ cell tumours (most of which are occur in the ovaries and testes) and the group of cancers that includes melanoma.

In contrast, five-year survival was more moderate (between 70% to 75%) for children with tumours of the liver, the central nervous system (mainly brain tumours) and neuroblastoma. Five-year survival for tumours of the central nervous system has only slightly improved from 71% in 1994-2003 to 74% in 2004-2013.

The incidence of liver cancer in children is increasing by 2.5% per year, compared to a stable trend of 0.2% per year increase in the rate for all childhood cancers combined.

The causes of liver cancer in children are largely unknown. Hepatoblastoma, a type of liver cancer that occurs in children aged under four, can occur in association with certain genetic syndromes such as familial adenomatous polyposis and Beckwith-Wiedemann syndrome, also known as overgrown syndrome. It has also occurred more frequently among infants delivered prematurely.

The risk of hepatic carcinoma, a type of liver cancer mainly affecting children aged over ten, appears to increase among those who have had other liver diseases such as cirrhosis, metabolic diseases or chronic hepatitis.

The reasons for the apparent increase in the incidence of liver cancer are unknown and an international study involving the Australia Paediatric Cancer Registry is being planned to examine issues around childhood liver cancer.

Children who survive cancer can suffer serious long-term consequences resulting from their treatment. These late effects are many and variedand depend on factors such as the type of cancer and the treatment the child received.

Some examples include learning and behavioural problems, vision and hearing deficiencies, stunted growth, heart disease, reduced lung capacity, dental issues, impaired sexual development and a higher risk of second cancers.

As well as improving survival, it’s important to find better therapies that do not impact on long-term health and quality of life.

This article originally appeared on The Conversation.