Increase in Childhood Cancer, but Survival Rates High

Kristin Jenkins

April 12, 2017

The incidence of childhood cancers has increased in recent decades, but the survival rates for childhood leukemia are very high, particularly in developed countries.

These are main findings from two in-depth studies published this week in the Lancet.

Of the many statistics reported, the one that is likely to get the most attention is the reported 13% increase in overall incidence rates of childhood cancers, says Prof Philippe Autier of the University of Strathclyde Institute of Global Public Health at the International Prevention Research Institute in Lyon, France, in a linked commentary.

The slow but steady rise in the incidence of many childhood cancers is real. Dr Philippe Autier

Although the authors do not give many possible explanations for this increase, Dr Autier agrees that "the slow but steady rise in the incidence of many childhood cancers is real, especially for acute leukemia in some areas." He also finds it interesting that the worldwide increase has occurred in all regions of the world except sub-Saharan Africa.

There is still a lot we don't know about the causes of childhood cancer, Dr Autier pointed out. Until we do, he added, we should not try to compensate "with explanations that are not based on evidence."

Increase in Incidence

The increase in the worldiwde incidence of childhood cancers comes from a study published online April 11 in the Lancet Oncology.

"This study updates information on cancer incidence in children published almost 20 years ago and adds the first global overview of cancer incidence in young people aged 15-19 years," write the authors, headed by Eva Steliarova-Foucher, PhD, from the Division of Cancer Control and Population Sciences, at the National Cancer Institute in Bethesda, Maryland.

The study was coordinated by the International Agency for Research on Cancer (IARC), and the findings were highlighted by the agency in a press release.

The study shows that during the period 2001-2010, childhood cancer was 13% more common than in the 1980s, reaching an annual incidence rate of 140 per million children aged 0 to 14 years worldwide, the IACR notes. Part of this increase may be due to better or earlier detection of these cancers, it adds.

The research team collected data from 153 population-based cancer registries in 62 countries on all malignancies and nonmalignant neoplasms of the central nervous system (CNS) diagnosed before age 20 years. The IACR notes that these data cover approximately 10% of the world's population of children. They are based on child population coverage of almost 100% in North America and Western Europe but of 5% or less in Africa and Asia.

The team collected data globally on almost 300,000 cancer cases in children younger than 15 years who were diagnosed in 2001-2010, notes the IACR.

Among children younger than 15 years, leukemia was the most common cancer, constituting almost a third of childhood cancer cases. Tumors of the CNS ranked second (20% of cases), and lymphomas accounted for 12% of cases. In children younger than 5 years, a third of the cases were embryonal tumors, such as neuroblastoma, retinoblastoma, nephroblastoma, or hepatoblastoma.

This study reports for the first time on cancer occurrence in adolescents (aged 15 to 19 years), the IACR notes. The annual incidence rate was 185 per million adolescents, as determined on the basis of records of about 100,000 cancer cases. The most common cancers were lymphomas (23%), followed by the cases classified as carcinomas and melanoma (21%).

"Cancer is a significant cause of death in children and adolescents, in spite of its relatively rare occurrence before the age of 20 years," IARC director Christopher Wild, PhD, said in a statement. "This extensive new set of information on the pattern and incidence of cancer in young people is vital to raise awareness and to better understand and combat this neglected area of health early in life."

The IACR also noted that cancers in children are more likely to be triggered by genetic predisposition in comparison with cancers in adults. In addition, the agency noted that "this study suggests that the incidence of childhood cancers may be influenced by doctors' changing awareness about childhood cancer or by effects of external factors, such as infection or some environmental pollutants."

Survival Rates for Leukemia High, but Not Everywhere

The second report, published online April 11 in the Lancet Haematology, documents survival rates for children diagnosed with leukemia.

A team led by Audrey Bonaventure, MD, of the Cancer Survival Group at the London School of Hygiene and Tropical Medicine, reports data from CONCORD-2, a population-based study of almost 90,000 children from 198 cancer registries in 53 countries.

The results show substantial improvements in survival from childhood acute myeloid leukemia (AML) in most countries during the period 1995-2009.

The probability of surviving at least 5 years after diagnosis (5-year net survival) for children with acute myeloid leukemia (AML) was as high as 90% in countries such as Germany and Austria. It was 80% for children with acute myeloid leukemia (AML), they report.

However, in other countries, survival remained below 60% for both types of leukemia. "There is room for improvement in the management of childhood leukaemia in many countries," the authros note.

Between 1995-1999 and 2005-2009, 5-year net survival for childhood ALL increased from 79% to 89% in the United Kingdom and from 83% to 88% in the United States. For AML, 5-year survival increased from 59% to 68% in the United Kingdom and from 52% to 63% in the United States.

Survival in China increased substantially, from 11% to 69% for ALL survival and from 4% to 41% for AML survival.

The study also showed that 5-year net survival was consistently lower for children with ALL than for those with AML. However, after 2000, that difference was smaller in most countries, the researchers say.

Children aged 1 to 9 years who were diagnosed with either ALL or AML had higher 5-year net survival than older or younger children, the study showed. By 2009, survival for children aged 10 to 14 years had also improved, although infants younger than 1 year still had the lowest 5-year net survival following a diagnosis of either ALL or AML.

"The results suggest that good access to health care and appropriate treatment have a clear population effect on survival for children with leukaemia," the authors write.

Initiatives to improve outcomes in childhood malignancy, such as enrollment in clinical trials, international collaboration, and the development of treatment guidelines, need to be more widely implemented, with more resources to improve treatment delivery in poorer countries, they add.

Since the 1980s, the global age-standardized incidence rates (WSRs) of registered cancers in children aged 0 to 14 years of age has increased from 124.0 to 140.6 per million person-years, the researchers report. The most common cancers in this age group included leukemia (WSR, 46.4), followed by CNS tumors (WSR, 28.2) and lymphomas (WSR, 15.2).

In children aged 15 to 19 years, the age-specific incidence rate (ASR) was 185.3 per million person-years. Lymphomas were the most common cancer type (ASR, 41.8), followed by epithelial tumors and melanoma (ASR, 39.5).

The authors also acknowledge the "shortage of high-quality local information," suggesting that this "should stimulate formation of new and more accurate data sources." To acquire high-quality data that is internationally comparable, better cancer registration needs to be supported at all levels, they say. In his linked commentary, Dr Autier writes that the improvements in cancer survival achieved by high-income countries reporting 5-year net survival of 80% "should not distract from the dire reality that about 80% of leukemia cases in children occur in low-income and middle-income countries (LMICs).

"From a worldwide perspective, it is the adoption by LMICs of affordable, locally adapted, multidisciplinary management programmes that is likely to translate into the largest gains in survival for children with hematological cancer," he adds.

In addition, cancer registries intended to improve survival need to record the probable cause of death — or at least the health causes associated with death, he suggests. "Knowing the causes of death might inform about whether children died from the cancer itself, or from a consequence of their management, or from another cause. This knowledge might help reveal associations between health problems, treatments, socioeconomic status, and other factors."

The worldwide incidence of childhood cancer study was supported by the International Agency for Research on Cancer and the Union for International Cancer Control. The childhood leukemias survival study was funded by Canadian Partnership Against Cancer, Cancer Focus Northern Ireland, Cancer Institute New South Wales, Cancer Research UK, US Centers for Disease Control and Prevention, Swiss Re, Swiss Cancer Research Foundation, Swiss Cancer League and the University of Kentucky. The worldwide incidence of childhood cancer study was supported by the International Agency for Research on Cancer and the Union for International Cancer Control. Dr Bonaventure and colleagues, Dr Steliarova-Foucher and colleagues, and Dr Autier have disclosed no relevant financial relationships.

Lancet Oncol. published online April 11, 2017. Full text

Lancet Haematol. Published online April 11, 2017. Full text

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