Division of Pediatric Hem/Oncology, Coordinator for the Technical Committee of the National Council for the Prevention and Treatment of Childhood Cancer, National Institute of Pediatrics, Mexico City, Mexico
Division of Pediatric Hem/Oncology, National Institute of Pediatrics, Insurgentes Sur 3700-C, Mexico City, Mexico 04530
Prior to 2005, 51% of children in Mexico diagnosed with cancer received no standardized optimal multidisciplinary medical care. A government-subsidized national cancer treatment program was therefore created for these patients and a National Cooperative Childhood Cancer Treatment Group was consequently formed for these patients. Pediatric patients with a proven diagnosis of leukemia, lymphoma or solid tumor and who were registered in the Popular Medical Insurance (PMI) program from January 2007 to December 2010, are described in this report. These patients had been enrolled and registered in one of the 49 nationwide certified medical institutions in Mexico. The national incidence and frequency data for childhood cancers were analyzed for the whole program. At the end of a 4-year study, the analysis revealed that 8,936 children from across Mexico had been diagnosed with cancer. The incidence rate for the PMI patients was 150.3/million/year (2010) for children of 0–18 years. The highest age incidence rate was 51.9 between 0 and 4 years and boys were the predominant group for all types of cancer. The leukemia incidence was 75.3/million/year (2010), and an average frequency of 50.75% throughout the 4 years. The overall mortality rate was measured at 5.4/100,000/year (2010). This study demonstrates a high frequency and incidence of childhood cancer and a beneficial impact of the PMI program over the quality of life in these children.
Childhood cancer between the ages of 4–15 years represents the second leading cause of mortality in Mexico.1, 2 Publicly funded healthcare in Mexico provides full coverage for 49% of the population. This socialized medical program contains large hospitals and clinics nationwide and has been run by the Federal Government Socialized Program for >50 years. Until 2003, the Mexican health system was based on a segmented model. Formal sector workers and their families had been able to access pooled, prepayment options through public social security programs. The social security packages had full medical coverage. Only 5–7% of Mexicans have private medical health insurance.
The poorest Mexicans, who are mostly nonsalaried workers, rural residents and the unemployed, constitute 50% in the years 2006–2010 of the total population. Currently, all Mexicans who do not have access to social security are eligible for PMI. Federal funding, contributions from states, and a sliding scale prepayment by households (which is zero for all families living in poverty) finance PMI. All children in this economic demographic qualify for PMI, which offers full medical coverage for children with all types of cancer up to 18 years of age and enables these patients to be treated through previously accredited nationwide medical institutions by the Federal Government Health Department. This program was established in 2005.
The Mexican National Registry for Childhood Cancer started in 2006 and since 2007 the results reported are within the whole scope of the health systems.3
The aim of the current report is to publish the frequency of childhood cancer, the incidence, diagnosis and mortality for children with cancer in Mexico within the PMI program and report on the development of the first National Cooperative Treatment Program under the auspices of the PMI national agenda.
Patients and Methods
A retrospective analysis of all children with the diagnosis of cancer enrolled and treated at previously accredited institutions from January 2007 to December 2010 was performed. Age and gender were registered for this group. Bone marrow aspiration diagnoses in the case of leukemia and pathologic diagnoses of lymphoma and solid tumor were performed in each patient in accordance with the guideline of the International Classification of Childhood Cancers (ICCC-3).4
A central office at the PMI program with staff trained in data management administers the registration of these patients nationwide through an online process. The principal exclusion criterion was previous registration through other health insurance plans, either private or public. All of the children with cancer enrolled at the PMI underwent treatment protocols for the corresponding disease category.5 The national coordinator and associates for each protocol had originally developed the treatment regimens based on internationally recognized benchmarks.
This study comprises a descriptive analysis of the data collected from the 49 accredited institutions in Mexico. Although this program officially commenced in January 2005, it was not until January 2007 that the patient registration process was standardized. The program stipulated there be at least one certified pediatric hem/oncologist working every accredited institution. Mexico is strategically divided into six geographical zones, with at least five states in each. A coordinator was assigned to supervise the accredited hospitals in each region. This involved monitoring the criteria used for the initial evaluation in each patient to ensure compliance, managing direct local hospital-cancer care issues, and maintaining the surveillance of oncology medications and follow-up protocols.
The definition of childhood cancer frequency in this report is the percentage of this disease among Mexicans of 0–18 years at a given time. The incidence rate for children with cancer was defined as the total number of newly diagnosed cases per year/ the total population under 18 years by 1,000,000 population/year. Age-specific incidence was defined as the total number of cases of a specific age group/the total population registered in that age group by 1,000,000 population/year. The incidence rates were calculated for cancer/year and the overall mortality rate was determined by the number of patients/100,000/year. Patients registered in private or socialized public healthcare systems were not included. Descriptive statistical analysis was performed using GraphPad Instant version 3.0.
A total of 8,936 patients of <18 years of age were registered between January 2007 and December 2010 (Table 1) at the PMI. The most common disease was leukemia (50.8%). The second most frequent malignancy was lymphoma (10.1%) followed by central nervous system tumors (9.0%). The absolute number of patients with medulloblastoma and astrocytomas was identical. The miscellaneous reticular neoplasm's category included only the cases of Langerhans-cell histiocytosis.
Table 1. Frequency/incidence of PMI childhood and adolescent cancers 2007–2010
The number and percentage of patients by age group in 2010 revealed that between 0 and 4 years there were 830 (34.5%) patients, between 5 and 9 years 636 (26.4%) children, 10 and 14 years were 555 (23%) and 15 and 18 years revealed 382 (15.9%) cases. The highest age-specific incidence rate between 0 and 4 years was 51.9 in the year 2010 (Fig. 1). In terms of gender, males predominated (55%) in a ratio ranging from 1.3 to 3.1, depending upon the type of childhood malignancy. Males accounted for 54% of patients with acute leukemia, 54% with brain tumors and 64% of the lymphoma cases (both Hodgkin's and non-Hodgkin's subtypes).
The national childhood cancer incidence in 2010 in the PMI program was 150.3 /million (0–18)/year (2010) (Table 2). It was taken into account in this calculation that the population of Mexico increased from 106,900,000 in 2007 to 112,336,538 in 2010. In 2010 the census reported 31,972,300 Mexicans between 0 and 18 years (28.4%), however 15,986,150 is the population from 0 to 18 years registered at the PMI for medical-healthcare services.
Table 2. Incidence of childhood cancer in Mexico
The number of patients registered through the 4 years (Fig. 2) clearly indicates that the participation of the PMI accredited institutions and their respective regional coordinators had a beneficial effect in terms of treatment compliance in spite of the low number of pediatric oncologists registered in the program. Through these years the number of patients that abandon treatment has decreased significantly (Fig. 3). Since 2007 the percent of patients that abandon treatment has remained stable. The overall mortality rate was 5.4/100,000/year (2010).3
Table 3. Leukemias registered at the PMI headquarters from 2007 to 2010
The burden of childhood cancer is increasing worldwide, particularly in developing countries.6, 7 To address this problem in Mexico, several key initiatives have been established by the Federal Government, the development of the PMI applies a diagonal approach to health insurance. Horizontal, population based coverage is provided for all public and community health services. A package of essential health services is managed at the state-level for all those enrolled with the PMI.
The initiatives of this program involve supporting hospital accreditation and providing financial assistance to each institution for the treatment of children with cancer who qualify. These initiatives also include the endorsement of treatment protocols/guidelines, the supply of hospital equipment to pediatric oncology units and technical and financial support for pediatric oncology training programs. At present, only 87/135 (64%) pediatric hem/oncologists in Mexico are working in accredited hospitals under the PMI program. Rigorous evaluation processes have been underway since the PMI was established, and the results are encouraging for childhood cancer. Adherence to treatment prior to the PMI program was 48% and by 2011 is 95%.
There were 14,992 children treated for cancer among the 49 PMI accredited Mexican institutions during the 4-year period of analysis in this study, which included new patients plus 6,056 follow-up patients by the end of 2010. That being said, a pediatric oncologist in the PMI program treats an average of 172 patients per year. In institutions that have one pediatric oncologist only for an entire state, the burden of patient load increases significantly with the imperative to provide a continuously high standard of patient care. On the other hand, few institutions in Mexico have as many as eight pediatric oncologists on their full time staff. This patient load is obviously higher than recommended for developing countries.
Some studies have reported that the incidence of childhood cancer in low-income countries is lower than in industrialized countries.8 The incidence of childhood cancer in Mexico thus merits further epidemiologic explanation but it must be noted that this incidence is becoming more common in other developing countries.9–11 In our current study, we report the findings from a large number of patients from the Mexican PMI program which represents partial data (50%) from a national cancer registry and shows that the number of children with cancer registered at the PMI program is very significant and merits further analysis. The national childhood cancer incidence3 in Mexico in the year 2010 was of 145.5/million/year, which included those registered at the PMI plus those patients from socialized public healthcare systems which accounted to 4653 children. The previously published SEER data from the United States12 has indicated an incidence of childhood cancer (0–19 years) of 166/million person/year. In our current study, we have found a high incidence in Mexican children which indicates that a more vigorous national public health approach is needed into the future with the active participation of the federal government in trying to identify new children with cancer.
The high frequency of leukemia in our current patient cohort has also been observed in a recent study in the Mexico City area.13 This might be partially due to external factors as outlined by others.14–16
Recent studies17 have suggested that the incidence of acute leukemia among children living in poverty is much higher than in more affluent populations. This deficiency might be a related factor that can account for the higher incidence of acute lymphoblastic leukemia in comparison for those children treated by the socialized public healthcare systems in Mexico. The occurrence of acute leukemia in our series is due mainly to the predominance of acute lymphoblastic leukemia, leaving a relatively low frequency of acute myeloblastic leukemia. In developed countries, this later type of leukemia in children shows a rate of 15–25%.18
Mexico has shown progress in decreasing the mortality rate from childhood infections, newborn illness, malnutrition, pneumonia and gastroenteritis. This is due to improvements in public health measures imposed by the Federal Health Department. It is ironic that the improved survival rates in children may be a factor in the increased rates of childhood cancer. However, incidence and mortality rate are not necessarily correlated in Mexico, as has been outlined previously19 but the standard of medical care is constantly improving and the PMI program has had a very beneficial impact on the prognosis for low-income pediatric cancer patients.
In 2004, the Federal Health Department and a group of pediatric hematologists/oncologists produced technical protocols for treating the most commonly occurring childhood malignancies experienced in Mexico. It took us >1 year to formulate 26 treatment protocols based on international treatment guidelines, which included multidisciplinary treatment approaches for childhood cancers. An office located in Mexico City was assigned by the Department of Health-Health Services from the National Commission on Health Social Protection (PMI program) to register patients nationwide. Since the program's inception, all patients have been registered through an online process from the participating institutions. When the program commenced, acute leukemia was the primary disease group but by January 2007, all forms of childhood cancer were incorporated. One of the principal achievements of this program is the progressive decline in the number of children that discontinued treatment due to the financial burden.
There is little doubt that as Mexico becomes a more industrialized and developed country; there will be increased exposure of children to external factors such as infections,20 radiation, tobacco and chemical substances and thus a higher risk of cancer.21 Some earlier studies22, 23 have outlined that cancer is the third leading cause of pediatric death in developing countries. Notably however, the national statistics in Mexico indicate that cancer is the second leading cause of mortality2 among children aged between 4 and 15 years. The standardized mortality rate (per 100,000) among boys and girls in the period 2005–2006 was of 6.45 and 5.42, respectively10; however in 2010 the overall mortality rate was of 5.4. No question that it is a high rate compared to other Latin American countries10, 24–26 in spite of the PMI program. The years of life potentially lost in Mexican children (<18 years) with cancer that died had an average of 10.8 years and therefore impede living on an average of 59.2 years,3 while in developed countries the impact of life in childhood cancer is different and better.27
In summary the national childhood cancer registration in the PMI program denotes a high incidence among Mexican children. Mortality continues to denote the need for a further enhancement in the program. The current experience demonstrates that the creation of a cooperative treatment group in childhood cancer from a developing nation can be accomplished through the efforts of a multidisciplinary approach. The combination of horizontal coverage of personal health services with a catastrophic fund28 makes it possible to offer financial protection for childhood cancer, as well as investing in early detection and survivorship care. Our future goal is to continue improving the treatment and outcome of these children. We believe that children with cancer worldwide deserve a stronger focus on their needs than they are currently receiving, especially in resource-poor countries.