Objective. The primary purpose of this study was to examine the occurrence of cancer in Alaska Native (AN) children (under age 20). Although several studies have compared differences in cancer incidence between white and black children, few have examined cancer among Alaska Natives/American Indians. We know of no published article describing cancer incidence in AN children. We compared our findings with those of American Indian children of New Mexico and of Alaska white children. Data on mortality, survival, and prevalence are also included. Alaska Native is the term used collectively for the inhabitants whose ancestors occupied the area before European contact of what is now the state of Alaska. Alaska Natives include Eskimo, Indian, and Aleut groups. Although the 3 major groups differ in culture, language, and probably genetics, there are similarities in numerous social and economic indicators. The Northern Eskimo of Alaska (Inupiat) are related to Canadian and Greenland Inuit. Indians in Alaska include Athabaskan (in the interior of the state), who share commonalities with Canadian Athabaskan as well as with Navajo and Apache in the southwestern United States. Tlingit, Haida, and Tsimshian groups reside primarily in the southeast panhandle of the state. The panhandle Indian groups are similar to those of British Columbia.
Methods. Data on cancer incidence are from the Alaska Native Tumor Registry, 1969–1996. We studied children under age 20 to make our results comparable to national data as presented in the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) Pediatric Monograph. Population data for AN are based on census data and Indian Health Service intercensal estimates. Data for US whites and New Mexico Indians are from the National Cancer Institute’s SEER program. Calculations were made using SEERStat software. Data for Alaska whites are for the years 1996–2000. (The Alaska Cancer Registry has collected data for all Alaskans only since 1996). Odds ratios (ORs) of rates with 95% confidence intervals (CIs) were calculated.
Results. The rate among all AN children (both sexes) for all cancers combined is similar to that of US whites (OR: 1.0; 95% CI: 0.8–1.1). Examination of childhood cancer rates by ethnicity, however, reveal that rates are significantly lower for Indian (OR: 0.6; 95% CI: 0.4–0.8) but not significantly different for Eskimo or Aleut children. For most International Classification of Childhood Cancers groups, incidence rates for AN children are also similar to those of US whites. However, AN children are at significantly higher risk for hepatic tumors (OR: 13.1; 95% CI: 7.9–20.5), particularly hepatocellular carcinoma (OR: 43.8; 95% CI:24.4–75.1) and retinoblastoma (OR: 2.8; 95% CI: 1.3–5.3). By ethnic group, rates for hepatocellular carcinoma are significantly high only for Eskimo. Rates for all AN children are lower for neuroblastoma (OR: 0.1; 95% CI: 0.1–0.6) and lymphoma (OR: 0.5; 95% CI: 0.3–0.9), particularly Hodgkin’s disease (OR: 0.2; 95% CI: 0.0–0.5). On the basis of 5 years of data, rates for Alaska white children do not seem to differ from those of US white children. Because of our findings of differences between AN and US whites, we reviewed data of other relevant populations, specifically American Indian data from the New Mexico SEER registry. Using SEER data and SEER software, we calculated rates for New Mexican American Indians (NMAI) and compared them with US white rates. Rates for all cancers combined among NMAI are significantly lower than for US white (OR: 0.8). However, similar to AN children, the rate among NMAI for retinoblastoma is higher compared with US whites (OR: 2.5; 95% CI:1.4–4.5). Similar to AN, NMAI also seem to be at low risk for neuroblastoma (OR: 0.2; 95% CI: 0.1–0.7), lymphoma as a group (OR: 0.1; 95% CI: 0.0–0.3), and, specifically, Hodgkin’s disease (OR: 0.1; 95% CI: 0.0–0.4). Rates among NMAI children are low for central nervous system tumors (OR: 0.5; 95% CI: 0.3–0.7). The average annual age-adjusted cancer mortality rate among AN children is lower but not significantly lower than that of US white children (28.6 vs 37.3 per million).
Conclusions. Comparison of AN rates for all cancers combined are similar to those of US and Alaska white children but seem higher than those of NMAI. Differences between AN and US whites exist for select International Classification of Childhood Cancers groups. The most striking rate differences are found in hepatic tumors, largely because of elevated rates of hepatitis B-associated hepatocellular carcinoma. All children in our study with hepatocellular carcinoma were hepatitis B antigen positive. A statewide hepatitis B virus immunization program was begun in late 1982. Although 16 children who were born before 1983 developed hepatocellular carcinoma, no children who were born in the 20 years since hepatitis B immunization was instituted among infants have received a diagnosis of hepatocellular carcinoma, a significant difference. Comparing AN and US white childhood cancer rates after removing hepatocellular carcinoma cases from both populations results in an OR of 0.8 (95% CI: 0.7–1.0). Thus, if no increase in other childhood cancers occurs in the coming generations, then rates for childhood cancer may soon be significantly lower than those in US white children. Rates are low for all lymphomas, largely because of very low rates of Hodgkin’s disease. Rates are also low for neuroblastoma. It is reassuring that rates for AN children are not in excess and do not seem to be increasing. There is concern among the population regarding environmental exposure, including ionizing radiation. Our data do not show excess childhood leukemia or thyroid cancers, malignancies for which radiation is known to increase risk.
Compared with cancers that occur in adults, childhood cancers are rare, comprising only 1.0% of all cancers in the United States. However, cancer is the number 1 cause of disease-related deaths in children.1,2 Childhood cancer comprises a variety of malignancies with incidence varying worldwide by age, sex, ethnicity, and geography.3 These variations in the incidence of cancer, particularly those among racial/ethnic groups and/or geography, have provided important insights into cancer etiology. Although several studies have compared differences in cancer incidence between white and black children, few have examined cancer among Alaska Natives/American Indians.1,4 We know of no published article describing cancer incidence in Alaskan Native (AN) children.
Alaska Native is the term used collectively for the inhabitants whose ancestors occupied the area before European contact of what is now the state of Alaska. AN include Eskimo, Indian, and Aleut groups. Although the 3 major groups differ in culture, language, and probably genetics, there are similarities in numerous social and economic indicators. The Eskimo of Alaska are composed of 2 main groups, the Inupiat and the Yup’ik. The Inupiat are related to Canadian and Greenland Inuit. Indians in Alaska include Athabaskan (in the interior of the state), and Tlingit, Haida, and Tsimshian groups, who reside primarily in the southeast panhandle of the state. Alaskan Athabaskan have commonalities with Canadian Athabaskan as well as with Navajo and Apache in the southwestern United States. The southeast panhandle Indians are similar to the Indians of British Columbia.5
Cancer incidence among AN of all ages was first reported in 19766 and has been reported subsequently in numerous publications.7–11 Cancer, once thought to be a rare disease among AN, has increased, and rates for all cancers combined now exceed those of US whites. In addition, there are many differences in site-specific cancer incidence rates among AN compared with US whites.10
This study examined cancer in AN children (under age 20), comparing incidence rates in AN children with those of US whites by sex, age group (0–4, 5–9, 10–14, and 15–19), and ethnicity (Indian, Aleut, and Eskimo). We also compared our data with that of New Mexican American Indians (NMAI) and with Alaska whites. Data on AN cancer survival, prevalence, and mortality are also included.
Incidence data in this report are for AN patients under age 20 in the Alaska Native Tumor Registry. This registry includes all AN patients statewide who received a diagnosis of invasive cancer while a resident of Alaska. Data for the years 1969–1996 were examined for this study. However, to confirm a finding of the study, the registry was searched at a later date to identify liver cancers diagnosed through 2002. Data collection methods have been previously described.6–11 Data were collected in accordance with the National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) program.12 To make our results most easily comparable to national data, our analysis was designed to mirror that used in the National Cancer Institute’s SEER Pediatric Monograph.1 Classification of ethnicity (Indian, Aleut, and Eskimo) is based on self-classification by the parents of the patient at the time of registration to the hospital/clinic. Classification of tumors followed the International Classification of Childhood Cancers (ICCC).13 The ICCC divides cancers into 12 major groups each with up to 6 subgroups. Data for US whites and NMAI aged 0 to 19 years from the SEER program for 1973–1996 were used for comparison. We also analyzed data for Alaska white children provided by the State of Alaska for the years 1996–2000 (the only years available). All incidence rates were adjusted to the 1970 US standard population under age 20. AN rates for all cancers and for each group and subgroup of cancer (classified by the ICCC) were calculated using 1969–1996 data.
Death data for AN were obtained from the State of Alaska Bureau of Vital Statistics and were available for 1979 to 1996. Deaths among US whites for the same time period were obtained from the National Center for Health Statistics.
Population estimates for AN were based on census data and Indian Health Service population estimates for 1970–1996. The ethnic composition of AN children in the 1990 census was 11% Aleut, 34% Indian, and 54% Eskimo and was similar for 1970 and 1980 censuses. Age distribution among the population of AN under 20 years of age has fluctuated somewhat during this period. Interpolations of population estimates for intercensal years were estimated using cubic splines.14 Odds ratios (ORs; and associated 95% confidence intervals[CIs]) for comparisons were calculated using exact methods. Poisson regression was used to model trends over time. Kaplan Meier curves and log-rank tests were used for examination and comparison of relative survival data. All analyses were performed using S-Plus 2000, StatExact 4.0.1, and Epi Info 2000 software.
From 1969 to 1996, a total of 131 cases of cancer were diagnosed among AN under age 20. One patient had 2 different cancers (central nervous system [CNS], germ cell) diagnosed 6 years apart. Of the 131, more were male (78) than female (53). Cancer in AN children was most frequently diagnosed within the first year of life. Children of ages 0 to 4 and 15 to 19 accounted for more cases than those ages 5 to 9 and 10 to 14. The distribution by ethnicity was 26 Indians, 24 Aleut, and 81 Eskimo.
Distribution of Cancers
Table 1 compares rank order of cancers by ICCC classification of AN to US whites. The 5 most frequently diagnosed cancers, in rank order among AN children, are leukemia, hepatic tumors, CNS tumors, lymphoma, and germ cell tumors. Together, these cancers compose >70% of all AN childhood cancers. Four of these cancer groups—leukemia, CNS, lymphoma, and germ cell tumors—are among the 5 most frequent in US white children. Rank order is similar, except in the US whites, carcinoma ranks fourth after lymphoma. Among AN, hepatic tumors rank second and compose 15% of childhood cancers, whereas among US whites, hepatic tumors rank 11th and account for only 1%. Although lymphoma ranked among the top 5 cancers in both AN and US white children, it ranked fourth in AN, composing 8%, and third in US white children (17%). The category carcinoma accounts for 10% of cancers among US white children (and ranks fourth) but accounts for only 5% of cancers among AN children (and ranks 10th). Neuroblastomas ranked lower (11th) among AN than US whites (eighth). Distribution of cancer by sex was remarkable for the higher ranking of hepatic tumors in both AN boys (second) and girls (fifth) and higher ranking of retinoblastoma and renal tumors in AN girls.
Rank order of AN childhood cancers was examined by ethnic group: Indian, Aleut, and Eskimo (data not shown). Leukemia ranked first in all ethnic groups. Distribution was similar between ethnic groups, with the exception of hepatic tumors. Hepatic tumors were the second most common cancer among Eskimo children but ranked fifth and seventh among Indians and Aleuts, respectively.
Within nearly all major ICCC groups, the distributions of cancers by subgroup seem to be similar for AN and US whites. An exception again is hepatic tumors. Among AN children, 16 (84%) of 19 cases of hepatic tumors were hepatocellular carcinoma, and only 3 were hepatoblastoma. Among US whites, hepatoblastoma occurs much more frequently in children than hepatocellular carcinoma. Only 56 (28%) of 199 cases of hepatic tumors among US whites were hepatocellular carcinoma.
There may also be differences in distribution in the ICCC group “carcinoma.” Among US white children, the majority of the carcinomas were thyroid (36%), malignant melanoma (35%), and “other and unspecified carcinomas” (25%). Of the 7 AN children who had a diagnosis of carcinoma, only 1 cancer was thyroid carcinoma and none was melanoma. The remaining 6 were “other and unspecified carcinomas” (colon, rectum, cervix, stomach, brain, and 1 unknown site).
The distribution of cancers by 5-year age group was reviewed. The age distributions of AN and US white children with cancer by ICCC group are similar, again with the exception of hepatic tumors. Among US white children, most hepatic tumors (primarily hepatoblastoma) occur under age 5, whereas among AN children, the highest percentage of hepatic tumors occurs in the 15 to 19 age group (hepatocellular carcinoma).
In the US, childhood cancer occurs most frequently in the first year of life. AN children are similar. Thirteen AN infants received a diagnosis of cancer, the largest number with cancer in any year of age in our study. These 13 include leukemia (5); retinoblastoma (3); and 1 infant each with neuroblastoma, lymphoma, soft tissue, renal, and CNS tumors. Rank order among infants with cancer in the US is generally neuroblastoma, CNS tumors, leukemia, retinoblastoma, and renal tumors.14
In US whites, cancers occur more often in male than female children. Among AN children in this study, there were also more cancers in boys (78) than in girls (53). The ratio of boys to girls seems to be higher in AN but is not significantly different.
Table 2 shows average annual age-adjusted incidence rates of childhood cancer and ORs for AN compared with US whites. Rates among AN children for all cancers combined are similar to those of US whites (OR: 1.0; 95% CI: 0.8–1.1). Rates by age and sex were also calculated (data not shown). ORs of AN to US whites for all cancers combined were 1.1 and 0.9 for boys and girls and did not differ significantly. Age-specific rates of all cancers combined among AN children display a pattern by age similar to that observed among US whites. Specifically, rates are high among young AN children (160 per million among age 0–4), decline somewhat in age groups 5 to 9 and 10 to 14 (116 and 119 per million, respectively), and then increase again in older children (188 per million in age group 15–19).
For most ICCC cancer groups, incidence rates for AN children are similar to those of US whites. However, AN children are at significantly higher risk for all hepatic tumors (OR: 13.1; 95% CI: 8.0–20.5) and especially for hepatocellular carcinoma (OR: 43.8; 95% CI: 24.4–75.1). AN risk of hepatocellular carcinoma is also significantly increased for each sex separately. The rate for hepatoblastoma for both sexes combined was not significantly high; however, on the basis of the 3 cases (all male), AN boys seem to be at higher risk for hepatoblastoma compared with US white boys (OR: 4.80; 95% CI: 1.20–13.45).
All children in our study with hepatocellular carcinoma were hepatitis B antigen positive. We therefore evaluated the impact of a statewide hepatitis B virus (HBV) immunization program begun in late 1982 on the occurrence of hepatic tumors among AN children. Although 16 children who were born before 1983 developed hepatocellular carcinoma, no children who were born in the 20 years since HBV immunization was instituted among infants have received a diagnosis of hepatocellular carcinoma. The difference in hepatocellular carcinoma rates between these 2 birth cohorts, 1950–1982 and 1983–2002, is significant at P < .05.
The only other category for which AN rates are increased is retinoblastoma (OR: 2.8; 95% CI: 1.3–5.3). Eight children received a diagnosis of retinoblastoma in this population, 6 female and 2 male. All but 1 was diagnosed under age 2, and 3 patients had synchronous bilateral disease. Review of medical records did not indicate that any of the children were related, although detailed family pedigrees have not been done. Tumor registry information does not include information on genetic testing, and many of the patients’ cancers were diagnosed before genetic testing became available.
Lower rates were found for AN children compared with US whites for lymphoma and for neuroblastoma. The rate for the lymphoma category is significantly low for both sexes combined (OR: 0.5; 95% CI: 0.3–0.9) and for girls separately. The low rate for this cancer is largely attributable to low rates for Hodgkin’s disease (OR: 0.2; 95% CI: 0.0–0.5). Only 2 patients with Hodgkin’s disease, both male, were identified in the 18-year period. The rate for non-Hodgkin’s lymphoma (NHL) also seems low but not significantly different from the US white rate.
Only 1 AN patient received a diagnosis of cancer in the sympathetic nervous system (SNS) category, specifically neuroblastoma. On the basis of this 1 case, the rate for neuroblastoma in AN seems to be significantly lower than in US whites (OR: 0.1; 95% CI: 0.1–0.6).
The rate of leukemia was similar in AN and US white children (OR: 1.0; 95% CI: 0.7–1.4), and distribution by subcategory also seemed to be similar. Of the 35 cases of leukemia diagnosed among AN children, 24 (66%) were acute lymphoblastic leukemia (ALL), 6 (17%) were acute myeloid leukemia (AML), 3 (9%) were chronic myeloid leukemia (CML), and 2 (6%) were unspecified. Data for AN leukemia were also similar to US whites in that boys have higher incidence and leukemia occurs most frequently in the 0- to 4-year age group.
We calculated overall age-adjusted childhood cancer rates for each of the 3 major ethnic groups among AN (data not shown). Compared with US whites, rates were significantly lower for Indians (OR: 0.6; 95% CI: 0.4–0.8) and not significantly different for Eskimo (OR: 1.1; 95% CI: 0.9–1.3) or Aleut (OR: 1.4; 95% CI: 0.9–2.1). Comparisons of AN rates with US whites by ethnic group for separate ICCC groups are difficult because of limited numbers of cases. Our data indicate that rates for hepatic cancer are significantly higher only among Eskimo (OR: 23.9; 95% CI: 13.9–38.8). Retinoblastoma may be higher in all 3 ethnic groups, but none was significantly higher.
Rates for AN for all lymphomas are significantly low relative to US whites. Numbers of cases (11) were too small for analysis by ethnic group. Patients from all 4 ethnic groups were among the 11 patients who had a diagnosis of lymphoma.
Cancer-specific mortality rates were calculated using death data for AN and all US whites, 1979–1996. Twenty-three AN children died from cancer during the period studied. The average annual age-adjusted cancer mortality rate among AN children was lower but not significantly lower than that of US white children (28.6 vs 37.3 per million). US white cancer mortality decreased in children during this period, but no similar trend was evident among AN cancer mortality rates.
Survival and Prevalence
For all childhood cancers, relative 5-year survival for AN is lower than for US whites (60% vs 70%; P < .05). The numbers of cases were too small to calculate survival by ICCC group or subgroup. Of all AN children who received a diagnosis of cancer from 1969 through 1996, 58 had died by January 1, 1997, 43 (74%) from cancer, 7 from other causes, and 8 from unknown causes. The 72 survivors originally had a diagnosis of leukemia (14); germ cell (10) and hepatic tumors (10); retinoblastoma (8); renal (7) and CNS (6) tumors; lymphoma (6), soft tissue (5), bone (3), and SNS (1) tumors; and carcinoma (2). All children who had a diagnosis of retinoblastoma, germ cell tumors, and neuroblastoma and all but 1 of 8 who had a diagnosis of renal tumor were known to be alive on January 1, 1997.
Because of our findings of differences between AN and US whites, we reviewed data of other relevant populations, specifically, American Indian data from the New Mexico SEER registry. Using SEER data and SEER software, we calculated rates for NMAI and compared them with US whites (Table 3). Rates for all cancers combined among NMAI were significantly lower than for US white (OR: 0.8). Rates are similar between NMAI and US white children for most ICCC groups, with a few exceptions. Similar to AN children, the rate among NMAI for retinoblastoma was higher compared with US whites (OR: 2.5; 95% CI: 1.4–4.5). The rate for osteosarcoma among NMAI seems to be higher (OR: 1.8; 95% CI: 1.0–3.4), although the rate for bone tumors as a group was not significantly higher. Similar to AN, NMAI also seem to be at low risk for neuroblastoma (OR: 0.2; 95% CI: 0.1–0.7), lymphoma as a group (OR: 0.1; 95% CI: 0.0–0.3), and, specifically, Hodgkin’s disease (OR: 0.1; 95% CI: 0.0–0.4). In addition, rates among NMAI children are low for CNS tumors (OR: 0.5; 95% CI: 0.3–0.7).
We also examined statewide incidence data for Alaska whites. Data for this population have been collected only since 1996. However, the Alaska white population is nearly 5 times that of Natives in Alaska. During the period 1996–2000 (data not shown), 92 resident white children of Alaska under age 20 at diagnosis were identified. We found no evidence that Alaska whites were at increased risk for hepatic tumors or retinoblastoma or that particularly low rates occur for the lymphomas, Hodgkin’s disease in particular, or neuroblastoma among Alaska whites. Alaska white childhood cancer rates seem to be similar to those of US whites.
Cancer incidence patterns for AN of all ages have been well described.7–11 These reports indicate that the rate of all cancers combined among AN of all ages and both sexes currently exceed the rates for US whites. Compared with US whites, rates are similar for AN men but 18% higher among AN women.11 In addition, many site-specific rates differ. For many sites, rates in AN exceed those of US whites, whereas other cancer sites occur less frequently.
This is the first study to focus on cancer in AN children (under age 20). The incidence rate for all cancers and both sexes of AN under age 20 is similar to that of US whites.
Mortality rates from all cancers for all ages were much higher (30%) in AN compared with US whites during the 1990s.15 Data on cancer deaths for children for 1979–1996 result in a cancer mortality rate for AN children that is lower (28.6 per million), although not significantly lower, than the rate for US white children (37.3 per million).
Comparison of rates of AN childhood cancers by ICCC groups and subgroups with US whites shows more similarities than differences, with some marked exceptions. In comparison with US whites, AN children have excess hepatic tumors (OR: 13.1) and retinoblastoma (OR: 2.8). Conversely, AN have significantly lower rates of SNS tumors (OR: 0.1) and lymphoma (OR: 0.5).
The most striking differences between AN and US white childhood cancers are found in the hepatic tumor category, specifically hepatocellular carcinoma (OR: 43.8). Most childhood hepatic cancer in the US is hepatoblastoma, but among AN children, the incidence of hepatocellular carcinoma is much higher than that of hepatoblastoma. Although the number of male children with hepatocellular carcinoma was nearly 3 times greater than for female, the rate of hepatocellular carcinoma is significantly increased over US whites for both AN boys and girls.
Chronic infection with HBV has been implicated as the leading cause of hepatocellular carcinoma in this population.16 All children in our study with hepatocellular carcinoma were hepatitis B antigen positive. A hepatitis B program was instituted in Alaska in the early 1980s, including universal immunization of AN infants at birth and immunization of all serosusceptible AN. More than 90% of the AN population was tested for HBV in the mid-1980s and immunized as needed.17 The region of Alaska with the highest infection rate of HBV experienced an immediate decrease in annual incidence of acute asymptomatic HBV infection from 215 to 14 per 100 000 after the immunization campaign. A screening program for hepatocellular carcinoma using α-fetoprotein has resulted in improvement in survival rates for patients with hepatocellular carcinoma.18
For this study, we evaluated the impact of the program on the occurrence of hepatic tumors among AN children. The statewide HBV immunization program began in late 1982. Although 16 children who were born before 1983 developed hepatocellular carcinoma, no children who were born in the 20 years since HBV immunization was instituted among infants have received a diagnosis hepatocellular carcinoma. In contrast, hepatoblastoma has occurred since 1983. There is no known association between hepatoblastoma and hepatitis B, so a protective effect would not be expected.
Because hepatocellular carcinoma occurs in such excess among AN children and is the second leading cancer, we calculated a rate for all cancers in AN children excluding hepatocellular carcinoma. Comparing AN and US white childhood cancer rates after removing hepatocellular carcinoma cases from both populations resulted in an OR of 0.8 (95% CI: 0.7–1.0). Thus, if no increase in other childhood cancers occurs in the coming generations, then rates for childhood cancer may soon be significantly lower than those in US white children.
The only other cancer for which AN children seemed to be at increased risk was for retinoblastoma. Retinoblastoma has not been found to have any race or sex predilection.19 A retinoblastoma gene was identified and reported in 1986 and is transmitted in a dominant manner. The gene Rb1 functions as a tumor suppressor. Hereditary cases are thought to compose 40% of cases in the United States. Hereditary cases tend to occur in younger (mean age: 1) than sporadic cases (mean age: 2) and are more often bilateral. Although a review of records did not indicate that any of the children in this study were related, the occurrence of bilateral disease and diagnosis at young age suggests that heredity may play a role in some of these patients.
Lymphoma occurs in AN children at half the rate of that in US white children (OR: 0.5). Among both AN and US white children, the incidence is lower among girls than boys. The lymphoma category is composed of Hodgkin’s disease and NHL. The low overall OR of lymphoma among AN children is primarily attributable to the very low occurrence of Hodgkin’s disease (OR: 0.2). Only 2 cases (both male) of Hodgkin’s disease occurred among AN children, classified as nodular sclerosis and lymphocyte depletion.
Although Hodgkin’s disease was described >200 years ago, the cause of the disease and the origin of the malignant cell remain unknown. The epidemiology and pathology of the disease have strongly implicated an infectious cause, especially viral. A variety of infectious agents have been suggested to play a role in Hodgkin’s disease; the case for Epstein-Barr virus (EBV) seems to be strongest.20 Risk varies worldwide, and occurrence of disease is greater among people with higher socioeconomic status. The role of infectious agent(s) may be associated with the finding of higher rates among those of higher socioeconomic status. Genetic predisposition is implicated because positive family history of Hodgkin’s disease increases risk. Seroprevalence surveys of AN in the 1980s found that AN children were all EBV antibody positive by age 4 (AP Lanier, unpublished observations). If EBV is confirmed to play a role in the development of Hodgkin’s disease or other lymphomas, then the fact that AN children are known to be infected early in life (and infectious mononucleosis occurs rarely) may be relevant.
NHL generally comprises approximately 60% of lymphoma in children and adolescents.21 In our study, NHL was diagnosed in 9 of 11 lymphoma patients. Rates of NHL are higher in whites than in blacks in the United States. The frequency and relative proportion of NHL subtypes differ worldwide. In parts of Africa, Burkitt’s lymphoma accounts for a large percentage of lymphomas in childhood. In our study, only 1 patient was classified as having Burkitt’s lymphoma. The relatively low rates of lymphoma in AN children parallels our findings in previous studies of AN of all ages.7–11,22 Compared with US whites, rates for AN of all ages are low for all lymphomas combined, especially for Hodgkin’s disease (OR: 0.58 and 0.16, respectively). Comparison of age-specific rates for AN with US whites for the period 1973–1996 shows lower rates for all AN age groups for lymphoma and Hodgkin’s disease.
The findings of our study were also remarkable in the relative absence of SNS tumors in AN children (OR: 0.1). In US whites, these tumors are the most common malignancies in infants and compose 5% of all childhood cancers. SNS tumors are predominantly neuroblastomas.23 Only 1 AN child had a diagnosis of SNS tumor, specifically, neuroblastoma. In the United States, this tumor occurs at similar rates in whites and blacks. The cause is unknown. However, it has been noted that microscopic neuroblastoma nodules are observed in most fetuses and in infants under age 3 who die of causes other than cancer.23 It has been hypothesized that these lesions may be neuroblastoma precursors and may spontaneously regress. If this hypothesis is valid, then the finding of infrequent occurrence of this neoplasm in this population would suggest an absence of a factor(s) that promotes neuroblastoma or the presence of a factor(s) that enhances regression.
Because AN are heterogeneous, including multiple ethnic, linguistic, and cultural groups, we reviewed the occurrence of childhood cancer by the 3 major ethnic groups: Eskimo, Indian, and Aleut. The rate for Alaska Indian children was lower than US white rates for cancer overall and for most of the common childhood tumors. The low rate among Alaska Indians agrees with the only previous report on childhood cancer in American Indian/AN. Among NMAI children under age 15 for the years 1970–1982, NMAI rates per million were significantly lower (75.5 for boys and 78.0 for girls) than non-Hispanic whites in the state.4 On the basis of SEER data 1990–1995, NMAI had the lowest childhood cancer rate (79.6 per million) of 4 ethnic groups analyzed; blacks had 124.6, Asian Pacific Islanders had 136.8, and whites had 161.7 per million.1
We compared NMAI childhood cancer incidence data with that of US whites for 1973–1996. As would be expected from the studies cited above, we found the rate for all cancers combined among NMAI to be significantly lower than the US white rate (OR: 0.7). Leukemia, especially ALL, was the leading cancer in children of all groups—AN, NMAI, and US whites—and rates were similar. NMAI do not experience an excess of hepatic tumors. In fact, no NMAI children received a diagnosis of hepatocellular carcinoma; all were hepatoblastoma. Of interest is that elimination of hepatic tumors from calculations of rates for AN children results in rates similar to NMAI. Similar to AN children, the rate among NMAI for retinoblastoma was also higher than US white rates. The rate for osteosarcoma among NMAI seems to be higher than US whites, although the rate for bone tumors as a group was not significantly higher. Among all 3 populations, osteosarcomas are the most frequently diagnosed bone tumors. Because the overall rates for childhood cancer in NMAI are low, it is not surprising that rates are low for various ICCC groups. Similar to AN, NMAI also seem to be at low risk for neuroblastoma, lymphoma as a group, and Hodgkin’s disease. In addition, rates are low among NMAI children for CNS tumors.
Our report indicates that rates of all childhood cancers combined among AN are similar to US whites, although rates differ for select ICCC groups. Age-adjusted rates for AN for all ages have increased 38% during the past 30 years and now exceed those of US whites. It is reassuring that rates for AN children are not in excess and do not seem to be increasing. There is concern among the population regarding environmental exposure, including ionizing radiation. Our data do not show excess childhood leukemia or thyroid cancers, malignancies for which radiation is known to increase risk. Our data suggest that the HBV immunization program has already resulted in a decrease in hepatic cancers in children. Hepatic tumors rank second and compose 15% of AN childhood cancers in our study. In the future, elimination of most hepatic tumors should result in even lower rates of childhood cancer than we report in this study. The reasons for very low rates of Hodgkin’s disease and neuroblastoma are not known.
Partial funding for the Alaska Native Tumor Registry is provided through an Interagency Agreement (9 UBI 94 00003-04) with the National Cancer Institute.
We thank Bonnie Smith, RN, CTR; Terrie McEvoy, RN, MS, CTR; and Jeannine Maxwell, CTR, at the Alaska Native Medical Center. We also thank tumor registrars, health information systems personnel, and many others throughout the state who helped ensure the completeness and accuracy of data in the Alaska Native Tumor Registry. Finally, we thank the staff of the New Mexico Tumor Registry, University of New Mexico (Albuquerque, NM); the Cancer Surveillance System, Fred Hutchinson Cancer Research Center (Seattle, WA); Lynn Ries, Brenda Edwards, Judith Swan, Barry Miller, and others at the National Cancer Institute (Bethesda, MD); and Jeanne Roche and the staff of the Alaska Cancer Registry, Epidemiology Section (Anchorage, AK).
- ↵Ries LAG, Smith MA, Gurney JG, et al, eds. Cancer Incidence and Survival Among Children and Adolescents: United States SEER Program 1975–1995. Bethesda, MD: National Cancer Institute, SEER Program; 1999 (NIH Pub. No. 99-4649)
- ↵Muir CS, Nectoux J. International patterns of cancer. In: Schottenfeld D, Fraumeni JF Jr. eds. Cancer Epidemiology and Prevention. 2nd ed. New York, NY: Oxford University Press; 1996: 141–167
- ↵Fitzhugh WW, Crowell A, eds. Crossroads of Continents: Cultures of Siberia and Alaska. Washington, DC: Smithsonian Institution Press; 1988
- ↵Lanier AP, Blot WJ, Bender TR, Fraumeni JF Jr. Cancer in Alaskan Indians, Eskimos and Aleuts. J Natl Cancer Inst.1980;65 :157– 1159
- Lanier AP. Cancer incidence in Alaska Natives: comparison of two time periods, 1989–1993 vs 1969–1973. Cancer.1998;83(suppl) :1815– 1818
- ↵Lanier AP, Maxwell J, McEvoy T, Day GE, Sandidge J. Alaska Native cancer update—1988–2000. Anchorage, AK: Alaska Native Tribal Health Consortium, Office of Alaska Native Health Research;2002
- ↵Ries LAG, Eisner MP, Kosary CL, et al. SEER Cancer Statistics Review 1973–1995;1996. National Cancer Institute. Available at: http://seer.cancer.gov/csr/1973_1995/Index.html
- ↵Kramarova E, Stiller CA. International Classification of Childhood Cancer; Lyon, France: World Health Organization; 1996
- ↵Venables W, Ripley B. Modern Applied Statistics System S-Plus. 2nd ed. New York, NY: Springer Verlag;1997:323– 331
- Copyright © 2003 by the American Academy of Pediatrics