Evaluation of the Association Between Congenital Cytomegalovirus Infection and Pediatric Acute Lymphoblastic Leukemia.

Importance: Acute lymphoblastic leukemia (ALL) is the most common form of pediatric cancer, and a leading cause of death in children. Understanding the causes of pediatric ALL is necessary to enable early detection and prevention; congenital cytomegalovirus (cCMV) has recently been identified as a potential moderate-to-strong factor associated with risk for ALL. Objective: To compare the prevalence of cCMV infection between ALL cases and matched controls. Design, Setting, and Participants: In this population-based case-control study of ALL cases and matched controls, cases consisted of children aged 0 to 14 years between 1987 and 2014 with an ALL diagnosis identified through the Michigan Cancer Surveillance Program and born in Michigan on or after October 1, 1987. Cancer-free controls were identified by the Michigan BioTrust for Health and matched on age, sex, and mother's race and ethnicity. Data were analyzed from November to May 2022. Exposures: cCMV infection measured by quantitative polymerase chain reaction in newborn dried blood spots. Main Outcomes and Measures: ALL diagnosed in children aged 0 to 14 years. Results: A total of 1189 ALL cases and 4756 matched controls were included in the study. Bloodspots were collected from participants at birth, and 3425 (57.6%) participants were male. cCMV was detected in 6 ALL cases (0.5%) and 21 controls (0.4%). There was no difference in the odds of cCMV infection comparing ALL cases with controls (odds ratio, 1.30; 95% CI, 0.52-3.24). Immunophenotype was available for 536 cases (45.1%) and cytogenetic data for 127 (27%). When stratified by subtype characteristics, hyperdiploid ALL (74 cases) was associated with 6.26 times greater odds of cCMV infection compared with unmatched controls (95% CI, 1.44-27.19). Conclusions and Relevance: In this case-control study of cCMV and pediatric ALL, cCMV was associated with increased risk of hyperdiploid ALL. These findings encourage continued research.

Personal history of autoimmune disease and other medical conditions and risk of myelodysplastic syndromes.

BACKGROUND: Autoimmune diseases and hematopoietic malignancies are known to cluster within individuals, suggesting intertwined etiologies. A limited number of studies have evaluated pre-existing medical conditions as risk factors for myelodysplastic syndromes (MDS). We evaluated associations between autoimmune disease and other medical conditions and risk of MDS. METHODS: Cases were identified through the Minnesota Cancer Reporting System. Controls were identified through the Minnesota State driver's license/identification card list. History of autoimmune disease and other medical conditions was based on self-report; proxy interviews were not conducted. Unconditional logistic regression was used to calculate adjusted odds ratios (aORs) and 95% confidence intervals (CI). RESULTS: We included 395 cases and 694 controls. Cases were significantly more likely to report a diagnosis of any autoimmune disease when compared with controls (aOR=1.41, 95% CI: 1.05-1.89) after adjustment for age, sex, education, NSAID use, exposure to benzene and body mass index. When we evaluated specific autoimmune conditions, a statistically significant association was observed for hypothyroidism (aOR=2.16, 95% CI: 1.39-3.34) and odds ratios were elevated for inflammatory bowel disease (aOR=1.75) and systemic lupus erythematosus (SLE; aOR=3.65), although these associations did not reach statistical significance. Presence of an autoimmune condition did not impact overall survival (p = 0.91). CONCLUSION: Our results validate previous findings of an association between autoimmune disease and MDS. Further studies are required to determine whether this association is due to shared etiology, treatment for autoimmune diseases, or altered immune surveillance or bone marrow damage caused by the autoimmune condition.

Risk factors for de novo and therapy-related myelodysplastic syndromes (MDS).

PURPOSE: Myelodysplastic syndromes (MDS) are classified as de novo and therapy-related (tMDS). We evaluated associations between MDS risk factors separately for de novo and tMDS. METHODS: The study population included 346 de novo MDS cases, 37 tMDS cases and 682 population controls frequency matched by age and sex. Polytomous logistic regression was performed to calculate odds ratios (OR) and 95% confidence intervals (CI). RESULTS: After adjustment, former smoking status (OR = 1.45, 95% CI: 1.10-1.93), personal history of autoimmune disease (OR = 1.34, 95% CI: 0.99-1.82) and exposure to benzene (OR = 1.48, 95% CI: 1.00-2.19) were associated with de novo MDS. Risk estimates for the associations between smoking, autoimmune disease, and benzene exposure were similar in magnitude but non-significant in tMDS cases. Among individuals with a previous diagnosis of cancer, de novo MDS cases and controls were more likely to have had a previous solid tumor, while tMDS cases more commonly had a previous hematologic malignancy. CONCLUSIONS: We observed similar associations between smoking, history of autoimmune disease and benzene exposure in de novo and tMDS although estimates for tMDS were imprecise due to small sample sizes. Future analyses with larger sample sizes will be required to confirm whether environmental factors influence risk of tMDS.

Alcohol use is not a significant contributor to myelodysplastic syndromes.

PURPOSE: Myelodysplastic syndromes (MDS) are a class of clonal neoplastic disorders of largely unknown etiology, and published data remain inconclusive regarding the association between lifetime alcohol consumption and MDS risk. In these analyses, data from a population-based case-control study were used to investigate this association. METHODS: Eligible cases of MDS were identified through the Minnesota Cancer Reporting System; controls were matched by sex and age-decile. A central review process was used to confirm MDS diagnosis and classify subtypes. Unconditional and polytomous logistic regression were used to calculate odds ratios (OR) and 95% confidence intervals (CI). Kaplan-Meier curves were used to compare survival by category of lifetime alcohol consumption. RESULTS: In total, 398 cases of MDS and 698 controls were included. Alcohol consumption at 23-30, 31-49, and 50-65 years of age, recent consumption 1 year before diagnosis/interview, and lifetime consumption were not found to be significantly associated with MDS in males (OR range 0.63-0.99) or females (OR range 0.58-1.70). Analysis by MDS subtype further suggested there was not a significant association between recent alcohol consumption and odds of disease by subtype (OR range 0.39-1.13). Lifetime alcohol consumption was not significantly associated with survival after diagnosis of MDS CONCLUSIONS: Previously reported associations between alcohol consumption and MDS risk were inconsistent. Results from our analyses by sex and disease subtype do not support alcohol as a significant contributor to risk of MDS.

Field Application of Digital Technologies for Health Assessment in the 10,000 Families Study.

BACKGROUND: We field tested new-to-market portable, digital applications to assess hearing, pulmonary, and cognitive function to determine the feasibility of implementing these applications across a range of age groups in the pilot phase of the 10,000 Families Study (10KFS), a new Minnesota family-based prospective cohort study. METHODS: We followed manufacturer recommended protocols for audiometry (SHOEBOX Inc), spirometry (NuvoAir), and the digital clock drawing test (dCDT; Digital Cognition Technologies Inc). RESULTS: These digital devices were low cost and readily implemented in a 2.5-hour health fair visit with minimal training (2-3 hours) of study staff. To date, we have performed these measurements on 197 eligible 10KFS participants during an in-person clinic visit. A total of 37 children (age 4-17 years), 107 adults (18-64 years), and 53 seniors (≥65 years) were eligible to undergo hearing and pulmonary assessments. Children were less likely to successfully complete the hearing test (76%) compared with adults (86%) and seniors (89%). However, successful completion of the pulmonary assessment was high across all groups: 100% of children and seniors and 98% of adults. The dCDT was performed among those over the age of 40, and completion rates were 92% for those aged 41-64 and 94% for those ≥65 years. CONCLUSIONS: Our field testing indicates these digital applications are easy and cost-effective to implement in epidemiologic studies. IMPACT: Digital applications provide exciting opportunities to collect data in population studies. Issues related to data privacy, data access, and reproducibility of measurements need to be addressed before deploying digital applications in epidemiologic studies.See all articles in this CEBP Focus section, "Modernizing Population Science."

Factors predicting early mortality after new diagnosis of myelodysplastic syndrome: A population-based study.

OBJECTIVE: Little prospective data regarding factors determining patient outcomes in myelodysplastic syndromes (MDS) are available. To establish features of early mortality in MDS, we compare characteristics of patients dying within 1 year of diagnosis with those surviving longer. METHODS: We prospectively enrolled adults with a new MDS diagnosis in a population-based case-control study. Logistic regression was used to calculate odds ratios and 95% confidence intervals for potential predictors of early mortality. Subgroup analyses were conducted within the following groups: high-/very-high-risk IPSS-R; very-low-/low-/intermediate-risk IPSS-R; treated patients; and supportive care only patients. RESULTS: We observed early mortality in those with abnormal cytogenetics (OR: 3.36, 95% CI: 1.52-7.46), three or greater cytogenetic abnormalities (OR: 3.48, 95% CI: 1.51-7.99), treatment at a community medical center (versus academic) (OR: 2.55, 95% CI: 1.18-5.47), and with 2-3 concurrent medical comorbidities (OR: 2.14, 95% CI: 1.08-4.22). Similarly, in subgroup analyses, abnormal cytogenetics remained the main predictor of early mortality. CONCLUSION: Complex cytogenetics and prognostic risk category have been associated with early mortality without intervention. Our data confirm these associations in a large, prospectively followed cohort and highlight the significance of cytogenetic abnormalities and complexity regardless of IPSS-R risk categorization or treatment.

Cesarean Delivery and Risk of Infant Leukemia: A Report from the Children's Oncology Group.

Background: Studies have reported increased risks of pediatric acute lymphoblastic leukemia (ALL) among children born by cesarean delivery (CD). However, no previous study has examined the impact of CD on risk of infant leukemia specifically.Methods: In this study, 443 infants diagnosed with acute leukemia, including both ALL and acute myelogenous leukemia (AML), were identified at Children's Oncology Group institutions between January 1996 and December 2006; 324 controls frequency matched by year of birth were identified though random digit dialing and random selection from U.S. birth registries. Using interview data and, for a subset of participants, medical record data, we analyzed CD overall and by indications that likely resulted in pre-labor CD (PLCD) or emergency CD (ECD). Odds ratios (ORs) and 95% confidence intervals (CIs) for risk of ALL and AML were estimated using multivariable unconditional logistic regression models, adjusted for year of birth, birth weight, and maternal race.Results: We observed an increased point estimate for the association between CD and ALL (OR, 1.52 and 95% CI, 1.02-2.25). We did not observe an association between CD and AML (OR, 1.02 and 95% CI, 0.64-1.62). In analyses of indication for CD, we observed elevated effect estimates for the associations of both PLCD and ECD and infant ALL.Conclusions: Our analysis suggests an increased risk of infant ALL following CD, including both PLCD and ECD. Altered microbiota colonization may be involved in development of leukemia in infants, but clear biological mechanisms have yet to be determined.Impact: This study provides the first in-depth examination of CD and infant leukemia. Cancer Epidemiol Biomarkers Prev; 27(4); 473-8. ©2018 AACR.

Obesity over the life course and risk of acute myeloid leukemia and myelodysplastic syndromes.

BACKGROUND: Overweight and obesity are known risk factors for a number of cancers, with recent evidence suggesting that risk of hematologic cancer is also increased in obese individuals. We evaluated associations between body mass index (BMI) at differing time points during the life course in population-based case control studies of acute myeloid leukemia (AML) and myelodysplatic syndromes (MDS). METHODS: Cases were identified by the Minnesota Cancer Surveillance System. Controls were identified through the Minnesota State driver's license/identification card list. BMI was calculated using self-reported height and weight at ages 18, 35, and 50 years and two years prior to interview, and categorized as normal (18.5-25 kg/m(2)), overweight (25-29.9 kg/m(2)), obese class I (30-34.9 kg/m(2)), and obese class II/III (35+ kg/m(2)). All analyses were stratified by sex. Unconditional logistic regression was used to calculate odds ratios and 95% confidence intervals. RESULTS: We included 420 AML cases, 265 MDS cases and 1388 controls. Obesity two years prior to diagnosis was associated with AML in both males and females (OR=2.22, 95% CI 1.28, 3.85 and OR=1.85, 95% CI 1.08, 3.15 for BMI≥35 vs. BMI 18.5-24.9, respectively). In contrast, associations between obesity and MDS were observed only in females. Weight change in adulthood was not consistently associated with either outcome. CONCLUSION: Our results extend the emerging literature suggesting that obesity is a risk factor for hematologic malignancy and provide evidence that that the association remains regardless of timing of obesity. Obesity in adulthood is a modifiable risk factor for both MDS and AML.

Factors associated with hematopoietic cell transplantation (HCT) among patients in a population-based study of myelodysplastic syndrome (MDS) in Minnesota.

Myelodysplastic syndrome (MDS) is a clonal hematopoietic stem cell disorder characterized by dysplastic changes in the bone marrow, ineffective erythropoiesis, and an increased risk of developing acute myeloid leukemia. Treatment planning for patients with MDS is a complex process, and we sought to better characterize hematopoietic cell transplantation (HCT) outcomes and the factors that play into decision-making regarding referral of adults with MDS for definitive therapy with HCT. Patients enrolled in a population-based study of MDS between April 2010 and January 2013 who underwent HCT within the first year after enrollment were included in this analysis. Age- and risk-matched MDS patient controls also enrolled during that time period were used as a comparison. Survival was significantly better in the HCT group (48 vs. 21 %, log-rank p value 0.009). Non-HCT patients were more likely to have comorbidities, and HCT patients were more likely to have a college degree and an income >$80,000. All three of these variables were independently associated with HCT, but none impacted survival. Patients with MDS in our study who underwent HCT had better survival than a comparable group of patients who did not undergo HCT. With refined treatment techniques, more patients may be able to be considered for this therapy. More work needs to be done to determine why education and income appear to impact the decision to pursue HCT, but these factors may impact referral to an academic center where aggressive therapy like HCT is more likely to be considered.

Differences in community and academic practice patterns for newly diagnosed myelodysplastic syndromes (MDS) patients.

PURPOSE: The heterogeneous nature of myelodysplastic syndromes (MDS) complicates therapeutic decision making, particularly for newly diagnosed disease. Factors impacting the treatment plan in this early period of disease course are poorly defined. This study determines whether therapeutic choices for newly diagnosed MDS are associated with location of treatment (community or academic), prognostic risk category, and patient age. METHODS: The adults in Minnesota with myelodysplastic syndromes (AIMMS) database was utilized in this statewide, prospective population-based study conducted by the University of Minnesota (UMN), Mayo Clinic, and Minnesota Department of Health. Adult (age 20+ years) cases of MDS newly diagnosed starting in April 2010 were invited to participate. This analysis includes patients enrolled during the first study year with 1-year follow-up data. Treatment choices (supportive, active, and transplant) were stratified by the international prognostic scoring system (IPSS) and the revised-IPSS (IPSS-R), then separated into groups by location of care and age (<65 or 65+ years). Academic-based care was any contact with the UMN and Mayo Clinic; community-based care was all other clinical sites. RESULTS: Stratification by IPSS and IPSS-R showed supportive care decreased and active care increased with advancing risk categories (p<0.0001). Comparing treatment setting, community-based care had 77% supportive and 23% active treatment; academic-based care was 36% supportive, 41% active, and 23% transplant (p<0.0001). By age groups, patients <65 years with intermediate, high, or very high risk disease by IPSS-R received 97% active care/transplant, compared to only 52% of patients age 65+. CONCLUSIONS: Younger patients and those treated at academic centers had a more aggressive treatment approach. Whether these treatment differences convey improved disease control and mortality, and therefore should be extended more frequently to older and community-based patients, is the subject of ongoing prospective study.

Immune-related conditions and acute leukemia in children with Down syndrome: a Children's Oncology Group report.

BACKGROUND: Children with Down syndrome have unique immune profiles and increased leukemia susceptibility. METHODS: Mothers of 158 children with Down syndrome diagnosed with acute leukemia at 0 to 19 years in 1997 to 2002 and 173 children with Down syndrome but no leukemia were interviewed. Associations were evaluated via multivariable unconditional logistic regression. RESULTS: No associations were detected for asthma, eczema, allergies, or hypothyroidism. Diabetes mellitus associated with leukemia (OR = 9.23; 95% confidence interval 2.33-36.59); however, most instances occurred concurrent with or after the leukemia diagnosis. CONCLUSIONS AND IMPACT: Children with Down syndrome who develop leukemia have increased diabetes risk, likely due to treatment and underlying susceptibility factors.

Medical conditions and risk of adult myeloid leukemia.

PURPOSE: Although a few previous studies have reported positive associations between adult myeloid leukemia and a history of certain medical conditions, the etiology of most cases remains largely unknown. Our purpose was to examine associations between certain medical conditions and adult myeloid leukemia. METHODS: Using logistic regression, we evaluated associations between 16 self-reported medical conditions and myeloid leukemia in a case-control study of 670 cases [including 420 acute myeloid leukemia (AML) and 186 chronic myelogenous leukemia (CML)] and 701 population-based controls. RESULTS: We observed significant positive associations between AML and ulcerative colitis (odds ratio (OR) = 3.8; 95 % confidence interval (CI), 1.1-13) and between CML and peptic ulcer (OR = 2.0; 95% CI, 1.1-3.8). A personal cancer history increased both AML (OR = 2.6; 95% CI, 1.7-3.9) and CML (OR = 3.5; 95% CI, 2.0-5.8) risk even after excluding individuals who reported prior radiation and/or chemotherapy treatment. CONCLUSION: Certain inflammatory medical conditions and a personal history of cancer, independent from therapy, are associated with an increased risk of myeloid leukemia.

Self-report versus medical record - perinatal factors in a study of infant leukaemia: a study from the Children's Oncology Group.

In a case-control study of infant leukaemia, we assessed agreement between medical records and mother's self-reported pregnancy-related conditions and procedures and infant treatments. Interview and medical record data were available for 234 case and 215 control mothers. Sensitivity, specificity and predictive values for maternal report were estimated for case and control mothers separately, taking the medical record as correct. For most perinatal conditions, sensitivity and specificity were over 75%. Low sensitivity was observed for maternal protein or albumin in the urine (cases: 12% [95% exact confidence interval (CI) 8%, 18%]; controls: 11% [95% CI 7%, 17%]) and infant supplemental oxygen use (cases: 25% [95% CI 11%, 43%]; controls: 24% [95% CI 13%, 37%]). Low specificity was found for peripheral oedema (cases: 47% [95% CI 37%, 58%]; controls: 54% [95% CI 43%, 64%]). Sensitivity for maternal hypertension appeared much lower for cases (cases: 46% [95% CI 28%, 66%]; controls: 90% [95% CI 70%, 99%]; P = 0.003). We did not detect other case-control differences in recall (differentiality), even though the average time between childbirth and interview was 2.7 years for case and 3.7 years for control mothers. Many conditions exhibited notable differences between interview and records. We recommend use of multiple measurement sources to allow both cross-checking and synthesis of results into more accurate measures.

Feasibility of neonatal dried blood spot retrieval amid evolving state policies (2009-2010): a Children's Oncology Group study.

Dried blood spots (DBS) are collected uniformly from US newborns to test for metabolic and other disorders. Because evidence exists for prenatal origins of some diseases, DBS may provide unique prenatal exposure records. Some states retain residual DBS and permit their use in aetiological studies. The primary study aim was to assess the feasibility of obtaining residual DBS from state newborn screening programmes for paediatric and adolescent cancer patients nationwide with parental/subject consent/assent. Families of leukaemia and lymphoma patients aged ≤21 years diagnosed from 1998 to 2007 at randomly selected Children's Oncology Group institutions across the US were questioned (n = 947). Parents/guardians and patients aged ≥18 years were asked to release DBS to investigators in spring 2009. DBS were then requested from states. Overall, 299 families (32%) released DBS. Consenting/assenting patients were born in 39 US states and 46 DBS were obtained from five states; 124 DBS were unobtainable because patients were born prior to dates of state retention. State policies are rapidly evolving and there is ongoing discussion regarding DBS storage and secondary research uses. Currently, population-based DBS studies can be conducted in a limited number of states; fortunately, many have large populations to provide reasonably sized paediatric subject groups.

Nonsteroidal anti-inflammatory drug and acetaminophen use and risk of adult myeloid leukemia.

BACKGROUND: Little is known about the causes of adult leukemia. A few small studies have reported a reduced risk associated with regular use of nonsteroidal anti-inflammatory drugs (NSAID). METHODS: In a population-based case-control study, we evaluated analgesic use among 670 newly diagnosed myeloid leukemia cases [including 420 acute myeloid leukemias (AML) and 186 chronic myeloid leukemias (CML)] and 701 controls aged 20 to 79 years. Prior use of aspirin, ibuprofen, acetaminophen, other NSAIDs, and COX-2 inhibitors was assessed and included frequency, duration, and quantity. ORs and 95% CIs were calculated using unconditional logistic regression adjusting for potential confounders. RESULTS: Regular/extra strength aspirin use was inversely associated with myeloid leukemia in women (OR = 0.59, 95% CI = 0.37-0.93) but not in men (OR = 0.85, 95% CI = 0.58-1.24). In contrast, acetaminophen use was associated with an increased risk of myeloid leukemia in women only (OR = 1.60, 95% CI = 1.04-2.47). These relationships were stronger with increasing dose and duration. When stratified by leukemia type, aspirin use was inversely associated with AML and CML in women. No significant overall associations were found with ibuprofen or COX-2 inhibitors for either sex; however, a decreased risk was observed with other anti-inflammatory analgesic use for women with AML or CML (OR = 0.47, 95% CI = 0.22-0.99; OR = 0.31, 95% CI = 0.10-0.92, respectively). CONCLUSIONS: Our results provide additional support for the chemopreventive benefits of NSAIDs, at least in women. Because leukemia ranks fifth in person-years of life lost due to malignancy, further investigation is warranted. IMPACT: NSAIDs may reduce, whereas acetaminophen may increase, myeloid leukemia risk in women.

Infant leukemia and congenital abnormalities: a Children's Oncology Group study.

BACKGROUND: Leukemia in infants is rare and has not been well studied apart from leukemia in older children. Differences in survival and the molecular characteristics of leukemia in infants versus older children suggest a distinct etiology, likely involving prenatal factors. PROCEDURE: We examined the association between eight categories of maternally reported congenital abnormalities (CAs) (cleft lip or palate, spina bifida or other spinal defect, large or multiple birthmarks, other chromosomal abnormalities, small head or microcephaly, rib abnormalities, urogenital abnormalities, and other) and infant leukemia in a case-control study. The study included 443 cases diagnosed at <1 year of age at a Children's Oncology Group Institution in the United States or Canada from 1996 to 2006 and 324 controls. Controls were recruited from the cases' geographic area either by random digit dialing (1999-2002) or through birth certificates (2003-2008) and were frequency-matched to cases on birth year. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by unconditional logistic regression after adjustment for birth year and a measure of follow-up time to account for differences in the CA observation period. RESULTS: No statistically significant associations were observed between infant leukemia and any CA (OR = 1.2; 95% CI: 0.8-1.9), birthmarks (OR = 1.4; 95% CI: 0.7-2.5), urogenital abnormalities (OR = 0.7; 95% CI: 0.2-2.0), or other CA (OR = 1.4; 95% CI: 0.7-2.8). Results were similar for acute lymphoblastic and myeloid leukemia cases. Fewer than five subjects were in the remaining CA categories precluding analysis. CONCLUSIONS: Overall, we did not find evidence to support an association between CAs and infant leukemia.

Infant leukemia and parental infertility or its treatment: a Children's Oncology Group report.

BACKGROUND: Little is known about the potential risk factors for infant leukemia. With its very young age at diagnosis, exposures occurring in the perinatal period are suspected. Parental infertility and infertility treatment have been studied with regard to childhood cancer in general, but rarely in individual cancer subtypes. METHODS: A case-control study of infant leukemia was conducted through the Children's Oncology Group, including cases diagnosed from January 1996 to December 2006 and controls selected through random digit dialing and birth certificate tracing. Maternal phone interviews were conducted to obtain information about infertility, infertility treatment and demographic factors. All cases as well as subgroups defined by mixed lineage leukemia (MLL) translocation status and leukemia subtype were examined. Statistical analysis was performed using multivariate logistic regression models. RESULTS: No significant associations between infertility or its treatment and combined infant leukemia were found. In subgroup analyses, there was a significant increase in the risk of MLL--leukemia for children born to women not trying to conceive compared with those trying for <1 year for all types combined [odds ratio (OR) = 1.62, 95% confidence interval (CI) = 1.01-2.59] and for acute lymphoblastic leukemia (OR = 2.50, 95% CI = 1.36-4.61). CONCLUSIONS: There were no positive associations between parental infertility or infertility treatment and infant leukemia. While this is the largest study to date, both selection and recall bias may have impacted the results. However, for infant leukemia, we can potentially rule out large increases in risk associated with parental infertility or its treatment.

Comparability and representativeness of control groups in a case-control study of infant leukemia: a report from the Children's Oncology Group.

Traditionally, controls in US pediatric cancer studies were selected through random digit dialing. With declining participation and lack of nonparticipant information, random digit dialing (RDD) controls may be substandard. Birth certificate (BC) controls are an alternative, because they are population based and include data from nonparticipants. The authors examined controls collected by random digit dialing and birth certificates for a Children's Oncology Group case-control study of infant leukemia in 1995-2006. Demographic variables were used to assess differences in RDD and BC controls and their representativeness. RDD and BC controls did not differ significantly with regard to maternal variables (age, race, education, marital status, alcohol during pregnancy) or child variables (sex, gestational age, birth weight), but they varied in smoking during pregnancy (22% RDD controls, 12% BC controls) (P = 0.05). The study's combined control group differed significantly from US births: Mothers of controls were more likely to be older (29.8 vs. 27.2 years), white (84% vs. 59%), and married (85% vs. 67%) and to have >16 years of education (37% vs. 25%). Control children were more often full term (88% vs. 81%) and heavier (3,436 vs. 3,317 g). Finally, participating BC mothers were likely to be older and to have more education than nonparticipants. Thus, the study's control groups were comparable but differed from the population of interest.