Study design, Database and Case Identification
We conducted a retrospective cohort study using population-based data.
Incidence of malignant neoplasms among infants (age <365 days)
diagnosed between January 1, 1975 and December 31, 2014 were extracted
from the SEER registry using the International Classification
Childhood Cancer (ICCC-3)(11), 3rd Edition . Infant cancer cases were
collected from 9 population-based cancer incidence registries (SEER 9)
that provided continuing data for the 40-year observation period and
represent approximately 10% of the U.S. population.(12) The registries
include broad geographic and racial distributions of persons in the
states of Connecticut, Hawaii, Iowa, New Mexico, and Utah and the
metropolitan areas of Atlanta, Georgia; Detroit, Michigan; San
Francisco-Oakland, California; and Seattle-Puget Sound, Washington. The
raw data in our study were downloaded from the SEER website via
SEER*Stat in client-server mode after we submitted a request for access
and signed the SEER research data agreement.(12) This study was
classified as exempt by the Institutional Review Board at the Baylor
College of Medicine in Houston, Texas.
Numerators for incidence rates comprise the total number of cancer cases
occurring among infants from 1975 to 2014. Denominators for calculation
of incidence rates were population counts for infants aged <1
year in each of the 9 SEER programs included in this report. Since the
number of cancers diagnosed per year among infants was often quite
small, some trends were calculated after combining cases diagnosed in
two-year. Race was grouped as white, black, and other. Approximately
96% of all cases were confirmed microscopically. Only infants diagnosed
with malignant tumors were included in the analyses. Diagnoses were
classified into 12 main tumor groups and 47 subgroups according to the
ICCC version 3 (ICCC-3). These 12 groups were described as follows: (1)
leukemia: leukemias, myeloproliferative and myelodysplastic diseases;
(2) lymphoma: lymphomas and reticuloendothelial neoplasms; (3) CNS
neoplasms: CNS and miscellaneous intracranial and intraspinal neoplasms;
(4) neuroblastomas: neuroblastoma and ganglioneuroblastoma; (5)
Sarcomas: soft tissue and other extraosseous sarcomas; (6) germ cell:
germ cell tumors (GCTs), trophoblastic tumors, and neoplasms of the
gonads; (7) Retinoblastoma: Retinoblastoma; (8) Hepatic tumor: Hepatic;
(9) Renal tumors: Renal; (10) Bone: Malignant bone tumors; (11) Other
and unspecified malignant neoplasms; and (12) other: other malignant
epithelial neoplasms and malignant melanomas. Bone (10), other and
unspecified (11) and other (12) tumors were excluded from analysis due
to the small number of cases (<50).