Time and spatial trends in lymphoid leukemia and lymphoma incidence and survival among children and adolescents in Manitoba, Canada: 1984-2013
April
Time and spatial trends in lymphoid leukemia and lymphoma incidence and survival among children and adolescents in Manitoba, Canada: 1984-2013
Xibiao Ye 0 2 3 4
Mahmoud Torabi 0 2 3 4
Lisa M. Lix 0 2 3 4
Salaheddin M. Mahmud 0 2 3 4
0 Funding: This research was funded by the Manitoba Medical Service Foundation (
1 317309). The funders had no role in study design , data
2 Data Availability Statement: Data are available from the Manitoba Centre for Health Policy for researchers who meet the criteria for access to confidential data. Data access requests can be sent to
3 Department of Community Health Sciences, Max Rady College of Medicine, Rady Faculty of Health Sciences, University of Manitoba , Winnipeg, Manitoba , Canada , 2 George & Fay Yee Centre for Healthcare Innovation, University of Manitoba , Winnipeg, Manitoba , Canada
4 Editor: Ji-Hyun Lee, UNM Cancer Center , UNITED STATES
To test for time and spatial trends in lymphoid malignancies, including lymphoid leukemia (LL), Hodgkin lymphoma (HL), and non-Hodgkin lymphoma (NHL), in children and adolescents in the province of Manitoba, Canada.
Objectives
Methods
Results
Incident cases diagnosed between 1984 and 2013 were identified from the Manitoba
Cancer Registry. We assessed time trends in age-standardized incidence rates using joinpoint
regression and in 5-year relative survival using Poisson regression model. Kulldorff's scan
method was used to assess spatial variation and clustering.
Age-standardized incidence rates (per million person-years) in males and females were
34.0 (95% confidence interval [CI] 28.9±39.1) and 26.2 (95% CI 21.5±30.7) for LL, 10.5
(95% CI 7.7±13.3) and 12.5 (95% CI 9.4±15.7) for HL, 12.5 (95% CI 9.3±15.4) and 7.7 (95%
CI 5.2±10.2) for NHL (except for Burkitt lymphomas), and 3.2 (95% CI 1.6±4.7) and 1.5
(95% CI 0.4±2.5) for Burkitt lymphomas. Age- and sex- standardized LL incidence rate
increased 1.4% (95% CI 0.3%-2.5%) per year, while the changes for HL and NHL incidence
rates were not statistically significant. There were geographic differences in
age-standardized incidence rates for LL, HL, and NHL and spatial clusters were detected in southern part
of the province. Five-year relative survival has improved over time and there was no
difference between rural and urban areas.
Conclusions
Lymphoid leukemia incidence rate increased over time and varied by geographic area.
Further research should examine the factors contributing to these trends.
collection and analysis, decision to publish, or
preparation of the manuscript.
Competing interests: SMM has received
unrestricted research grants from GlaxoSmithKline,
Sanofi Pasteur and Pfizer for unrelated studies.
There are no patents, products in development or
marketed products to declare. This does not alter
our adherence to all the PLOS ONE policies on
sharing data and materials. The data that support
the findings of this study are available from the
Manitoba Centre for Health Policy but restrictions
apply to the availability of these data, which were
used under license for the current study, and so
are not publicly available. Data are however
available from the authors upon reasonable request
and with permission of the Manitoba Centre for
Health Policy.
Abbreviations: 95% CI, 95% confidence interval;
APC, annual percentage change; BL, Burkitt
lymphomas; HL, Hodgkin lymphoma; HR, hazard
ratio; ICCC-3, International Classification of
Childhood Cancer, 3rd Edition; ICD, International
Classification of Diseases; LL, lymphoid leukemia;
NHL, non-Hodgkin lymphoma; RS, relative
survival.
Introduction
Hematological malignancies as a group are the most common cancer in children (under age of
15 years) and adolescents (15±19 years) and account for 40% of total cancer cases in this
population [1]. Acute lymphoid leukemia (ALL) is the most common hematological malignancy,
followed by Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) [1]. Little is
known about the etiology of the cancers and there are only a few established risk factors,
including high-level ionizing radiation [
2
], certain chemotherapeutic agents [
3
] (e.g.,
diethylstilbestrol [
4
]), certain genetic disorders (e.g., Down syndrome [
5
]), and congenital
immunodeficiency diseases [1].
Analyzing time and spatial trends of cancer incidence may provide useful information to
generate new hypotheses for etiological research. Despite extensive research on time trends in
hematological malignancy incidence in adults, few studies have been conducted in children
and adolescents. A recent international comparative analysis showed differences in temporal
trends in leukemia and lymphoma incidence rates in children by country [
6
]. Data have also
shown geographical variations in incidence among children and adolescents at the country
level [7±11], but less is known about the variation within smaller areas (e.g., provinces or
regions). Short-term and long-term survival of hematological malignancy patients (...truncated)