The term “leukemia” and “brain tumors” refers to a collection of neoplasms, each with its own biology, prognosis, and treatment. Leukemia is a type of cancer that affects blood cells. The cancer originates in the bone marrow where blood cells are formed (Hunger, 2015). For unknown reasons, these cells fail to develop properly into mature blood cells, and multiply at rapid rates crowding out other normal blood cells (Hunger, 2015). In the United States, acute lymphoblastic leukemia (ALL) is the most common cancer among children and the most frequent cause of death from cancer before the age of 20 (Hunger, 2015). The incidence of ALL before the age of 20 is about 30 cases per million persons, with the peak incidence occurring at 3 to 5 years
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One of many strengths of a cohort study include the ability to examine multiple outcomes from a given exposure or multiple exposures from a defined population (Gordis, 2013). One can also gather data regarding the sequence of events, known as the temporal relationship, and therefore, assess the strength of association and other parameters through absolute, relative, and attributable risk (Gordis, 2013). Moreover, cohort studies are best known for investigating rare exposures and rates of disease in both exposed and unexposed groups (Gordis, 2013). In a retrospective study, like our article, the study may generally be less expensive and faster to complete than a prospective study (Song, 2010). Some limitations of cohort studies include cost and long-term follow-up of subjects in prospective studies, large population size required for both prospective and retrospective studies, limited control over data collection in retrospective studies, and very importantly, various types of bias, such as, bias in assessment of the outcome, information bias, bias from nonresponse and losses to follow-up, and analytic bias in both prospective and retrospective studies (Gordis, 2013). One limitation noted in this article was that the data for the machine settings, that was known to influence the dose of radiation such as milliampere seconds and peak kilovoltage, were not available for every individual patient from the electronic databases during the study period (Pearce,
One of many strengths of a cohort study include the ability to examine multiple outcomes from a given exposure or multiple exposures from a defined population (Gordis, 2013). One can also gather data regarding the sequence of events, known as the temporal relationship, and therefore, assess the strength of association and other parameters through absolute, relative, and attributable risk (Gordis, 2013). Moreover, cohort studies are best known for investigating rare exposures and rates of disease in both exposed and unexposed groups (Gordis, 2013). In a retrospective study, like our article, the study may generally be less expensive and faster to complete than a prospective study (Song, 2010). Some limitations of cohort studies include cost and long-term follow-up of subjects in prospective studies, large population size required for both prospective and retrospective studies, limited control over data collection in retrospective studies, and very importantly, various types of bias, such as, bias in assessment of the outcome, information bias, bias from nonresponse and losses to follow-up, and analytic bias in both prospective and retrospective studies (Gordis, 2013). One limitation noted in this article was that the data for the machine settings, that was known to influence the dose of radiation such as milliampere seconds and peak kilovoltage, were not available for every individual patient from the electronic databases during the study period (Pearce,