Study Design
This study was conducted in two hospitals in Turkey, namely Ankara University Faculty of Medicine Children’s Hospital and Ankara City Hospital, Bilkent between 2018 and 2020. The study comprised 104 pediatric cancer patients and 99 healthy children, all of whom were below the age of 18.
Participants in the case group were diagnosed with malignancy based on the International Classification of Childhood Cancer, Third Edition (ICCC-3) and had sufficient hair samples for analysis. Patients with relapsed cancer were excluded from the study. Controls were selected from volunteers who visited general pediatrics outpatient clinics had no history of malignancy and matched in age and gender with the case group. Although it was initially planned to exclude any controls diagnosed with malignancy during the study, no such cases were observed. All participants provided informed consent before participating in the study.
ETS exposure was evaluated using both questionnaire and hair cotinine enzyme-linked immunosorbent assay (ELISA) methods. The questionnaire was utilized to collect information on, parental smoking habits (pre-conceptional, during pregnancy and current smoking status), ETS exposures experienced by children, cancer risk factors (living place; birth weight; gestation week; parental age at birth; family malignancy history; congenital anomalies; chronic illnesses; ionized radiation exposure; use of category C, D, X drugs in pregnancy; infectious agents) as well as socio-demographic characteristics such as age, gender, number of siblings, and the education level of parents.
To perform hair cotinine analysis, hair samples were collected from the occipital region of scalp with a stainless-steel scissors. Each hair samples were at least two centimeters in lenght, 90 miligrams, and concisted of approximately 90-100 strands of hair\sout. All samples were stored at room temparute in ziplock bags in a dark place until they were processed in the laboratory.