title: Fertility studies in female childhood cancer survivors: selecting appropriate comparison groups.
abstract: Little information is available on the use of appropriate comparison groups for studies investigating late effects of childhood cancer. Two comparison groups in a nationwide study on reproductive function and ovarian reserve in female childhood cancer survivors were recruited (The Dutch Childhood Oncology Group Long-Term Effects After Childhood Cancer Cohort Study). Experiences of this process are reported. Two types of comparison groups were used: sisters of participating survivors and controls from the general population. A total of 352 out of 580 (61%) of the participating survivors who had a sister gave permission to invite them for the study. The participation rate of sisters was much higher than control participants from the general population (74% versus 21%, respectively), whereas considerably more effort was involved in recruiting controls from the general population. Participants in this group were significantly older and more highly educated than sister controls (P < 0.001 for both groups). No significant differences were observed between both types of comparison groups in several fertility-related characteristics, suggesting minimal bias owing to selective participation. Researchers setting up a study to investigate late effects among survivors of childhood cancer should carefully consider the advantages and disadvantages of using various types of comparison groups.
authors.affiliation: Department of Paediatrics, Division of Paediatric Oncology/Haematology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands. Electronic address: mh.vandenberg@vumc.nl.
authors.forename: Mh
authors.initials: M
authors.lastname: van den Berg
authors.affiliation: Department of Paediatrics, Division of Paediatric Oncology/Haematology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: van Dulmen-den Broeder
authors.affiliation: Department of Paediatrics, Division of Paediatric Oncology/Haematology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands; Department of Obstetrics and Gynaecology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Overbeek
authors.affiliation: Department of Paediatric Oncology, Emma Children's Hospital, Academic Medical Center, PO Box 22660, 1100 DD, Amsterdam, The Netherlands.
authors.forename: Cm
authors.initials: C
authors.lastname: Ronckers
authors.affiliation: Department of Paediatrics, Division of Paediatric Oncology/Haematology, ErasmusMC University Medical Center, PO Box 2060, 3000 CB, Rotterdam, The Netherlands; Department of Obstetrics and Gynaecology, Division Reproductive Medicine, ErasmusMC University Medical Center, Rotterdam, The Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: van Dorp
authors.affiliation: Department of Paediatric Oncology, Emma Children's Hospital, Academic Medical Center, PO Box 22660, 1100 DD, Amsterdam, The Netherlands.
authors.forename: Lc
authors.initials: L
authors.lastname: Kremer
authors.affiliation: Department of Paediatrics, Division of Paediatric Oncology/Haematology, ErasmusMC University Medical Center, PO Box 2060, 3000 CB, Rotterdam, The Netherlands.
authors.forename: Mm
authors.initials: M
authors.lastname: van den Heuvel-Eibrink
authors.affiliation: Department of Paediatric Oncology, Beatrix Children's Hospital, University of Groningen, University Medical Center Groningen, PO Box 30.001, 9700 RB, Groningen, The Netherlands.
authors.forename: Ga
authors.initials: G
authors.lastname: Huizinga
authors.affiliation: Department of Paediatric Oncology, Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
authors.forename: Jj
authors.initials: J
authors.lastname: Loonen
authors.affiliation: Department of Paediatric Oncology, Wilhelmina's Children's Hospital, University Medical Center, PO Box 85500, 3508GA, Utrecht, The Netherlands.
authors.forename: Ab
authors.initials: A
authors.lastname: Versluys
authors.affiliation: Willem-Alexander Children's Hospital, Leiden University Medical Center, PO Box 9600, 2300 RC, Leiden, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Bresters
authors.affiliation: Department of Obstetrics and Gynaecology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands.
authors.forename: Cb
authors.initials: C
authors.lastname: Lambalk
authors.affiliation: Department of Paediatrics, Division of Paediatric Oncology/Haematology, VU University Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands.
authors.forename: Gjl
authors.initials: G
authors.lastname: Kaspers
authors.affiliation: Department of Epidemiology, Netherlands Cancer Institute, PO Box 90203, 1006 BE, Amsterdam, The Netherlands.
authors.forename: Fe
authors.initials: F
authors.lastname: van Leeuwen
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D005298:Fertility / Q000502:physiology*; D006801:Humans; D009369:Neoplasms / Q000503:physiopathology*; D018579:Patient Selection; D012107:Research Design; D035781:Siblings; D011795:Surveys and Questionnaires; D017741:Survivors
keywords: childhood cancer survivors; comparison groups controls; female fertility; late effects