P-464 Childbirth after cancer treatment among young women in Denmark
Authors: Bentsen L , Pappot H , Colmorn L , Tryde Macklon K , Vassard D 
Published: June 2023

Abstract

Study question
Do young women with cancer have children after cancer treatment comparable to the background population?

Summary answer
Results show differences between young women with cancer and those without cancer including that young woman with cancer more often have children prior to diagnosis.

What is known already
Each year approximately 900 young women are diagnosed with cancer in Denmark. Due to advanced cancer therapy many of them face long-term survival after cancer. A well-known consequence of cancer treatment is the risk of reduced fertility. Also, cancer types in the reproductive organs or diagnosis affecting the hormone-system are accountable for infertility in this population. The last decades have entailed great development in fertility preservation such as cryopreservation of oocytes, embryos or ovarian tissue and therefore increased the possibilities of having children in the future, however, international cohort studies still report less pregnancies and childbirth compared to control populations.

Study design, size, duration
This is a national, register-based study based on the DANAC II cohort. Women diagnosed with cancer as adolescents and young adults (aged 18-39) were registered in the Danish Cancer Register from 1978–2016. According to diagnosis onset, the young women with cancer were randomly age-matched with 60 undiagnosed women from the background population at the time of diagnosis. The primary outcome was childbirth. The women were followed until end of study, death and migration (31/12-2017).

Participants/materials, setting, methods
Both childbirth and IVF treatment before and after cancer treatment were compared with the aged-matched comparison group in all statistical analysis. Cancer diagnoses were divided into sub-groups. We adjusted for having children prior to cancer diagnosis in the statistical analysis. Death was also incorporated as a competing risk in all analyses.

Main results and the role of chance
The study population consisted of 21.596 young women diagnosed with cancer between 1978-2016 and 1.295.760 young women in the age-matched comparison group (CG). The study population consisted of a haematological subgroup (n = 1110), median age at diagnosis 29,7 (IQR 24,0-35,4) and an oncology subgroup (n = 20.486), median age at diagnosis 33,7 (IQR 29,1-37,2). The five-year mortality for haematological cancer was 26% and for oncological cancer 17%.
Among all women diagnosed with cancer 57% had children prior to cancer diagnosis compared to 47% in the age-matched CG. After cancer diagnosis, 19% of women with cancer had children compared to 30% in the CG.
Including children before and after diagnosis, 23% of women with cancer had no children vs 23% in the CG; 20 % had 1 child vs 16% in the CG; 39% had 2 children vs 39% in the CG and 17% had 3 or more children vs 22% in the CG.
Among women with hematological cancer 38% had no children during the observation-period, with a corresponding percentage for oncological cancer of 22%.
In the hematological and oncology sub-group seeking of ART-treatment before cancer diagnosis was 3%. After diagnosis, 5% in the hematological subgroup, 4% in the oncology subgroup sought ART-treatment.

Limitations, reasons for caution
Our study is based on registry data. Information about fertility preservation prior to cancer treatment, desire to- or deliberate opt-out of children after cancer treatment could have provided more insights. Also, we have in these preliminary results not yet adjusted for level of education.

Wider implications of the findings
A cancer diagnosis during the reproductive lifespan can affect childbearing substantially and result in fewer children. Although women diagnosed with cancer had similar levels of childlessness and seeking of ART treatment, vulnerable groups such as women with hematological cancer should be prioritized.

Trial registration number
NA