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Pregnancy and lactation

Session: Poster Session B

(296) Pregnancy and infant outcomes in gestationally-diagnosed breast cancer: A pilot study in Finland and Norway from the IMI ConcePTION project

Tuesday, August 27, 2024
8:00 AM – 6:00 PM CEST
Location: Convention Hall II

    Presenting Author(s)

  • Alexis Krumme, ScD (she/her/hers)

    Associate Director
    Johnson & Johnson, Titusville, New Jersey, USA, United States

    • Co-Author(s)

  • DM

    Ditte Mølgaard-Nielsen, PhD

    Novo Nordisk, Denmark

  • VM

    Visa Martikainen

    Data manager, statistician
    Knowledge Brokers, Finnish Institute for Health and Welfare, Helsinki, Finland, Finland

  • MG

    Mika Gissler, PhD

    Professor
    Knowledge Brokers, Finnish Institute for Health and Welfare, Helsinki, Finland, Finland

  • JM

    Joan K. Morris

    Professor
    Population Health Research Institute, St George’s, University of London, UK, United Kingdom

  • Cori Campbell, DPhil

    Assistant Professor
    Department of Data Science & Biostatistics, Julius Global Health, University Medical Center Utrecht (UMCU), Utrecht, the Netherlands, Netherlands

  • SH

    Saeed Hayati

    Pharmacoepidemiology and Drug Safety Research Group, Department of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway, Norway

  • Hedvig M.E Nordeng, PhD (she/her/hers)

    Professor
    Pharmacoepidemiology and Drug Safety Research Group, Department of Pharmacy, University of Oslo (UiO), Oslo, Norway
    Oslo, Norway

  • Maarit K. Leinonen, MD, PhD

    Associate professor
    Knowledge Brokers, Finnish Institute for Health and Welfare; Teratology Information Service, Emergency Medicine and Services, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
    Helsinki, Finland

Background: Breast cancer occurring in pregnancy, while uncommon, is associated with poorer prognosis compared to diagnoses outside of pregnancy. Less is known about the association of gestationally-diagnosed breast cancer (GBC) with adverse pregnancy outcomes. With support from Innovative Medicines Initiative 2 (grant no. 821520), this study evaluates pregnancy outcomes in a novel database of linked health and cancer registry data in two Nordic countries.

Objectives: To estimate and compare prevalence of live birth, preterm live birth, small for gestational age (SGA), and Cesarean section in pregnancies with GBC and non-gestationally diagnosed breast cancer (Non-GBC) in national healthcare databases from Finland (FI) and Norway (NO).

Methods: Data from cancer registries were linked to patient, prescription, birth and cause of death registry data transformed into the ConcePTION common data model. The study population included pregnancies among women with breast cancer in the study period (1996 – 2018 FI; 2004 – 2020 NO). Exposure groups were GBC (breast cancer diagnosis during pregnancy), Non-GBC Prior (diagnosis before pregnancy), and Non-GBC Post (diagnosis after pregnancy). Women could contribute multiple pregnancies to one or more exposure groups. Prevalence of pregnancy outcomes, identified using birth registry and maternal medical record data, was compared by breast cancer group by unadjusted risk ratios (RR) and 95% confidence intervals (CI).

Results: In Finland and Norway, respectively, 71 and 65 GBC pregnancies, 257 and 204 Non-GBC Prior pregnancies, and 11,315 and 4,975 Non-GBC Post pregnancies were included. Prevalence of preterm live birth in GBC was 39% in Finland and 60% in Norway and significantly elevated compared to Non-GBC Prior (RR (95% CI): 10.14 (5.17 – 19.86) FI; 6.80 (4.19 – 11.03) NO) and Non-GBC Post (RR (95% CI): 8.31 (6.16 – 11.21) FI; 11.94 (9.46 – 15.06) NO). One quarter of deliveries in GBC were by Cesarean section in Finland versus 42% in Norway, a prevalence that was significantly elevated in Norway but not Finland compared to Non-GBC Prior (RR (95% CI): 1.23 (0.77 – 1.96) FI; 2.02 (1.36 – 2.99) NO) and Non-GBC Post (RR (95% CI): 1.46 (0.98 – 2.18) FI; 2.43 (1.81 – 3.26) NO). SGA prevalence was similar in GBC, Non-GBC Prior and Non-GBC Post.

Conclusions: Pregnancies with GBC were delivered earlier than non-GBC pregnancies with no evidence of intrauterine growth restriction. Pregnancies with GBC tended to be more often managed by Cesarean section. Limited breast cancer therapy options during pregnancy and concerns of disease progression may lead to earlier elective delivery. These findings contrast with treatment guidelines recommending carrying a pregnancy to full term as a management goal.