Rapid Fire Oral Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2026

Age standardised incidence rate, risk factors, and outcomes of pregnancy associated cancer: a Queensland population data linkage study (142792)

Muyun (Sarah) Cao 1 , Lingjun Chen 2 , Hana Zhao 3
  1. Mater Hospital Sydney, Sydney, NSW
  2. Royal Melbourne Institute of Technology, Melbourne, VIC
  3. University of Queensland, Brisbane, QLD

Pregnancy-associated cancer (PAC) is commonly defined as cancers diagnosed during pregnancy or within 1 year postpartum, and is associated with increased maternal complications and poorer outcomes compared with non-pregnancy-associated cancers (non-PAC). However, comparative population-level analyses of incidence between PAC and non-PAC remain limited. Recently, the definition of PAC has been extended to include diagnoses up to 10 years postpartum, suggesting that pregnancy may exert longer-term biological influences on carcinogenesis than previously recognised. The temporal distribution of cancer incidence across pregnancy and the extended postpartum period also remains poorly characterised.

This study aims to address these gaps using population-based data linkage of Queensland women who gave birth between 01/07/2007 and 31/12/2022, including all live births and stillbirths ≥20 weeks’ gestation or ≥400 g birthweight. We will compare annual age-standardised incidence rates (ASIR) of PAC (during pregnancy to 10 years postpartum) and non-PAC (beyond 10 years postpartum or nulliparity); compare adverse maternal and pregnancy outcomes across PAC and no-cancer cohorts; compare cancer risk factors between PAC and non-PAC groups; and comparePAC and non-PAC survival outcomes up to 15 years postpartum in women diagnosed in 2007 by cancer type. 

In 1,972,049 pregnancies, 21,062 women were diagnosed with PAC from pregnancy to 10-year postpartum, among which most common PAC types were gynaecological (10,133 cases), skin (4,798 cases), and breast (2,602 cases). 698 cancer cases were diagnosed during pregnancy, 2,944 cases during 1-year postpartum, 8,568 cases during 1 to 5 years postpartum, and 8,852 cases during 5–10 years postpartum.

Future work will explore PAC etiology, including postpartum mammary involution, gene expression changes, tumour subtype variation, and serum biomarker. We will link digitised hospital records and code tumour histopathogenomic data with SNOMED. This integrated approach aims to improve understanding of PAC heterogeneity and ultimately inform personalised early diagnosis and improved outcomes.

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