Long-term Mortality in Individuals Diagnosed With Cancer During Pregnancy or Postpartum.

Importance: Outcomes among patients with pregnancy-associated cancers (diagnosed during pregnancy or 1-year postpartum) other than breast cancer have received relatively little research attention. High-quality data from additional cancer sites are needed to inform the care of this unique group of patients. Objective: To assess mortality and survival in premenopausal women with pregnancy-associated cancers, with a particular focus on cancers other than those of the breast. Design, Setting, and Participants: This population-based retrospective cohort study included premenopausal women (aged 18-50 years) living in 3 Canadian provinces (Alberta, British Columbia, and Ontario) diagnosed with cancer between January 1, 2003, and December 31, 2016, with follow-up until December 31, 2017, or date of death. Data analysis occurred in 2021 and 2022. Exposures: Participants were categorized as being diagnosed with cancer during pregnancy (from conception to delivery), during the postpartum period (up to 1 year after delivery), or during a time that was remote from pregnancy. Main Outcomes and Measures: Outcomes were overall survival at 1 and 5 years and time from diagnosis to death due to any cause. Cox proportional hazard models were used to estimate mortality adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs), adjusting for age at cancer diagnosis, cancer stage, cancer site, and days from diagnosis to first treatment. Meta-analysis was used to pool results across all 3 provinces. Results: During the study period there were 1014, 3074, and 20 219 participants diagnosed with cancer during pregnancy, postpartum, and periods remote from pregnancy, respectively. One-year survival was similar across the 3 groups, but 5-year survival was lower among those diagnosed with cancer during pregnancy or postpartum. Overall, there was a greater risk of death due to pregnancy-associated cancer among those diagnosed during pregnancy (aHR, 1.79; 95% CI, 1.51-2.13) and postpartum (aHR, 1.49; 95% CI, 1.33-1.67); however, these results varied across cancer sites. Increased hazard of mortality was observed for breast (aHR, 2.01; 95% CI, 1.58-2.56), ovarian (aHR, 2.60; 95% CI, 1.12-6.03), and stomach (aHR, 10.37; 95% CI, 3.56-30.24) cancers diagnosed during pregnancy, and brain (aHR, 2.75; 95% CI, 1.28-5.90), breast (aHR, 1.61; 95% CI, 1.32-1.95), and melanoma (aHR, 1.84; 95% CI, 1.02-3.30) cancers diagnosed postpartum. Conclusions and Relevance: This population-based cohort study found that pregnancy-associated cancers had increased overall 5-year mortality, though not all cancer sites presented the same risk.