Safety of fertility preservation in breast cancer patients in a register-based matched cohort study

Abstract

Purpose

To determine if women with breast cancer that undergo fertility preservation (FP), with or without hormonal stimulation, present with an increased risk of breast cancer recurrence.

Methods

A matched cohort study on women with breast cancer attempting to ensure FP in Stockholm from 1999 to 2013 [exposed women (n = 188), age-matched unexposed controls (n = 378)] was designed using the Stockholm regional data from the Swedish National Breast Cancer Quality Register. Breast cancer relapse rates [incidence rate ratio (IRR)] and 95% confidence interval (CI) were estimated using Cox regression and adjusted for potential confounding factors. Completeness of the registry at the time of the study was close to 99%.

Results

Most women attempted FP by hormonal stimulation treatment (n = 148, 79%) with the objective of freezing their eggs or embryos. A smaller group elected FP methods without hormone stimulation (n = 40, 21%). Women who received hormone stimulation did not present with a higher relapse rate than unexposed control women in a model adjusted for age and calendar period of diagnosis (IRR 0.59, 95% CI 0.34–1.04). The results remained virtually unchanged after adjustment for tumor size, estrogen receptor status, affected lymph nodes, and chemotherapy treatment (IRR 0.66, 95% CI 0.37–1.17).

Conclusion

Evidence was not found that fertility preservation, with or without hormonal stimulation, was associated with an increased risk of breast cancer recurrence. The high coverage rate of this population-based study supports the safe practice of fertility preservation in young women with breast cancer.

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