ESR1 and breast cancer: There was no evidence of a statistically significant effect for fertility preservation effect with or without hormonal stimulation on the rate of breast cancer relapse after adjustment for age at diagnosis, period of diagnosis, tumor size, estrogen receptor status, affected lymph nodes, and chemotherapy treatment (IRR 0.66, 95% CI 0.37–1.17 and IRR 0.83, 95% CI 0.42–1.67), respectively) (Table 2).