Use of cryopreserved ovarian tissue in the Danish fertility preservation cohort

Objective: To evaluate the use of cryopreserved ovarian tissue in the Danish fertility preservation cohort. Design: Retrospective cohort study. Setting: University hospitals and fertility clinics. Patient(s): Ovarian tissue cryopreservation (OTC) was performed for 1,186 Danish girls and women from 1999–2020, of whom 117 subsequently underwent ovarian tissue transplantation (OTT). Subgroup 1 included 759 patients with a follow-up period of >5 years. Out of these, OTT rates were further analyzed for those patients who were alive and aged >24 years in July 2020 (subgroup 2; n = 554). Intervention(s): OTC and OTT. Main Outcome Measure(s): OTT, death, donation of tissue. Result(s): In subgroup 1, 14% of the patients had undergone OTT, 18% had died, 9% had donated their tissue for research, and 59% still had their tissue stored. In subgroup 2, 19% had undergone OTT and for most diagnoses the OTT rates ranged from 15% to 22% with benign hematologic diseases having the highest OTT rate (35%). On the basis of the entire cohort, stratified age analysis indicated that women aged ≥30 years at OTC were more likely to return for OTT than women aged 18–29 years at OTC; mean storage times were 3.7 and 3.6 years, respectively. Only 4% of the girls aged <18 years at OTC had undergone OTT. Conclusion(s): The OTT rates depended on the diagnosis, age at OTC, and follow-up time. Specific criteria are needed for reporting and comparing OTT rates. Six out of 10 patients still had their cryopreserved tissue stored and longer follow-up is needed, especially for younger girls.