Cryopreservation of in vitro matured oocytes in addition to ovarian tissue freezing for fertility preservation in paediatric female cancer patients before and after cancer therapy.

Abir R1, Ben-Aharon I2, Garor R3, Yaniv I4, Ash S4, Stemmer SM2, Ben-Haroush A3, Freud E5, Kravarusic D5, Sapir O3, Fisch B3.

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Abstract

STUDY QUESTION:

Is a protocol that combines in vitro maturation of germinal vesicle-stage oocytes and their vitrification with freezing of cortical ovarian tissue feasible for use in fertility preservation for both chemotherapy-naive paediatric patients as well as patients after initiation of cancer therapy?

SUMMARY ANSWER:

Follicle-containing ovarian tissue as well as oocytes that can undergo maturation in vitro can be obtained from paediatric patients (including prepubertal girls) both before and after cancer therapy.

WHAT IS KNOWN ALREADY:

Anticancer therapy reduces the number of follicles/oocytes but this effect is less severe in young patients, particularly the paediatric age group. Autotransplantation of ovarian tissue has yielded to date 60 live births, including one from tissue that was cryostored in adolescence. However, it is assumed that autografting cryopreserved-thawed ovarian cortical tissue poses a risk of reseeding the malignancy. Immature oocytes can be collected from very young girls without hormonal stimulation and then matured in vitro and vitrified. We have previously shown that there is no difference in the number of ovarian cortical follicles between paediatric patients before and after chemotherapy.

STUDY DESIGN, SIZE, DURATION:

A prospective study was conducted in a cohort of 42 paediatric females with cancer (before and after therapy initiation) who underwent fertility preservation procedures in 2007-2014 at a single tertiary medical centre.

PARTICIPANTS/MATERIALS, SETTING, METHODS:

The study group included girls and adolescent females with cancer: 22 before and 20 after chemotherapy. Following partial or complete oophorectomy, immature oocytes were either aspirated manually ex vivo from visible small antral follicles or filtered from spent media. Oocytes were incubated in oocyte maturation medium, and those that matured at 24 or 48 h were vitrified. Ovarian cortical tissue was cut and prepared for slow-gradual cryopreservation. Anti-Mullerian hormone (AMH) levels were measured in serum before and after oophorectomy.

MAIN RESULTS AND ROLE OF CHANCE:

Ovarian tissue was successfully collected from 78.7% of the 42 patients. Oocytes were obtained from 20 patients before chemotherapy and 13 after chemotherapy. The youngest patients from whom oocytes were retrieved were aged 2 years (two atretic follicles) and 3 years. Of the 395 oocytes collected, ∼30% were atretic (29.6% in the pre-chemotherapy group, 37% in the post-chemotherapy group). One hundred twenty-one oocytes (31%) were matured in vitro and vitrified: 67.8% from patients before chemotherapy, the rest after chemotherapy. Mature oocytes suitable for vitrification were obtained from 16/20 patients before chemotherapy and from 12/13 patients after chemotherapy (maturation rate, 32 and 26.4%, respectively). There were significant correlations of the number of vitrified oocytes with patient age (more matured oocytes with older age) (P = 0.001) and with pre-oophorectomy AMH levels (P = 0.038 pre-chemotherapy group, P = 0.029 post-chemotherapy group). Oocytes suitable for vitrification were obtained both by manual aspiration of antral follicles (45%) and from rinse solutions after dissection. There were significantly more matured oocytes in the pre-chemotherapy group from aspiration than in the post-chemotherapy group after both aspiration (P < 0.033) and retrieval from rinsing fluids (P < 0.044). The number of pre-antral follicles per histological section did not differ in the pre- versus post-chemotherapy. AMH levels dropped by approximately 50% after ovarian removal in both groups, with a significant correlation between pre- and post-oophorectomy levels (P = 0.002 pre-chemotherapy group, P = 0.001 post-chemotherapy group).

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2016年2月13日