The improvement in the survival of children and young women with cancer has led to consideration of the long-term side-effects of treatments. One of these side-effects is premature ovarian failure (Stillman et al., 1981
; Teinturier et al., 1998; Byrne, 1999). Therefore, health professionals must consider the future fertility of cancer patients prior to chemotherapy and/or radiotherapy, which may be toxic for the gonads (Meirow, 2000). When the deleterious effects of the treatment are not reversible, mature oocytes, embryos and ovarian tissue may be cryopreserved to restore fertility following the completion of the treatment.
Mature oocytes cannot be cryopreserved easily. The cytoplasm volume and water content is much higher than in other cells but also the nucleus is blocked in metaphase II of meiosis which makes the spindle very fragile and sensitive to heat and osmotic stress (Glenister et al., 1987). Nevertheless, good oocyte survival rate (Fabbri et al., 2001) and successful pregnancies (Chen, 1986; Porcu et al., 1997) have been described after the cryopreservation of mature oocytes. However, the collection of mature oocytes requires ovarian stimulation, which is not always possible because the high levels of oestrogen induced may be deleterious in some cancers (Tavani and La Vecchia, 1999). Furthermore, this procedure should only be used in adult patients.
Embryo cryopreservation is an established clinical technique which results in acceptable pregnancy rates, depending on the age of the patient (Mandelbaum et al., 1998; Troup et al., 1990). However, the patient must have a partner or be in a stable relationship at the time of the treatment and again women with oestrogen-sensitive cancers cannot undergo the necessary ovarian stimulation before IVF.
Cryopreservation of prophase I oocytes contained in primordial follicles could be an attractive alternative for many reasons. Cytoplasmic differentiation is not complete in immature oocytes; nuclei are blocked in the germinal vesicle stage. There is a large number of immature oocytes in the ovarian cortex, so the method can be used for prepubertal girls and some promising uses of frozen ovarian cortex have been shown (Oktay and Karlikaya, 2000; Oktay, 2001; Radford et al., 2001). Thus, the cryopreservation of ovarian tissue is a potential alternative or addition to the cryopreservation of embryos or mature oocytes for women at risk of premature ovarian failure (Oktay et al., 1998; Pfeifer and Coutifaris, 1999).
We evaluated the feasibility of long-term cryopreservation of ovarian tissue in women and young girls admitted to undergo treatments that would probably render them sterile.
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