The Biology of Fertility Loss in Oncology Patients and Advances in Fertility Preservation Strategies (#21)
Chemotherapy causes a dose and time-related loss of ovarian follicles that is also related to the age and follicular reserve of the patient. The degree of follicular depletion causes a spectrum of disorders ranging from temporary infertility and cessation of menses, to permanent infertility and premature menopause. Fertility preservation (FP) strategies include controlled ovarian hyper stimulation (COH) to produce mature oocytes which can either be vitrified immediately or fertilised in vitro (IVF) to form embryos, but the 12 day delay for COH may be incompatible with cancer management. The collection and in vitro maturation (IVM) of immature oocytes avoids the need for COH, but current IVM, ovarian transplant and vitrification protocols need improvement to provide FP options that are comparable to COH.
The autologous transplantation of ovarian tissue has resulted in few pregnancies in cancer survivors, and the very low success rates appear to be partially related to tissue damage caused by the freeze-thaw procedures. Immature oocytes are damaged by freezing, and have poor post-thaw IVM and fertilisation rates. These problems are being addressed by improving vitrification methods, and by applying increased understanding of the in vivo physiology of oocyte maturation to IVM protocols. These advances in vitrification and IVM protocols are being enabled by the development of innovative laboratory tests. Another approach is to improve ‘short’ regimes for administration to patients which promote in vivo oocyte maturation to a level compatible with vitrification.
‘Oncofertility’ is not yet an integrated discipline; instead oncologists and fertility specialists tend to echo similar words to separate forums. A close collaboration between reproductive scientists, fertility experts and oncologists is required to translate innovative advances in the laboratory into clinical practice.