Ovarian tissue cryopreservation (OTC) for fertility preservation in young cancer survivors- Comparison of slow freezing and vitrification techniques

Recent advancements have improved survival of cancer patients. Treatment is gonadotoxic resulting in loss of reproductive functions. Oncofertility involves managing cancer survivors with options of fertility preservation (FP) prior to chemo/radiotherapy. Options in females include stimulating ovaries and harvesting oocytes or creating embryos and freezing them in unmarried and married females respectively. This requires a hiatus of 2-3 weeks pre therapy. Oocyte and embryo cryopreservation are established methods of FP for adults. However, for pubertal and young girls who do not have sufficient mature oocytes ovarian tissue cryopreservation (OTC) and auto-transplantation is the only option.  OTC is still considered experimental, perhaps setting and standardization of techniques are challenging. The standard process of OTC has been slow freezing programmed with defined cryoprotectants. The other technique is vitrification which is associated with less cellular damage with no intra-cellular ice crystal formation. Though favoured for gametes and embryos, vitrification is still not widely accepted for OTC and studies comparing both techniques suggest conflicting results.