In vitro maturation improves oocyte or embryo cryopreservation outcome in breast cancer patients undergoing ovarian stimulation for fertility preservation

This study tested in-vitro maturation (IVM) as a complementary strategy to improve the mature oocyte yield of breast cancer patients undergoing ovarian stimulation for fertility preservation. Secondary analysis of prospectively collected data is performed for 32 breast cancer patients undergoing oocyte or embryo cryopreservation before chemotherapy. Total number of oocytes and/or embryos cryopreserved following IVM is compared with the total number cryopreserved before IVM. Overall, 464 oocytes were retrieved, of which 274 were mature. Following IVM, the number of total mature oocytes increased to 399 (45% increase in mature oocyte yield, P < 0.0001). Fertilization rate after IVM was statistically significantly higher than the fertilization of already mature oocytes at retrieval (86% versus 73%, respectively, P < 0.05). The total number of oocytes and embryos frozen before IVM was 207 (45% of all oocytes retrieved). This number increased to 320 (69% of all oocytes retrieved) following IVM (P < 0.0001). IVM is a useful strategy to improve the mature oocyte yield of fertility preservation cycles. Immature oocytes retrieved during oocyte/embryo cryopreservation cycles should not be discarded to improve the future potential of fertility.