A Japanese nationwide survey on the cryopreservation of embryos, oocytes and ovarian tissue for cancer patients

Aim: The survival rates of cancer patients have greatly improved owing to the advances in oncology. The preservation of fertility in cancer patients is an important task. To determine the reality of cryopreservation of embryos, oocytes and ovarian tissue in cancer patients, large-scale survey analysis was performed in Japan. Methods: We sent 613 Japan Society of Obstetrics and Gynecology-certified assisted reproductive technology institutions a questionnaire about their experience of performing cryopreservation for cancer patients between January 2011 and December 2015. Subsequently, the institutions that conducted cryopreservation for cancer patients were sent a second questionnaire. Results: We received replies from 481 (78.5%) institutions. Among them, 126 (26.2%) conducted cryopreservation for cancer patients. These 126 institutions were sent a second questionnaire. Of these, 108 (85.7%) institutions responded. At the 108 institutions, 1085 embryo or oocyte cryopreservation procedures and 122 ovarian tissue cryopreservation procedures were conducted for cancer patients. Cryopreservation was mainly performed for breast cancer patients (~70%), followed by patients with hematological malignancy. A total of 361 and 19 embryo transfer cycles were performed for patients whose embryos and oocytes were cryopreserved, respectively, and 42 and seven institutions reported pregnancy outcomes after embryo transfer in patients that underwent embryo and oocyte cryopreservation, respectively. However, pregnancy was not observed in the seven cases that underwent ovarian tissue transfer. Conclusion: Indications, age limits and ovarian stimulation protocols for cryopreservation widely varied between the institutions. A national registration system for oncofertility must be established to evaluate the safety and efficacy of the current system.