Long term results with vitrification compared to slow freeze of ovarian tissue

Abstract

To determine the best method of freezing, and report overall duration of function and live baby rate, after ovary tissue freeze and transplant for young cancer patients. 13 patients over an eight year period underwent thaw and transplantation of ovarian tissue that had been frozen up to 19 years earlier, with detailed follow-up of hormones, menstruation, pregnancies, and birth. Seven had undergone slow freeze, and 6 had undergone vitrification. All cancer patients varying from age 18 to age 31 who returned with POF to have their frozen ovary tissue transplanted back from 10 years ago to 2 years ago (over an 8 year period) are included in this retrospective cohort study. Their ovary tissue was frozen from 19 years ago to 5 years ago. Slow freeze was used until 10 years ago, after which only vitrification was employed exclusively. We now have long term follow-up of these 13 cases, with monthly evaluation of hormones, cycling, pregnancy, and live birth rate, and we can compare the results of slow freeze cases with those who had undergone vitrification. A total of 90 patients have undergone ovary tissue freeze, but only 13 have returned for the transplant. All patients had return of ovarian function from 4 to 5 months post-op. In all cases the return of function was accompanied by a very sharp rise in AMH for 4 months, with a subsequent decline to low levels. 8 of the 13 are still functioning. Duration of function varied from 561 days to 1,641 days (this graft is still functioning). Five of the 13 are still functioning for over 3 ½ years. There are 9 healthy babies (69%) from 10 pregnancies (76%). Slow freeze resulted in 5 healthy babies out of 7 transplants. Vitrification resulted in 4 healthy babies out of 6 transplants. However slow freeze cases had a shorter duration of function (614 to 1155 days) and 5 of the 7 are no longer functioning, whereas vitrification cases are all still functioning over 3 ½ years (1281 days to 1641 days). Ovary tissue freezing is a robust method for preserving fertility in young cancer patients. Slow freeze yields pregnancy results equivalent to vitrification. However vitrified transplants have a longer duration of function, verifying our in vitro report earlier of higher oocyte survival with vitrification compared to slow freeze.