With the pediatric cancer survival rate exceeding 80%, “we can reasonably suspect that most of these children will survive more than 5 years from their diagnosis and then go on to puberty,” when they may have to deal with the consequences of cancer treatment, according to Rebecca Flyckt, MD, Division Director, Reproductive Endocrinology and Infertility, University Hospitals of Cleveland, Case Western Reserve University. For girls, these consequences can include damage to the ovaries and infertility. Ovarian tissue cryopreservation prior to cancer treatment and then later reimplantation may be the best way to preserve fertility.
Rebecca Flyckt, MD
Erin E. Rowell, MD
“For me, the question comes down to, how much tissue is needed to preserve fertility and feel relatively assured of a successful live birth,” Dr. Flyckt said. “Do you take the whole ovary out, or do you do an ovarian cortical biopsy, where you shave the outer cortex, which is what contains the primordial follicles, and then reimplant that onto the scaffolding or the medulla that is left over when you take the cortex?”
In a collegial debate on this issue at the 2019 Annual Oncofertility Conference in Chicago, Dr. Flyckt was tasked with presenting arguments in favor of ovarian cortical biopsy,1 and Erin E. Rowell, MD, was asked to make the case for unilateral oophorectomy.2 Dr. Rowell is Medical Director, Fertility & Hormone Preservation & Restoration Program, Ann & Robert Lurie Children’s Hospital of Chicago, and Co-Director, Pediatric Surgery, Chicago Institute for Fetal Health.
Ovarian Tissue Freezing
“Pediatric ovarian tissue freezing is such an exciting idea,” Dr. Flyckt said. Compared with egg freezing, where the average number of eggs procured at one time is 8 to 12 eggs, “with ovarian tissue, we can freeze thousands of eggs within a single sample of tissue. For prepubertal girls, this is often their only option to preserve fertility,” she noted.
“The major concern when we are using ovarian tissue freezing for patients with cancer is the potential to reintroduce cancer cells,” Dr. Flyckt stated. She said that others who had frozen ovarian cortex tissue from women with leukemia and then reimplanted it have reported that those women “have not demonstrated reactivation of their disease so far. However, I don’t know that I would be willing to do that for my patients with leukemia.” Dr. Flyckt added that although she had “frozen tissue for many dozen women and girls,” she had not yet reimplanted tissue outside of animal models.
"The major concern when we are using ovarian tissue freezing for patients with cancer is the potential to reintroduce cancer cells."— Rebecca Flyckt, MD
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For patients who are undergoing surgery to remove ovarian tissue for freezing, “I almost always try to do it with another surgical procedure. That way, the cost can be decreased and so too can the distress that comes from going through surgery,” Dr. Flyckt commented.
“The American Society for Reproductive Medicine is expected to lift its experimental designation of ovarian tissue freezing,” according to Dr. Flyckt. “I think the reason is because we’ve established a strong trend of live births around the country and around the world.”
Patient Selection and Surgical Technique
Guidelines for selecting patients for ovarian tissue cryopreservation are known as the Edinburgh criteria3 and include the following:
“These criteria are the reference standard,” Dr. Flyckt said. “However, what you do in your practice may vary, depending upon what an individual or family wants and what your institution will support.”
With ovarian tissue, cryopreservation, the question of how much tissue is needed to feel relatively assured of a live birth “has a lot to do with follicle density, and the ability of those primordial follicles to withstand cryopreservation,” Dr. Flyckt explained. Other factors to consider are the age and overall condition of the patient, whether she has had chemotherapy, other treatment planned, the likelihood of primary ovarian insufficiency, a history of ovarian surgery, and whether other surgeries that will alter the pelvic anatomy are planned.
Concerning the best surgical method to procure and reimplant tissue, “some people say laparoscopic surgery; some people say robotic surgery,” continued Dr. Flyckt. “And some people still do a minilaparoscopy.” The best method of cryopreservation—slow freeze or vitrification—is also undecided. “The history certainly supports slow freezing,” she said, but for a long while, that was the only option. “Many of us have moved to vitrification, and there are live births now from vitrifcation as well.”
Still a Relatively New Option
Ovarian tissue cryopreservation “is still relatively new,” Dr. Flyckt reminded conference participants. “The first live birth occurred in 2004. Now, there have been more than 150 live births from orthotopic tissue reimplantation.” She noted that this option is offered only in the United States under independent review board–approved registries.
Among patients having reimplantation, “about one-half will become pregnant, and one-third will achieve a live birth,” Dr. Flyckt reported. “Most of our success is with adult women. What is really exciting about this conference is that we are starting to focus on this pediatric population.”
There have been two live births after reimplantation of tissue taken from prepubertal girls: one who had tissue frozen at age 14 and the other, at age 9. “The data will start to accumulate, and with more data, we can have better understanding,” Dr. Flyckt said. Citing a saying that multiple anecdotes do not equal data, she added, “Right now, we are in the multiple-anecdotes phase.”
Summing up the advantages of cortical biopsy vs oophorectomy, Dr. Flyckt cited ease of tissue dissection and preparation and less potential for ureteric injury, and showed surgical images demonstrating this technique. Cortical biopsy also “leaves more native ovary, so, if residual function is achieved after chemotherapy, it may reactivate,” she continued. “We take the ovary out and then put it right back in its native site.” Because there have been live births using this method, “We actually do have data that using the native ovary as scaffolding can be effective.”
Dr. Flyckt pointed to a study of residual ovarian function after autologous bone marrow transplantation.4 “Among 17 patients, the recovery rate for ovarian function, as determined by pregnancy or regular menses, was 29%. “For women younger than age 25, the recovery rate “can be up to 80%,” noted Dr. Flyckt. “So, are we really doing these women a service by taking out their whole ovary?”
After Unilateral Oophorectomy
For unilateral oophorectomy, “the live birth rate, as reported worldwide after reimplantation, ranges between 23% and 41%,” Dr. Rowell noted. The first step in a successful procedure is “to remove the healthiest possible tissue. This tissue will be stored long term, and for a pediatric patient, that may be decades,” she said.
“Surgical handling of tissues in and of itself can cause damage. Laparoscopic graspers, particularly with teeth, can crush tissue,” and “heat sources can cause burn injuries,” Dr. Rowell noted. “We need precise hemostasis, and usually that means the need for heat or some sort of mechanical source to seal the vessel. That is important in pediatric patients, where the blood volume is less and major bleeding from the ovarian artery could be life-threatening and delay their medical therapy; this is a strong reason to be careful about precise hemostasis.” The ovaries in a prepubertal patient are very small, Dr. Rowell noted, and it is critical in these very tiny ovaries to be precise with tissue handling and hemostasis.”
"The ovaries in a prepubertal patient are very small, and it is critical in these very tiny ovaries to be precise with tissue handling and hemostasis."— Erin E. Rowell, MD
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“After an oophorectomy, the remaining ovary compensates,” explained Dr. Rowell. “It is not the same as removing half the fertility and hormone potential in a person. The remaining ovary can maintain the same levels of serum hormones and support transition through puberty, and we know that the remaining ovary can release more eggs when it is stimulated for assisted reproductive technologies.”
Dr. Rowell continued: “Oocytes are finite resources. Baby girls are born with the most oocytes they will ever have over a lifespan.” Although there is “this huge primordial reserve,” she added, “a young pediatric patient might go through high-risk treatments that will impact that primordial reserve and can potentially expect to go through menopause early. Therein is the definition of premature ovarian insufficiency. Even if the ovary recovers after therapy, that person will go through menopause on average perhaps 20 years earlier than expected, and what do we do about that?”
Improving Surgical Techniques
Dr. Rowell and colleagues conducted a meta-analysis of surgical techniques.5 The ages of the patients ranged widely, from 1.6 years to 43 years in a variety of publications, and “the number of patients ranged from 1 in a case study up to 246,” she reported.
“The ovarian tissue harvest method included a wide variety of procedures, from unilateral oophorectomy to bilateral biopsies, bilateral hemi-oophorectomy, cortical biopsies, removing two-thirds of the ovarian cortex. However, of the 22 papers, 13 of them used unilateral oophorectomy.” Although many of the papers reported no complications, there was “one clinically significant episode of bleeding, hemorrhage in a postoperative pediatric patient, and that was in a patient who had bilateral hemi-oophorectomy.”
Then Dr. Rowell’s group looked at how to develop their own model of laparoscopic oophorectomy in a pediatric patient. “We tried to mimic the precise conditions that we encounter in the operating room, using the same equipment,” she revealed. To do so, they used a porcine model, with the pigs at 19 to 21 weeks of age, so they were all prepubertal or peripubertal.6
“The porcine model at this young age mimics the laparoscopic oophorectomy in pediatric patients, and the ovarian cortical tissue that is harvested using an advanced ultrasound energy device does experience altered metabolism compared with controls. We recommend for dissection at least 1 cm away from the cortical surface, and if possible 2 cm, although anatomically it is not always possible,” explained Dr. Rowell. They also aim to continue this work and use it as preliminary data for future studies—ones that look at other surgical techniques and perhaps combinations of surgical techniques to secure the best tissue for long-term freezing and then use that as a model of reimplantation.
"After an oophorectomy, the remaining ovary compensates. It can maintain the same levels of serum hormones and support transition through puberty."— Erin E. Rowell, MD
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Dr. Rowell explained the concept of ovarian follicles being sensitive to the microenvironment. “We always had this concern of cutting across that cortical surface and know that the structure of the ovary in these niches for the follicles is important,” she said.7 “So, what happens when we leave a raw surface behind? Whether you have hemostasis or not, and whether you use a heat source or not, there is still that surface in the cortex that has been disrupted. Is there then a proliferation of follicles inside the patient prior to the start of therapy that apoptose and are lost? Much evidence suggests that probably is the case.”
Compartmentalization is known to exist, according to Dr. Rowell. “These follicles are in different compartments, and when we cut across them, we release them. If we are not going to harvest all of them for future use, they will be damaged or lost.” In fact, the patients that qualify for this procedure have the highest increased risk of losing ovarian function.
With the small prepubertal ovary, Dr. Rowell emphasized the importance of saving as much tissue as possible. “The preparation of cortical thinning for cryopreservation,” she noted, involves looking for tissue pieces and “maybe other oocytes that could potentially be matured and saved for the patient.”
DISCLOSURE: Drs. Flyckt and Rowell reported no conflicts of interest.
1. Flyckt R: Ovarian cortical biopsy for fertility preservation. 2019 Oncofertility Conference. Presented November 13, 2019.
2. Rowell E: The case for unilateral oophorectomy. 2019 Oncofertility Conference. Presented November 13, 2019.
3. Wallace WH, Smith AG, Kelsey TW, et al: Fertility preservation for girls and young women with cancer. Lancet Oncol 15:1129-1136, 2014.
4. Schimmer AD, Quatermain M, Imrie K, et al: Ovarian function after autologous bone marrow transplantation. J Clin Oncol 16:2359-2363, 1998.
5. Corkum KS, Laronda MM, Rowell EE: A review of reported surgical techniques in fertility preservation for prepubertal and adolescent females facing a fertility threatening diagnosis or treatment. Am J Surg 214:695-700, 2017.
6. Rowell EE, Corkum KS, Even KA, et al: Ovarian tissue health after laparoscopic unilateral oophorectomy. J Pediatr Surg. January 10, 2020 (early release online).
7. Henning NF, LeDuc RD, Even KA, et al: Proteomic analyses of decellularized porcine ovaries identified new matrisome proteins and spatial differences across and within ovarian compartments. Sci Rep 9:20001, 2019.