Luteal phase oestradiol suppression by letrozole: a pilot study in oocyte donors

Letrozole and Ovarian Hyperstimulation Syndrome (OHSS): A Promising Prevention Strategy

Ovarian Hyperstimulation Syndrome (OHSS) is an uncommon but serious complication occurring in patients undergoing ovarian stimulation. It is characterized by ovarian enlargement, nausea, vomiting, abdominal pain/distension, and reduction in urine output. However, OHSS may rarely evolve into a life-threatening condition with ascites, hemoconcentration and hypercoagulability. Prevention of OHSS consists of an integrated approach that associates behavioral aspects with administration of pharmacological compounds. Among drugs used to manage OHSS, Letrozole has recently been proposed as an effective option for prevention of the syndrome. However, despite the promising findings reported by several studies, to date Letrozole is not yet officially mentioned in the guidelines for "Prevention and Treatment of moderate and severe ovarian hyperstimulation syndrome". In this scenario, the current study discusses Letrozole approaches scientifically available to prevent OHSS.

Whether Letrozole could reduce the incidence of early ovary hyperstimulation syndrome after assisted reproductive technology? A systematic review and meta-analysis

Background

Letrozole can significantly decrease the estrogen level, and has been administrated to prevent the incidence of early ovary hyperstimulation syndrome (OHSS). However, the effect of Letrozole on prevention of OHSS reached to controversial conclusions. The present meta-analysis aim to examine whether Letrozole could reduce the incidence of early OHSS after assisted reproductive technology (ART).

Methods

An exhaustive electronic literature search was conducted on MEDLINE, Google Scholar, CNKI and WANFANG MED ONLINE, from inception until May 2018. We include clinical trials that examined the effect of Letrozole on the prevention of early OHSS. The main outcome measures were the incidence of total early OHSS, mild early OHSS, moderate early OHSS, and severe early OHSS.

Results

Eight studies included in the review. Of these, five publications evaluated the effect of Letrozolel on the prevention of total, mild, moderate, and severe OHSS, respectively. The results indicated that there was a significantly decreased incidence of total OHSS with Letrozole compared with control group, and there were no significantly differences in the incidence of mild, moderate, and severe OHSS between study group with Letrozole and control group. Eight studies reported the incidence of moderate + severe OHSS. We found a significant decrease in incidence of moderate + severe OHSS in high-risk women with Letrozole.

Conclusions

Letrozole has no beneficial effect on the prevention of mild, moderate, and severe OHSS, individually; Letrozole should not be considered as the first-line treatment for prevention of OHSS. Further cohort studies are required to explore the effect of Letrozole on the prevention of OHSS.

Plain English Summary

This study aimed to examine whether Letrozole could reduce the incidence of early OHSS after assisted reproductive technology (ART). A meta-analysis including 8 studies was conducted. There were no significantly differences in the incidence of mild, moderate, and severe OHSS between study group with Letrozole and control group. Letrozole has no beneficial effect on the prevention of mild, moderate, and severe OHSS, individually.

Effect of letrozole on moderate and severe early-onset ovarian hyperstimulation syndrome in high-risk women: a prospective randomized trial

BACKGROUND

Ovarian hyperstimulation syndrome is an iatrogenic complication of controlled ovarian stimulation. Early ovarian hyperstimulation syndrome occurs during luteal phase of controlled ovarian stimulation within 9 days after human chorionic gonadotropin trigger and reflects an acute consequence of this hormone on the ovaries. Late ovarian hyperstimulation syndrome occurs 10 or more days after human chorionic gonadotropin trigger and reflects increased endogenous human chorionic gonadotropin levels following pregnancy. Human chorionic gonadotropin stimulates granulosa-lutein cells to produce vascular endothelial growth factor messenger RNAs, which in turn raises serum vascular endothelial growth factor concentration and increases vascular permeability in women with ovarian hyperstimulation syndrome. Efforts to reduce the incidence and severity of ovarian hyperstimulation syndrome after oocyte retrieval, and in particular primary prevention efforts, are vital to prevent thrombogenesis and other serious complications.

OBJECTIVE

The objective of the study was to compare the efficacy of letrozole, an aromatase inhibitor, with aspirin in primary prevention of early ovarian hyperstimulation syndrome and to compare vascular endothelial growth factor levels between groups.

STUDY DESIGN

Participants in this prospective randomized trial included 238 participants undergoing cryopreservation of the whole embryos after oocyte retrieval with at least 1 of the following high-risk factors for ovarian hyperstimulation syndrome: oocyte retrieval ≥25; estradiol level ≥5000 pg/mL on the day of human chorionic gonadotropin administration; and clinical or ultrasonographic evidence of ovarian hyperstimulation syndrome on the day of oocyte retrieval, such as ultrasonographic evidence of ascites. After human chorionic gonadotropin triggering, experimental (119 cases) and control (119 cases) groups received letrozole and aspirin, respectively, for 5 days. The 5 categories of ovarian hyperstimulation syndrome include no, yes-mild, yes-moderate, yes-severe, and yes-critical. The primary outcome was the incidence and severity of early ovarian hyperstimulation syndrome. The secondary outcome included vascular endothelial growth factor level both on the second and seventh day after the human chorionic gonadotropin trigger, and clinical and laboratory features of ovarian hyperstimulation syndrome symptoms.

RESULTS

The incidence of ovarian hyperstimulation syndrome was significantly higher in women receiving aspirin, compared with letrozole (90.2% vs 80.4%, P = .044). Moderate and severe ovarian hyperstimulation syndrome was also higher in the aspirin group, 45.1%, compared with the letrozole group, 25.0% (P = .002). Moreover, the duration of luteal phase was shortened in letrozole group compared with aspirin group (8.1 ± 1.1 days vs 10.5 ± 1.9 days, P < .001). The vascular endothelial growth factor level was significantly higher in the letrozole-treated group than aspirin-treated group (0.49 ± 0.26 vs 0.42 ± 0.22, P = .029).

CONCLUSION

Letrozole was more effective than aspirin in decreasing the incidence of moderate and severe early-onset ovarian hyperstimulation syndrome. Our results indicate that ovarian hyperstimulation syndrome might be caused through a luteolytic effect rather than through modulation of vascular endothelial growth factor, racing by a decline in estradiol and termination of early-onset ovarian hyperstimulation syndrome in advance in high-risk women with cryopreservation of the whole embryos.

Can steroidal ovarian suppression during the luteal phase after oocyte retrieval reduce the risk of severe OHSS?

Background

Ovarian stimulation in IVF cycle results in luteal supraphysiological steroid concentrations especially for high response patients. The aim of this study was to evaluate the efficacy of ovarian steroid hormone suppression in luteal phase after oocyte retrieval for preventing severe ovarian hyperstimulation syndrome (OHSS) in high-risk patients with embryo cryopreservation.

Methods

281 patients with high risk of OHSS were enrolled in this study among 4735 infertile women undergoing their first IVF treatment. The subjects were allocated into treatment and control group. The treatment group (n = 161) received letrozole (n = 43), mifepristone (n = 51), cetrotide (n = 39) and three-drug combinations (n = 28) during the luteal phase after oocyte retrieval, respectively. The control group (n = 120) received no medicine. Fertilization rate, good embryo rate, serum steroid concentration, clinical outcome, and incidence of severe OHSS were compared between the two groups.

Results

On days 2, 5 and 8 after oocyte retrieval, serum estradiol levels in the letrozole and three-drug combination therapy group were significantly lower than in the other three groups at the same time (P < 0.001, respectively). There were no significantly difference of serum luteinizing hormone concentration on days 2, 5 and 8 and progesterone concentration on day 8 after oocyte retreival among the five groups (P > 0.05, respectively). Compared with the control group, the incidence of severe OHSS, the paracentesis rate, the duration of hospitalization and the days of luteal phase in each subgroup of treatment groups was not significantly decreased (P > 0.05, respectively).

Conclusions

Our findings indicate that steroidal ovarian suppression in luteal phase after oocyte retrieval seems to be unable to prevent severe OHSS in high-risk patients with embryo cryopreservation.

Cetrotide administration in the early luteal phase in patients at high risk of ovarian hyperstimulation syndrome: A controlled clinical study

The aim of the present pilot study was to assess the feasibility and efficacy of Cetrotide administration in the early luteal phase in patients at high risk of ovarian hyperstimulation syndrome (OHSS), undergoing embryo cryopreservation following superovulation. A total of 135 patients at high risk of OHSS and undergoing embryo cryopreservation were divided into two groups. In the treatment group (n=39), the patients received daily subcutaneous injections of 0.25 mg Cetrotide between days 1 and 5 following ooctye retrieval, and volume expansion and symptomatic treatment were also provided. In the control group (n=96), the patients received routine treatments, including volume expansion therapy. The serum steroid hormone concentrations of the patients were measured on days 2, 5 and 8 following ooctye retrieval, while the incidence of moderate or severe OHSS, self-evaluated clinical symptoms and various clinical indicators were recorded. The serum estradiol (E₂), luteinizing hormone and progesterone levels in the treatment group on days 2, 5 and 8 following oocyte retrieval were not found to differ significantly when compared with the patients in the control group (P>0.05). The incidence of severe OHSS did not differ significantly between the two groups (P>0.05). The average length of hospital stay and length of luteal phase were not found to be significantly different between the treatment and control groups (P>0.05). In conclusion, Cetrotide injections in the early luteal phase did not alter the serum steroid levels of patients at high risk of OHSS undergoing embryo cryopreservation, and were unable to reduce the incidence of severe early OHSS. However, further randomized studies are required to evaluate the effectiveness of Cetrotide in the prevention of OHSS.

Ovarian hyperstimulation syndrome inhibition by targeting VEGF, COX-2 and calcium pathways: a preclinical randomized study

OBJECTIVE

The efficacy of vascular endothelial growth factor (VEGF), COX-2, calcium and aromatase inhibitors in an ovarian hyperstimulation syndrome (OHSS) rat model was tested.

METHODS

One hundred and eight female Wistar rats were randomly divided in nine groups. The control group received saline, while the OHSS group received rec-FSH for 4 consecutive days. The other seven groups received rec-FSH (4d) and Bevacizumab twice, Parecoxib daily, Verapamil daily, Parecoxib daily and Bevacizumab twice, Verapamil daily and Bevacizumab twice, Parecoxib and Verapamil daily, Letrozole and Meloxicam daily, respectively. All groups received also hCG at the 5th day.

RESULTS

All intervention groups were characterized by reduced vascular permeability compared to the OHSS group, which in the groups of Verapamil (Calcium inhibition) and Parecoxib + Verapamil (COX-2 + Calcium inhibition) presented significant statistical difference. The Verapamil group showed the lowest corpus luteum formation, while the Parecoxib (COX-2 inhibition), the Parecoxib + Verapamil (COX-2 + Calcium inhibition), the Bevacizumab + Parecoxib (VEGF + COX-2 inhibition) and the Bevacizumab + Verapamil (VEGF + Calcium inhibition) groups were also characterized by lower corpus luteum numbers compared to the OHSS group. Furthermore, lower graafian follicle formation was observed in the above groups, while the ovarian weight and the hormonal profile were not significantly affected.

CONCLUSIONS

Studying the different check points of the VEGF pathway, we conclude that targeting calcium pathways could be beneficial for the vascular permeability control in an OHSS animal model.

Pharmaceutical options for triggering of final oocyte maturation in ART

Since the pioneering days of in vitro fertilization, hCG has been the gold standard to induce final follicular maturation. We herein reviewed different pharmaceutical options for triggering of final oocyte maturation in ART. The new upcoming agent seems to be GnRHa with its potential advantages over hCG trigger. GnRHa triggering elicits a surge of gonadotropins resembling the natural midcycle surge of gonadotropins, without the prolonged action of hCG, resulting in the retrieval of more mature oocytes and a significant reduction in or elimination of OHSS as compared to hCG triggering. The induction of final follicular maturation using GnRHa represents a paradigm shift in the ovulation triggering concept in ART and, thus, a way to develop a safer IVF procedure. Kisspeptins are key central regulators of the neuroendocrine mechanisms of human reproduction, who have been shown to effectively elicit an LH surge and to induce final oocyte maturation in IVF cycles. This new trigger concept may, therefore, offer a completely new, "natural" pharmacological option for ovulation induction. Whether kisspeptins will be the future agent to trigger ovulation remains to be further explored.

Current evidence supporting "letrozole" for ovulation induction

Aromatase inhibitor “letrozole” was first introduced as a potential ovulation induction (OI) drug almost a decade back. Large number of studies has been published using letrozole for OI: In polycystic ovary syndrome (PCOS) women, clomiphene citrate (CC) resistant women, for intrauterine insemination and also in various protocols of mild stimulation for in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI). Letrozole appears to be a good option, with its oral route of administration, cost, shorter half-life and negligible side effects. However, the verdict on efficacy and safety of letrozole is still uncertain. This review explores the current scientific data supporting letrozole for OI.

The use of aromatase inhibitors in in vitro fertilization

The use of aromatase inhibitors (AIs) in IVF patients remains controversial. AIs can be considered for ovulation induction for IVF in women who are normal and poor responders, are at risk of ovarian hyperstimulation syndrome or thrombosis, who have endometriosis, and/or are undergoing fertility preservation procedures as a result of estrogen-dependent cancers, primarily breast and endometrial cancers. Although the biologic plausibility of the capacity of AIs in IVF patients is promising, results should be interpreted with caution, because the efficacy of AIs needs to be proven in randomized trials.

Endometrial gene expression in the early luteal phase is impacted by mode of triggering final oocyte maturation in recFSH stimulated and GnRH antagonist co-treated IVF cycles

STUDY QUESTION

Do differences in endometrial gene expression exist after ovarian stimulation with four different regimens of triggering final oocyte maturation and luteal phase support in the same patient?

SUMMARY ANSWER

Significant differences in the expression of genes involved in receptivity and early implantation were seen between the four protocols.

WHAT IS KNOWN ALREADY

GnRH agonist triggering is an alternative to hCG triggering in GnRH antagonist co-treated cycles, resulting in an elimination of early ovarian hyperstimulation syndrome. Whereas previous studies have revealed a low ongoing clinical pregnancy rate after GnRH agonist trigger due to a high early pregnancy loss rate, despite supplementation with the standard luteal phase support, more recent studies, employing a 'modified' luteal phase support including a bolus of 1500 IU hCG on the day of oocyte aspiration, have reported ongoing pregnancy rates similar to those seen after hCG triggering.

STUDY DESIGN, SIZE DURATION

A prospective randomized study was performed in four oocyte donors recruited from an oocyte donation program during the period 2010-2011.

PARTICIPANTS, MATERIALS, SETTING, METHODS

Four oocyte donors in a university IVF center each prospectively underwent four consecutive stimulation protocols, with different modes of triggering final oocyte maturation and a different luteal phase support, followed by endometrial biopsy on Day 5 after oocyte retrieval. The following protocols were used: (A) 10 000 IU hCG and standard luteal phase support, (B) GnRH agonist (triptorelin 0.2 mg), followed by 1500 IU hCG 35 h after triggering final oocyte maturation, and standard luteal phase support, (C) GnRH agonist (triptorelin 0.2 mg) and standard luteal phase support and (D) GnRH agonist (triptorelin 0.2 mg) without luteal phase support. Microarray data analysis was performed with GeneSpring GX 11.5 (RMA algorithm). Pathway and network analysis was performed with the gene ontology software Ingenuity Pathways Analysis (Ingenuity® Systems, www.ingenuity.com, Redwood City, CA, USA). Samples were grouped and background intensity values were removed (cutoff at the lowest 20th percentile). A one-way ANOVA test (P< 0.05) was performed with Benjamini-Hochberg multiple testing correction.

MAIN RESULTS

Significant differences were seen in endometrial gene expression, related to the type of ovulation trigger and luteal phase support. However, the endometrial gene expression after the GnRH agonist trigger and a modified luteal phase support (B) was similar to the pattern seen after the hCG trigger (A).

LIMITATIONS, REASONS FOR CAUTION

The study was performed in four oocyte donors only; however, it is a strength of the study that the same donor underwent four consecutive stimulation protocols within 1 year to avoid inter-individual variations.

WIDER IMPLICATIONS OF THE FINDINGS

These endometrial gene-expression findings support the clinical reports of a non-significant difference in live birth rates between the GnRH agonist trigger and the hCG trigger, when the GnRH agonist trigger is followed by a bolus of 1500 IU hCG at 35 h post trigger in addition to the standard luteal phase support.

STUDY FUNDING/ COMPETING INTERESTS

This study was supported by an un-restricted research grant by MSD Belgium.

TRIAL REGISTRATION NUMBER

EudraCT number 2009-009429-26, protocol number 997 (P06034).

Aromatase inhibitors in stimulated IVF cycles

Aromatase inhibitors have been introduced as a new treatment modality that could challenge clomiphene citrate as an ovulation induction regiment in patients with PCOS. Although several randomized trials have been conducted regarding their use as ovulation induction agents, only few trials are available regarding their efficacy in IVF stimulated cycles. Current available evidence support that letrozole may have a promising role in stimulated IVF cycles, either when administered during the follicular phase for ovarian stimulation. Especially for women with poor ovarian response, letrozole appears to have the potential to increase clinical pregnancy rates when combined with gonadotropins, whereas at the same time reduces the total gonadotropin dose required for ovarian stimulation. However, given that in all of the trials letrozole has been administered in GnRH antagonist cycles, it is intriguing to test in the future how it may perform when used in GnRH agonist cycles. Finally administration of letrozole during luteal phase in IVF cycles offers another treatment modality for patients at high risk for OHSS taking into account that it drastically reduces estradiol levels.

GnRH agonist for triggering of final oocyte maturation: time for a change of practice?

BACKGROUND

GnRH agonist (GnRHa) triggering has been shown to significantly reduce the occurrence of ovarian hyperstimulation syndrome (OHSS) compared with hCG triggering; however, initially a poor reproductive outcome was reported after GnRHa triggering, due to an apparently uncorrectable luteal phase deficiency. Therefore, the challenge has been to rescue the luteal phase. Studies now report a luteal phase rescue, with a reproductive outcome comparable to that seen after hCG triggering.

METHODS

This narrative review is based on expert presentations and subsequent group discussions supplemented with publications from literature searches and the authors' knowledge. Moreover, randomized controlled trials (RCTs) were identified and analysed either in fresh IVF cycles with embryo transfer (ET), oocyte donation cycles or cycles without ET; risk differences were calculated regarding pregnancy rate and OHSS rate.

RESULTS

In fresh IVF cycles with ET (9 RCTs) no OHSS was reported after GnRHa triggering [0% incidence in the GnRHa group: risk difference 5% (with 95% CI: -0.07 to 0.02)]. Importantly, the delivery rate improved significantly after modified luteal support [6% risk difference in favour of the HCG group (95% CI: -0.14 to 0.2)] when compared with initial studies with conventional luteal support [18% risk difference (95% CI: -0.36 to 0.01)]. In oocyte donation cycles (4 RCTs) the OHSS incidence is 0% [10% risk difference (95% CI: 0.02-0.40)].

CONCLUSIONS

GnRHa triggering is a valid alternative to hCG triggering, resulting in an elimination of OHSS. After modified luteal support there is now a non-significant difference of 6% in delivery rate in favour of hCG triggering.