The VEGF and PEDF levels in the follicular fluid of patients co- treated with LETROZOLE and gonadotropins during the stimulation cycle

Impact of 2.5 mg versus 5 mg letrozole co-treatment in an antagonist protocol for IVF: a retrospective study

Objective

The present study aimed to compare the effectiveness of two different doses of letrozole (2.5 mg and 5 mg daily) in an antagonist protocol for infertile women with normal ovarian reserve.

Methods

This retrospective cohort study included infertile women who underwent in vitro fertilization treatment with letrozole co-treatment at doses of 2.5 mg and 5 mg from 2007 - 2021 at Shanghai Ninth People's Hospital (Shanghai, China). The control group comprised infertile women who received gonadotropin-releasing hormone antagonist alone. The primary outcome was the cumulative live birth rate, while secondary outcomes included follicular phase endocrine parameters, ovarian stimulation outcomes, pregnancy outcomes, and the incidences of maternal and neonatal complications. Baseline and follow-up data were compared between the groups using ANOVA for normally distributed variables, the Kruskal-Wallis test for non-normally distributed variables, and the Chi-square test for categorical variables.

Results

A total of 422 participants were enrolled in the study, with 211 women in the antagonist group, 109 women in the 2.5 mg letrozole co-treatment group, and 102 women in the 5 mg letrozole co-treatment group. Letrozole co-treatment significantly suppressed oestradiol and follicle-stimulating hormone concentrations from stimulation day 5 and onwards, while increasing luteinizing hormone levels on stimulation day 5 and trigger day. The effect was more pronounced with a 5 mg dose of letrozole compared to a 2.5 mg dose (P < 0.05). Administration of 5 mg letrozole reduced the gonadotropin dose (P < 0.05) without negatively affecting the number of oocytes retrieved and subsequent embryo parameters (P > 0.05). The analysis of cumulative live birth rates showed rates of 29.4% in the letrozole 5 mg group, 27.5% in the letrozole 2.5 mg group, and 33.6% in the control group, with no statistically significant difference (P > 0.05). There were no reported pregnancy complications in the two letrozole groups. Additionally, there were no significant differences among the three groups in terms of gestational age and birth weight for both singleton and twin births.

Conclusion

This study indicates that the administration of letrozole in an antagonist protocol, at both 2.5 mg and 5 mg dosages, results in comparable clinical outcomes.

The impact of letrozole on oocyte quality in assisted reproductive technology (ART); a randomized double-blind clinical trial

OBJECTIVE

To examine the effect of letrozole on oocyte quality and pregnancy outcome in assisted reproductive technology (ART).

METHODS

This double blind placebo controlled clinical trial was conducted in Vali-Asr Infertility Center. Infertile women candidate for IVF that underwent antagonist protocol were selected. Eligible women randomly allocated into treatment (letrozole/Let group) and control (placebo) group. Participants received letrozole 5 mg/day or placebo at the time of gonadotropin start until trigger day in the same manner. Number of oocyte retrieved, metaphase II oocyte number, high grade oocyte number (G1), high quality embryo, Chemical and clinical pregnancy rate and OHSS (ovarian hyperstimulation syndrome) rate was recorded. 216 infertile women (104 in letrozole and 112 in the control group) were evaluated.

RESULTS

In the Let group estradiol level was significantly lower (p_value < .001) and testosterone significantly higher than in the control group (p_value = .02). The number of retrieved oocytes, MII oocytes, G1 oocytes, and 2PN was significantly lower in the Let group (p < .05). No significant difference was found in the day of stimulation, total gonadotropin dose, OHSS rate, and clinical pregnancy rate between the two groups (p > 0.05).

CONCLUSIONS

According to the results, letrozole may reduce oocyte quality and cause poor IVF outcomes as well.

Ginkgo biloba extract 761 reduces vascular permeability of the ovary and improves the symptom of ovarian hyperstimulation syndrome in a rat model

AIMS

Ginkgo biloba extract (EGb) has been widely applied in the treatment of cerebrovascular and neurological diseases. However, the effect of EGb761 on ovarian hyperstimulation syndrome (OHSS), a vascular disorder and life-threatening complication of in vitro fertilization and intracytoplasmic sperm injection therapy (IVF/ICSI), has not been evaluated.

MATERIALS AND METHODS

Forty female Wistar rats aged 22-days old (D22) were divided into eight groups: Control rats received intraperitoneal injection of saline for five consecutive days (D22-D26); OHSS model group received 10 IU equine chorionic gonadotropin (eCG) for four consecutive days (D22-D25) and 30 IU of human chorionic gonadotropin (hCG) on the 5th day (D26); Prophylactic treatment group received three doses of EGb761 (50, 100, and 200 mg/kg/day) 1 h before injection of eCG (hCG) for seven consecutive days; Therapeutic treatment group received three doses of EGb761 (50, 100, and 200 mg/kg/day) 48 h after injection of eCG (hCG) for seven consecutive days.

RESULTS

All three doses of EGb761 therapeutic medication significantly reduced ovarian mass index of OHSS model rats (p ≤ .01). Furthermore, therapeutic treatment group exhibited improved vascular permeability, decreased estradiol and progesterone levels, lower corpus luteum, and higher follicle numbers compared with the OHSS model. Elevated protein expression of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) in both ovary and kidney of the OHSS model was restrained by EGb761 therapeutic treatment.

CONCLUSIONS

EGb761 therapeutic medication decreases vascular permeability in OHSS rat model by inhibiting VEGF and VEGFR expression, which may contribute to the treatment of OHSS.

Ginkgo biloba extract 761 reduces vascular permeability of the ovary and improves the symptom of ovarian hyperstimulation syndrome in a rat model

AIMS

Ginkgo biloba extract (EGb) has been widely applied in the treatment of cerebrovascular and neurological diseases. However, the effect of EGb761 on ovarian hyperstimulation syndrome (OHSS), a vascular disorder and life-threatening complication of In Vitro Fertilization and Intracytoplasmic Sperm Injection therapy (IVF/ICSI), has not been evaluated.

MATERIALS AND METHODS

Forty female Wistar rats aged 22-days old (D22) were divided into eight groups: Control rats received intraperitoneal injection of saline for 5 consecutive days (D22-D26); OHSS model group received 10 IU equine chorionic gonadotropin (eCG) for 4 consecutive days (D22-D25) and 30 IU of human chorionic gonadotropin (hCG) on the 5th day (D26); Prophylactic treatment group received three doses of EGb761 (50, 100, and 200 mg/kg/d) one hour before injection of eCG (hCG) for 7 consecutive days; Therapeutic treatment group received three doses of EGb761 (50, 100, and 200 mg/kg/d) 48 h after injection of eCG (hCG) for 7 consecutive days.

RESULTS

All three doses of EGb761 therapeutic medication significantly reduced ovarian mass index in the OHSS model (p ≤ .01). Further, the therapeutic treatment group exhibited improved vascular permeability, decreased estradiol and progesterone levels, lower corpus luteum, and higher follicle numbers compared with the OHSS model. Elevated protein expression of vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) in both ovary and kidney of the OHSS model was restrained by EGb761 therapeutic treatment.

CONCLUSIONS

EGb761 therapeutic medication decreases vascular permeability in OHSS rat model by inhibiting VEGF and VEGFR expression, which may contribute to the treatment of OHSS.

Pigment epithelium-derived factor negates oxidative stress in mouse oocytes

Molecular changes, caused by various environmental factors, affect the quality and developmental potential of oocytes. Oxidative stress (OS) is a major factor involved in various gynecologic disorders and/or in aging. Recent studies suggest that elevated reactive oxygen species (ROS) hamper oocyte quality and future embryonic development. Pigment epithelium-derived factor (PEDF) is a pleiotropic protein, known for its antiangiogenic, anti-inflammatory, and antioxidative properties. Our previous findings demonstrate the antioxidative role of rPEDF in maintaining granulosa cell viability. In the current study, we examined the ability of PEDF to negate the adverse impact of OS on oocytes. Maturation rate of oocytes exposed to OS was significantly lower than that of control oocytes. The number of mtDNA copies in OS-exposed oocytes was significantly higher than in control oocytes (>3 times), whereas ATP concentration was significantly lower. Oocytes exposed to OS demonstrated impaired chromosome arrangement at the metaphase plate. PEDF significantly improved maturation rate of untreated OS-exposed oocytes. Moreover, mtDNA copy number, ATP concentration, and chromosome arrangement at the metaphase plate in rPEDF-treated OS-exposed oocytes were restored to the level of control oocytes. Our findings demonstrate that OS hampers the ability of oocytes to undergo proper in vitro maturation. The energetic balance of OS-exposed oocyte is characterized by excessive mtDNA replication and reduced ATP concentration; it hampers the ability of oocytes to perform high fidelity chromosome segregation. PEDF alleviates this damage, improves the rate of oocyte maturation, and preserves mtDNA level and ATP content, thus enabling oocytes to form proper metaphase plate and improve oocyte competence.

Severe hemoperitoneum resulting from restart of letrozole after oocyte retrieval procedure: a case report

BACKGROUND

In the field of oncofertility, patients with breast cancer are often administered letrozole as an adjuvant drug before and after oocyte retrieval to prevent an increase in circulating estradiol.

CASE PRESENTATION

We report a case of abdominal hemorrhage due to an ovarian rupture in a 29-year-old Japanese patient who restarted letrozole 2 days after an oocyte retrieval procedure in which 14 mature oocytes were retrieved. The patient had sought embryo cryopreservation as a fertility preservation option before undergoing treatment for recurrent breast cancer. A day after restarting letrozole treatment, the patient unexpectedly developed severe abdominal pain. Laparoscopic hemostasis was performed to manage the ovarian swelling and hemorrhage.

CONCLUSIONS

The ovaries can be restimulated by restart letrozole after an oocyte retrieval procedure. Therefore, reproductive-medicine practitioners should understand the potential complications of letrozole administration in such cases and take steps to ensure that they are minimized.

Investigating apoptotic, inflammatory, and growth markers in poor responders undergoing natural in vitro fertilization cycles: a pilot study

This study investigates follicular fluid (FF) from patients with poor and normal ovarian response undergoing natural assisted reproductive technology cycles. We report about (1) cell-free DNA (cfDNA), which reflects apoptosis; (2) corticotropin-releasing hormone (CRH); (3) interleukin (IL)-15, which reflects inflammation; (4) granulocyte colony-stimulating factor (G-CSF); (5) vascular endothelial growth factor (VEGF); and (6) insulin-like growth factor I (IGF-I), which reflects follicular growth. Forty-four poor responders and 44 normal responders-according to the Bologna criteria-were recruited. FF samples were prepared for cfDNA quantification employing Q-PCR and for CRH, IL-15, G-CSF, VEGF, and IGF-I quantification employing ELISA. Statistically nonsignificant different levels of FF cfDNA, CRH, IL-15, VEGF, and IGF-I were observed. Interestingly, statistically significant higher G-CSF levels were observed in normal responders (302.48 ± 474.36 versus 200.10 ± 426.79 pg/mL, P = 0.003). Lower cfDNA integrity was observed in cycles resulting in clinical pregnancy for both groups (normal: 0.07 ± 0.04 versus 0.25 ± 0.17 ng/μL, P < 0.001; poor: 0.10 ± 0.06 versus 0.26 ± 0.12 ng/μL, P < 0.001). The results predominantly showcase similarities between normal and poor responders pertaining to inflammatory, apoptotic, and growth factors. This may be attributed to the employment of natural cycles in order to exclude controlled ovarian stimulation as a factor-indicating its detrimental effect. As G-CSF levels presented significantly higher in normal responders, its vital role in understanding a compromised ovarian response is highlighted.

Efficacy and Safety of Controlled Ovarian Stimulation With or Without Letrozole Co-administration for Fertility Preservation: A Systematic Review and Meta-Analysis

Background: The co-administration of letrozole during controlled ovarian stimulation (COS) with gonadotropins is used to limit the potentially harmful effects of a supra-physiological rise in estrogen levels on hormone-sensitive cancers. However, the efficacy and safety of adding letrozole to COS remain debated.

Methods: This is a systematic review and meta-analysis of published studies that compared the efficacy and safety of COS with co-administration of letrozole vs. COS without letrozole in all patient populations. A secondary analysis was done including only the studies in breast cancer patients. The primary efficacy endpoint was the number of retrieved mature Metaphase II (MII) oocytes. Secondary efficacy and safety endpoints were total number of oocytes, maturation rate, fertilization rate, number of cryopreserved embryos, peak estradiol levels, progesterone levels, and total gonadotropin dose. Data for each endpoint were reported and analyzed thorough mean ratio (MR) with 95% confidence interval (CI).

Results: A total of 11 records were selected including 2,121 patients (990 patients underwent COS with letrozole and 1,131 COS without letrozole). The addition of letrozole to COS did not have any negative effect on the number of mature oocytes collected (MR = 1.00, 95% CI = 0.87–1.16; P = 0.967) and the other efficacy endpoints. COS with letrozole was associated with significantly decreased peak estradiol levels (MR = 0.28, 95% CI = 0.24–0.32; P < 0.001). Similar results were observed in the secondary analysis including only breast cancer patients.

Conclusions: These findings are reassuring on the efficacy and safety of COS with gonadotropins and letrozole and are particularly important for fertility preservation in women with hormone-sensitive cancers.

A review of the physiology behind letrozole applications in infertility: are current protocols optimal?

Letrozole is a targeted aromatase inhibitor which has primarily been used in post-menopausal women with breast cancer. Recently, it has been utilized in infertile pre-menopausal women because of its ability to enhance FSH production for ovulation induction. However, the ovarian follicle’s response to FSH is only a part of the endocrine events occurring in a developing follicle. The health of the small antral follicles is driven primarily by androgens, which contribute to granulosa cell mitosis, sensitivity to FSH, and resistance to atresia. In contrast, elevated androgens in the late antral to pre-ovulatory follicle have a negative impact on follicle health and lead to atresia and cystic follicle formation. This ovarian physiologic data suggests that current applications of letrozole to infertility may be squandering some of the primary benefits available in using letrozole to promote follicle development. Four applications of letrozole to infertility that have appeared in the medical literature are reviewed. Androgen-related benefits are reviewed and various questions put forward about how letrozole could be more effectively used to help patients in these settings.

An attempt to potentiate the ovarian superstimulatory response in cattle by co-treatment with an aromatase inhibitor

Letrozole is used for the treatment of subfertility in women undergoing ovarian superstimulation, but the mechanism of action has not been investigated critically. The objective was to test the hypothesis that treatment with letrozole will potentiate the superstimulatory response following gonadotropin treatment by increasing the number of follicles present at ovarian follicular wave emergence in cattle. In Experiment 1, ovarian follicular wave emergence was synchronized among beef heifers (n = 8) by transvaginal ultrasound-guided follicle ablation. On Day 0 (wave emergence), a letrozole-releasing device (LRD) was placed intravaginally for 5 days, followed again by transvaginal follicle ablation on Day 5. The number of follicles ≥3 mm was recorded by transrectal ultrasonography on Days 0 and 6.5 (i.e., pre- vs. post-LRD treatment). In Experiment 2, non-lactating dairy cows were assigned randomly to one of two groups (n = 15/gp) after follicle ablation-induced synchronization of wave emergence (Day 0), and given either an LRD or sham device for 5 days. Superstimulatory treatment was initiated on Day 0, consisting of 8 doses of 50 mg of porcine FSH im at 12 h intervals, and luteolytic doses of prostaglandin on Days 3 and 3.5. The LRD/sham devices were removed on Day 3.5, GnRH was given im on Day 5, estrus response was determined on Days 5 and 6, and the ovarian response was recorded by ultrasonography on Days 0, 3.5, 5, 6.5, and 12. In Experiment 1, no difference was detected in the number of antral follicles at wave emergence pre- vs. post-LRD treatment (23.2 ± 3.2 vs. 23.5 ± 3.8 follicles; P = 0.67; mean ± SEM). In Experiment 2, the interval from prostaglandin treatment to estrus was longer (50.3 ± 1.1 vs. 40.7 ± 2.0 h; P < 0.001) and less variable (residuals: 3.1 ± 0.5 vs. 6.7 ± 0.9 h; P < 0.01) in the LRD vs. sham group. The proportion of ovulations (number of CL on Day 12 over the number of follicles ≥3 mm on Day 0) did not differ (0.65 ± 0.02 vs. 0.70 ± 0.02; P = 0.15) nor did the number of CL on Day 12 (15.9 ± 2.5 vs. 19.0 ± 2.0; P = 0.32) between the LRD and sham groups. In summary, treatment with letrozole did not increase the number of antral follicles at wave emergence or the superstimulatory response, but increased precision in the interval to estrus and may be useful for artificial insemination at a fixed time in superstimulatory protocols.

Effect of adding letrozole to gonadotropin on in vitro fertilization outcomes: An RCT

Background

Aromatase inhibitors prevent the aromatization of androgens into estrogens, which reduces the negative feedback of estrogen on the hypothalamic-pituitary axis. It is clear that increasing the secretion of follicle-stimulating hormones results in an increased follicular growth.

Objective

This study aimed to evaluate the effect of adding letrozole to gonadotropin on in vitro fertilization outcomes in normal responders.

Materials and Methods

In this randomized clinical trial, 100 normal responder women candidate for controlled ovarian stimulation were randomly enrolled in two groups (n = 50/each). In the case group letrozole was added to gonadotropin in the antagonist protocol. The control group received the conventional antagonist protocol. The main outcome was clinical and chemical pregnancy; and the second outcomes were the number of mature oocytes, the fertilization rate, estradiol level, and the total dose of gonadotropins.

Results

Basic clinical and demographic features were comparable between the groups. Estradiol level on the day of human-chorionic-gonadotropin administration and the total gonadotropin consumption were significantly higher in the control group than the case group (p = 0.045). In addition, the number of MII oocytes was higher (but not significantl) in the case group than the control group (p = 0.09). Moreover, the endometrial thickness was significantly lower in the case group. There were no significant differences in fertilization rate and chemical and clinical pregnancy rates between the two groups.

Conclusion

Although adding letrozole to gonadotropin in normal responders reduces the total dose of gonadotropin, it does not improve the pregnancy outcomes.

The role of Letrozole (LE) in controlled ovarian stimulation (COS) in patients at high risk to develop ovarian hyper stimulation syndrome (OHSS). A prospective randomized controlled pilot study

BACKGROUND

Recently, it has been shown that PCOS patients with extremely high anti-Mullerian hormone (AMH) level are more likely to experience OHSS during IVF, compared to PCOS patients with lower AMH level. While recent data questioned the effect of Letrozole (LE) on the occurrence of OHSS in non-PCOS patients, it role in PCOS patients with very high AMH level was never investigated in a prospective manners. Hence, our main objective was to evaluate the clinical outcome of PCOS patients at very high risk for OHSS undergoing two different COS protocols (with or without LE).

METHODS

A prospective randomized controlled study (RCT) of 51 patients with specifically high levels of AMH undergoing one of two COS protocols. The control group (group A) consisted of 24 PCOS women who received low-dose gonadotropins using the multiple-dose GnRH-antagonist protocol, GnRH agonist-triggered and "freeze all". The study group (group B) consisted of 24 women with PCOS who received the same protocol combined with LE. High risk criteria for OHSS were: PCOS patients with low BMI, young age, and extremely high level of serum AMH (inclusion criteria for AMH > 50 pmol/L).

RESULTS

Cumulative live birth rates per retrieval were similar in both groups. While no single case of severe OHSS was observed in, in the study group (group B), the rate of moderate and mild OHSS was 5 times lower compared to the control group (P < 0.05).

CONCLUSION

In PCOS patients with extremely high AMH levels the LE co-administration to GnRH-Ant protocols results in reduced incidence of OHSS than conventional GnRH-Ant protocols. LE co-administration may prove to be highly effective in preventing OHSS, even in the women who are at high risk to these dangerous complications.

Letrozole supplementation during controlled ovarian stimulation in expected high responders: a pilot randomized controlled study

BACKGROUND

Almost all of the previous studies related with co-administration of letrozole in IVF cycles were performed in poor responders and letrozole may reduce the total gonadotropin dose required for ovarian stimulation, and the pregnancy rate did not decrease in poor responders. This study aimed to assess whether high responders co-treatment with letrozole reduced supraphysiological late follicular phase estradiol levels and the incidence of premature progesterone elevated at the end of the follicular phase, thereby impacting positively on endometrial receptivity.

METHODS

A randomized parallel controlled study in a university-affiliated center include 130 high responders between October 2015 and August 2016. The patients were randomized on the first stimulation day of the IVF cycle and from stimulation day 5 receive letrozole (group A) or without letrozole treatment (group B).

RESULTS

Although estradiol levels were significantly lower in the letrozole group (group A) (P < 0.001), progesterone elevation (> 1.5 ng/mL was considered as a rise) on the day of hCG triggering (15.4, 7.7%) was not statistically significant (P = 0.170). RecFSH, the recovery rate of eggs, the high-quality embryo rate, and the thickness of endometrium (P = 0.776) were similar between the letrozole group(group A) and control groups (group B). Clinical pregnancy rates were 53.1% (26/49) and 72.9% (35/48) in the letrozole and control groups, respectively, with a statistical significance (P = 0.043).Live birth rates were 42.9% (21/49) and 62.5% (30/48),showed a marginally significant difference (P = 0.053). The miscarriage rate did not significantly differ between the two groups.

CONCLUSIONS

In this pilot study, letrozole supplementation could not reduce the incidence of premature progesterone rise during the late follicular phase in stimulated in vitro fertilization cycles in expected high responders, producing a harmful effect on the pregnancy outcome.

TRIAL REGISTRATION

China Clinical Trial Registration Center: ChiCTR-IPR-15006211 URL of the trial registry record: http://www.chictr.org.cn/showproj.aspx?proj=10731 . Trial registration date: 8 April, 2015. Date of first patient's enrolment: 5 October, 2015.

Concentration of stromal cell-derived factor-1 (SDF-1/CXCL12) in the follicular fluid is associated with blastocyst development

PURPOSE

To study the association between stromal cell-derived factor-1 (SDF-1/CXCL12) and vascular endothelial growth factor (VEGF) concentrations in individual human ovarian follicles and IVF outcomes.

METHODS

Concentrations of SDF-1 and VEGF in 261 follicular fluid samples were measured with enzyme-linked immunosorbent assay. IVF outcome parameters were included in fertilization rate, cleavage rate, embryo morphology on day 3, and blastocyst morphology on day 5.

RESULTS

The follicular concentration of SDF-1 and VEGF was not significantly associated with fertilization and cleavage outcome, and embryo morphology. The rates of full blastocysts and good-quality blastocysts were significantly higher in follicles with an SDF-1 concentration of 275-350 pg/mL than in the follicles with SDF-1 concentrations of <200 and ≥350 pg/mL (P < 0.05). The follicular concentration of VEGF was not associated with the blastocyst morphology.

CONCLUSION

Our findings showed that follicular concentration of SDF-1, and not VEGF, may be a valuable biochemical marker of blastocyst development.

Letrozole-associated controlled ovarian hyperstimulation in breast cancer patients versus conventional controlled ovarian hyperstimulation in infertile patients: assessment of oocyte quality related biomarkers

BACKGROUND

Fertility preservation (FP) protocols in case of breast cancer (BC) include mature oocyte cryopreservation following letrozole associated controlled ovarian hyperstimulation (Let-COH). To date, the impact of Let-COH on the follicular microenvironment has been poorly investigated, although a high androgen/estrogen ratio was previously associated with low oocyte quality.

METHODS

In this prospective study, follicular fluid (FF) steroid levels (estradiol, testosterone, progesterone) and cumulus cell (CC) gene expression related to oocyte quality (HAS2, PTGS2, GREM1) were compared between 23 BC patients undergoing Let-COH for FP and 24 infertile patients undergoing conventional COH without letrozole. All patients underwent an antagonist COH cycle, and ovulation was triggered with hCG or GnRHa in both groups.

RESULTS

FF estradiol levels were significantly lower while testosterone levels were significantly higher in the study group compared to controls irrespective of the trigger method. However, estradiol levels increased significantly with GnRHa triggering compared to hCG in the study group (median = 194.5 (95.4-438) vs 64.4 (43.8-152.4) ng/ml, respectively, p < 0.001), but not in the control group (median = 335.5 (177.5-466.7) vs 354 (179-511) ng/ml, respectively). After hCG trigger, Cumulus cell (CC) gene expression was lower in the study group compared to the control group, and difference was significant for PTGS2. Conversely, CC gene expression of PTGS2 and GREM1 was significantly higher in the study group compared to controls when ovulation was triggered with GnRHa.

CONCLUSIONS

Let-COH triggered with hCG may negatively impact oocyte quality. However, ovulation triggering with GnRHa may improve the oocyte microenvironment and cumulus cell genes expression in Let-COH, suggesting a positive impact on oocyte quality in breast cancer patients.

TRIAL REGISTRATION

Clinicaltrials.gov - NCT02661932 , registered 25 January 2016, retrospectively registered.