Aromatase inhibitor letrozole: a novel treatment for ectopic pregnancy

Comparing the effectiveness of letrozole versus methotrexate for treatment of ectopic pregnancy: A randomized controlled trial

OBJECTIVE

To evaluate the efficacy of two different regimens of Letrozole, an aromatase inhibitor, in the management of ectopic pregnancy compared to methotrexate.

STUDY DESIGN

This randomized controlled trial was conducted on 88 women diagnosed with ectopic pregnancy with a baseline level of serum beta-human chorionic gonadotropin under 3000 mIU/mL between June 30, 2023, and December 30, 2023, at the Department of Obstetrics and Gynecology of the Vali-e-Asr Hospital affiliated with Tehran University of Medical Sciences. Participants were allocated into either methotrexate (n = 43), 5-day course Letrozole (n = 24), or 10-day course Letrozole (n = 21) treatments. The methotrexate group received a single dose of 50 mg/m2 dosage intramuscular methotrexate. The 5-day Letrozole group received a 2.5 mg Letrozole tablet three times daily for 5 days, whereas the 10-day Letrozole group received a 2.5 mg Letrozole tablet twice daily for 10 days. The primary outcome was the treatment response, defined as the achievement of a negative serum beta-human chorionic level without the need for additional methotrexate treatment or surgery. The secondary outcomes were the need for additional methotrexate dose or laparoscopic surgery intervention. The trial protocol was prospectively registered in ClinicalTrials.gov with code NCT05918718.

RESULTS

The treatment response rates in methotrexate, 5-day Letrozole, and 10-day Letrozole groups were 76.7 %, 75.0 %, and 90.5 %, respectively, with no significant differences between the groups (P-value = 0.358). A total of 10 (23.3 %) patients from the methotrexate group, 3 (12.5 %) from the 5-day Letrozole group, and 2 (9.5 %) from the 10-day Letrozole group required an additional methotrexate dose, with no significant differences between the groups (P-value = 0.307). Furthermore, only 3 (12.5 %) patients, all from the 5-day Letrozole group, were suspected of tubal rupture and underwent surgery (P-value = 0.016).

CONCLUSION

Our findings suggest Letrozole as a safe alternative to methotrexate in treating stable ectopic pregnancies, with a favorable treatment response rate. However, there is still a need for future larger studies to determine the applicability of Letrozole in the EP management. Also, the non-significant higher effectiveness of the 10-day Letrozole regimen than the 5-day Letrozole group underscores the need for future research to determine the optimal Letrozole regimen for the management of ectopic pregnancy.

Effect of Aromatase Inhibitor Letrozole on the Placenta of Adult Albino Rats: A Histopathological, Immunohistochemical, and Biochemical Study

Background

Letrozole, an aromatase inhibitor, has recently been introduced as the preferred treatment option for ectopic pregnancy. To date, no study has investigated the effect of letrozole alone on placental tissue. The present study aimed to evaluate the effect of different doses of letrozole on the placenta of rats and to clarify the underlying mechanism.

Methods

Sixty pregnant female rats were equally divided into three groups, namely the control group (GI), low-dose (0.5 mg/Kg/day) letrozole group (GII), which is equivalent to the human daily dose (HED) of 5 mg, and high-dose (1 mg/Kg/day) letrozole group (GIII), equivalent to the HED of 10 mg. Letrozole was administered by oral gavage daily from day 6 to 16 of gestation. Data were analyzed using a one-way analysis of variance followed by Tukey's post hoc test and Chi square test. P<0.05 was considered statistically significant.

Results

Compared to the GI and GII groups, high-dose letrozole significantly increased embryonic mortality with a high post-implantation loss rate (P<0.001) and significantly reduced the number of viable fetuses (P<0.001) and placental weight (P<0.001) of pregnant rats. Moreover, it significantly reduced placental estrogen receptor (ER) and progesterone receptor (PR) (P<0.001) and the expression of vascular endothelial growth factor (P<0.001), while increasing the apoptotic index of cleaved caspase-3 (P<0.001).

Conclusion

Letrozole inhibited the expression of ER and PR in rat placenta. It interrupted stimulatory vascular signals causing significant apoptosis and placental vascular dysfunction. Letrozole in an equivalent human daily dose of 10 mg caused a high post-implantation loss rate without imposing severe side effects.

Future Perspectives of Ectopic Pregnancy Treatment-Review of Possible Pharmacological Methods

Ectopic pregnancy, that is, a blastocyst occurring outside the endometrial cavity of the uterus, affects nearly 2% of pregnancies. The treatment of ectopic pregnancy is surgical or pharmacological. Since surgical management is associated with numerous serious side effects, conservative treatment is sought. The treatment of choice in the majority of cases is based on pharmacotherapy with methotrexate (MTX) in a single- or multi-dose regimen. Although the efficacy of methotrexate reaches between 70 and 90%, its use requires specific conditions regarding both the general condition of the patient and the characteristic features of the ectopic pregnancy. Moreover, MTX can cause severe adverse effects, including stomatitis, hepatotoxicity and myelosuppression. Therefore, clinicians and researchers are still looking for a less toxic, more effective treatment, which could prevent surgeries as a second-choice treatment. Some studies indicate that other substances might constitute a good alternative to methotrexate in the management of ectopic pregnancies. These substances include aromatase inhibitors, especially letrozole. Another promising substance in EP treatment is gefitinib, an inhibitor of EGFR tyrosine domain which, combined with MTX, seems to constitute a more effective alternative in the management of tubal ectopic pregnancies. Other substances for local administration include KCl and absolute ethanol. KCl injections used in combination with MTX may be used when foetal heart function is detected in cervical ectopic pregnancies, as well as in heterotopic pregnancy treatment. Absolute ethanol injections proved successful and safe in caesarean scar pregnancies management. Thus far, little is known about the use of those substances in the treatment of ectopic pregnancies, but already conducted studies seem to be promising.

Evaluation of Different Doses of the Aromatase Inhibitor Letrozole for the Treatment of Ectopic Pregnancy and Its Effect on Villous Trophoblastic Tissue

Letrozole, an aromatase inhibitor, has recently been introduced as a favorable medical treatment for ectopic pregnancy. We aimed at evaluating the effects of different doses of letrozole for termination of ectopic pregnancy and study their effects on villous trophoblastic tissue. Sixty patients with undisturbed ectopic pregnancy were classified into three equal groups. Group I: the control group that contained women who underwent laparoscopic salpingectomy, Group II: patients who received letrozole (5 mg day⁻¹) for 10 days, and Group III: patients who received letrozole (10 mg day⁻¹) for 10 days. Subsequently, the β-hCG levels were determined on the first day and after 11 days of treatment. Group IV consisted of patients of GII and GIII; their β-hCG did not drop below 100 mIU/ml within 11 days, and underwent salpingectomy. Placental tissues from patients undergoing salpingectomy either from the control group or GIV were processed for the evaluation of estrogen (ER) and progesterone (PR) receptors, vascular endothelial growth factor (VEGF), and cleaved caspase 3 (CC-3) expression. Cases exposed to high dose letrozole 10 mg day⁻¹ resulted in a higher ectopic pregnancy resolution rate of 85% (17/20), while the resolution rate of the low dose letrozole-treated group (5 mg day⁻¹) was 65% (13/20), and also showed a significant reduction in β-hCG levels on the 11th day, 25.63 ± 4.29 compared to the low dose letrozole group 37.91 ± 7.18 (P < 0.001), Meanwhile, the letrozole-treated group GIV showed markedly reduced expression of ER, PR, and VEGF and a significant increase in the apoptotic index cleaved caspase-3 compared to the control group (P < 0.001). The utilization of letrozole at a dose of 10 mg day⁻¹ for medical treatment of ectopic pregnancy results in a high-successful rate without any severe side effects. Letrozole depriving the placenta of estrogen that had vascular supporting signals resulted in destroying the vascular network with marked apoptosis.

Cancer and Pregnancy: A Comprehensive Review

Cancer diagnosis and treatment in pregnant women is a challenging situation. A multidisciplinary network of specialists is required to guide both, the expecting mother and the unborn child through the diagnostic workup and the cytotoxic therapy, by balancing the respective risks and benefits. Tumor entity, stage, biology and gestational week at diagnosis determine the appropriate approach. As premature delivery emerged as one of the main risk factors for adverse long-term outcome of the progeny, it should be avoided, if reasonable from the oncological perspective. This article offers a comprehensive review with respect to the various aspects of cancer in pregnancy.