Letrozole and norethisterone acetate in rectovaginal endometriosis

A review of phase II and III drugs for the treatment and management of endometriosis

INTRODUCTION

Endometriosis is an estrogen-dependent disease that gives rise to pelvic pain and infertility. Although estroprogestins and progestins currently stand as the first-line treatments for this condition, demonstrating efficacy in two-thirds of patients, a significant portion of individuals experience only partial relief or symptom recurrence following the cessation of these therapies. The coexistence of superficial, deep endometriosis, and ovarian endometriomas, as three distinct phenotypes with unique pathogenetic and molecular characteristics, may elucidate the current heterogeneous biological response to available therapy.

AREAS COVERED

The objective of this review is to furnish the reader with a comprehensive summary pertaining to phase II-III hormonal treatments for endometriosis.

EXPERT OPINION

Ongoing research endeavors are directed toward the development of novel hormonal options for this benign yet debilitating disease. Among them, oral GnRH antagonists emerge as a noteworthy option, furnishing rapid therapeutic onset without an initial flare-up; these drugs facilitate partial or complete estrogen suppression, and promote prompt ovarian function recovery upon discontinuation, effectively surmounting the limitations associated with previously employed GnRH agonists. Limited evidence supports the use of selective estrogen and progesterone receptor modulators. Consequently, further extensive clinical research is imperative to garner a more profound understanding of innovative targets for novel hormonal options.

A Systematic Review of Systematic Reviews on the Use of Aromatase Inhibitors for the Treatment of Endometriosis: The Evidence to Date

Endometriosis is a chronic gynecologic condition that affects around 6-10% of reproductive age women. This clinical entity is characterized with pelvic pain, dysmenorrhea, dyspareunia, and infertility which are the most often presenting symptoms. Aromatase P450 is the key enzyme for ovarian estrogen biosynthesis and there is evidence that endometriotic lesions express aromatase and are able to synthesize their own estrogens. Aromatase inhibitors (AIs) are potent drugs that suppress the estrogen synthesis via suppression of aromatase. We performed a systematic review of systematic reviews and narrative reviews on the use of aromatase inhibitors in the medical management of endometriosis. We searched: PubMed (1950-2022), Google Scholar (2004-2022), Cochrane Library (2010-2022) and Researchgate (2010-2022). The search included the following medical subject headings (MeSH) or keywords: "Aromatase Inhibitors" AND "Endometriosis" AND "Systematic reviews" OR "Systematic review" AND "Reviews" OR "Reviews" AND "Endometriosis". The electronic database search yielded initially 12,106 studies from the different databases. Further assessment of the studies resulted in exclusion of (n = 12,015) studies due to duplicates and irrelevance; Finally, 24 studies were selected for inclusion, 5 were Systematic reviews and 19 were Narrative reviews. The 5 systematic reviews were assessed by AMSTAR-2 criteria and were found to have low quality. Narrative reviews were assessed with SANRA criteria and were found to have high-quality aromatase inhibitors are potent drugs that can manage the endometriosis-related symptoms in cases where initial medical management has failed to show positive results. However, their use is limited by the adverse effects that are linked with menopausal symptoms. aromatase inhibitors can be administered as an alternative treatment in patients. Future studies with randomized design are required to reach safer conclusions and further investigation. These studies should define the therapeutic dose, new add-back therapy modalities. Future directions should examine the most-appropriate way of administration and the duration of therapy.

Surgery vs. hormone-based treatment for pain control in deep infiltrating endometriosis: a retrospective cohort study

OBJECTIVE

To evaluate the outcome of surgical or hormone-based pharmacological treatment for deep infiltrating endometriosis (DIE) in patients with pain symptoms.

STUDY DESIGN

A retrospective cohort study of 122 women with DIE of the bowel was conducted: 61 women underwent surgical treatment due to poor pain control and 61 received hormone-based treatment alone for at least six months. Chronic pelvic pain, dysmenorrhea, deep dyspareunia, dyschezia and dysuria were evaluated by a visual analog scale (VAS) to measure pain on a scale from 0 to 10. Dyspareunia was further evaluated using the Deep Dyspareunia Scale (scores of 0-3).

RESULTS

Surgery (n = 61 women) was performed at a mean of 3.3 ± 1.6 years previously, while hormone-based treatment alone (n = 61 women) was used for a mean of 3.0 ± 1.41 years. After surgery, women without a desire to procreate received hormone-based treatment. Before treatment, the most intense endometriosis-related pain in the surgical treatment group and hormone-based treatment group alone were chronic pelvic pain (VAS = 9.48 ± 1.49; 8.57 ± 2.22), dysmenorrhea (VAS = 9.61 ± 1.45; 9.02 ± 1.35) and deep dyspareunia (VAS = 8.04 ± 2.82; 7.47 ± 3.21, respectively), all with mean pain scores of around 8 (0-10) in both groups. Both treatments were effective at reducing all symptoms (p < .001). The surgical treatment proved to be more effective and more enduring at improving chronic pelvic pain (p < .001), dyschezia (p = .003) and deep dyspareunia (p < .001). Regarding deep dyspareunia, using the deep dyspareunia scale, ∼70% of surgically treated women scored 0 or 1 (absent or mild deep dyspareunia) after treatment, compared to scores 2 or 3 (intense dyspareunia) in about 70% of the group using hormone-based treatment (p < .001).

CONCLUSION

Both types of treatment, surgical and pharmacological, effectively improved pain symptoms associated with DIE. However, improvement in chronic pelvic pain, dyschezia and deep dyspareunia was greater and longer-lasting after surgery.

Use of aromatase inhibitors in menopausal deep endometriosis: a case report and literature review

We report and review the clinical effectiveness of aromatase inhibitors in a patient with refractory, recurrent and infiltrating endometriosis. We demonstrate excellent clinical, radiological and endoscopic responses after failure of multiple other modalities. Our case and the literature show that single-agent letrozole is capable to treat deep infiltrative endometriosis involving the rectum and the urinary tract. The use of aromatase inhibitor treatment of endometriosis in postmenopausal women makes sense, is safe and is well tolerated. Difficult cases of deep infiltrative endometriosis might require use of combined surgical and medical treatment modalities. Multidisciplinary involvement of the gynecologist, bowel surgeon, urologist and invasive radiologist might be needed. Aromatase inhibitors should be considered to be an integral part of the armamentarium in the management of women with endometriosis, especially in refractory cases that have failed conventional therapeutic modalities.

Aromatase inhibitors for the treatment of endometriosis: a systematic review about efficacy, safety and early clinical development

INTRODUCTION

Pharmacotherapy has a key role in endometriosis treatment and management, however, a significant proportion of patients have only intermittent or limited benefits with current treatment options. Therefore, novel therapeutic approaches are necessary.

AREAS COVERED

This systematic review provides an overview of the efficacy and safety of aromatase inhibitors (AIs) as monotherapies and combination therapies for endometriosis. A systematic literature search was performed from January 1990 to April 2020 in the electronic database MEDLINE, EMBASE, The Cochrane Library, and Web of Science.

EXPERT OPINION

Based on the critical role of estrogens and the rate-limiting step in the production of the estrogens represented by the aromatase enzyme, AIs are a potential therapeutic option for women affected by endometriosis. Nevertheless, further research is needed to clarify the efficacy of AIs in this setting. Adverse effects need to be investigated to clarify the preventive role of add-back therapy. On that basis, AIs should be adopted only as second-line therapy in patients who are refractory to standard treatments in the setting of scientific research. Further studies should define best dosages, appropriate add-back therapies, administration routes, treatment length, and which patients may benefit more from AIs.

Advances in the medical management of bowel endometriosis

Endometriosis infiltrating the bowel can be treated medically in accurately selected women not seeking conception and without overt obstructive symptomatology. When the rectosigmoid junction is involved, the probabilities of intestinal symptoms relief, undergoing surgery after treatment failure, and developing bowel obstruction during hormonal treatment are around 70%, 10%, and 1-2%, respectively. When the lesion infiltrates exclusively the mid-rectum, thus in cases of true rectovaginal endometriosis, the probabilities of intestinal symptoms relief and undergoing surgery are about 80% and 3%, respectively. Endometriotic obstructions of the rectal ampulla have not been reported. A rectosigmoidoscopy or colonoscopy should be performed systematically before starting medical therapies, also to rule out malignant tumours arising from the intestinal mucosa. Progestogens are safe, generally effective, well-tolerated, inexpensive, and should be considered as first-line medications for bowel endometriosis. Independently of symptom relief, intestinal lesions should be checked periodically to exclude nodule progression during hormonal treatment.

[New medical treatments for painful endometriosis: CNGOF-HAS Endometriosis Guidelines]

OBJECTIVE

The objective of this work is to evaluate the place of new treatments in the management of endometriosis outside the context of infertility.

METHODS

A review of the literature was conducted by consulting Medline data until July 2017.

RESULTS

Dienogest is effective compared to placebo in short term (NP2) and long term (NP4) for the treatment of painful endometriosis. In comparison with GnRH agonists, dienogest is also effective in terms of decreased pain and improved quality of life in non-operated patients (NP2) as well as for recurrence of lesions and symptomatology postoperatively (NP2). Data on GnRH antagonists, selective progesterone receptor modulators as well as selective inhibitors (anti-TNF-α, matrix metalloprotease inhibitors, angiogenesis growth factor inhibitors) are insufficient to provide evidence of interest in clinical practice for the management of painful endometriosis (NP3).

CONCLUSION

Dienogest is recommended as second-line therapy for the management of painful endometriosis (Grade B). Because of lack of evidence, aromatase inhibitors, elagolix, SERM, SPRM and anti-TNF-α are not recommended for the management of painful endometriosis (Grade C).

Future Directions in Endometriosis Research and Therapeutics

Background

Endometriosis is a disease common among women of reproductive age characterized by pain, anxiety and infertility. Defined as the growth of endometrial tissue in ectopic locations, endometriosis remains an enigmatic disease for which current treatments are less than ideal. Much of these shortcomings to current therapy stem from our incomplete understanding on the pathogenesis of the disease. It is generally accepted that endometriosis is an estrogen-dependent disease and, as such, the majority of treatment approaches aim at reducing estrogen action and/or production. Unfortunately, this approach is not effective in all women with endometriosis and in those women where success is achieved with their use, there is potential for health-comprising side effects.

Objective

The objective of this review is to summarize current approaches for treatment of endometriosis, discuss their limitations and potential reasons for lack of progress towards better therapeutics for this disease.

Results

In this review we summarize the current approaches for treatment of endometriosis, discuss their limitations and potential reasons for lack of progress towards better therapeutics for this disease.

Conclusion

Based upon the current state of knowledge, there is a strong necessity for through assessment at the level of the genome, miRNAome and proteome as well as the importance of integrating clinically-relevant endpoints in future studies which evaluate potential endometriosis therapies in experimental models of endometriosis.

[Medical treatment of endometriosis: Hormonal treatment of pain, impact on evolution and future perspectives]

CONTEXT

Endometriosis is a chronic painful disease, for which hormone therapy is usually offered as a first line option to women not willing to conceive.

OBJECTIVES

To analyse and synthesize the literature, from 2006 onwards, on pain control, and disease evolution in oemn using combined hormonal contraceptives, progestins and GnRH analogs. Data on other current and future treatment perspectives is included as well.

SOURCES

Medline (Pubmed), the Cochrane Library, and endometriosis treatment recommendations published by European Society of Human Reproduction and Embryology (ESHRE), National Institute for health and Care Excellence (NICE), American College of Obstetricians and Gynecologists (ACOG), Royal College of Obstetricians and Gynaecologists (RCOG) and Société des Obstétriciens et Gynécologues du Canada (SOGC).

STUDY SELECTION

Meta-analysis and clinical trials are included.

RESULTS

Study quality is heterogeneous in general. Hormone therapy inconstantly allows pain relief and prevention of endometrioma and rectovaginal wall nodules recurrence. Available molecules and routes of administration as well as risk benefit balance are evaluated. Data on future perspectives are limited to date and do not allow use in routine.

CONCLUSION

Hormonal treatment of endometriosis relies on combined hormonal contraceptives (using different routes of administration), progestins and particularly the levonorgestrel-releasing IUS, and GnRH analogs as a last option, in combination with an add-back therapy. Promising alternatives are currently under preclinical and clinical evaluation.

Expression of aromatase in the rostral ventromedial medulla and its role in the regulation of visceral pain

AIMS

Estrogens are known to exert a wide spectrum of actions on brain functions including modulation of pain. Besides the circulating estrogens produced mainly by the ovaries, many brain regions are also capable of de novo synthesizing estrogens, which may exert important modulatory effects on neuronal functions. This study was aimed to test the hypothesis that aromatase, the enzyme that catalyzes the conversion of testosterone to estradiols, may be distributed in the rostral ventromedial medulla (RVM), where it may impact on visceral pain.

METHODS AND RESULTS

Adult female rats were treated with cyclophosphamide (CPM, 50 mg/kg, ip, once every 3 days) or saline. At approximately day 10 following the 3rd injection, CPM-treated rats exhibited colorectal hyperalgesia as they showed significantly greater abdominal withdrawal responses (AWR) to graded colorectal distension (CRD, 0-100 mm Hg) than the saline group. Immunofluorescent staining and Western blot assay revealed that CPM-induced colorectal hyperalgesia was associated with significantly increased expression of aromatase and phosphorylated μ-type opioid receptor (pMOR) and decreased expression of total MOR in the RVM. Intracisternal application of aromatase inhibitors, fadrozole, and letrozole reversed CPM-induced colorectal hyperalgesia and restored pMOR and MOR expression in the RVM.

CONCLUSIONS

Our observations confirmed the expression of aromatase in the RVM, a pivotal brain region in descending modulation of pain and opioid analgesia. The results support the hypothesis that locally produced estrogens in the RVM may be involved in the maintenance of chronic visceral hyperalgesia and the downstream signaling may involve phosphorylation of MOR.

Reevaluating response and failure of medical treatment of endometriosis: a systematic review

Objective

To assess patient response rates to medical therapies used to treat endometriosis-associated pain.

Design

A systematic review with the use of Medline and Embase.

Setting

Not applicable.

Patient(s)

Women receiving medical therapy to treat endometriosis.

Interventions(s)

None.

Main Outcome Measure(s)

The proportions of patients who: experienced no reduction in endometriosis-associated pain symptoms; had pain symptoms remaining at the end of the treatment period; had pain recurrence after treatment cessation; experienced an increase or no change in disease score during the study; were satisfied with treatment; and discontinued therapy owing to adverse events or lack of efficacy. The change in pain symptom severity experienced during and after treatment, as measured on the visual analog scale, was also assessed.

Result(s)

In total, 58 articles describing 125 treatment arms met the inclusion criteria. Data for the response of endometriosis-associated pain symptoms to treatment were presented in only 29 articles. The median proportions of women with no reduction in pain were 11%–19%; at the end of treatment, 5%–59% had pain remaining; and after follow-up, 17%–34% had experienced recurrence of pain symptoms after treatment cessation. After median study durations of 2–24 months, the median discontinuation rates due to adverse events or lack of efficacy were 5%–16%.

Conclusion(s)

Few studies of medical therapies for endometriosis report outcomes that are relevant to patients, and many women gain only limited or intermittent benefit from treatment.

"Per vaginam" topical use of hormonal drugs in women with symptomatic deep endometriosis: a narrative literature review

PURPOSE

We aim to provide a comprehensive overview of the role of the vagina as a route for drug delivery and absorption, with a particular focus on the use of vaginal hormonal compounds for the treatment of deep infiltrating symptomatic endometriosis.

METHODS

A MEDLINE search through PubMed was performed to identify all published studies in English language on vaginal hormonal treatments for symptomatic endometriosis.

RESULTS

Main advantages of the vaginal route include avoidance of the hepatic-first pass metabolic effect, the possibility of using lower therapeutic dosages, and the reduction of side effects compared with the oral administration. Studies on endometriosis treatment mainly focused on the use of vaginal danazol (n = 6) and the contraceptive vaginal ring (n = 2). One pilot study evaluated the efficacy of vaginal anastrozole in women with rectovaginal endometriosis. Most investigations evaluated the vaginal use of hormonal agents in women with deep infiltrating endometriosis/rectovaginal endometriosis. Overall, a substantial amelioration of pelvic pain symptoms associated with endometriosis was observed, particularly of dysmenorrhea. A significant reduction in rectovaginal endometriotic nodule dimensions measured at ultrasound examination was detected by some but not all authors.

CONCLUSIONS

The vaginal route represents a scarcely explored modality for drug administration. High local hormonal concentrations might achieve a greater effect on endometriotic lesions compared with alternative routes. Future studies should focus on the use of the vagina for delivering target therapies particularly in patients with deeply infiltrating rectovaginal lesions.

What Is Known and Unknown About the Association Between Endometriosis and Sexual Functioning: A Systematic Review of the Literature

It is well known that endometriosis is associated with an increase in the risk of deep dyspareunia, with potential negative effects on global female sexual functioning and couple relationship. The aims of this study were to review the literature on the impact of endometriosis on female sexual functioning and to suggest new avenues for future research and treatment strategies. An electronic database research was performed to identify all the studies on the relation between endometriosis and sexual functioning published in the period 2000 to 2016. This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. After the screening process, a total of 9 studies investigating the relation between endometriosis and female sexual functioning were considered. Overall, these studies indicated that around two thirds of women with endometriosis have some form of sexual dysfunction not limited to deep dyspareunia. These findings suggest that the global sexual impact of endometriosis requires further investigation, focusing not only on pain during intercourse but also on psychological and relational dimensions, including partner's sexual functioning. Because sexual functioning is a complex, multidimensional phenomenon, the ideal treatment for endometriosis-related sexual dysfunctions should be conducted by a multidisciplinary team composed of gynecologists, sexologists, and psychologists/psychotherapists.

Evaluation of endometriosis-associated pain and influence of conventional treatment: a systematic review

SUMMARY Endometriosis is a chronic gynecological disease characterized by sustained painful symptoms that are responsible for a decline in the quality of life of sufferers. Conventional treatment includes surgical and pharmacological therapy aiming at reducing painful symptoms. This study aimed to evaluate pain levels in women with endometriosis, focusing on the influence of conventional treatment in controlling this variable. To do so, a literature search was conducted in the Medline/Pubmed databases, with 119 scientific articles found. After applying the inclusion and exclusion criteria, 27 were selected for reading and elaboration of this review. Thus, 9 studies evaluated the contribution of surgery, 17 the use of drugs to reduce pain levels in patients with endometriosis and one assessed surgical and medical treatment. The main results of these searches are presented and discussed in this revision. Surgery and the use of drugs provided reduced pain scores in patients with endometriosis but nevertheless exhibit disadvantages, such as risk of recurrence and side effects, respectively. Treatment of endometriosis is, therefore, a challenge for gynecologists and patients, as they must select the best therapeutic approach for this disease. However, improved quality of life in these patients has been obtained with the use of conventional treatment.

Endometriosis: alternative methods of medical treatment

Endometriosis is an inflammatory estrogen-dependent disease defined by the presence of endometrial glands and stroma at extrauterine sites. The main purpose of endometriosis management is alleviating pain associated to the disease. This can be achieved surgically or medically, although in most women a combination of both treatments is required. Long-term medical treatment is usually needed in most women. Unfortunately, in most cases, pain symptoms recur between 6 months and 12 months once treatment is stopped. The authors conducted a literature search for English original articles, related to new medical treatments of endometriosis in humans, including articles published in PubMed, Medline, and the Cochrane Library. Keywords included "endometriosis" matched with "medical treatment", "new treatment", "GnRH antagonists", "Aromatase inhibitors", "selective progesterone receptor modulators", "anti-TNF α", and "anti-angiogenic factors". Hormonal treatments currently available are effective in the relief of pain associated to endometriosis. Among new hormonal drugs, association to aromatase inhibitors could be effective in the treatment of women who do not respond to conventional therapies. GnRH antagonists are expected to be as effective as GnRH agonists, but with easier administration (oral). There is a need to find effective treatments that do not block the ovarian function. For this purpose, antiangiogenic factors could be important components of endometriosis therapy in the future. Upcoming researches and controlled clinical trials should focus on these drugs.

Systematic review of endometriosis pain assessment: how to choose a scale?

BACKGROUND

Numerous studies concerning endometriosis and pain have been reported. However, there is no consensus on the best method to evaluate pain in endometriosis and many scales have been used. Moreover, there are only a few descriptions of minimal clinically important differences after treatment (MCID) to evaluate variations in pain. In our study, we aim to identify pain scales used in endometriosis pain treatment, to address their strong and weak points and to define which would be the ideal scale to help clinicians and researchers to evaluate endometriosis-related pain.

METHODS

A search of the MEDLINE and EMBASE databases was carried out for publications in English, French or Portuguese from 1980 to December 2012, for the words: endometriosis, treatment, pain. Studies were selected if they studied an endometriosis treatment and a pain scale was specified. A quantitative and a qualitative analysis of each scale was performed to define strong and weak points of each scale (systematic registration number: CRD42013005336).

RESULTS

A total of 736 publications were identified. After excluding duplications and applying inclusion criteria 258 studies remained. We found that the visual analog scale (VAS) is the most frequently used scale. Both VAS and the numerical rating scale (NRS) show a good balance between strong and weak points in comparison with others such as the Biberoglu and Behrman scale. Concerning MCID, only VAS, NRS and Brief Pain Inventory scales have reported MCID and, among these, only VAS MCID has been studied in endometriosis patients (VAS MCID = 10 mm). Adding the Clinical Global Impression score (CGI) to the pain scale allows calculation of the MCID.

CONCLUSIONS

When using pain scales their strengths and weaknesses must be known and included in the analysis. VAS is the most frequently used pain scale and, together with NRS, seems the best adapted for endometriosis pain measurement. The use of VAS or NRS for each type of typical pain related to endometriosis (dysmenorrhea, deep dyspareunia and non-menstrual chronic pelvic pain), combined with the CGI and a quality-of-life scale will provide both clinicians and researchers with tools to evaluate treatment response.

Medical treatments for endometriosis-associated pelvic pain

The main sequelae of endometriosis are represented by infertility and chronic pelvic pain. Chronic pelvic pain causes disability and distress with a very high economic impact. In the last decades, an impressive amount of pharmacological agents have been tested for the treatment of endometriosis-associated pelvic pain. However, only a few of these have been introduced into clinical practice. Following the results of the controlled studies available, to date, the first-line treatment for endometriosis associated pain is still represented by oral contraceptives used continuously. Progestins represent an acceptable alternative. In women with rectovaginal lesions or colorectal endometriosis, norethisterone acetate at low dosage should be preferred. GnRH analogues may be used as second-line treatment, but significant side effects should be taken into account. Nonsteroidal anti-inflammatory drugs are widely used, but there is inconclusive evidence for their efficacy in relieving endometriosis-associated pelvic pain. Other agents such as GnRH antagonist, aromatase inhibitors, immunomodulators, selective progesterone receptor modulators, and histone deacetylase inhibitors seem to be very promising, but there is not enough evidence to support their introduction into routine clinical practice. Some other agents, such as peroxisome proliferator activated receptors-γ ligands, antiangiogenic agents, and melatonin have been proven to be efficacious in animal studies, but they have not yet been tested in clinical studies.

Potential role of aromatase inhibitors in the treatment of endometriosis

Endometriosis is an estrogen-dependent chronic inflammatory disease affecting 5%–10% of reproductive-age women, with a prevalence of 5%–50% in infertile women and >33% of women with chronic pelvic pain. Third-generation aromatase inhibitors (AIs) are approved adjuvants for the treatment of estrogen receptor-positive breast cancer. Molecular studies have revealed the presence of aromatase P450, the key enzyme in the biosynthesis of ovarian estradiol, inside the endometriotic tissue, indicating local synthesis of estradiol. Thereby, AIs represent an appealing medical option for the management of different aspects of this enigmatic disease, especially pelvic pain and infertility. Accordingly, this review aims to evaluate the potential role of AIs in the treatment of endometriosis-associated symptoms, mainly pain and infertility. Notably, several studies have demonstrated that the combination of AIs with conventional therapy as oral contraceptive pills, progestins, or gonadotropin-releasing hormone analogs can be used to control endometriosis-associated pain and pain recurrence in premenopausal women, particularly those with pain due to rectovaginal endometriosis refractory to other medical or surgical treatment. Some case reports have shown promising results in the treatment of postmenopausal endometriosis as first-line treatment, when surgery is contraindicated, or as second-line treatment in the case of postoperative recurrence. Third-generation AIs, especially letrozole, have challenged clomiphene citrate as an ovulation-induction agent in patients with polycystic ovary syndrome and in cases of unexplained infertility. However, few studies are available regarding the use of AIs to treat endometriosis-associated infertility. Therefore, larger multicenter randomized trials using AIs for the treatment of endometriosis-associated infertility are needed to clarify its effect. The safety of AIs for ovulation induction or superovulation has generated a lively discussion. Data from recent retrospective and prospective studies have supported its safety.

Aromatase inhibitor treatment limits progression of peritoneal endometriosis in baboons

OBJECTIVE

To determine the effect of inhibiting aromatase activity on endometrial lesion growth and aromatase expression in a baboon model of induced endometriosis.

DESIGN

Prospective study.

SETTING

Primate research institute.

ANIMAL(S)

Sixteen olive baboons.

INTERVENTION(S)

Sixteen olive baboons with induced endometriosis were examined with laparoscopy 10 months after disease inoculation. Animals in group 1 (n = 10) were treated with 1.25 mg/d of the aromatase inhibitor (AI) letrozole, and animals in group 2 (n = 6) were given a placebo for a total of 6 months.

MAIN OUTCOME MEASURE(S)

Total number of endometriotic lesions, morphology, and volume of lesions, as well as semiquantitative reverse transcription-polymerase chain reaction and quantitative polymerase chain reaction for levels of aromatase cytochrome messenger RNA were measured. Ovarian volumes were evaluated before treatment initiation and every 2 months during the study.

RESULT(S)

Treatment of group 1 animals with an AI significantly decreased lesion volume from baseline measurements, whereas the placebo-treated animals showed an increase in lesion volume. Aromatase messenger RNA levels in lesions in the AI-treated animals were significantly lower compared with the placebo-treated animals. Ovarian volumes were significantly increased at 6 months of AI treatment compared with pretreatment volumes.

CONCLUSION(S)

These findings suggest that suppression of aromatase cytochrome P450 may inhibit the in vivo growth of endometriotic lesions in baboons.

Aromatase inhibitors for the treatment of endometriosis

OBJECTIVE

To review the use of aromatase inhibitors (AIs) for the treatment of endometriosis.

DESIGN

Literature review.

CONCLUSION(S)

Most studies show that in reproductive-age women, the combination of AI with conventional therapy alleviates endometriosis-related pain. In postmenopausal women, using an AI alone has been shown to be an effective treatment, although more studies are needed in this subgroup. Side effects of using AIs appear to be tolerable in most women, although special consideration should be given to monitoring bone mineral density. More studies need to be done examining pregnancy rates and outcomes after AI treatment for endometriosis. In addition, larger randomized clinical trials using AIs need to be done. In summary, AIs may be effective in treating endometriosis-related chronic pelvic pain in both reproductive-age and postmenopausal women.

New trends for the medical treatment of endometriosis

INTRODUCTION

Endometriosis is a benign sex hormone-dependent gynecological disease, characterized by the presence and growth of endometrial tissue outside the uterus; it affects 10% of women of reproductive age and is associated with infertility and pain. Treatment of endometriosis involves conservative or radical surgery, or medical therapies. The goals for endometriosis treatment may be the relief of pain and/or a successful pregnancy achievement in infertile patients. Treatment must be individualized with a multidisciplinary approach. The classical treatments carry adverse side effects and in some cases a negative impact on quality of life. New agents promise a distinct perspective in endometriosis treatment.

AREAS COVERED

The aim of this paper is to systematically review the literature evidence of new medical treatments for endometriosis, defined as pharmacological treatments not yet commonly available and currently under investigation.

EXPERT OPINION

These new medical therapies would be used associated with surgical treatment and, in the future, will render possible the association of hormone therapy with non-hormonal treatment for endometriosis.

The emerging use of aromatase inhibitors for endometriosis treatment

Endometriosis is defined as the growth of endometrial tissue outside of the uterine cavity. The disease occurs primarily in women of reproductive age but recurrent endometriosis is also detected in post-menopausal women. Regardless of age, endometriosis is associated with pain and reduces the quality of life for millions of women world-wide. Conventional therapies focus on reducing systemic levels of estrogen which results in cessation of endometriotic implant growth and pain symptoms associated with the disease. However, these treatments are not effective in all women and are not without side effects. Based upon the discovery that endometriotic tissue over-expresses aromatase, an enzyme critical for estrogen production, emphasis has been placed upon the use of aromatase inhibitors for the treatment of endometriosis and its associated symptoms. This article will review the rationale behind the use of aromatase inhibitors in treating endometriosis and summarize those studies which have evaluated the use of aromatase inhibitors in the treatment of endometriosis and its associated symptoms.

Letrozole and norethisterone acetate versus letrozole and triptorelin in the treatment of endometriosis related pain symptoms: a randomized controlled trial

BACKGROUND

When aromatase inhibitors are used to treat premenopausal women with endometriosis, additional drugs should be used to effectively down-regulate gonadal estrogen biosynthesis. This randomized prospective open-label study compared the efficacy in treating pain symptoms and the tolerability of letrozole combined with either norethisterone acetate or triptorelin.

METHODS

Women with pain symptoms caused by rectovaginal endometriosis were treated with letrozole (2.5 mg/day) and were randomized to also receive either oral norethisterone acetate (2.5 mg/day; group N) or intramuscular injection of triptorelin (11.25 mg every 3 months; group T). The scheduled length of treatment was 6 months. A visual analogue scale and a multidimensional categorical rating scale were used to assess the severity of pain symptoms. The volume of the endometriotic nodules was estimated by ultrasonography using virtual organ computer-aided analysis. Adverse effects of treatment were recorded.

RESULTS

A total of 35 women were randomized between the two treatment protocols. Significantly more patients in group N rated their treatment as satisfactory or very satisfactory (64.7%) as compared to group T (22.2%; p=0.028). The intensity of both non-menstrual pelvic pain and deep dyspareunia significantly decreased during treatment in both study groups, though no statistically meaningful difference between the two groups was apparent. Reduction in the volume of endometriotic nodules was significantly greater in group T than in group N. Interruption of treatment due to adverse effects significantly differed between the groups, with 8 women in group T (44.4%) and 1 woman in group N (5.9%) interrupting treatment (p=0.018). Similarly, 14 women included in group T (77.8%) and 6 women included in group N (35.3%) experienced adverse effects of treatment (p=0.018). During treatment, mineral bone density significantly decreased in group T but not in group N.

CONCLUSIONS

Aromatase inhibitors reduce the intensity of endometriosis-related pain symptoms. Combining letrozole with oral norethisterone acetate was associated with a lower incidence of adverse effects and a lower discontinuation rate than combining letrozole with triptorelin.

Use of aromatase inhibitors to treat endometriosis-related pain symptoms: a systematic review

This systematic review aims to assess the efficacy of aromatase inhibitors (AIs) in treating pain symptoms caused by endometriosis. A comprehensive literature search was conducted to identify all the published studies evaluating the efficacy of type II nonsteroidal aromatase inhibitors (anastrozole and letrozole) in treating endometriosis-related pain symptoms. The MEDLINE, EMBASE, PubMed, and SCOPUS databases and the Cochrane System Reviews were searched up to October 2010. This review comprises of the results of 10 publications fitting the inclusion criteria; these studies included a total of 251 women. Five studies were prospective non-comparative, four were randomized controlled trials (RCTs) and one was a prospective patient preference trial. Seven studies examined the efficacy of AIs in improving endometriosis-related pain symptoms, whilst three RCTs investigated the use of AIs as post-operative therapy in preventing the recurrence of pain symptoms after surgery for endometriosis. All the observational studies demonstrated that AIs combined with either progestogens or oral contraceptive pill reduce the severity of pain symptoms and improve quality of life. One patient preference study demonstrated that letrozole combined with norethisterone acetate is more effective in reducing pain and deep dyspareunia than norethisterone acetate alone. However, letrozole causes a higher incidence of adverse effects and does not improve patients' satisfaction or influence recurrence of symptoms after discontinuation of treatment. A RCT showed that combining letrozole with norethisterone acetate causes a lower incidence of adverse effects and lower discontinuation rate than combining letrozole with triptorelin. Two RCTs demonstrated that, after surgical treatment of endometriosis, the administration of AIs combined with gonadotropin releasing hormone analogue for 6 months reduces the risk of endometriosis recurrence when compared with gonadotropin releasing hormone analogue alone. In conclusion, AIs effectively reduce the severity of endometriosis-related pain symptoms. Since endometriosis is a chronic disease, future investigations should clarify whether the long-term administration of AIs is superior to currently available endocrine therapies in terms of improvement of pain, adverse effects and patient satisfaction.

Aromatase inhibitors in the treatment of bladder endometriosis

BACKGROUND

Aromatase inhibitors have recently been proposed for the treatment of endometriosis; however, no previous study examined the effects of these agents on pain and urinary symptoms of premenopausal women with bladder endometriosis.

CASE

Two premenopausal patients with bladder endometriosis were treated with letrozole (2.5 mg/day), norethisterone acetate (2.5 mg/day), elemental calcium and vitamin D3 for 6 months. The double-drug regimen quickly improved pain and urinary symptoms in both patients. One patient had no significant adverse effect and continued the therapy for 14 months. The other patient developed myalgia and severe arthralgia; pain and urinary symptoms recurred few months after the interruption of the 6-month treatment and the patient underwent laparoscopic partial cystectomy.

CONCLUSION

Aromatase inhibitors improve pain and urinary symptoms in patients with bladder endometriosis; however, severe side effects of treatment may occur. These agents should be administered only to patients who refuse surgery and fail to respond to other therapies.

Current pharmacotherapy for endometriosis

IMPORTANCE OF THE FIELD

Medical therapy is the most commonly used treatment for endometriosis. In particular, the administration of hormonal therapies aims to improve symptoms with minimal adverse effects.

AREAS COVERED IN THIS REVIEW

Observational and randomized studies evaluating the efficacy of medical therapy on symptoms associated with endometriosis were reviewed. We searched Medline, Embase and the Cochrane Library up to December 2009.

WHAT THE READER WILL GAIN

The reader will obtain information on the available medical therapies used to treat endometriosis-related symptoms either after surgery or as an alternative to the surgical excision of endometriosis. The effectiveness of therapies, the dose of drugs, the length of treatment and the adverse effects are examined.

TAKE HOME MESSAGE

Medical therapies can efficaciously reduce the severity of pain symptoms caused by endometriosis. Recurrence of symptoms is common after discontinuation of medical therapies; therefore, the choice of the therapy should be based not only on the improvements of symptoms but also on the potential adverse effects and patients' satisfaction.

Letrozole and norethisterone acetate in colorectal endometriosis

OBJECTIVE

Up to now limited attention has been given to the medical treatment of bowel endometriosis. This study evaluates the efficacy of aromatase inhibitors and norethisterone acetate in treating pain and gastrointestinal symptoms caused by bowel endometriosis.

STUDY DESIGN

This prospective pilot study included six women with colorectal endometriosis; all women had intestinal nodules infiltrating at least the muscularis propria of the bowel and did not have a stenosis of the bowel lumen >60%; the patients suffered from pain and intestinal symptoms. The study subjects received letrozole (2.5 mg/day) and norethisterone acetate (2.5 mg/day) continuously for 6 months. The presence and intensity of symptoms were evaluated before starting the treatment, and after 3 and 6 months of treatment.

RESULTS

The double-drug regimen improved pain, non-menstrual pelvic pain, deep dyspareunia, dyschezia, symptoms mimicking diarrhoea-predominant irritable bowel syndrome, intestinal cramping, abdominal bloating and passage of mucus in the stools, and 67% of the patients declared that the treatment improved their gastrointestinal symptoms.

CONCLUSIONS

The administration of letrozole and norethisterone acetate reduces pain and gastrointestinal symptoms of women with colorectal endometriosis, particularly when patients suffer from symptoms mimicking diarrhoea-predominant irritable bowel syndrome.

Pharmacological treatment of endometriosis: experience with aromatase inhibitors

Current treatment of endometriosis is mainly based on surgery and ovarian suppressive agents. In the last 10 years, it has been demonstrated that aromatase P450, a key enzyme for estrogen biosynthesis, may have a pathogenic role in endometriosis because it is aberrantly expressed in endometriotic implants and in eutopic endometrium of women with endometriosis. Therefore, inhibition of aromatase activity may represent a new therapeutic option for endometriosis. Case reports and observational studies have shown that pain symptoms caused by endometriosis quickly improve after administration of aromatase inhibitors. Limited data are available on the long-term course of pain symptoms after completion of treatment with aromatase inhibitors; however, some recent studies suggest that symptoms may recur at short-term follow-up. A range of results are reported on the effects of aromatase inhibitors on endometriotic lesions, with some authors describing improvements and other authors reporting persistence of pelvic lesions at second-look laparoscopy after treatment. No severe adverse effect has been reported during treatment with aromatase inhibitors both in pre- and postmenopausal women. On the basis of the available data, administration of aromatase inhibitors should now be offered only to the small number of women who have severe pain despite previous surgical and hormonal therapies. Further research in the form of randomized controlled trials will be required before recommending the routine use of these agents.