Aromatase inhibition: a potential target for the management of recurrent or metastatic endometrial cancer by letrozole: more questions than answers?

Local estrogen metabolism (intracrinology) in endometrial cancer: A systematic review

Endometrial cancer (EC) is the most common malignancy of the female gynaecological tract and increased exposure to estrogens is a risk factor. EC cells are able to produce estrogens locally using precursors like, among others, adrenal steroids present in the serum. This is referred to as local estrogen metabolism (or intracrinology) and consists of a complex network of multiple enzymes. Particular relevant to the final generation of active estrogens in endometrial cells are: steroid sulfatase (STS), estrogen sulfotransferase (SULT1E1), aromatase (CYP19A1), 17β-hydroxysteroid dehydrogenase (HSD17B) type 1 and type 2. During the last decades, a plethora of studies explored the level of these enzymes in EC but contrasting data were reported, which generated vigorous debate and controversies. Several reviews attempted at clarifying some of the debated issues, but published reviews are based on investigator-defined bibliography selection and not on systematic analysis. Therefore, we performed a systematic review of the literature reporting about the level of STS, SULT1E1, CYP19A1, HSD17B1 and HSD17B2 in EC. Additional intracrine enzymes and networks (e.g., HSD17Bs other than types 1 and 2, aldo-keto reductases, progesterone and androgen metabolism) were non-systematically reviewed as well.

Effect of letrozole in carcinogen-plus-estrogen-induced endometrial hyperplasia in mice

PURPOSE

To evaluate the effects of letrozole (Ltz) in carcinogen+estrogen-induced endometrial hyperplasia.

METHODS

BALB/c female mice were divided into four groups of 12 animals each receiving an intrauterine dose of N-ethyl-N-nitrosourea (ENU) and weekly subcutaneous injections of estradiol hexaidrobenzoate (EHB), except for group I(control). The groups were divided in I (control), II (ENU+EHB), III (ENU+EHB+MPA) and IV (ENU+EHB+Ltz). Group III also received intramuscular injections of MPA (medroxy progesterone acetate) every four weeks, while group IV received oral doses of Ltz daily. At the end of 16 weeks, the animals were sacrificed, and blood samples were collected for the measurement of serum estradiol and progesterone levels. Uterine histological sections were made to evaluate the presence of endometrial proliferative lesions. Differences between groups were evaluated with student's t test, ANOVA and chi-square test.

RESULTS

Groups ENU+EHB, ENU+EHB+MPA and ENU+EHB+Ltz showed varying degrees of endometrial hyperplasia. The incidence of hyperplasia in groups ENU+EHB and ENU+EHB+Ltz was higher and more severe than in group ENU+EHB+MPA. Control group showed lower levels of serum estradiol than the other groups.

CONCLUSION

There was no evidence that letrozole could act as an antiestrogenic drug in the development of endometrial proliferative lesions.

Non-steroidal anti-inflammatory drugs and endometrial cancer risk in the VITamins And Lifestyle (VITAL) cohort

OBJECTIVE

Chronic inflammation may be an important factor in the initiation and promotion of endometrial cancer. Use of non-steroidal anti-inflammatory drugs (NSAIDs), however, has been inconsistently associated with endometrial cancer risk.

METHODS

22,268 female residents of western Washington State, ages 50-76, completed a baseline questionnaire in 2000-2002 and reported on their use of individual NSAIDs over the past 10years. Use was categorized as none, low (<4days/week or <4years), and high (≥4days/week and ≥4years). Over 9years of follow-up, 262 incident invasive endometrial cancers were identified. Multivariable proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI).

RESULTS

Relative to non-use, high use of aspirin was inversely associated with endometrial cancer risk (HR 0.64, 95% CI: 0.41-1.01; P trend=0.03). Findings were stronger for regular-strength than low-dose aspirin. High use of non-aspirin NSAIDs (HR 1.15, 95% CI: 0.68-1.95), including ibuprofen (HR 1.29, 95% CI: 0.73-2.28), and naproxen (HR 1.08, 95% CI: 0.39-2.95) was not associated with risk. In subgroup analyses, findings for aspirin were strongest for cancers of endometrioid histology and were restricted to non-smokers.

CONCLUSIONS

This study provides additional evidence that use of aspirin, but not non-aspirin NSAIDs, may reduce the risk of endometrial cancer, especially in estrogen-mediated cases; however additional prospective studies with high-quality measurement of NSAID use are needed. Aspirin should continue to be examined as a potential agent for cancer chemoprevention.