Common endometrial decidual reaction in postmenopausal breast cancer patients treated with tamoxifen and progestogens

The levonorgestrel-releasing intrauterine device induces endometrial decidualisation in women on tamoxifen

There is conflicting literature on whether the levonorgestrel-releasing intrauterine system (LNG-IUS; Mirena^®) induces decidualisation in the tamoxifen-treated endometrium. The expression of the decidualisation marker IGFBP-1 was measured using immunohistochemistry in endometrial biopsies and in serum (using ELISA) of 20 postmenopausal women at the start of tamoxifen-treatment for breast cancer. Ten women were then fitted with LNG-IUS and the other ten received tamoxifen-treatment only and acted as controls. Samples were taken at baseline and after 12 months. At baseline, all endometrial samples were negative for IGFBP-1 and at 12 months, IGFBP-1 was only expressed in the endometria of women fitted with the LNG-IUS, confirming the observed histological features of decidualisation. By contrast, serum IGFBP-1 concentrations were increased by tamoxifen, but not in the group receiving LNG-IUS. In conclusion, tamoxifen induces a rise in serum IGFBP-1 suggesting a systemic, possibly hepatic effect, whilst LNG abrogates this in both the liver and endometrium. Impact statement What is already known on this subject? Previous reports of the use of LNG-IUS in women on tamoxifen have provided conflicting evidence as to whether the endometrium exhibited decidualisation or not. These reports were however based solely on histological examination and lacked supporting biochemical data. What do the results of this study add? After 12 months of treatment with LNG-IUS, the endometria of women on tamoxifen show histological features of decidualisation and the presence of the decidualisation marker IGFBP-1, suggesting that levonorgestrel protects the tamoxifen-treated uterus from additional pathology by causing decidualisation. Serum levels of IGFBP-1 were expected to be a reflection of uterine production, but contrary to expectations, higher levels were identified in women on tamoxifen alone. These data suggest that an inhibition of tamoxifen-induced serum IGFBP-1 production (possibly from a hepatic source) by LNG-IUS occurred and indicates independent systemic effects of both drugs in post menopausal breast cancer patients. What are the implications of these findings for clinical practice and/or further research? This research demonstrated a mechanism for endometrial protection in women on tamoxifen. It also alerts clinicians to the fact that both tamoxifen and LNG-IUS exert systemic effects in this patient group.

Safety and adverse effects associated with raloxifene: multiple outcomes of raloxifene evaluation

OBJECTIVE

To examine the effect of raloxifene on major adverse events that occur with postmenopausal estrogen therapy or tamoxifen.

METHODS

The Multiple Outcomes of Raloxifene Evaluation, a multicenter, randomized, double-blind trial, enrolled 7,705 postmenopausal women with osteoporosis. Women were randomly assigned to raloxifene 60 mg/d or 120 mg/d or placebo. Outcomes included venous thromboembolism, cataracts, gallbladder disease, and endometrial hyperplasia or cancer.

RESULTS

During a mean follow-up of 3.3 years, raloxifene was associated with an increased risk for venous thromboembolism (relative risk [RR] 2.1; 95% confidence interval [CI] 1.2-3.8). The excess event rate was 1.8 per 1,000 woman-years (95% CI -0.5-4.1), and the number needed to treat to cause 1 event was 170 (95% CI 100-582) over 3.3 years. Risk in the raloxifene group was higher than in the placebo group for the first 2 years, but decreased to about the same rate as in the placebo group thereafter. Raloxifene did not increase risk for cataracts (RR 0.9; 95% CI 0.8-1.1), gallbladder disease (RR 1.0; 95% CI 0.7-1.3), endometrial hyperplasia (RR 1.3; 95% CI 0.4-5.1), or endometrial cancer (RR 0.9; 95% CI 0.3-2.7).

CONCLUSION

Raloxifene was associated with an increased risk for venous thromboembolism, but there was no increased risk for cataracts, gallbladder disease, endometrial hyperplasia, or endometrial cancer.

LEVEL OF EVIDENCE

I

The effects of tamoxifen on proliferation and steroid receptor expression in postmenopausal endometrium

AIM

To study the effects of tamoxifen on the proliferation index and oestrogen receptor (ER) and progesterone receptor (PR) expression in postmenopausal endometrium.

METHODS

A total of 125 endometrial specimens of postmenopausal women, comprising benign endometria from tamoxifen users (n = 35) and non-users (n = 24), and endometrial cancer from tamoxifen users (n = 15) and non-users (n = 51), were immunohistochemically examined using MIB-1, anti-ER, and anti-PR antibodies in endometrial epithelium and stroma.

RESULTS

In benign endometrium the mean MIB-1 index in the epithelium was higher in tamoxifen users than in non-users (mean, 13% (SD, 13%) v mean, 2% (SD, 2%); p < 0.05), whereas in endometrial cancer the MIB-1 index was higher, but similar in tamoxifen users and non-users (mean, 32% (SD, 24%) and mean, 35% (SD, 18%)). The expression of ER was comparably high in benign epithelium from tamoxifen users and non-users (97% and 92%, respectively), but in endometrial cancer it was lower in tamoxifen users (60% and 88%; p < 0.05). The expression of PR in stromal cells was higher in tamoxifen users, both in benign (84% v 54%) and in malignant endometrium (33% v 10%; p < 0.05).

CONCLUSION

The proliferation index (as measured by MIB-1) in benign endometrial epithelium is higher in tamoxifen users than in non-users, and this might play a role in the reported higher incidence of endometrial cancer in postmenopausal tamoxifen users. The increased expression of PR in stroma from tamoxifen users with both benign and malignant endometrium demonstrates an additional oestrogenic effect of tamoxifen on the endometrial stroma.

Tamoxifen and secondary tumours. An update

The nonsteroidal antiestrogen tamoxifen is the most widely used anticancer drug. In women with breast cancer, adjuvant therapy with tamoxifen reduces relapse and improves overall survival. In advanced breast cancer, the response rate is more than 50% in hormonal dependent disease. In women treated with adjuvant tamoxifen the incidence of new primary breast cancers is decreased. This latter observation has led to the initiation of prevention trials. In 1989 the first report from a large prospective randomised trial showed a significant increase of endometrial carcinoma among women treated with adjuvant tamoxifen. This effect may be linked to the somewhat paradoxical estrogenic properties of tamoxifen. The endometrial effects should be considered in the long term use of tamoxifen, and should also be taken into account in the evaluation of the prevention trials. Animal data indicate that tamoxifen can induce tumours in other organ systems, for example the liver, but no increase in primary liver cancer has been reported from the randomised trials. In some of these trials an increase in other gastrointestinal cancers (e.g. colon and gastric carcinoma) has been observed. The mechanism behind this may be different from that of the endometrium. In animal systems, tamoxifen has shown to induce DNA damage, with formation of DNA adducts. The risk of secondary gastrointestinal cancer needs to be further evaluated. The adverse effects of tamoxifen have led to the development of new anti-estrogenic drugs and other estrogen reducing agents (e.g. aromatase inhibitors).