Hormonal changes during a prolonged tamoxifen treatment in patients with advanced breast cancer

The effect of tamoxifen on estradiol, SHBG, IGF-1, and CRP in women with breast cancer or at risk of developing breast cancer: a meta-analysis of randomized controlled trials

BACKGROUND AND AIM

The effects of tamoxifen on the serum levels of hormones and acute phase reactants have been studied previously, but study results have been inconsistent, especially in women with breast cancer. Hence, we conducted this meta-analysis of randomized controlled trials (RCTs) to try to clarify the effects of tamoxifen on estradiol, insulin-like growth factor 1 (IGF-1), sex hormone binding globulin (SHBG), and C-reactive protein (CRP) serum levels in women with breast cancer or at risk of developing breast cancer.

METHODS

Databases were systematically searched up to December 2023. The meta-analysis was generated through a random-effects model and is presented as the weighted mean difference (WMD) and 95 % confidence intervals (CI).

RESULTS

Nine publications were included in the present meta-analysis. The comprehensive findings from the random-effects model revealed an elevation in estradiol (WMD: 13.04 pg/mL, 95 % CI: 0.79, 25.30, p = 0.037) and SHBG levels (WMD: 21.26 nmol/l, 95 % CI: 14.85, 27.68, p = 0.000), as well as a reduction in IGF-1 (WMD: -14.41 μg/L, 95 % CI: -24.23, -4.60, p = 0.004) and CRP concentrations (WMD: -1.17 mg/dL, 95 % CI: -2.29, -0.05, p = 0.039) following treatment with tamoxifen in women with breast cancer or at risk of developing breast cancer, with no impact on IGFBP-3 levels (WMD: 0.11 μg/mL, 95 % CI: -0.07, 0.30, p = 0.240).

CONCLUSION

Tamoxifen administration seems to increase estradiol and SHBG levels and reduce CRP and IGF-1 levels in women with breast cancer or at risk of developing breast cancer. Further studies are needed to determine whether these changes have any clinical relevance.

Behaviour of vaginal epithelial maturation and sex hormone binding globulin in post-menopausal breast cancer patients during the first year of tamoxifen therapy

To evaluate the effect of tamoxifen on vaginal epithelial maturation and on oestrogen-related hepatic synthesis, we prospectively studied the karyopyknotic index (KPI), the maturation index (MI), expressed as a percentage of parabasal (MI-1), intermediate (MI-2) and superficial (MI-3) cells, as well as the serum levels of the oestrogen-dependent sex hormone binding globulin (SHBG). Tests were performed at baseline, after 1, 3, 6 and 12 months of therapy in 64 post-menopausal breast cancer patients. Basal KPI ranged from 0 to 9 (mean 1.5 +/- 0.3) and rose 13.5-fold to 21 +/- 2.5 (P = 0.000) after the first 30 days of tamoxifen. Absence of KPI rise was observed in 23% of patients. Pretreatment MI figures 1, 2 and 3 were 56.9 +/- 5.6, 41.7 +/- 5.4 and 1.4 +/- 0.3, respectively, and sharply shifted to the right (P = 0.000) after 1 month of therapy, indicating an increase of vaginal epithelial maturation. At baselines the SHBG mean value was 62.1 +/- 3.3 nmol/l and underwent an increase of 44% (P = 0.000) after 30 days of tamoxifen. All of these observed 1-month modifications remained stable up to the studied 12 months of therapy. Present findings indicate an early and persistent oestrogenic effect of tamoxifen on the vaginal epithelium and the hepatic synthesis of SHBG.

Changes in serum estrogen levels in women during tamoxifen therapy

BACKGROUND

Tamoxifen is considered an antiestrogen against breast cancer, yet it has known estrogenic side effects. We hypothesized that long-term administration of tamoxifen may significantly increase circulating estrogen levels in women with breast cancer.

METHODS

Serum dehydroepiandrosterone (DHEA), estrone (E1), and estradiol (E2) levels were prospectively measured in 47 breast cancer patients before and during tamoxifen therapy for 2 years. Differences in baseline and peak hormone levels during treatment were compared, and significance was determined by paired Student's t test.

RESULTS

Mean DHEA levels increased by 133% from 61 mg/L to 142 mg/L (P <0.001) and mean E2 levels increased by 239% from 28 pg/mL to 95 pg/mL (P <0.05). Mean E1 levels increased by 264% from 42 pg/mL to 153 pg/mL (P = 0.06).

CONCLUSIONS

Long-term tamoxifen therapy can be associated with increased serum levels of DHEA, E1, and E2. Elevated serum estrogens may explain tamoxifen's estrogenic effects and may represent a mechanism for the development of drug resistance.

Mechanisms of action of endocrine treatment in breast cancer

Endocrine treatment plays an important role in the therapy of breast cancer. While the basic mechanisms are understood, additional mechanisms may be of importance to their action and they may also contribute to the mechanism(s) of acquired resistance. Currently, several novel drugs are entering into clinical trials. Observations of the absence or presence of cross resistance to novel 'pure' steroidal antiestrogens and the non-steroidal tamoxifen may add important information to our understanding of the mechanisms of action of both classes of drugs. Similarly, exploration of different aromatase inhibitors in sequence or concert, as well as the combining of different endocrine treatment options may be warranted. Additionally, alterations in different biochemical parameters such as growth factors should not only be carefully explored in relation to treatment options but should also be followed during the course of treatment to asess alterations over time and in relation to the development of drug resistance.

Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women

The influence of a diet containing soy protein on the hormonal status and regulation of the menstrual cycle was examined in six premenopausal women with regular ovulatory cycles. Soy protein (60 g containing 45 mg isoflavones) given daily for 1 mo significantly (P < 0.01) increased follicular phase length and/or delayed menstruation. Midcycle surges of luteinizing hormone and follicle-stimulating hormone were significantly suppressed during dietary intervention with soy protein. Plasma estradiol concentrations increased in the follicular phase and cholesterol concentrations decreased 9.6%. Similar responses occur with tamoxifen, an antiestrogen undergoing clinical trial as a prophylactic agent in women at high risk for breast cancer. These effects are presumed to be due to nonsteroidal estrogens of the isoflavone class, which behave as partial estrogen agonists/antagonists. The responses to soy protein are potentially beneficial with respect to risk factors for breast cancer and may in part explain the low incidence of breast cancer and its correlation with a high soy intake in Japanese and Chinese women.

Influence of toremifene on the endocrine regulation in breast cancer patients

In a combined phase I-II study, the hormonal effects of toremifene (TOR) were investigated in 30 patients. Half of the patients received continuous therapy of TOR 60 mg and half 300 mg of TOR orally daily. Serum concentrations of oestradiol (E2), progesterone (PROG), testosterone (TE), follicle stimulating hormone (FSH), luteinising hormone (LH), prolactin (PRL), human growth hormone (hGH) and sex hormone binding globulin (SHBG) were monitored prior to the treatment and at the second, sixth, eighth and twelfth weeks. The influence of TOR upon the hypothalamo-hypophyseal axis was investigated by the TRH (thyroid-stimulating hormone releasing hormone) functional test using 400 micrograms intravenous injection of TRH for stimulation of PRL secretion. The concentration of E2 decreased during the TOR therapy with 60 mg and 300 mg causing 82 and 71% decreases, respectively (non-significant). PRL was significantly (P < 0.001) suppressed. Both these effects reflect the anti-oestrogenic action of TOR. SHBG increased significantly at both doses of TOR, probably due to a direct oestrogen-like effect of TOR in the liver. TE decreased as a consequence of the elevated SHBG. The TRH-induced PRL release was suppressed by both doses of TOR. There were 17 and 27% reductions at 12 weeks in the 60 and 300 mg groups, respectively. Other hormones measured were not significantly affected by TOR. The hormonal effects of 60 and 300 mg doses of TOR did not differ significantly. Anti-oestrogenic (i.e. decrease of E2), and partially oestrogenic (i.e. increase of SHBG) properties as well as the antiprolactinic effects of TOR may have an overall beneficial effect in the clinical management of breast cancer patients.

Studies of tamoxifen as a promoter of hepatocarcinogenesis in female Fischer F344 rats

Tamoxifen, an antiestrogen used in the treatment of breast cancer, was assessed for carcinogenic potential in the two-stage model of experimental hepatocarcinogenesis. Groups of female Fisher F344 rats were initiated with a non-necrogenic, subcarcinogenic dose of diethylnitrosamine (DEN; 10 mg/kg, po) and fed tamoxifen at a concentration of 250 mg per kg of AIN-76A diet for 6 or 15 months. The livers of these animals exhibited an increase in size and number of altered hepatic foci compared with those animals which were initiated with DEN but not exposed to tamoxifen. This finding indicates that tamoxifen may have a carcinogenic potential in the rat liver. After 6 months of treatment, neoplastic nodules were observed in 3/8 rats in the DEN-initiated, tamoxifen-treated group. In the initiated group provided with tamoxifen for 15 months, neoplastic nodules were observed in 7/8 rats and hepatocellular carcinomas in 3/8 rats. The serum level of tamoxifen in these rats was 200-300 ng/ml. The ratio of tamoxifen, 4-hydroxy tamoxifen, and N-desmethyl tamoxifen was 1:0.1:0.5-1 in the serum. When adjusted for age-related weight increases, the serum and liver levels of tamoxifen and its N-desmethyl metabolite did not change over the 15 months. In the rat liver, the level of tamoxifen and its N-desmethyl metabolite was 10-29 micrograms/g liver after 6 or 15 months of chronic dietary administration. The ratio of tamoxifen:4-hydroxy tamoxifen:N-desmethyl tamoxifen was 1:0.1.3-3.3 in the liver. Therefore, the liver had 20- to 30-fold more tamoxifen and 4-hydroxy tamoxifen and at least 100-fold more N-desmethyl tamoxifen than the serum (assuming 1 gram of tissue is equivalent to 1 ml of serum). These results indicate that tamoxifen is a promoting agent for the rat liver at serum levels found in patients given the usual therapeutic course of tamoxifen. The high concentrations of tamoxifen attained in the rat liver indicate that actions other than its known estrogenicity for liver could contribute to its promoting action. In addition, these results indicate that the pharmacodynamic differences in tamoxifen metabolism in rats and humans and at low versus high doses should be determined. Thus, the therapeutic indications for tamoxifen should be balanced by the potential risk it may present as a promoting agent in mammalian liver.

Hormonal effects of toremifene in breast cancer patients

The effect of toremifene treatment on the serum levels of sex steroids (estradiol, progesterone, testosterone), FSH, LH, prolactin, TSH, T3, T4 and SHBG was investigated. Basal prolactin level and the "prolactin reserve capacity" of the hypophysis was also studied by the TRH functional test. Steroid hormone receptors were detected in the patients where a tumor biopsy could be obtained. In a randomized trial patients were treated by 60 and 300 mg of toremifene per os, daily. Hormone levels were assayed prior to treatment and at the 2nd, 6th, 8th and 12th week of tormifene therapy. The hormonal effects of toremifene were the most marked at the 2nd and at the 8th week. Estradiol decreased continuously, SHBG increased slightly and the high initial value of basal prolactin level decreased. The TRH-induced prolactin release was suppressed by tormifene after an 8-week period. No clinical response-related tendency was found.

Tamoxifen. A reappraisal of its pharmacodynamic and pharmacokinetic properties, and therapeutic use

Tamoxifen, a non-steroidal antioestrogen, represents a significant advance in treatment of female breast cancer. In trials of tamoxifen as postsurgical adjuvant treatment of early breast cancer, disease-free survival is consistently prolonged, representing an enhanced quality of life in association with tamoxifen's favourable adverse effect profile. Moreover, overview analysis indicates a survival benefit of approximately 20% at 5 years for all women, most clearly evident in women over 50 years, while a survival benefit independent of menopausal, nodal or oestrogen receptor status has been demonstrated in some individual trials. Thus, for postmenopausal women, tamoxifen is clearly optimal adjuvant treatment, although the relative benefit of adjuvant chemotherapy in node-negative patients requires clarification. A survival benefit for women under 50 has not been clearly demonstrated in overview analysis, but is not precluded by these rather limited data, and adjuvant treatment of premenopausal women with tamoxifen may also warrant serious consideration. Response rates to tamoxifen in advanced breast cancer are around 30 to 35%, increasing with patient selection for oestrogen receptor positivity. Tamoxifen must be regarded as first-line endocrine treatment in postmenopausal women, and may represent an alternative to first-line ovarian ablation in premenopausal women. An emergent role in primary therapy of elderly and frail patients with operable disease is apparent. Tamoxifen is also of benefit following surgery in male breast cancer, and may have a role as first-line endocrine treatment. Tamoxifen also has a potential role in other hormone-sensitive malignancies such as pancreatic carcinoma, and in treatment of benign breast disease. Finally, tamoxifen has a place in treatment of male and female infertility. because of adverse effects is rarely necessary. The most frequent adverse effects are related to the drug's anti-oestrogenic activity, and include hot flushes, nausea and/or vomiting, vaginal bleeding or discharge, and menstrual disturbances in premenopausal patients. Thus, tamoxifen continues to play a major role in management of female breast cancer in both early and advanced stages of disease, with a place also in treatment of male breast cancer and of infertility.

Alternating tamoxifen and medroxyprogesterone acetate in postmenopausal advanced breast cancer patients--short and long term endocrine effects

The endocrine effects of alternating tamoxifen and medroxyprogesterone acetate have been evaluated in 26 post-menopausal patients with metastatic breast cancer. Endocrine evaluations included the RIA determination of plasma levels of sex-hormone binding globulin, follicle-stimulating hormone, luteinizing hormone, estradiol, prolactin, cortisol, and testosterone. The evaluation of the study parameters at different intervals during therapy indicates that with this schedule an alternate sequential effect on the endocrine system is achievable because each drug exerts its own endocrine activity that is completely reversed when the other drug is administered. We can hypothesize that the same alternate activity as seen on the endocrine system could be obtained also on other tissues and organs including tumors.