Effect of adjuvant tamoxifen on the endometrium in women with breast cancer: a prospective study using office endometrial biopsy

The effect of SERMs on the endometrium

Tamoxifen, the first clinically available SERM, was developed in 1966 and approved by the FDA (United States Food and Drug Administration) in 1978. It is the most prescribed antineoplastic drug in the world, with approximately 10 million women-use-years of experience. Tamoxifen has proved efficacious in all settings of breast cancer. However, in the mid-to-late 1980s, a series of letters to the editor and case reports announced an association between tamoxifen therapy in women with breast cancer and the development of endometrial carcinoma. Subsequently, in 1998, the observation of a significant 49% reduction in invasive breast cancer relative to placebo in a cohort of women at increased risk for the disease resulted in the early stopping of the National Surgical Adjuvant Breast and Bowel Project's (NSABP) P-1: Breast Cancer Prevention Trial (BCPT). Importantly, this was the first time that information became available about the effects of tamoxifen in healthy women, that is, women who did not already have breast cancer. In this healthy population, the relative risk of developing endometrial carcinoma in the tamoxifen arm was 2.54, although when stratified by age, in women over 50, the risk grew to 4.01. Thus, the risk appears to be confined to women over 50 because, in contrast, in women under 50 there was no statistically significant increase in the risk of endometrial carcinoma.

Systemic therapy

A large body of data on systemic therapy has been presented and published in the past year, including new information on primary risk reduction, patient selection for adjuvant systemic therapy, and anthracycline-analogs. New data on ongoing adjuvant trials (including taxane studies), unpublished updates from the fourth Oxford Overview in September 2000, and provocative data on ovarian ablation were important features of the November 2000 National Institutes of Health Consensus Development Conference on Adjuvant Therapy for Breast Cancer. Important new data on anti-estrogen therapy, including aromatase inhibitors and pure antiestrogens, further expand the role of the oldest targeted breast cancer therapy. Trastuzumab and other novel compounds are being investigated as single-agents and in combination with conventional systemic approaches. Discussions on the long-term effects of adjuvant therapy have taken center stage also. These and other important ongoing developments since 2000 are examined in this review article.

Tamoxifen and the female reproductive tract

The use of tamoxifen among women with breast cancer or at high risk of the disease has greatly expanded over the past several decades. Tamoxifen has a complex effect on the female reproductive tract and several tamoxifen-associated changes have been described among tamoxifen users. These include endometrial thickening, cervical and endometrial polyps, endometrial hyperplasia, endometrial adenocarcinoma, uterine sarcoma, increase in the size of uterine leiomyomata, exacerbation of endometriosis and ovarian cysts. The most common uterine change associated with tamoxifen is endometrial polyps. The annual incidence of endometrial cancer among women on tamoxifen is 2 per 1000 and seems to be related to the cumulative tamoxifen dose. It is not clear whether endometrial cancer occurring among women on tamoxifen is of worse prognosis than endometrial cancer occurring among women not receiving tamoxifen. Tamoxifen is associated with several sonographic changes which make the use of ultrasound in surveillance of these patients difficult. There is no indication to implement routine screening for endometrial cancer among all women on tamoxifen. However, endometrial biopsy, preferably via hysteroscopy, should be considered in women with uterine bleeding.

Endometrial evaluation with transvaginal US and hysterosonography in asymptomatic postmenopausal women with breast cancer receiving tamoxifen

PURPOSE

To determine performance characteristics of transvaginal ultrasonography (US) and hysterosonography for diagnosing endometrial abnormality in asymptomatic postmenopausal women with breast cancer receiving tamoxifen.

MATERIALS AND METHODS

The authors prospectively examined 138 women receiving tamoxifen by using transvaginal US, hysterosonography, and office hysteroscopy. The combined hysteroscopic-histopathologic diagnosis was the reference standard. Sensitivity, specificity, positive and negative predictive values, and likelihood ratios of transvaginal US and hysterosonography were calculated.

RESULTS

All 138 women underwent transvaginal US; 104, successful hysterosonography; and 117, successful hysteroscopy. Uterine abnormality was present in 47 (40.2%) of 117 women: 45 with polyps and two with submucosal fibroids. Receiver operating characteristic curve analysis revealed 6 mm to be the optimal endometrial thickness cutoff for diagnosing endometrial abnormalities. When a thickness greater than 6 mm or a focal endometrial finding was considered abnormal, transvaginal US had a sensitivity of 85.1% and a specificity of 55.7%. In 92 women who completed transvaginal US, hysterosonography, and hysteroscopy, hysterosonography was more specific (79.2%; P =.008) but not significantly more sensitive (89.7%; P =.508) than transvaginal US. When women with abnormal transvaginal US findings were further examined with hysterosonography, the sequential combination of transvaginal US and hysterosonography was more specific (77.1%) than transvaginal US alone (P <.001), without a significant decrease in sensitivity (78.7%; P =.25).

CONCLUSION

In asymptomatic postmenopausal women receiving tamoxifen, 6 mm is the optimal endometrial thickness cutoff for diagnosing endometrial abnormalities with transvaginal US. Further examination with hysterosonography can improve specificity by reducing the high false-positive rate of transvaginal US.

Effects of adjuvant tamoxifen on the endometrium in postmenopausal women with breast cancer: a prospective long-term study using transvaginal ultrasound

PURPOSE

To study the value of transvaginal ultrasound (TVS) in endometrial screening of postmenopausal breast cancer patients treated with tamoxifen.

PATIENTS AND METHODS

In 247 tamoxifen-treated (20 to 30 mg/d for >/= 2 years) women and 98 controls, the endometrium was prospectively followed-up by means of TVS every 6 months for up to 5 years. Patients with homogeneous endometrium of more than 10-mm thickness were then scanned repeatedly every 3 months.

RESULTS

The mean endometrial thickness was 3.5 +/- 1.1 mm before treatment and increased to a maximum of 9. 2 +/- 5.1 mm after 3 years of tamoxifen application (P: <.0001), which was significantly (P: <.0001) thicker compared with controls. Fifty-two asymptomatic patients with thickened or morphologically suspect endometrium underwent hysteroscopy and dilatation and curettage (D&C), resulting in four uterine perforations. Histopathologically, atrophy was found in 38 patients (73.1%), polyps in nine, hyperplasia in four, and endometrial cancer in one case. In 20 screened patients who reported vaginal bleeding, five atrophies (25%), five polyps, four hyperplasias, and two endometrial cancers were found. Before hysteroscopy and D&C were performed, 36 (69.2%) of 52 asymptomatic and four (20%) of 20 symptomatic patients were scanned by repeated TVS over 2 to 30 months. Invasive diagnostic procedures were significantly (P: <.05) more frequent in younger and obese patients. In the controls, one asymptomatic polyp and one symptomatic hyperplasia were found.

CONCLUSION

In tamoxifen-treated patients, TVS offered a high false-positive rate, even with a cutoff value of 10 mm for endometrial thickness and repeated TVS scans. Increased iatrogenic morbidity and only one asymptomatic endometrial carcinoma do not warrant endometrial screening by TVS in tamoxifen-treated patients.