64. Tamoxifen does not promote tumour progression in surgically treated endometrial cancer

The effects of tamoxifen on the female genital tract

Tamoxifen is an effective and relatively non-toxic compound used in palliative and adjuvant treatment of breast cancer. More recently its preventive role in breast cancer has also been demonstrated. However, tamoxifen use is related to some increase in the risk of endometrial cancer and to a significant rise in the incidence of benign endometrial pathologies. The activity of tamoxifen against breast cancer is mainly achieved by blocking the oestrogen receptor, whereas the effect of this compound on the female genital tract is mostly related to its agonistic properties. Despite numerous studies no effective methods of tamoxifen-user surveillance have been developed and currently no active screening for endometrial cancer, apart from yearly gynaecological examination, is recommended in these patients. In other parts of the genital tract, tamoxifen increases the risk of some benign conditions and may cause difficulties in the interpretation of cervical smears. Further studies are warranted to develop more effective surveillance and methods decreasing the detrimental effects of tamoxifen on the female genital tract.

Tamoxifen, screening and new oestrogen receptor modulators

Tamoxifen is a selective oestrogen receptor modulator (SERM) with anti-oestrogenic properties in the breast and oestrogenic effects in tissues such as bone and the cardiovascular system. It is an excellent breast cancer drug for all stages of the disease. Its SERM profile makes it a valuable alternative to hormone replacement therapy, especially for women at high risk of breast cancer. Tamoxifen, however, increases the incidence of benign and malignant lesions of the uterus. Secondary prevention of these, early detection and treatment, is feasible but not cost-effective in breast cancer patients because potential endometrial risks do not outweigh beneficial effects in the breast. This may be different in healthy women with an as yet unknown benefit on breast cancer mortality. We review the literature on the importance of tamoxifen's endometrial lesions and balance available evidence on whether and how best to screen them. In a subset of tamoxifen users it seems advisable to assess the uterine cavity prior to intake with a yearly endometrial assessment as pointed out, starting 3 years after initiation of treatment. In most cases there is endometrial thickening on ultrasonographic assessment and additional tests such as hydrosonography or hysteroscopy are required to confirm an empty atrophic uterus as remains the case in most asymptomatic women on tamoxifen. Newer compounds, such as raloxifene, have a similar SERM profile to tamoxifen but are neutral on the uterus. This has recently been proven by 3 years of endometrial follow-up data. Longer endometrial safety will hopefully confirm these early findings. Whether other SERMs in development are better, and which of them is better for the breast, is to be demonstrated in ongoing studies.