Introduction/Background Increasing evidence regarding the decrease and preventive effect of tamoxifen in Contralateral breast carcinoma has led to its increase use over the span of time. Surveillance for uterine safety becomes important and despite of well documented adverse effect of tamoxifen on endometrium the data is scarce regarding the endometrial findings with tamoxifen which led to planning of this study to investigate the effects of 5-year‘s use of tamoxifen in preventive setting on endometrium and gynaecological symptoms.

Methodology Altogether 750 patients diagnosed with breast carcinoma, who underwent mastectomy and were put on tamoxifen therapy from jan 2012 to 31 may 2013 were included in a hospital based cohort derived from database at Shaukat Khanum Memorial Cancer Hospital & Research Centre, Lahore During the extensive 5 year follow up (ending by 31 May 2018) the patients were inquired about gynaecological symptoms at each routine visit, surveillance of endometrial thickness at 2.5 & 5 yrs via ultrasound and evaluation of endometrium once symptomatic via sampling was done.

Results The discontinuation rate after the start of tamoxifen was 30%( n=225 ) and mean time was 18 months. The median endometrial thickness at 5 years after the use of tamoxifen was 4 mm. these findings were independent of menopausal status. Endometrial sampling was performed in 18 ( 2.4%) patients and mean time of referral was 2.5 years. Only 3 patients (0.4%) underwent hysterectomy and none was histologically proved to have endometrial carcinoma.

Conclusion Although the discontinuation rate was high and endometrial thickness was significantly increased during the tamoxifen treatment yet the serious adverse effects were not significantly high thereby the routine gynaecological surveillance in the preventive setting could not be recommended.

Disclosure Nothing to disclose.