Endometrial surveillance in tamoxifen users: role, timing and accuracy of hysteroscopic investigation: observational longitudinal cohort study.

To determine the role, timing and indications for endometrial hysteroscopic investigation in relation to the clinical, ultrasound and histological features of the endometrium during tamoxifen (TAM) use. We performed an observational longitudinal cohort study (years 2007-2012) that investigated the endometria of 151 TAM users with hysteroscopy and histology. For all patients, gynaecological history, years of adjuvant treatment, ultrasound endometrial thickness measurement and indications for hysteroscopy were recorded. Hysteroscopic findings showed that 100% of patients referred for simple follow-up had no evidence of endometrial disease. We found a strong correlation between previous history of abnormal uterine bleeding (with or without endometrial thickening) and hysteroscopic suspicion of endometrial atypia that was confirmed by histology. Hysteroscopy had 83.3% sensitivity, 99% specificity, 83.3% positive predictive value (PPV) and 99% negative predictive value (NPV) in detecting endometrial atypia. No significant correlation was found between endometrial thickening to >5 mm without bleeding and histological atypia. Similarly, the duration of treatment was not related to endometrial thickening and histological atypia. Endometrial stromal hyperplasia was detected by histology in 70.5% of patients with endometrial thickness measurements ranging from 5 to 10 mm. In contrast, no atypia was detected when endometrial thickness was <5 mm. Ultrasound performed using a 5-mm cut-off threshold for endometrial thickness resulted in 100% sensitivity, 15% specificity, 4% PPV and 100% NPV in detecting endometrial atypia, while a 10-mm cut-off threshold resulted in 84% sensitivity, 69% specificity, 10% PPV and 99% NPV. Low-risk TAM users do not require different endometrial surveillance than the general population. Hysteroscopy could play a fundamental role in determining the endometrial status of patients before the initiation of TAM treatment and in assessing the endometrial status of patients when bleeding occurs.