The natural history of endometrial polyps

Abstract

Study question: What is the natural history of endometrial polyps in women who are managed expectantly?

Summary answer: The growth rates of expectantly managed polyps vary considerably and cannot be accurately predicted.

What is known already: The majority of polyps detected on ultrasound are treated surgically, and therefore little is known about their natural history. Some polyps have been reported to regress spontaneously without the need for treatment; however, the factors predictive of regression are unknown.

Study design, size, duration: This was a retrospective cohort study conducted at the Department of Gynaecology, University College London Hospitals. We searched our ultrasound clinic database between July 1997 and September 2015, to identify women aged 18 years or older with endometrial polyps that were managed expectantly for ≥6 months. All women attended for a minimum of two ultrasound scans.

Participants/materials, setting, methods: A single expert operator performed all ultrasound scans. Those with <6-month follow-up and those who were taking hormonal contraception, HRT or tamoxifen were excluded from the study. The mean diameter of each polyp was calculated from the measurements in three perpendicular planes. The polyp growth rate was expressed as annual percentage change in the mean diameter. Non-parametric tests and the Fisher's exact test were used to compare differences in polyp mean diameters and growth rates between women of different demographic characteristics. To correct for multiple significance testing, we used the Bonferroni method, giving the level of probability at which findings were considered significant as P < 0.0029 (as 17 tests were undertaken).

Main results and the role of chance: We included 112 women with endometrial polyps, which were expectantly managed over a median period of 22.5 months (range, 6-136). The annual endometrial polyp growth rate varied with a median of 1.0% (interquartile range, -6.5 to 14.3). There was no association between women's demographic characteristics or polyps' morphology and their growth rates. Eleven out of 75 (15% (95% CI, 6.9%-23.1%)) women who initially did not have abnormal uterine bleeding subsequently developed abnormal bleeding during the follow-up period. Polyp growth rate was not associated with the subsequent development of abnormal uterine bleeding (P = 0.397). Seven out of 112 (6.3% (95% CI, 1.8%-10.8%)) women had complete regression of their polyps without treatment during a median follow-up period of 28 months (range, 9-56). Spontaneous regression appeared to occur more frequently in premenopausal women (P = 0.016) and in those who presented with abnormal uterine bleeding at diagnosis (P = 0.004); however, the differences did not reach statistical significance after correction for multiple comparisons.

Limitations, reasons for caution: This study was retrospective and therefore may be prone to selection and information biases. The lack of histological confirmation on all ultrasound diagnoses may also be considered as a limitation.

Wider implications of the findings: Women should be advised that the growth pattern of an individual polyp cannot be accurately predicted; however, a small proportion of polyps do regress spontaneously. There was no correlation between polyps' growth rate and the subsequent development of abnormal uterine bleeding. In view of that, routine monitoring of asymptomatic polyps by ultrasound is not helpful and encouraging women to report clinical symptoms is more useful in deciding whether treatment is required. In contrast to previous studies, we found that polyps may regress more frequently in premenopausal women and in those who presented with abnormal uterine bleeding; a larger sample size would give us greater power to detect a difference in these subgroups of women.

Study funding/competing interests: No study funding was received and no competing interests are present.

Trial registration number: N/A.

Keywords: endometrial polyp; expectant management; natural history; polyp regression; ultrasound.