Endometrial cancer is a common malignancy, and its incidence is growing with an ageing population, increasing obesity and a general decline in fertility. It occurs most often in postmenopausal women. Screening tests are available, but these are currently recommended only for women with the genetic condition Lynch syndrome, which greatly increases the lifetime risk of this disease.

Trans-vaginal ultrasound (TVS) is a technique that is used to measure the thickness of the endometrium, which correlates with cancer development. Although it is widely used for screening women with Lynch syndrome, few studies have been carried out into its utility for population screening of women without symptoms.

A group of researchers based mainly in the UK and led by Ian Jacobs of the UCL-EGA Institute for Women's Health in London used patient data from the UK Collaborative Trial of Ovarian Cancer Screening (UKTOCS)* to conduct a case-control trial of the sensitivity of this technique in detecting endometrial cancer¹.

A total of 48 230 women recruited in this trial and assigned to yearly TVS screening, and who had not previously had a hysterectomy, were included as cases or controls. Those women who received a diagnosis of endometrial cancer or an endometrial pre-cancerous condition during the study were termed cases, and all other women who received the screen were controls.

Endometrial thickness was measured routinely during the scans along with ovarian morphology and size, and any post-menopausal bleeding was recorded. Women with a measured endometrial thickness of 5 mm or above on screening were questioned more closely about possible symptoms of cancer.

133 women developed endometrial cancer or a pre-cancerous condition during the follow-up period of the study. The researchers compared the distribution of endometrial thickness during the study between these and all other screened women.

The cases had a mean endometrial thickness recorded in the last screen before diagnosis of 11.5 mm, compared to 3.5 mm for the controls; 19.5% of cases and 83.5% of controls had measurements below 5 mm. The optimum cutoff for a positive diagnosis of endometrial cancer or atypical endometrial hyperplasia (AEH; a pre-cancerous condition) was found to be 5.15 mm, which gave a sensitivity value (true positive rate) of 80.5% and a specificity value (true negative rate) of 86.2%.

Increasing the cut off increased the specificity while decreasing the sensitivity, and including other endometrial abnormalities increased the sensitivity while decreasing the specificity.

These results indicate that there is a very strong correlation between increased endometrial thickness and a subsequent diagnosis of endometrial cancer. However, the disease itself is uncommon enough to indicate that any population based screening programme would yield a large number of false positive results, which would waste the time and cost of follow-up and cause distress to the women involved. The test would be more cost-effective if it were restricted to women identified as being at high risk.

Writing in an accompanying commentary², Ignace Vergote and colleagues at University Hospitals Leuven in Belgium suggest that these important findings do not indicate that population screening for endometrial cancer should be introduced. Further investigations are necessary, in particular to determine whether early detection through screening has any survival benefit in this cancer.

In the mean time, these findings should prove valuable whenever increased endometrial thickness is detected in postmenopausal women undergoing pelvic scans for other reasons.

Reference

1. Jacobs, I., Gentry-Maharaj, A, Burnell, M. and 29 others (2010) Sensitivity of transvaginal ultrasound screening for endometrial cancer in postmenopausal women: a case-control study within the UKCTOCS cohort The Lancet Oncology, published online ahead of print 13 December 2010 doi:10.1016/S1470-2045(10)70268-0

2. Vergote, I., Amant, F. and Timmerman, D. (2010) Comment: Should we screen for endometrial cancer? The Lancet Oncology, published online ahead of print 13 December 2010

* Registered with ClinicalTrials.gov; registration # NCT00058032