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'Silent killer' cancer screening hopes

Ultrasound advances and tumour marker detection could cut ovarian cancer death rates

OnMedica staff

Wednesday, 11 March 2009

Ovarian cancer causes more deaths than any other cancer of the female reproductive system. It is often referred to as the "silent killer"  due to a lack of early symptoms and subsequent late diagnosis. 

But advances in transvaginal ultrasound and the development of a risk score to interpret the results of blood tests for the tumour marker CA125, suggest that screening for ovarian cancer could now be possible according to new research.

Both the CA125 blood test and transvaginal ultrasound screening strategies are feasible on a large scale and are capable of detecting early stage ovarian cancers, with almost half of all cancers detected in stage I/II.

These are the initial findings of the largest randomised trial of ovarian cancer screening to date, published Online First and in the April edition of The Lancet Oncology.

When it is detected early and confined to the ovary, the cancer is 90% curable. However, because there are few or no early symptoms, 70% of women with ovarian cancer are diagnosed with advanced-stage disease, when survival is only 20–30%. Currently, there is no effective screening test to detect early stage disease.

Ian Jacobs and Usha Menon from University College London, UK, and colleagues, examined the sensitivity and specificity of the initial screen of the United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). This study assesses the effect of ovarian cancer screening on mortality and performance of two screening strategies—multimodal screening (CA125 blood test as the primary screen with second-line transvaginal ultrasound) and ultrasound screening. Women in this trial will be screened until the end of 2012 and followed until the end of 2014.

Between 2001 and 2005, over 200,000 post-menopausal women aged 50–74 years were recruited through 27 regional Primary Care Trusts across the UK. Women were randomly assigned to no treatment (control), annual multimodal screening (MMS), or annual screening with transvaginal ultrasound (UUS) in a 2:1:1 ratio. Women with repeat abnormal screens underwent clinical evaluation and surgery.

Findings showed that the screening programme was able to detect most women who developed ovarian cancer—90% (34/38) using the MMS strategy and 75% (24/32) using the USS strategy.

Almost half of the cancers detected were in stage I/II. 24 of 58 of the invasive cancers detected were stage I: 14 in the MMS group and 10 in the USS group. The authors point out that the 48% of screen-detected stage I invasive ovarian cancers is encouraging, as only about 28% of invasive cancers are detected at this early stage in most ovarian cancer series.

Overall, the total number of cancer cases detected (87 primary ovarian and three tubal) in the screening groups was similar—42 in the MMS group and 45 in the USS group. The authors noted that specificity was significantly better in the MMS than in the USS group, resulting in fewer repeat tests and almost nine times fewer operations per cancer detected (35.2 surgeries per invasive cancer detected had to be done in the USS group, compared with 2.9 in the MMS group).

The authors say that these results show that both screening strategies have encouraging performance characteristics and are feasible on a large scale. They conclude: "Analysis of the psychosocial impact and cost effectiveness of these strategies is currently underway. The results of ongoing screening are required before a conclusion can be drawn regarding the effect of screening on mortality."

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