Ovarian Cancer Screening – Risks and Benefits

Ovarian cancer claims almost 400 lives a year in Scotland (ISD data), presenting with disease beyond the ovary in over 60% of women.

There has therefore been a prolonged quest for screening strategies to detect disease whilst still confined to the ovary, primarily using the CA125 blood test together with transvaginal pelvic ultrasound (TVS), but the outcomes of recent studies are disappointing. The ‘Prostate, Lung, Colon and Ovarian’ (PLCO) American trial showed no improvement in survival with screening; over two thirds of screen detected cancers had spread beyond the ovary at the time of diagnosis, and 18 operations were performed for every cancer detected with a ‘serious’ complication rate of 15%, leading to warnings that screening may do more harm than good¹.

The UK based Collaborative Trial of Ovarian Cancer screening (UKCTOCS) gave encouraging preliminary results², but fewer than half of the cancers detected were stage 1, with the worry that the mortality data (not available until 2015) will be disappointing.

Intrinsic problems with ovarian cancer screening include:

• The rarity of the disease
• The high incidence of incidental/benign ovarian pathology leading to ‘false positive’ TVS and potentially unnecessary surgery
• The absence of any precursor lesion. Benign ovarian cysts carry no significant risk of malignant transformation
• The non-specific nature of the CA125 test with ‘false positives’ from other conditions. Furthermore, not all cancers secrete CA125 : approximately one third of early cancers and 15% of advanced cancers will be associated with normal CA125 levels .
• The biological heterogeneity of the disease such that some tumour types remain confined to the pelvis whereas others are more likely to spread and present with advanced disease, sometimes in the absence of a pelvic mass

With uncertain screening strategies, there is a growing hope that increased awareness of ovarian cancer may lead to earlier diagnosis. Unfortunately this also has the potential to generate many false positives and worried women. Sadly, symptoms of ovarian cancer (persistent bloating, IBS type symptoms, pelvic pain, frequency of micturition) are extremely common, and may be due to other conditions that may be associated with elevated CA125.

However this is not to say that screening or early diagnosis is not worthwhile – delayed diagnosis, especially in symptomatic women, can lead to much anguish for patients, their families and their care-givers. Better screening tests are required to avoid unnecessary morbidity and it is hoped that future work will achieve robust screening tools.

For further information on ovarian cancer see http://www.targetovariancancer.org.uk.
http://www.ovacome.org.uk/campaigning-volunteering/beat/

Dr K Wendy McMullen, Ninewells Hospital, Dundee

1. Buys SS, Partridge E, Black A et Al Effect of screening on ovarian cancer mortality: the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Randomized Controlled Trial JAMA. 2011 Jun 8 ;305(22):2295-303.
2. Menon U, Gentry-Maharaj A, Hallett R, Ryan A, Burnell M, Sharma A, et al. Sensitivity and specificity of multimodal and ultrasound screening for ovarian cancer, and stage distribution of detected cancers: results of the prevalence screen of the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS). Lancet Oncol 2009;10:327–40.

This article was originally published in the SCPN Newsletter, Volume 3, Issue 4.
Read the full issue here: