Ovarian Cancer

The exact cause of ovarian cancer is unknown. Ovarian cancer represents the 9th most common cancer diagnosed in Australian women, but the 6th most common cause of cancer deaths in this group¹. The symptoms of ovarian cancer are often vague and non-specific and can be confused with common symptoms of other disorders. Often, by the time the cancer is diagnosed, the tumour may have spread beyond the ovaries and into the uterus, bladder, bowel, and omentum. These cells can begin forming new tumour growths before cancer is even suspected.

A woman’s risk of developing ovarian cancer increases with age and close to 80% of new ovarian cancer cases diagnosed are in women 50 years or older, with the median age of first diagnosis being 64 years¹. Around 1378 Australian women are expected to be diagnosed with ovarian cancer in 2010 and close to 800 Australian women die from this disease each year¹.

In Australia, 1 in 77 women will be diagnosed with ovarian cancer before the age of 85¹. Similarly, in the United States, the lifetime risk for a woman developing ovarian cancer is 1 in 71, while the lifetime risk of death is 1 in 95². More than half of the deaths from ovarian cancer occur in women between 55 and 74 years of age. Approximately one quarter of ovarian cancer deaths occur in women between 35 and 54 years of age.

(From: www.medscape.com)

Background and Literature Review

Epithelial ovarian cancer is a major cause of cancer mortality in women. The cancer is usually asymptomatic in early stage and thus is often first diagnosed at late stage. Despite advances in surgery, chemotherapy and radiotherapy techniques over the last few decades, epidemiological studies indicate these advances have had a marginal impact on the course of ovarian cancer. It is universally agreed that current therapy is inadequate because of the advanced stage at which most ovarian cancer cases present clinically. The vast majority of patients present with Stage 3/4 disease and have an extremely poor prognosis (~15-20% survive 5 years). Those patients who present with properly staged, well-differentiated Stage 1 disease have much better rates of survival (>90%). The development of an effective community-based screening programme for early detection of ovarian cancer, especially in high-risk women, is undoubtedly the number one priority for long-term reduction of the mortality due to ovarian cancer.

While no ovarian cancer test has been developed that is suitable for community-based screening, evidence supports the hypothesis that certain epithelial ovarian cancers may be detectable up to two years prior to their clinical presentation^3,4. Should it become possible to screen for Stage 1 disease with an accuracy of 80% an overall ovarian cancer death reduction of the order of 50% should be achieved.

Contemporary screening approaches have focused on plasma/serum biomarkers (including the current gold standard CA125 for monitoring disease treatment) and imaging techniques. While a significant proportion of asymptomatic ovarian cancers can be identified by measurement of plasma CA125⁵, by real time ultrasonography⁶ and by colour-flow Doppler⁷, these screening modalities, even when applied in combination, have an unacceptably low positive predictive value and to date no effective population-based screening strategy for ovarian cancer exists. Some further advantages have been suggested by more recent studies employing annual CA125 screening with transvaginal ultrasound as a second line test⁸ although it will still be several years until definitive data on the effects of this screen on mortality can be determined.

1. National Breast and Ovarian Cancer Centre, http://nbocc.org.au

2. Ovarian Cancer National Alliance, http://www.ovariancancer.org/

3. Jacobs I J; Rivera H; Oram D H; Bast R C, Differential diagnosis of ovarian cancer with tumour markers CA 125, CA 15-3 and TAG 72.3., British journal of obstetrics

and gynaecology 1993;100(12):1120-4.

4. Jacobs I J; Skates S; Davies A P; Woolas R P; Jeyerajah A; Weidemann P; Sibley K; Oram D H, Risk of diagnosis of ovarian cancer after raised serum CA 125 concentration: a prospective cohort study,.BMJ (Clinical research ed.) 1996;313(7069):1355-8.

5. Skates S J; Xu F J; Yu Y H; Sjövall K; Einhorn N; Chang Y; Bast R C; Knapp R C, Toward an optimal algorithm for ovarian cancer screening with longitudinal tumor markers. Cancer 1995;76(10 Suppl):2004-10.

6.  Karlan B Y; Platt L D, Ovarian cancer screening. The role of ultrasound in early detection. Cancer 1995;76(10 Suppl):2011-5.

7. Bourne T; Campbell S; Steer C; Whitehead M I; Collins W P, Transvaginal colour flow imaging: a possible new screening technique for ovarian cancer. BMJ (Clinical research ed.) 1989;299(6712):1367-70.

8. Menon et al (2009) 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)