Ovarian cancer screening ‘has potential’ reports BBC News. Many cases of ovarian cancer are only diagnosed at an advanced stage, so accurate early-stage tests for ovarian cancer are urgently needed…
Ovarian cancer screening ‘has potential’ reports BBC News.
Many cases of ovarian cancer are only diagnosed at an advanced stage, so accurate early-stage tests for ovarian cancer are urgently needed.
The news is based on research into a two-stage screening test for ovarian cancer among postmenopausal women in the US. Screening was based on measuring a protein called CA125 that is associated with ovarian cancer.
However, a raised CA125 result is not always caused by ovarian cancer, but can be caused by other conditions such as fibroids or endometriosis.
To get round this, the researchers categorised women’s CA125 readings as normal risk, intermediate risk and high risk. Women identified as ‘high risk’ had an ultrasound and were referred to a gynaecologist, who assessed the need for surgery to confirm the cancer.
Over 11 years, 10 women from 4,501 (0.2%) underwent surgery. Of these 10 women, four were found to have high-grade ovarian cancer and two had early stage ovarian tumours. While it is good that these tumours were detected, it does not provide conclusive proof that this is a good screening test. We need larger randomised controlled trials to confirm the findings and see whether screening reduces deaths from ovarian cancer.
Can screening solve all our health problems?
At first glance, screening for life-threatening conditions is a ‘win-win’ idea. However, it is important to weigh up the risks and benefits of all screening tests. False-positive test results may wrongly indicate you have a disease; this is of particular concern for ovarian cancer as currently the only way to confirm a diagnosis is with surgery – and nobody wants to undergo unnecessary surgery.
Screening can also cause “overdiagnosis” of a disease, where it is rightly diagnosed but it turns out not to have any significant impact on health or life expectancy, yet the anxiety caused by the diagnosis of a life-threatening condition impacts on quality of life.
For these reasons it is important to establish that screening for a condition can save lives.
Where did the story come from?
The study was carried out by researchers from the University of Texas MD Anderson Cancer Center (sic) in the US. It was funded by grants from the MD Cancer Center at the University of Texas among other foundations and philanthropic support. The study was published in the peer-reviewed medical journal Cancer.
The story was picked up by a variety of UK media sources and most reported the study appropriately. Some of the coverage reported that the research suggests detecting the cancer ‘in time to save lives’. Whether screening for ovarian cancer would save lives is currently unproven, so these statements are incorrect.
What kind of research was this?
This was a prospective cohort study of postmenopausal women in the US. The study aimed to determine how accurate a 2-stage screening strategy was at correctly identifying women who did and didn’t have ovarian cancer. The screening test involved categorising risk depending on levels of a particular protein in the blood, called CA125. This protein is commonly referred to as a ‘tumour marker’, as levels tend to be raised in women with ovarian cancer. However, it is not a specific indicator of cancer as many other conditions can cause raised levels, such as fibroids or endometriosis.
Ovarian cancer is the fifth most common cancer in the UK among women and is the most common among postmenopausal women. It is often diagnosed at an advanced stage of disease and as the symptoms can be ‘non-specific’ and similar to other conditions (such as abdominal pain and bloating), it can be difficult to recognise.
Currently, screening is only available for women who are considered at high risk of developing the disease due to a strong family history or inheritance of a faulty gene. Cervical screening (‘smear tests’) is used to detect cervical cancer only, and cannot detect ovarian cancer.
However, all screening tests include weighing up the risks against the benefits. Risks include “false positive” results which may lead to unnecessary anxiety and further invasive testing – which may involve internal examination, such as vaginal ultrasound, and possibly surgical exploration, such as a laparoscopy.