Commentary: Diagnosing ovarian cancer—more problems than answers

The primary care based case-control study by Hamilton and colleagues (doi:10.1136/bmj.b2998) identified seven symptoms associated with ovarian cancer: abdominal distension, urinary frequency, abdominal pain, postmenopausal bleeding, loss of appetite, rectal bleeding, and abdominal bloating. The report of the first three of these symptoms at least six months before diagnosis was significantly associated with ovarian cancer. The positive predictive values were below 1%, except for abdominal distension, which had a positive predictive value of 2.5%. This study adds to the evidence base derived from primary care of red flag symptoms for several cancers.1 This is important as most patients in the United Kingdom present initially to primary rather than secondary care.

These findings are broadly concordant with the recent UK consensus statement on ovarian cancer regarding symptoms that could indicate ovarian cancer.2 This proposes that “increased abdominal size/persistent bloating—not bloating that comes and goes”—might indicate ovarian cancer. The study by Hamilton and colleagues, however, also found abdominal bloating to be independently associated with ovarian cancer, though with a positive predictive value of only 0.3%. The difficulty here, as acknowledged by Hamilton and colleagues, is to understand what is meant by “bloating” when it is recorded in the medical record. Is it referring to something that comes and goes (as commonly seen in irritable bowel syndrome) or persistent (increased abdominal girth/abdominal distension)? This is important as referral guidance from the Scottish Intercollegiate Guidelines Network (SIGN)3 and the National Institute for Health and Clinical Excellence (NICE)4 currently refer to abdominal bloating but not distension.

Medical records from primary care in the UK are a rich source of data that are used to populate databases—such as the THIN (the health improvement network) and GPRD (the general practice research database)—that have produced several valuable studies. To improve the quality of these data we need to standardise terminology and improve our Read coding in primary care. This has been one of the positive spin-offs of the UK quality and outcomes framework (QOF). This phenomenon was seen in the study of Hamilton and colleagues, whereby the “incidence” of ovarian cancer seemed to increase after the creation of a cancer register became a requirement for the framework.

There is now increasing evidence that ovarian cancer is not a “silent killer” but one that presents with vague symptoms2 that have a low positive predictive value for cancer. When a woman presents with such ongoing symptoms and a careful history and abdominal and pelvic examination have not identified a cause, pelvic ultrasonography should be considered. This has a reasonably high sensitivity and specificity for identifying ovarian cancer.5 In its key messages for ovarian cancer for health professionals, the Department of Health proposes that women should be tested for CA125 as part of the initial diagnostic investigation,6 but this is not supported by current SIGN guidelines3 because of the test’s low sensitivity and specificity.5 7 CA125 concentrations have been used as part of the ongoing UK collaborative trial for ovarian cancer screening,8 but this involves serial measurements in women without symptoms. In primary care it might be more logical to measure CA125 concentrations in patients with abnormal results on pelvic ultrasonography, pending gynaecological referral.