Only one in 100 women with symptoms typical of ovarian cancer, such as persistent bloating or pelvic pain, actually has the disease, researchers reported on Thursday.
Several medical societies recommend the use of these and other symptoms to detect ovarian cancer early before it spreads, but the new study found no evidence that symptoms could speed up detection.
"We'd all like to find ways to diagnose this cancer earlier," Mary Anne Rossing, who led the investigation, told Reuters Health. "What this (study) suggests is that it's going to be hard to move the diagnosis of ovarian cancer forward."
Rossing, an epidemiologist at the University of Washington, and her colleagues asked some 800 women who had been treated for ovarian cancer about the symptoms they had before their diagnosis. They compared their answers to those of a control group of more than 1300 women without cancer.
About 60 to 70 percent of the cancer patients had experienced symptoms almost daily for more than at few weeks during the year leading up to their diagnosis. The symptoms were most frequent in patients diagnosed with late-stage cancers, and the majority of the women only began experiencing symptoms a few months before their diagnosis.
However, they estimate that 100 women with symptoms would need to be evaluated to detect one woman with ovarian cancer.
Among women without ovarian cancer, only 6 percent had persistent symptoms. But because the disease is rare, chances are that women with symptoms don't have it.
In the U.S., ovarian cancer kills more than 14,000 women every year, according to the American Cancer Society. And experts estimate that about one in 2,500 American women has the disease without being aware of it.
Still, women are advised against routine screening because the tests frequently turn up false positives and have been shown to trigger a large number of unnecessary surgeries.
The current study, Rossing and colleagues say, "argues for a cautious approach to the use of symptom patterns to trigger extensive medical evaluation for ovarian cancer."
"Ovarian cancer is a very difficult disease," said Rossing, whose study is published in the Journal of the National Cancer Institute. On the other hand, she said she would not discourage women with persistent symptoms from seeing a physician, but that they should be aware that it is unlikely to be ovarian cancer.
Dr. Barbara Goff, who was not involved in the study, told Reuters Health: "The bottom line is that if you have symptoms, you need to be evaluated, whether or not it will lead to an earlier diagnosis."
Goff, a gynecologic oncologist at the University of Washington, added that, even if the symptoms aren't due to ovarian cancer, it still makes sense to see a doctor. "It could be something else, it could be irritable bowel syndrome, it could be colon cancer, it could be that you had a bad infection," she explained. Based on her experience, "it's a very, very low percentage that needs to go on to surgery even if they have symptoms."
Goff also noted that the current study was limited because it was based on women's recollection of symptoms they experienced many months ago.
"Importantly," write the authors of a commentary published with the study, "these findings remind us that wide recognition of symptoms alone will not incrementally improve the overall survival from ovarian cancer."
"Rather, they highlight the urgent need to develop better molecular markers and improved imaging modalities for ovarian cancer screening," conclude Drs. Beth Y. Karlan and Ilana Cass from Cedars-Sinai Medical Center in Los Angeles, California.