New ovarian cancer findings small but significant step toward early detection
Researchers at Fred Hutchinson Cancer Research Center have taken a small but potentially significant step toward early detection of ovarian cancer, finding that protein "biomarkers" released by tumors show up in women's bloodstreams years before symptoms appear, though not necessarily early enough to save lives.
Seattle Times health reporter
Local researchers have taken a small but potentially significant step closer to early detection of ovarian cancer, a sneaky disease that's often diagnosed too late for effective treatment.
Various cancer "biomarkers" begin to show up in blood tests long before symptoms occur, but aren't accurately predictive until later, when tumors likely have reached an advanced stage, Fred Hutchinson Cancer Research Center researchers have found.
The study, published Wednesday in the Journal of the National Cancer Institute, was headed by Garnet Anderson and Nicole Urban of the Hutchinson center's Division of Public Health Sciences
"What this study did was move one step closer to early detection," said Anderson, a biostatistician. "It gives us an idea of where we want to go but doesn't solve the problem."
For several years, the ovarian-cancer researchers have focused on biomarkers, proteins secreted by tumors, hoping to find one or more that show up early in the disease's progress. Now, most ovarian-cancer cases aren't diagnosed in the early stages, when treatment has a high cure rate.
The researchers analyzed stored blood samples collected over many years for a previous large research study involving women smokers. Ultimately, 34 of those women were diagnosed with ovarian cancer.
Looking at the blood samples, taken periodically up to 18 years before diagnosis, the researchers found that three of six biomarkers, including one known as CA125, increased in cancer patients up to three years before diagnosis, compared with patients without ovarian cancer.
But at that early stage, the levels weren't high enough to accurately predict the disease, researchers found. A high degree of accuracy is required for such tests, the researchers wrote, "because a definitive diagnosis requires surgery."
Only at a year or less before the women were diagnosed with ovarian cancer did the blood levels of the biomarkers become more accurate. While the researchers said they didn't know whether that was sufficient time to help women live longer, a local cancer authority who was not involved in the study said any lead time may help.
"Finding ovarian cancer a year earlier could have a significant impact," said Dr. Barbara Goff, a surgeon and director of gynecologic oncology at the University of Washington. "Even three months makes a huge difference when you're going into someone's belly."
While the cancer's stage may indeed be advanced at that point, what really makes a difference in survival time, she said, is whether a surgeon can remove all the cancer. Sometimes, "even a three month lead time may make it easier for the surgeon" to do that.
Goff, like the researchers, said results may have been skewed by samples having been taken from smokers. "It's unclear whether that could have altered the biologic nature of these biomarkers."
Even so, she termed the study's results "incredibly exciting — but very, very preliminary."
In the U.S., nearly 15,000 women died from ovarian cancer last year, according to the American Cancer Society. That same year, more than 21,000 were diagnosed with the disease.
A woman's risk of getting invasive ovarian cancer increases with age; overall, she has a 1 in 71 chance of contracting the disease. It is particularly scary to women because early symptoms such as bloating and abdominal pain can be mistaken for common ailments, causing a missed diagnosis.
Biomarkers have drawn interest from researchers hoping for early detection for many types of cancer. But they haven't always worked out as well as the biomarker for prostate cancer known as the PSA test. In the case of CA125, the best-known biomarker linked to ovarian cancer, researchers found other ovarian conditions can produce the protein, and tumors often don't produce enough of the protein to be detected.
Preliminary results of a British study reported earlier this year showed some success in early ovarian-cancer detection using biomarkers; however, final data won't be evaluated until 2014.
For all the studies, Anderson said, the goal is not simply early detection, but helping women live longer.
Because ovarian cancer is rare, designing research to identify effective screening tools has been a challenge, noted Patricia Hartge in an accompanying editorial in the journal.
"We confront daunting arithmetic to avert premature death from ovarian cancer," wrote Hartge, a senior scientist at the National Cancer Institute.
The need to screen a large number of patients to catch one early ovarian cancer means the test must be not only specific and sensitive, but inexpensive, cancer researchers have noted.
For Urban, the challenge is personal, as well as professional. Nearly four decades ago, as a graduate student at Harvard's School of Public Health, she was diagnosed with very early ovarian cancer, almost by accident while she was being treated for another ovarian condition. When she came to the Hutchinson center, "I thought it would be a good idea to work in ovarian cancer."
Hartge praised the study as a "valuable step" in the process to identify effective screening. But, she added: "For now, we do not have a proven biomarker, panel of biomarkers, or overall screening program that works well."
Even so, don't count such biomarkers out, because they'll likely form a key element in any future screening regimen, Hartge added. "The results of Anderson et al. are not the last word in serum markers or in combinations of markers."
Carol M. Ostrom: 206-464-2249
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