Ovarian Cancer Screening Does Not Prevent Deaths

Emma Hitt, PhD

June 07, 2011

June 7, 2011 — Screening for ovarian cancer does not appear to reduce mortality from the disease; furthermore, false-positive screening tests may cause unnecessary complications, according to new findings from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial.

Saundra S. Buys, MD, from the Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, and colleagues with the PLCO Project Team reported their findings in the June 8 issue of JAMA.

According to the researchers, symptoms of ovarian cancer are generally nonspecific, meaning that ovarian cancer is not usually diagnosed until an advanced stage — one that has a 5-year survival of about 30%. Thus, detecting ovarian cancer early in the course of the disease has the potential to improve prognosis, particularly because ovarian cancer confined to just the ovaries has a much higher 5-year survival rate of 92%.

In the current study, the researchers randomly assigned 78,216 women aged 55 to 74 years to undergo either annual screening or usual care at 10 screening centers across the United States between November 1993 and July 2001.

Patients in the screening group underwent annual screening with CA-125 for 6 years and transvaginal ultrasound for 4 years. Patients in the control group received their usual medical care, but no screening for ovarian cancer. All participants underwent follow-up for a diagnosis of cancer for 11 to 13 years.

Of the participants, 212 women in the screening group developed ovarian cancer (5.7/10,000 person-years), and 176 women (4.7/10,000 person-years) developed ovarian cancer in the control group, which was not significantly different.

There was no benefit in reduction of mortality with screening. In the screening group, there were 118 deaths resulting from ovarian cancer (3.1/10,000 person-years) in the intervention group and 100 deaths (2.6/10,000 person-years) in the usual care group (mortality rate ratio, 1.18; 95% confidence interval, 0.82 - 1.71).

Deaths from other causes, excluding ovarian, colorectal, and lung cancer, were comparable between the 2 groups.

In addition, screening resulted in a large proportion of complications after surgical procedures. In 3285 women with false-positive results, 1080 underwent surgical follow-up, and of those, 163 women experienced at least 1 serious complication (15%), with 222 distinct major complications in all, which translated into a rate of 20.6 complications per 100 surgeries.

Women in the intervention group also had a higher rate of oophorectomy than women in the usual care group. Using data from 22,955 and 22,542 women who responded to the supplemental questionnaire from the intervention and control groups, respectively, 1771 women in the intervention group (7.7%) underwent oophorectomy compared with 1304 (5.8%) in the control group.

"Annual screening for ovarian cancer as performed in the PLCO trial with simultaneous CA-125 and transvaginal ultrasound does not reduce disease-specific mortality in women at average risk for ovarian cancer but does increase invasive medical procedures and associated harms," Dr. Buys and colleagues conclude.

According to the researchers, it is possible that, if used differently, CA-125 and transvaginal ultrasound may have the potential to be beneficial. For example, assessing the changes in CA-125 over time, rather than using a single CA-125 value, as was the case in this study, may allow detection of cancers at an earlier stage, when cure is possible, the authors suggest.

However, there is no evidence from other clinical trials to support this approach at this time. The authors add that "even an optimized program of annual screening may be insufficient to detect cancers early enough to reduce mortality."

The study was supported by The National Cancer Institute and the Intramural Research Program of the Division of Cancer Epidemiology and Genetics in the National Cancer Institute, National Institutes of Health. One study author disclosed a financial relationship with Human Genome Science Inc. The other authors have disclosed no relevant financial relationships.

JAMA. 2011;305:2295-2303. Full text

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