Screening may not decrease ovarian cancer mortality rates, study finds

Screening for ovarian cancer with CA-125 tests and transvaginal ultrasound may not reduce mortality rates, a new study suggests.

To determine the effect of ovarian cancer screening on mortality, researchers from the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening trial randomly assigned women to an intervention group (screening with CA-125 and transvaginal ultrasound at baseline, annual transvaginal ultrasound for three additional years, and annual CA-125 for five additional years) or a usual care group (usual medical care with no annual screening). The study was conducted at 10 U.S. screening centers from November 1993 to July 2001. The primary outcome measure was death from ovarian cancer, and secondary outcome measures were incidence of ovarian cancer and complications of screening and diagnostic tests. The study was published early online June 4 by the Journal of the American Medical Association.

Study participants ranged in age from 55 to 74 years at study entry and were followed for a median of 12.4 years (range, 10.9 to 13.0 years). Overall, 39,105 women were assigned to the intervention group and 39,111 were assigned to the usual care group. Two hundred twelve women in the intervention group and 176 in the usual care group were diagnosed with ovarian cancer (5.7 per 10,000 person-years and 4.7 per 100,000 person-years, respectively; rate ratio [RR], 1.21; 95% CI, 0.99 to 1.48), and 118 and 100 women, respectively, died of the disease (3.1 per 10,000 person-years vs. 2.6 per 10,000 person-years; RR for mortality, 1.18; 95% CI, 0.82 to 1.71).

A total of 3,285 women in the intervention group had false-positive results on screening; of these, 1,080 had surgical follow-up, and of these, 163 had one or more serious complications, defined as infection, direct surgical complications, cardiovascular or pulmonary complications, or other. In the usual care group, 2,914 women died of causes other than ovarian, colorectal and lung cancer versus 2,924 women in the intervention group (76.2 per 10,000 person-years vs. 76.6 per 10,000 person-years; RR, 1.01; 95% CI, 0.96 to 1.06).

The authors acknowledged that their study did not collect data on all aspects of treatment, such as type of systemic therapy. They also noted that although the study was powered to detect a mortality reduction of 35%, smaller effect sizes could also be considered worthwhile from a public health perspective, and that the screening tests studied might be more useful if different cutoffs were used to define positive results. However, they concluded that in the U.S., the screening strategy used in the PLCO trial “does not reduce disease-specific mortality in women at average risk for ovarian cancer but does increase invasive medical procedures and associated harms.”