Screening Does Not Reduce Ovarian Cancer Mortality

Screening Does Not Reduce Ovarian Cancer Mortality
Elsevier Global Medical News. 2011 Jun 3, K Wachter

Annual screening with the CA 125 blood test and transvaginal ultrasound for ovarian cancer did not reduce the risk of dying from the disease for women with average risk, according to results of a multicenter screening study of nearly 80,000 women.

The screening tests did result in a large number of false positives, invasive follow-up testing, and related complications, according to the study that will appear in the June 8 issue of JAMA (2011;305:2295-303). The study was one of several cancer studies released early to coincide with presentation of the data on June 4 at the annual meeting of the American Society of Clinical Oncology .

Among women who underwent screening, 118 died of ovarian cancer, whereas 100 women who received usual care died as a result of the disease. The difference was not significant.
"It is possible that even an optimized program of annual screening may be insufficient to detect cancers early enough to reduce mortality. Evidence from modeling suggests that aggressive cancers progress rapidly through the early stages, limiting the ability to detect these cancers with yearly screening," wrote Dr. Saundra S. Buys, the medical director of Huntsman Cancer Institute's high-risk breast cancer clinic in Salt Lake City, and her coinvestigators.

More ovarian cancers were diagnosed in the screened women (212 vs. 176), although this difference was not significant. This suggests "that some of the additional cancers detected by screening were not clinically important and, if left undetected, may never have caused any symptoms or affected the women during their lifetimes," for example, with overdiagnosis, the researchers observed. Stage III and IV cancers were the most common in each group (77% of the screening group and 78% of the usual care group).

The women in this study were part of the PLCO (Prostate, Lung, Colorectal and Ovarian) cancer screening trial. In all, 68,557 women aged 55-74 years were assigned to either annual screening (34,253 women) or usual care (34,304 women) in 1993-2001 and remained in the analysis. Women in the screening arm were offered annual CA 125 testing for 6 years and transvaginal ultrasound for 4 years. Those in the usual care arm were not offered the screening tests. The median follow-up was 12.4 years.

Women with a CA 125 level of 35 U/mL or greater were classified as abnormal. Transvaginal ultrasound was conducted using a 5-7.5 MHz transvaginal probe. Results were considered abnormal if the ovarian volume was greater than 10 cm³, if the cyst volume was greater than 10 cm³, if any solid area or papillary projection extending into the cavity of a cystic ovarian tumor of any size was present, or if any mixed (solid and cystic) component within a cystic ovarian tumor was present.

Both the women and their physicians were notified in writing about suspicious abnormalities found through screening. The women's primary care physicians were responsible for managing the diagnostic process to assess abnormalities.

Among women in the screening arm, there were a greater number of false positives (3,285 false positives vs. 212 true positives). Of women who had a false positive test, one-third (1,080 women) underwent surgery for biopsy to evaluate positive test results. Of these, 163 (15%) women had 222 distinct major complications.

One of the authors, Jonathan D. Clapp, reported having a financial interest in Human Genome Sciences Inc. The other authors reported that they had no relevant financial relationships. The National Cancer Institute funded the PLCO cancer screening trial.