Letters to the Editor: Karen K. Steinberg
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Letter to the editor,
As a member of a family carrying a BRCA mutation, I appreciate the ongoing dedication of Benigno and Skolnick to finding a screening test that will detect early ovarian cancer. Ovarian cancer is the deadliest gynecological cancer, with 19,680 cases and 12,740 deaths predicted to occur in the U.S. in 2024 (American Cancer Society). I am glad the Jewish Times is willing to inform the public on issues like this, but the risk of misinformation needs to be addressed.
In the Jewish Times article of June 30, 2024, Drs. Skolnick and Benigno refer to their 2024 Gynecologic Oncology article, in which they report a 98% “effective” test in identifying early-stage ovarian cancer. “Effectiveness” is not generally a technical term used to define the accuracy of a blood test for ovarian cancer. Drs. Skolnick and Benigno use the more technically correct term, Positive Predictive Value (PPV), in their Gynecologic Oncology article. PPV answers the patient’s question: now that I have gotten a positive screening test result, what is the probability that I really have ovarian cancer? This question must be answered before tests are recommended by organizations that write guidelines for testing, such as the American College of Obstetrics and Gynecology or the U.S. Preventive Services Task Force.
According to Skolnick and Benigno, the PPV for their test is 93% for the sample they created for their study. In this sample, which is not representative of the population that will actually be screened, 75% of women had ovarian cancer. Fortunately, in the real world, asymptomatic ovarian cancer is not nearly present in 75% of women at any one time but is present in about 50/100,000 women, or 0.05% of women over 50, again, not 75%.
Why is this important to doctor and patients? Because a PPV of 1% means that out of 100 women who have a positive test result for ovarian cancer, at least 99 will be false positives. This large population of healthy women with false positives will be subjected to anxiety and, in many cases, unnecessary and invasive procedures, including surgery.
That ovarian cancer is so rare is the main obstacle to developing an acceptable screening test. All rare diseases that have serious outcomes, as does ovarian cancer, must have a high enough accuracy (PPV) to be useful. A PPV of 10% in the general population is the threshold set by oncologists for screening for this kind of cancer. This would mean that for every 100 women who test positive, ten would be found to have the disease. The remaining ninety women would be false positives. Skolnick and Benigno’s test has a PPV of less than 1%.
Karen K. Steinberg, Ph.D., Centers for Disease Control and Prevention, retired, Atlanta
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