The Pap test has already reduced the incidence of cervical cancer by more than 60 percent. Now it can help in the early detection of two other gynecologic malignancies — ovarian and uterine cancer — that are notorious because they are typically caught so late.
A new study has found that genetically analyzing the harvesting of cells Using a Pap smear, physicians were able to identify 81 percent of endometrial cancers and 33 percent of ovarian cancers. Some of these cancers were in their earliest stages when they responded more to treatment.
When researchers at Johns Hopkins University tested an alternative means of collecting cells — a longer brush that wipes cells from the endometrium — they identified endometrial cancer in 93 percent of cases and ovarian cancer in 45 percent of cases.
And when they added a blood test to ovarian cancer screening, they were able to detect this fatal cancer in 63 percent of the patients
"The opportunity to detect these cancers earlier is very exciting," said Nickolas Papadopoulos, a co-chair. Author of the study published recently in the journal Science Translational Medicine.
It's a topical example of how scientists hope to detect cancer earlier and more accurately by searching for cells in blood and other readily available fluids that carry the telltale genetic mutations of cancer
While such "liquid Biopsies "are not yet widespread, they promise a revolution in cancer screening.
In January, the same research team presented promising results in the journal Science on a Blood Test —called CancerSEEK — that is able to detect malignant diseases of the liver, stomach, pancreas, esophagus, colon, lung and chest. Also last week, they published results in the journal eLife about a urine test to detect carcinomas of the urothelial tract or urinary bladder.
As a paper test for cervical cancer, the Pap smear has been a staple of gynecological examinations for more than six decades. It was named after George Papanicolaou, the doctor who first showed that cancer cells of the cervix could be detected by microscopic examination.
The Pap test has deaths from cervical cancer, which used to be one of the most common cancers, dramatically lowered woman. However, the test for detecting endometrial or ovarian cancer, which together kill about 25,000 women in the United States annually, is very poor.
Women who are believed to have a high risk for these cancers are sometimes examined with a blood test of an immune system biomarker called CA-125, or with a transvaginal ultrasound, which after significant thickening of the endometrial wall of the Uterus is searching. But these tests can not detect many cancers and they emit many false positives, so they are often not used until a woman complains about symptoms.
The result is often a diagnosis at an advanced stage when treatments are more invasive and less likely to succeed
In the new study, researchers have measured the accuracy of their PapSEEK test on 1,658 women. They already knew that 1,002 of the women were cancer free and that 656 of them had either ovarian or uterine cancer.
The researchers collected cervical fluid samples with a Pap smear brush and a slightly longer tool, a Tao brush behind the cervix and into the uterus, closer to where to hold ovarian and endometrial carcinomas. They then used the PapSEEK test to sequence the samples, focusing on 18 genes that tend to develop mutations in these cancers. The test also tested the samples for aneuploidy, the presence of abnormal numbers of chromosomes in cells.
When the researchers used the Tao brush, they were able to detect endometrial carcinoma in almost all but 7 percent of women who had this disease, almost half of those with ovarian cancer. Combined with the fact that these tests were performed with a mere wiping of the uterine wall, these measurements of sensitivity – the ability to detect actually existing cancers – represents a significant improvement over currently available screening tests.
When supplemented by the Analysis of Pap and Tao brush specimens with the search for mutant cells in the women's blood, they could detect ovarian cancer in well over half of those who had it.
When endometrial and ovarian cancers are particularly aggressive and advanced stages are advanced, they are easier to find using existing screening methods. But one important measure of the usefulness of a test is whether it can detect the most aggressive cancers before they have metastasized.
The PapSeek test also looked promising in this measure. When used to scan the Tao brush specimens, it identified 89 percent of high-grade endometrial carcinomas in patients, while their malignancy was still limited to the endometrium. It was also able to identify 80 percent of those with high-grade ovarian cancer before they spread.
The tests were remarkably good in avoiding false-positive signals that unnecessarily alert women and lead to more risky and invasive tests confirming a diagnosis. In both cancers, the "specificity" of the PapSEEK test — its ability to pinpoint the absence of disease — reached 100 percent.