NASHVILLE, TENN. – , according to findings in a prospective patient cohort.
The findings, which also suggest that the incidence of Lynch syndrome among endometrial cancer patients is higher than previously recognized, have “immediate and major implications for the individual patient with endometrial cancer ... and implications for related family members,” Maria Mercedes M. Padron, MD, reported during an e-poster session at the annual clinical and scientific meeting of the American College of Obstetricians and Gynecologists.
Of 71 patients included in the study, 67 were undergoing endometrial cancer treatment and 7 (3 among those undergoing endometrial cancer treatment and 4 who did not have endometrial cancer) were known to have Lynch syndrome.
Of the 67 undergoing treatment, 22 (33%) were identified by the direct sequencing panel as having Lynch syndrome mutations, and of those, 7 (10%) had mutations classified as high confidence inactivating mutations in either MLH1, MSH6, PMS2, or MSH2 genes, said Dr. Padron, a research scholar at Icahn School of Medicine at Mount Sinai, New York. The remaining 15 patients had rare mutations and met previously defined phenotypic criteria for Lynch syndrome pathogenicity, she reported.
The sequencing panel–based results were compared with commercially available gene tests, including immunohistochemistry (IHC) and microsatellite instability testing (MSI); 10 patients were identified by IHC to have loss of nuclear mismatch repair (MMR) protein expression, and 8 of those were Lynch syndrome mutation positive. In addition, two patients were MSI-high, and both of those were Lynch syndrome mutation positive.
Thus, two Lynch syndrome patients were missed by direct sequencing, noted Dr. Padron.
However, an additional 10 patients who were not identified as having Lynch syndrome by IHC and MSI testing were potentially identified as such using the sequencing panel, Dr. Padron said, noting that “the pathogenicity of these additional variants needs to be defined.”
Lynch syndrome is a hereditary cancer syndrome caused by germline mutations in DNA MMR genes; it is the third most common malignancy in women and it confers an increased risk of several types of cancer, including colorectal, ovarian, gastric, and endometrial cancer, among others.
“It is estimated that 3% to 5% of endometrial cancers will arise from Lynch syndrome,” Dr. Padron explained during the poster session.
Because the presence of Lynch syndrome directly affects immediate clinical management and future risk-reducing and surveillance strategies for patients and at-risk family members, screening is recommended in all women with endometrial cancer, she added, noting, however, that “the optimum screening method has yet to be established.”
The sequencing panel evaluated in this study – Swift’s Accel-Amplicon Plus Lynch Syndrome– requires only low input amounts of DNA, and in an earlier test using 10 control samples, it exhibited greater than 90% on-target and coverage uniformity. The work flow allowed for data analysis within 2 days, Dr. Padron noted.
The panel then was tested in the current cohort of patients who were referred to a gynecology oncology clinic for either treatment of endometrial cancer or for evaluation of risk for endometrial cancer.
Germline/tumor DNA was isolated and 10 ng DNA was used for targeted exon-level hotspot coverage of MLH1, MSH2, MSH6, and PMS2.
The findings suggest that the prevalence of Lynch syndrome may be six to seven times greater than previously estimated, Dr. Padron said during the poster presentation.
“If confirmed, this would have huge implications for our patients and health care system,” she said, adding that the ability to perform and analyze the sequencing within 48 hours of sample collection using a very low DNA input also was of note.
Taken together, “the findings of this study support future larger studies that can be performed concurrently with current standard of care technologies,” she and her colleagues concluded, noting that such studies would better determine more robust estimates of the prevalence of Lynch syndrome in women with endometrial cancer, help define improved standard-of-care guidelines, and provide future guidance for possible universal/targeted screening programs – all with the goal of improving the clinical care of women.
Dr. Padron reported having no relevant financial disclosures.