Targeted next-generation sequencing of endometrial cancer and matched circulating tumor DNA: identification of plasma-based, tumor-associated mutations in early stage patients

There is currently no blood-based marker in routine use for endometrial cancerpatients. Such a marker could potentially be used for early detection, but it could also help to track tumor recurrence following hysterectomy. This is important, as extra-vaginal recurrence of endometrial endometrioid adenocarcinoma is usually incurable. This proof-of-principle study was designed to determine if tumor-associated mutationscould be detected in cell-free DNA from the peripheral blood of early and late stage endometrial endometrioid carcinoma patients. Approximately 90% of endometrioid carcinomas have at least one mutationin the genes CTNNB1, KRAS, PTEN, or PIK3CA. Using a custom panel targeting 30 hotspot amplicons in these four genes, next-generation sequencing was performed on cell-free DNA extracted from plasma obtained from a peripheral blood draw at the time of hysterectomy and the matching tumor DNA from 48 patients with endometrioid endometrial carcinomas. At least one mutationin the tumor was detected in 45/48 (94%) of patients. Fifteen of 45 patients (33%) had a mutationin the plasma that matched a mutationin the tumor. These same mutationswere not detected in the matched negative control buffy coat. Presence of a plasma mutationwas significantly associated with advanced stage at hysterectomy, deep myometrial invasion, lymphatic/vascular invasion, and primary tumor size. Detecting a plasma-based mutationwas independent of the amount of cell-free DNA isolated from the plasma. Overall, 18% of early stage patients had a mutationdetected in the plasma. These results demonstrate that mutationsin genes relevant to endometrial cancercan be identified in the peripheral blood of patients at the time of surgery. Future studies can help to determine the post-operative time course of mutationclearance from the peripheral blood and if mutationre-emergence is predictive of recurrence.