Peritoneal washings analysis in endometrial cancer: Comparison of somatic mutation detection with panel sequencing and traditional cytology.

OBJECTIVES

The prognostic significance of positive pelvic washings in endometrial cancer (EC) remains unknown, and little data exist regarding washings as a source of genetic information in relation to a patient's tumor. We sought to assess the feasibility of identifying EC mutations in peritoneal washings.

METHODS

Peritoneal washings from 21 biopsy-confirmed newly diagnosed patients with EC across disease stages between 09/2018 and 07/2019 were collected. Peritoneal washings, primary EC, and normal DNA samples were subjected to next-generation sequencing targeting 468 cancer-related genes. Sequencing results were compared to cytological analysis.

RESULTS

For the 21 EC cases included, cytology found 8 (38 %) of the peritoneal washings as positive, 7 (33 %) as negative, and 6 (29 %) as suspicious or rare-atypical cells. Based on molecular analysis, tumor mutations (TMs) were detected in 18/21 (86 %) of peritoneal washings. Overall, 11/21 (52 %) samples demonstrated concordant results between cytologic and molecular analysis, and all positive cytologic results were confirmed with molecular analysis. However, of cases with negative or suspicious cytology results, 77 % (10/13) were found to have TMs in washings. Five patients with negative cytology were positive on molecular analysis (5/7, 71 %), and 5 patients with suspicious washings demonstrated TMs (5/6, 83 %). Of the 10 EC patients who developed recurrences, regardless of stage, 5/10 (50 %) patients had positive cytology, whereas 9/10 (90 %) had TMs based on molecular analysis.

CONCLUSIONS

Mutational analysis of peritoneal washings using panel sequencing in EC is feasible. A substantial subset of patients with cytology-negative or suspicious washings had TMs detected.