Objectives: Assess outcomes of a clinical cohort of patients with endometrioid endometrial cancer (EEC) harboring somatic POLE exonuclease domain mutations (EDMs).Methods: Patients were consented to a protocol of tumor-normal massively parallel sequencing of 410-468 cancer related genes. EECs subjected to sequencing from 2014 to 2018 were reviewed. Tumors with somatic POLE EDMs were identified. EECs were assessed for microsatellite instability (MSI) using MSIsensor and immunohistochemical analysis for mismatch repair (MMR) proteins.Results: Of the 451 EECs sequenced, 23 had a POLE EDM (5%): 20 primary and 3 recurrent tumors sequenced. Nineteen cases (83%) were stage I/II and 4 (17%) were stages III/IV. Thirteen EECs (57%) were of FIGO grades 1/2, 10 (43%) grade 3. All patients were treated with surgery and 17 (89%) received adjuvant therapy. Five (22%) demonstrated loss of DNA MMR protein expression, none were due to Lynch syndrome. MSIsensor scores were conclusive for 21 samples: 19 were microsatellite stable and 2 MSI-high. After median follow-up of 30 months, 4/23 (17%)Dr. Makker reports grants and personal fees from Esai; grants and personal fees from Merck; other from International PI 775-03/ E7080-G000-309; grants from Takeda (MSKCC PI C31004); personal fees from ArQule; grants and personal fees from Karyopharm; grants from AstraZeneca, grants from Lilly; personal fees from IBM Watson, outside the submitted work. Dr. Soslow reports personal fees from Ebix/Oakstone*; personal fees from Cambridge University Press**; personal fees from Springer Publishers**; personal fees from Roche***, outside the submitted work. (*Preparation of recorded lectures; **royalties; ***one lecture) Dr.

Objectives: Assess outcomes of a clinical cohort of patients with endometrioid endometrial cancer (EEC) harboring somatic POLE exonuclease domain mutations (EDMs).Methods: Patients were consented to a protocol of tumor-normal massively parallel sequencing of 410-468 cancer related genes. EECs subjected to sequencing from 2014 to 2018 were reviewed. Tumors with somatic POLE EDMs were identified. EECs were assessed for microsatellite instability (MSI) using MSIsensor and immunohistochemical analysis for mismatch repair (MMR) proteins.Results: Of the 451 EECs sequenced, 23 had a POLE EDM (5%): 20 primary and 3 recurrent tumors sequenced. Nineteen cases (83%) were stage I/II and 4 (17%) were stages III/IV. Thirteen EECs (57%) were of FIGO grades 1/2, 10 (43%) grade 3. All patients were treated with surgery and 17 (89%) received adjuvant therapy. Five (22%) demonstrated loss of DNA MMR protein expression, none were due to Lynch syndrome. MSIsensor scores were conclusive for 21 samples: 19 were microsatellite stable and 2 MSI-high. After median follow-up of 30 months, 4/23 (17%)Dr. Makker reports grants and personal fees from Esai; grants and personal fees from Merck; other from International PI 775-03/ E7080-G000-309; grants from Takeda (MSKCC PI C31004); personal fees from ArQule; grants and personal fees from Karyopharm; grants from AstraZeneca, grants from Lilly; personal fees from IBM Watson, outside the submitted work. Dr. Soslow reports personal fees from Ebix/Oakstone*; personal fees from Cambridge University Press**; personal fees from Springer Publishers**; personal fees from Roche***, outside the submitted work. (*Preparation of recorded lectures; **royalties; ***one lecture) Dr.

No abstract

Faculty Advisor: John Fischer, MD PURPOSE: To develop a low fidelity model for retroperitoneal dissection and identification of the ureter to improve resident's confidence and competency in the operating room. BACKGROUND: Work hour restrictions and few open laparotomies have created barriers to confident resident performance of retroperitoneal dissections. While simulation training models have been developed for laparoscopy, few have been created and validated for open laparotomies. METHODS: OB/GYN residents were divided into case (PGY3) and control (PGY4). A pretest questionnaire assessed operative experience. Both groups performed a videotaped low fidelity simulated retroperitoneal dissection that included identifying the course of the ureter. An instructional video was introduced and repeat simulation was performed by PGY3 trainees only. Three expert gynecologists independently scored performances using a checklist and global rating scale of operative performance (OSAT). PGY3 pretest/posttest scores were compared to PGY4 scores using the Wilcoxon rank sum test. Paired t-test was used for comparison of cases. P<.05. RESULTS: Median pretest checklist score for PGY4 was significantly increased compared to PGY3 (7.3 vs. 6.3, P=.0314) however the median pretest OSAT score was not. A statistically significant increase in average PGY3 scores between pre vs. post final checklist scores and final OSAT scores was noted. A statistically significant increase in the median scores between PGY4 pretest (control) vs. PGY3 posttest (case) final checklist scores and final global scores (7.3 vs. 9.2, P=.0052) and (24.2 vs. 28.2, P=.0042) was noted. DISCUSSION: The development of a low fidelity model for retroperitoneal dissection and use of an instructional video may complement traditional learning for this core competency.