5563 Background: PARP inhibitors (PARPi) are approved for maintenance treatment of platinum sensitive ovarian cancers either after front-line therapy or after treatment for recurrence. Current recommendations include retreatment with platinum-based chemotherapy (PC) after progression on maintenance PARPi. There exists a theoretical concern that progression of disease (POD) on PARPi is indicative of the development of platinum resistance due to similar DNA targets of platinum chemotherapy and PARPi. Our objective was to evaluate the response to subsequent chemotherapy in patients who progressed on PARPi maintenance. Methods: All patients with ovarian, fallopian tube, or primary peritoneal cancer treated with PARPi treatment from 2017 to 2021 at two academic tertiary care centers were retrospectively identified. Patients were assessed for treatment time on PARPi, time to POD on PARPi (PFS), type of chemotherapy regimen following PARPi maintenance, and time to disease progression on subsequent therapy following PARPi (PFS2). Comparative statistical analyses were performed with appropriate two-sided statistical tests. Time to progression on chemotherapy after PARPi was calculated using the Kaplan-Meier method. Results: A total of 83 ovarian cancer patients treated with PARPi were identified, and of these, 61 (73.5%) were treated with PARPi in the maintenance setting. Among the patients treated with PARPi maintenance, 22 (36.1%) remain on treatment. 19 (31.1%) patients were started on PARPi maintenance after front-line chemotherapy. While on PARPi maintenance, 63.9% discontinued PARPi, the majority due to POD, and 26.2% due to patient intolerance of side effects. Following POD, 21/29 (72.4%) received subsequent PC and 8/29 (27.6%) received non-platinum based chemotherapy (NPC). Treatment time, PFS, and PFS2 are listed in Table. Of the patients who received PC, 14/21 (66.7%) had a PFS2 of over six months and 5/21 (23.8%) had a PFS2 of over 12 months. Of the patients who received NPC, 7/8 (87.5%) had a PFS2 of over six months and 2/8 (25.0%) had a PFS2 of over 12 months. Conclusions: Following POD on PARPi, patients responded to both PC and NPC. Time to progression on subsequent chemotherapy after treatment with PARPi does not differ significantly between PC and NPC regimens. Many patients continue to see benefit from PC after PARPi maintenance. Retreatment with PC following POD on PARPi maintenance should still be considered.[Table: see text]

Surgical site infections (SSI) are the most common surgical complication. Perioperative antibiotics can reduce SSI when used properly. Despite guidelines from The American College of Obstetrics and Gynecology, non-indicated antibiotic use is widespread which exposes women to unnecessary risks. This study represents a quality improvement analysis assessing surgeon compliance with established guidelines regarding antibiotic use in gynaecological surgery. This is a single centre, retrospective study examining gynaecological procedures over two years. Cases were identified using Current Procedure Terminology codes. Perioperative antibiotics were used contrary to published guidelines in 199 of 1046 cases. Three variables were independently associated with inappropriate administration of perioperative antibiotics: entrance into abdominal cavity, higher EBL, and longer procedures. Impact statement Overuse of antibiotics has unintended consequences including allergic sequelae, extended length of hospital stay, increased healthcare costs, and the formation of antibiotic-resistant organisms. Antibiotic stewardship programmes have been shown to reduce the number of resistant pathogens, decrease incidence of Clostridium difficile colitis, and decrease length of hospital stay without increasing infection rates. Further outcomes-based research is needed regarding the use of antibiotic stewardship programmes in gynaecological surgery.

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The natural gas industry is a boon to the economy of the United States and will continue to expand in the following decades. Hydraulic fracturing (fracking), however, produces much waste and it must be determined how to dispose of unwanted byproducts of natural gas drilling, such as produced wastewater, solid scale, and oil. Radionuclides such as uranium were deposited in the Marcellus Shale millions of years ago and are now being returned to the surface in produced water from fracking. The presence of radionuclides creates a policy conflict between laws that protect public health and the economics of disposing of produced water. This case study will help readers understand how geologic history, hydrology, and present policy are intricately related in Pennsylvania. It will address possible methods for handling wastewater—storage, reuse, treatment, injection wells, and transport—and the degree to which state and federal policies protect drinking water from produced water. In addition, the Radium Girls factory case from California helps readers consider how the mode of exposure matters for the effects of human contact with radionuclides. Students of environmental policy will be better able to understand the linkages between policy and the physical sciences.

Uterine gas gangrene caused by Clostridium perfringens is a serious, often life-threatening infection that is rarely encountered in the practice of gynecologic oncology. However, the hypoxic nature of gynecologic cancers due to necrosis and/or prior radiation therapy creates a microenvironment optimal for proliferation of anaerobic bacteria such as the Clostridium species. Early recognition and aggressive treatment with IV antibiotics and surgical debridement remain the cornerstones of management in order to decrease morbidity and mortality. Here we present the case of a 52 year-old woman with a remote history of cervical cancer who was previously treated at our institution with primary chemotherapy and radiation and was then admitted decades later with Clostridium perfringens bacteremia and CT evidence of intrauterine abscess. The patient received a prolonged course of IV antibiotic therapy and subsequently underwent definitive surgical management with a total abdominal hysterectomy, bilateral salpingo-oophorectomy, small bowel resection with anastomosis for a utero-ileal fistula identified intraoperatively. Pathology from the uterine specimen demonstrated a primary poorly differentiated uterine adenocarcinoma. The patient recovered fully from her Clostridium perfringens infection and was discharged from the hospital shortly after surgical intervention.

e17027 Background: Vulvar carcinoma is a rare gynecologic malignancy which has seen a considerable evolution in surgical techniques over the last several decades. However, the morbidity associated with inguinal lymph node dissections remains significant. The majority of patients undergoing full lymphadenectomy will have some complication, with wound breakdown being the most common. In males, robotic inguinal lymph node dissection has been described for penile cancer. This report represents a first use of near-infared fluorescence for sentinel inguinal lymph node mapping, and the first description of complete robotic inguinal lymph node dissection for patients with vulvar malignancies. Methods: Bilateral robotic-assisted inguinal lymph node mapping and and lymphadenectomy was performed using the daVinci Xi system with a near-infared fluourescence. Results: The patient presented at 81 years old with a 3 cm lesion on the left labia. In the operating room, the vulvar lesion was injected circumferentially with indocyanine green. A 1 cm incision was made in the skin over the apex of the left femoral triangle carried past the underlying campers fascia. The tissue plain was developed overlying the femoral triangle using a tissue expander balloon. Under visual guidance, an 8 mm camera port and two 8 mm instrument ports were placed and the robot docked. The ipsilateral sentinel lymph nodes were identified using near-infared fluorescence and resected. We then performed a complete left superficial inguinal lymph node dissection. The right side was then performed in identical fashion. No sentinel node was identified on the right side. Radical hemivulvectomy was then performed without difficulty. All 11 lymph nodes were negative for disease. She was returned to the OR once for replacement of her JP drains. Her postoperative course was otherwise unremarkable and she is currently 15 months postoperative without complications or recurrence. Conclusions: Sentinel lymph node mapping and superficial inguinal lymph node dissection using robotic-assisted techniques and near-infared fluorescence is feasible and warrants further investigation.

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