Powell, Matthew A.

BACKGROUND Treatment of tubo-ovarian high-grade serous carcinoma (HGSC) includes cytoreductive surgery, platinum-based chemotherapy, and often poly(ADP-ribose) polymerase (PARP) inhibitors. While homologous recombination (HR) deficiency is a well-established predictor of therapy sensitivity, over 50% of HR-proficient HGSCs also exhibit sensitivity. Currently, there are no biomarkers to identify which HR-proficient HGSCs will be sensitive to standard-of-care therapy. Replication stress may serve as a key determinant of response. METHODS We evaluated phospho–RPA2-T21 (p-RPA2) foci via immunofluorescence as a biomarker of replication stress in formalin-fixed, paraffin-embedded HGSC samples collected at diagnosis from patients treated with platinum chemotherapy (discovery cohort, n = 31; validation cohort, n = 244) or PARP inhibitors ( n = 63). Recurrent HGSCs ( n = 38) were also analyzed. p-RPA2 score was calculated using automated imaging analysis. RESULTS Samples were defined as p-RPA2-high if more than 16% of cells had ≥2 p-RPA2 foci on automated analysis. In the discovery cohort, HR-proficient, p-RPA2-high HGSCs demonstrated significantly higher rates of a chemotherapy response score of 3 to platinum chemotherapy than HR-proficient, p-RPA2-low HGSCs. In the validation cohort, patients with HR-proficient, p-RPA2-high HGSCs had significantly longer survival after platinum treatment than those with HR-proficient, p-RPA2-low HGSCs. Additionally, the p-RPA2 assay effectively predicted survival outcomes in patients treated with PARP inhibitors and in recurrent HGSC samples. CONCLUSION Our study underscores the importance of considering replication stress markers, such as p-RPA2, alongside HR status in therapeutic planning. This approach has the potential to increase the number of patients receiving effective therapy while reducing unnecessary toxicity. FUNDING The Reproductive Scientist Development Program, GOG Foundation, Pilot Translational and Clinical Studies function of the Washington University Institute of Clinical and Translational Sciences, the Foundation for Barnes-Jewish Hospital, Washington University School of Medicine Dean’s Scholar Program, The Cancer Biology Pathway Training Grant (5T32CA113275-17), The Lucy, Anarcha, and Betsey (L.A.B.) Award from the Department of Obstetrics and Gynecology at Washington University School of Medicine, and Veterans Affairs Office of Research and Development (I01BX006020).

5503 Background: Pafolacianine sodium is under investigation as an adjunct to visual inspection and palpation by providing intra-operative imaging of folate receptor positive (FR+) ovarian cancer. Since complete resection (R0) is the strongest predictor of overall survival, methods to enhance detection of lesions are expected to benefit patient outcomes. Methods: For this phase 3, randomized, multicenter, single dose, open-label pivotal trial (NCT03180307), patients with ovarian cancer who were scheduled to undergo cytoreductive surgery were recruited from 11 sites in the US and Netherlands from March 2018 through April 2020. The study objectives were to confirm efficacy and safety of pafolacianine sodium (0.025 mg/kg i.v., ≥1 h prior to imaging) in combination with intraoperative near-infrared fluorescence (NIRF) imaging to detect additional lesions not detected by palpation and normal white light alone. Results: Pafolacianine sodium was administered to 150 total patients (safety analysis set); 109 patients comprised the full analysis set for efficacy analyses. Patients had primarily serous adenocarcinoma (n = 72; 68.6%) and advanced stage disease (n = 83; 76.1%). In 33% of patients (36 of 109), NIRF imaging with pafolacianine sodium identified additional lesions that were not planned for resection and were not detected by normal white light and palpation ( P < 0.001, 95% CI [0.243, 0.427]). Among patients who underwent interval debulking surgery, the rate was higher, at 39.7% of patients (23 of 58; 95% CI [0.270, 0.534]). At the individual lesion level, the accuracy of pafolacianine sodium with NIRF to detect ovarian cancer is reflected by sensitivity of 83% (95% CI [73.9, 89.4]) and a false positive rate of 32.7% (95% CI [25.6, 40.7]). Investigators reported achieving complete resection (R0) in 62.4% (68 of 109) of patients. Drug-related adverse events (AEs) were reported by 30% of patients (45 out of 150). The most frequently reported drug-related AEs were nausea (18.0%), vomiting (5.3%), and abdominal pain (4.7%). Infusion reactions at the time of the procedure were mostly (96%) mild or moderate in severity; 89% resolved within 24 hours of onset. No drug-related serious AEs or deaths were reported. Conclusions: This phase 3 trial of pafolacianine sodium with NIRF imaging met its primary endpoint, intraoperatively identifying additional cancer not planned for resection in a statistically significant number of patients. Therefore, pafolacianine sodium may offer a novel real-time adjunct to current surgical imaging practice in ovarian cancer surgery. Clinical trial information: NCT03180307.

Abstract Both metachronous and synchronous tumors pose a diagnostic and clinical challenge, more so when one of the specimens demonstrates the rare neuroendocrine histology. We describe a patient with sarcoidosis who was treated for endometrial and ovarian neoplasm, recurred with two separate histologies (adenocarcinoma and high grade neuroendocrine), both associated with microsatellite instability (MSI)-high status. Targeted next-generation sequencing of tumor with synonymous somatic alterations pointed to a common ancestry of all three tumors and patient was successfully treated with a tailored immunotherapy regimen. Her sarcoidosis worsened only slightly, and immunotherapy did not need to be discontinued. This case highlights the importance of molecular testing for the optimal therapy of complex synchronous tumors and the need for communication between surgical and medical oncologists in patients with MSI-high cancer. Key Points The case of a patient with a recurrent gynecological cancer presenting as microsatellite instability (MSI)-high endometrial adenocarcinoma and MSI-high neuroendocrine tumor is reported. This case demonstrated a common genetic lineage with good response to checkpoint inhibition without clinical worsening of autoimmune disease. This article adds to the literature, suggesting tumor evolution with neuroendocrine differentiation in some cancers, and argues that a molecular-based approach to treatment might achieve better understanding and possibly superior treatment outcomes.

Abstract MLH3 is a recently described member of the DNA mismatch repair gene family. Based on its interaction with the MutL homologue MLH1, it was postulated that MLH3 might play a role in tumorigenesis. Germ line and somatic mutations in MLH3 have been identified in a small fraction of colorectal cancers, but the role of MLH3 in colorectal cancer tumorigenesis remains controversial. We investigated MLH3's role in endometrial tumorigenesis through analysis of tumor and germ line DNA from 57 endometrial cancer patients who were at increased risk for having inherited cancer susceptibility. Patients with known MSH2 or MSH6 mutations were excluded as well as those who had MLH1-methylated tumors. Sixteen different variants were identified by single-strand conformational variant analysis. Of the 12 missense changes identified, three were somatic mutations. One patient had a germ line missense variant and loss of heterozygosity (LOH) in her tumor specimen. There was no evidence of MLH3 promoter methylation based on combined bisulfite restriction analysis. The identification of inherited missense variants, somatic missense mutations (present in 3 of 57 tumors), and LOH in the tumor from a patient with a germ line missense change suggest a role for MLH3 in endometrial tumorigenesis. (Cancer Res 2006; 66(15): 7502-8)