Narasimhan, Avantika Lakshmi

e22006 Background: Metastasectomy is recommended for select pediatric patients with osteosarcoma with resectable pulmonary parenchymal metastases. It is unclear whether pulmonary metastasectomy confers the same benefit to patients with hilar or mediastinal lymph node metastases (LNM). This study aims to characterize pediatric patients with osteosarcoma with thoracic LNM and their outcomes compared to those with only pulmonary parenchymal metastasis. Methods: This is a retrospective cohort study of patients aged 0-21 with osteosarcoma metastatic to the lung who underwent pulmonary metastasectomy between 2000-2024. Patients were categorized into groups based on the presence or absence of LNM on imaging reviewed by pediatric surgeons and radiologists. Descriptive statistics and Wilcoxon rank sum, chi-square or Fisher’s exact tests evaluated differences between patients with and without LNM. Kaplan-Meier survival curves with log-rank tests evaluated the relationship between the presence of LNM and outcomes. The primary outcome was overall survival (OS) with secondary outcomes of recurrence-free survival (RFS) and disease-free survival (DFS). Results: 39 patients met inclusion criteria for this study, of which 13 (33%) had LNM (Table). Of the 13 patients with LNM, 8 (62%) had a pulmonary metastasectomy after their LNM diagnosis. Patients with LNM had poorer OS after first metastasectomy (log-rank p = .027), DFS after first metastasectomy (p = .018), and RFS after diagnosis (p = .039) than patients with pulmonary parenchymal metastasis without LNM. Patients who underwent metastasectomy after their LNM diagnosis had improved OS after LNM diagnosis than patients who did not undergo metastasectomy (pairwise log-rank test with Bonferroni correction p = .015). Conclusions: Pediatric patients with osteosarcoma metastatic to the lung with LNM had poorer OS, DFS, and RFS compared to patients without LNM. These results confirm the importance of attention to the presence of nodal involvement in patients with pulmonary metastatic osteosarcoma. Despite their poor prognosis, these results suggest a persistent survival benefit to surgical intervention. Total N = 39 No LMN N = 26 LMNN = 13 p Age 13.7 (9.5, 16.1) 13.9 (9.0, 15.9) 13.7 (10.7, 16.5) .777 Female 15 (38%) 10 (38%) 5 (38%) > .999 Histology Chondroblastic Osteoblastic Telangiectatic 11 (39%)16 (57%)1 (3.6%) 9 (50%)8 (44%)1 (5.6%) 2 (20%)8 (80%)0 (0%) .162 Primary tumor site Chest wall Femur Humerus Pelvis Radius Tibia 2 (5.1%)24 (62%)5 (13%)2 (5.1%)1 (2.6%)5 (13%) 2 (7.7%)14 (54%)3 (12%)2 (7.7%)1 (3.8%)4 (15%) 0 (0%)10 (77%)2 (15%)0 (0%)0 (0%)1 (7.7%) .821 Lung metastases present at time of diagnosis 20 (51%) 13 (50%) 7 (54%) .821 Treatment protocol AOST0331 AOST06P1 CCG 7921 P9754 30 (81%)2 (5.4%)4 (11%)1 (2.7%) 19 (79%)1 (4.2%)3 (13%)1 (4.2%) 11 (85%)1 (7.7%)1 (7.7%)0 (0%) > .999 Lung nodules removed during first metastasectomy 3 (2, 6) 3 (2, 5) 6 (1, 20) .567

Background Bowel obstruction in the setting of peritoneal metastases is a complex clinical situation. Evidence for operative intervention in this setting remains unclear. This study aimed to compare outcomes between patients with bowel obstruction and peritoneal metastases who underwent operative intervention vs those who underwent conservative management. Methods This was a retrospective single center study of all patients that were consulted on by the Division of Colon and Rectal Surgery in the 6-year period between January 1st 2019 and December 31st 2024 for the management of bowel obstruction in the setting of peritoneal metastases. The study compared patients who underwent operative intervention vs those who underwent conservative management. The primary outcome measures were ability to tolerate solid food at discharge, median obstruction free survival, and median overall survival. Results A total of 100 patients were diagnosed with bowel obstruction in the setting of peritoneal carcinomatosis. 47 patients underwent operative intervention and 53 underwent non-operative management. Those who underwent operative intervention were more likely to tolerate solid food at discharge (78.72% vs 47.17%, P < 0.01) and had a longer median obstruction free survival (593 days vs 147 days, P = 0.01). No difference was identified in overall survival (133 days vs 99 days, P = 0.49). Conclusions Bowel obstruction in the setting of peritoneal metastases is a complex situation that requires a personalized and pragmatic approach for each patient. Selecting those who may benefit from operative intervention can be challenging, however, there are subsets of patients for whom surgical management may be offered with acceptable outcomes.