Naik‐Mathuria, Bindi

Objective: The purpose of this study was to describe management and outcomes from a contemporary cohort of children with Wilms tumor complicated by inferior vena caval thrombus. Background: The largest series of these patients was published almost 2 decades ago. Since then, neoadjuvant chemotherapy has been commonly used to manage these patients, and outcomes have not been reported. Methods: Retrospective review of 19 North American centers between 2009 and 2019. Patient and disease characteristics, management, and outcomes were investigated and analyzed. Results: Of 124 patients, 81% had favorable histology (FH), and 52% were stage IV. IVC thrombus level was infrahepatic in 53 (43%), intrahepatic in 32 (26%), suprahepatic in 14 (11%), and cardiac in 24 (19%). Neoadjuvant chemotherapy using a 3-drug regimen was administered in 82% and postresection radiation in 90%. Thrombus level regression was 45% overall, with suprahepatic level showing the best response (62%). Cardiopulmonary bypass (CPB) was potentially avoided in 67%. The perioperative complication rate was significantly lower after neoadjuvant chemotherapy [(25%) vs upfront surgery (55%); P=0.005]. CPB was not associated with higher complications [CPB (50%) vs no CPB (27%); P=0.08]. Two-year event-free survival was 93% and overall survival was 96%, higher in FH cases (FH 98% vs unfavorable histology/anaplastic 82%; P=0.73). Neither incomplete resection nor viable thrombus cells affected event-free survival or overall survival. Conclusions: Multimodal therapy resulted in excellent outcomes, even with advanced-stage disease and cardiac extension. Neoadjuvant chemotherapy decreased the need for CPB to facilitate resection. Complete thrombectomy may not always be necessary.

AbstractWilms tumor (WT) is the most common renal malignancy in children. Children with favorable histology WT achieve survival rates of over 90%. Twelve percent of patients present with metastatic disease, most commonly to the lungs. The presence of a pleural effusion at the time of diagnosis of WT may be noted on staging imaging; however, minimal data exist regarding the significance and prognostic importance of this finding. The objectives of our study are to identify the incidence of pleural effusions in patients with WT, and to determine the potential impact on oncologic outcomes. A multi‐institutional retrospective review was performed from January 2009 to December 2019, including children with WT and a pleural effusion on diagnostic imaging treated at Pediatric Surgical Oncology Research Collaborative (PSORC) participating institutions. Of 1259 children with a new WT diagnosis, 94 (7.5%) had a pleural effusion. Patients with a pleural effusion were older than those without (median 4.3 vs 3.5 years; P = .004), and advanced stages were more common (local stage III 85.9% vs 51.9%; P < .0001). Only 14 patients underwent a thoracentesis for fluid evaluation; 3 had cytopathologic evidence of malignant cells. Event‐free and overall survival of all children with WT and pleural effusions was 86.2% and 91.5%, respectively. The rate and significance of malignant cells present in pleural fluid is unknown due to low incidence of cytopathologic analysis in our cohort; therefore, the presence of an effusion does not appear to necessitate a change in therapy. Excellent survival can be expected with current stage‐specific treatment regimens.

Abstract Inflammatory myofibroblastic tumor (IMT) is a mesenchymal neoplasm of intermediate malignancy. We describe the largest cohort of IMT patients to date, aiming to further characterize this rare, poorly understood tumor. This is a multi‐institutional review of IMT patients ≤39 years, from 2000 to 2018, at 18 hospitals in the Pediatric Surgical Oncology Research Collaborative. One hundred and eighty‐two patients were identified with median age of 11 years. Thirty‐three percent of tumors were thoracic in origin. Presenting signs/symptoms included pain (29%), respiratory symptoms (25%) and constitutional symptoms (20%). Median tumor size was 3.9 cm. Anaplastic lymphoma kinase (ALK) overexpression was identified in 53% of patients. Seven percent of patients had distant disease at diagnosis. Ninety‐one percent of patients underwent resection: 14% received neoadjuvant treatment and 22% adjuvant treatment. Twelve percent of patients received an ALK inhibitor. Sixty‐six percent of surgical patients had complete resection, with 20% positive microscopic margins and 14% gross residual disease. Approximately 40% had en bloc resection of involved organs. Median follow‐up time was 36 months. Overall 5‐year survival was 95% and 5‐year event‐free survival was 80%. Predictors of recurrence included respiratory symptoms, tumor size and distant disease. Gross or microscopic margins were not associated with recurrence, suggesting that aggressive attempts at resection may not be warranted.

10024 Background: Inflammatory myofibroblastic tumor (IMT) is a mesenchymal neoplasm of intermediate malignancy, predominantly seen in children and young adults. Given its rarity, data are limited. We describe the largest cohort of patients with IMT to date, with an aim to further characterize this poorly understood tumor. Methods: A multi-institutional review was performed at 18 North American hospitals participating in the Pediatric Surgical Oncology Research Collaborative to identify IMT patients ≤39 years, diagnosed from 2000-2018. Descriptive statistics are described as median and interquartile range. Multivariable analysis was used to identify predictors of event free survival (EFS). Results: 182 patients were identified with a median age of 11 years (5-17); 52% were female. 33% of tumors were thoracic, 26% abdominal/pelvic, 20% head/neck, and 14% genitourinary. Common presenting symptoms included pain (29%), respiratory symptoms (24%), weight loss (12%), and a palpable mass (10%). Median tumor size was 3.9 cm (1.9-6.5). Anaplastic lymphoma kinase (ALK) overexpression was identified via immunohistochemistry in 53% of patients tested. One third of patients had abnormal cytogenetics, with 12% of the entire cohort having an ALK mutation. 7% of patients had distant disease at diagnosis. 13% of patients received neoadjuvant therapy including chemotherapy (3%), ALK inhibitor (4%), radiation (0.5%), non-steroidal anti-inflammatories (NSAIDs) (7%), or steroids (2%). Of those who underwent resection with known margin status (n = 158), 66% had complete resection, 20% had microscopic positive margins, and 14% had gross residual disease. Just over 40% of patients had an en bloc resection of involved organs, most commonly lung (26%). 21% of patients received adjuvant therapy, including chemotherapy (3%), ALK inhibitor (9%), radiation (0.5%), NSAIDs (8%), or steroids (5%). 12% of all patients received an ALK inhibitor: 24% neoadjuvant, 62% adjuvant, and 14% without surgery. Median follow-up time was 36 months (14-69). Overall 5-year survival (OS) was 95% and 5-year EFS was 80%. Predictors of recurrence included respiratory symptoms, larger tumor size, or distant disease at diagnosis. Gender, race, age and primary site were not predictive of EFS. Likewise, there was no association of ALK overexpression or ALK mutation with EFS. The presence of gross or microscopic margins following resection was not associated with recurrence. Conclusions: IMT is a rare tumor with favorable OS. Five year recurrence rate was 20%. Presenting with respiratory symptoms, larger tumor size, or metastatic disease was associated with recurrence, while ALK positivity was not. Notably, a positive margin after resection was not associated with increased recurrence, indicating that aggressive attempts at surgical resection that would compromise form or function may not be warranted.