Lautz, Timothy B.

11535 Background: Twenty-five percent of patients with Ewing Sarcoma (EWS) have metastatic disease at diagnosis, most commonly in the lungs. Our objectives were to compare overall (OS) and pulmonary disease-free survival (PDFS) between patients with metastatic EWS at diagnosis who achieve rapid complete response (RCR), defined as radiographic resolution of all pulmonary nodules at the end of induction chemotherapy, and those with residual pulmonary nodules after induction chemotherapy (non-RCR). Methods: This multi-center, retrospective cohort study included children under 20 years of age with metastatic EWS treated from 2007-2020 at 19 institutions participating in the Pediatric Surgical Oncology Research Collaborative. Chi-square tests were conducted for differences among groups, and p < 0.05 was considered significant. Kaplan-Meier curves were generated for OS and PDFS. Cox regression was performed for OS, controlling for whole lung irradiation (WLI), extrapulmonary metastases, and age. Results: Among 153 patients with metastatic EWS at diagnosis, 61 (40%) achieved RCR, and 87 (57%) did not (5 unknown). The median number of pulmonary nodules was 3.5 in the RCR vs 5 in the non-RCR groups (p = 0.02), while bilateral disease was present in 44 (72%) RCR vs 75 (86%) non-RCR patients (p = 0.03). Pulmonary relapse occurred in 58 (38%) patients, including 18 (29%) in the RCR and 36 (41%) in the non-RCR groups (p = 0.14). Factors associated with pulmonary relapse in the univariate analysis include median age [15 years (IQR: 12-17) with pulmonary relapse vs 12 years (IQR: 9-16) without (p = 0.03)] and extrapulmonary metastases at diagnosis [24 (41%) patients with pulmonary relapse vs 26 (27%) patients without pulmonary relapse (p = 0.05)]. WLI was performed in 100 patients and was not associated with a reduction in pulmonary relapse (p = 0.93). Complete surgical clearance of pulmonary disease was attempted in 29 (19%) patients, including 17 of the patients who met the criteria for RCR. On Kaplan-Meier analyses, 5-year PDFS did not significantly differ based on RCR (67%) vs. non-RCR (53%, p = 0.13), or WLI (61%) vs. no WLI (54%, p = 0.32). However, 5-year OS did vary significantly between patients with RCR and WLI (85%), RCR without WLI (55%), non-RCR with WLI (60%), and non-RCR without WLI (25%; p < 0.01). In Cox regression analysis, RCR was associated with improved OS after controlling for WLI, extrapulmonary metastases, and patient age (HR 0.51, p = 0.03). Conclusions: Patients with EWS who had pulmonary metastases at diagnosis had improved OS if they achieved RCR and received WLI, despite having no significant differences in rates of pulmonary relapse. Further research is needed to determine whether clearance of pulmonary disease achieved through surgical metastasectomy provides a comparable survival benefit and if any subsets of patients have a reduced risk of pulmonary relapse after resection.

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.

TPS11591 Background: Patients with high-risk rhabdomyosarcoma (HR-RMS) continue to have poor outcomes with 3-year event free survival (EFS) rates of 30% or less despite chemotherapy dose intensification on recent cooperative group RMS trials. Vinorelbine (VINO) has demonstrated clinical activity in RMS patients with relapsed/refractory disease and shown to provide a survival benefit when given with oral cyclophosphamide as maintenance chemotherapy for a select group of patients that achieved first complete remission. Methods: ARST2031 is a randomized Phase 3 trial with the primary aim to compare event-free survival (EFS) of patients with HR-RMS treated with vincristine, dactinomycin and cyclophosphamide (VAC) followed by maintenance with vinorelbine and oral cyclophosphamide (VINO-CPO) or vinorelbine, dactinomycin and cyclophosphamide (VINO-AC) followed by maintenance with VINO-CPO. Patients are stratified by histology and randomly assigned to VAC followed by VINO-CPO maintenance or VINO-AC followed by VINO-CPO maintenance. To be eligible, patients must be ≤ 50 years of age at the time of enrollment with newly diagnosed RMS except adult-type pleomorphic, based upon institutional histopathologic classification. All patients must have Stage 4 disease and patients diagnosed with embryonal RMS (ERMS) must be ≥ 10 years of age. Patients with malignant cytology in cerebrospinal fluid, intra-parenchymal brain metastases, or diffuse leptomeningeal disease are excluded. The study was activated on September 13, 2021 and is anticipated to enroll approximately 4 patients per month. The planned sample size is 100 patients, with approximately 50 patients randomized to each arm. Safety and feasibility of VINO-AC will be assessed in the first 8 patients prior to randomization. The study will have power of 0.8 to detect a hazard ratio of 0.61 (74 events in total) when the one-sided Type I error rate is 0.10, with 30 months of accrual and 2 years of follow-up. The hazard ratio of 0.61 was determined by assuming piecewise exponential distributions and specifying the 2-year EFS of 46% vs. 28% and long-term EFS of 32% vs. 16%, based on prior outcome data. Biospecimens will be collected and banked for future use. Clinical trial information: NCT04994132.

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.

Background Most children with intermediate‐risk rhabdomyosarcoma (RMS) have gross disease (group III) at the initiation of chemotherapy. Delayed primary excision (DPE) after induction chemotherapy allows for a reduction in adjuvant radiation dose, but with the risk of potential surgical morbidity. The objectives of this study were to compare outcomes in children with group III RMS who did and did not undergo DPE and to assess surgical morbidity. Methods The study included 369 patients who had clinical group III RMS at sites amenable to DPE from intermediate‐risk Children's Oncology Group studies D9803 (encouraged DPE) and ARST0531 (discouraged DPE). Results The primary tumor site was bladder/prostate (136 patients; 37%), extremity (97 patients; 26%), trunk (24 patients; 7%), retroperitoneum (91 patients; 25%), or intrathoracic/perineum/perianal (21 patients; 6%). In total, 112 patients (53.9%) underwent DPE in D9803, and 26 patients (16.2%) underwent DPE in ARST0531 ( P < .001), with loss of vital organ or function in 30 of 138 patients (22%). DPE allowed for a reduced radiation dose in 110 of 135 patients (81%; 51% were reduced to 36 Gy, and 30% were reduced to 42 Gy). Patients who underwent DPE had improved unadjusted overall survival ( P = .013). In adjusted regression analysis, the risk of death (hazard ratio, 0.71; 95% CI 0.43‐1.16) was similar for patients who did and did not undergo DPE and was improved for the subset of patients who had tumors of the trunk and retroperitoneum (hazard ratio, 0.44; 95% CI, 0.20‐0.97). Conclusions Children with group III RMS have equivalent or improved outcomes with DPE and can receive a decreased radiation dose for definitive local control. The choice of local control modality should weigh the potential morbidity of surgery versus that of higher dose irradiation.

Abstract The International Soft‐Tissue Sarcoma Consortium (INSTRuCT) was founded as an international collaboration between different pediatric soft‐tissue sarcoma cooperative groups (Children's Oncology Group, European Pediatric Soft‐Tissue Sarcoma Group, and Cooperative Weichteilsarkom Studiengruppe). Besides other tasks, a major goal of INSTRuCT is to develop consensus expert opinions for best clinical treatment. This consensus paper for patients with rhabdomyosarcoma of the female genital tract (FGU‐RMS) provides treatment recommendations for local treatment, long‐term follow‐up, and fertility preservation. Therefore, a review of the current literature was combined with recommendations of the treatment protocols of the appropriate clinical trials. Additionally, opinions of international FGU‐RMS experts were incorporated into recommendations. Results were that the prognosis of FGU‐RMS is favorable with an excellent response to chemotherapy. Initial complete surgical resection is not indicated, but diagnosis should be established properly. In patients with tumors localized at the vagina or cervix demonstrating incomplete response after induction chemotherapy, local radiotherapy (brachytherapy) should be carried out. In patients with persistent tumors at the corpus uteri, hysterectomy should be performed. Fertility preservation should be considered in all patients. In conclusion, for the first time, an international consensus for the treatment of FGU‐RMS patients could be achieved, which will help to harmonize the treatment of these patients in different study groups.

Background The International Soft Tissue Sarcoma Consortium (INSTRuCT) was founded as an international collaboration between different pediatric soft tissue sarcoma cooperative groups (COG, EpSSG, CWS). Besides other tasks, a major goal of the INSTRuCT is to develop consensus expert opinions for best clinical treatment. This consensus paper for patients with rhabdomyosarcoma of the female genital tract (FGU-RMS) provides treatment recommendations for local treatment, long term follow up and fertility preservation. Methods Review of the current literature was combined with recommendations of the treatment protocols of the appropriate clinical trials. Additionally, opinions of international FGU-RMS experts were incorporated into recommendations. Results The prognosis of FGU-RMS is favorable with an excellent response to chemotherapy. Initial complete surgical resection is not indicated, but diagnosis should be established properly. In patients with tumors localized at the vagina or cervix demonstrating incomplete response after induction chemotherapy, local radiotherapy (brachytherapy) should be carried out. In patients with persistent tumors at the corpus uteri, hysterectomy should be performed. Fertility preservation should be considered in all patients. Conclusion For the first time, an international consensus for the treatment of FGU-RMS patients could be achieved, which will help to harmonize the treatment in different study groups.

Background The objective of this study was to evaluate local control for patients with intermediate‐risk rhabdomyosarcoma (RMS) treated on Children's Oncology Group (COG) protocol ARST0531. Methods This study analyzed 424 patients with intermediate‐risk RMS. Patients were randomized to chemotherapy with either vincristine, dactinomycin, and cyclophosphamide (VAC) or VAC alternating with vincristine and irinotecan. With the goal of improving local control, radiation therapy (RT) was delivered early at week 4 and was concurrent with irinotecan in the experimental arm. Individualized local control plans for children 24 months old or younger were allowed. Local failure on ARST0531 was compared with local failure on the preceding COG intermediate‐risk study, D9803. Results For patients with group I/II alveolar RMS (n = 55), the 5‐year cumulative incidence of local failure was 13.4%; for group III alveolar RMS (n = 141), it was 20.2%; and for group III embryonal RMS (n = 228), it was 27.9% ( P = .03). Among patients with group III disease, local failure did not differ by histology, site, nodal status, RT modality, or treatment arm. Local failure was worse for a tumor size >5 cm (32.3% vs 16.7%; P = .001). Among patients with group III embryonal RMS, local failure was higher on ARST0531 than D9803 (27.9% vs 19.4%; P = .03). After the exclusion of patients 24 months old or younger or patients who did not receive radiation, local failure remained significantly increased on ARST0531 ( P = .02). After adjustments for clinical prognostic factors, event‐free survival and overall survival were worse on ARST0531 ( P = .004 and P = .05, respectively). Conclusions Despite interventions designed to enhance local control, local control was inferior on ARST0531 in comparison with D9803. The reason for this is unclear, but it could be the reduced cyclophosphamide dose on ARST0531.