Citations

10030 Background: CABO is a multi-targeted kinase inhibitor of VEGFR2, c-MET, AXL and RET and has shown clinical evidence of activity in two prior studies of adult and pediatric patients with advanced OS. We report results of a feasibility cohort of CABO + MAP chemotherapy in patients with newly diagnosed high-risk OS. Methods: Patients <40 years, body surface area ≥ 0.8 m 2 and new diagnosis of high-grade OS with metastatic disease and resectable primary tumor were eligible. Patients were enrolled to two CABO dose levels (Dose Level 1 (DL1) 25 mg/m 2 /day, maximum 40 mg/day; Dose Level 2 (DL2) 35 mg/m 2 /day; maximum 60 mg/day) using a modified IQ 3+3 design. CABO was orally administered concomitantly with six 35-day cycles of MAP (cisplatin 60 mg/m 2 on days 1-2 (cycles 1-4), doxorubicin 37.5 mg/m 2 on days 1-2 (with dexrazoxane), methotrexate 12 g/m 2 on days 22, 29) and for 24 weeks as maintenance monotherapy. CABO was held after 7 weeks and resumed during 4 th MAP cycle to allow for primary tumor resection and metastatic surgeries. Dose-limiting toxicities (DLT) were assessed during weeks 1-6 of treatment; additional monitoring for post-surgical complications was conducted through completion of 4 th MAP cycle. The primary endpoint for this cohort was feasibility of combination therapy. Results: Ten patients (median age 11.5 years, 70% male) were enrolled and treated with CABO + MAP (DL1, n=4; DL2, n=6). Median cumulative doses of all MAP agents were maintained throughout treatment with no dose reductions. Concomitant dosing of CABO with MAP was tolerated with no protocol-specified DLTs occurring during the evaluation period. DL2 (35 mg/m 2 ) was established as the recommended dose for further study of combination therapy. Commonly reported adverse events included hematologic toxicities, febrile neutropenia, and alanine/aspartate aminotransferase (AST/ALT) elevation. Interruption of CABO was required in 6 patients for Grade 3+ AST/ALT elevation following methotrexate (n=3), wound complications (n=3), and Grade 3 pneumothorax (n=1). Wounds included two Grade 3 port site events and one Grade 1 primary tumor resection site; two patients later resumed CABO after healing without wound recurrence. Dose reduction of CABO was required in one patient for Grade 4 amylase elevation. Conclusions: The combination of CABO + MAP is feasible with no protocol-specified DLTs during the evaluation period. Generalizability is limited based on cohort size. Further evaluation of CABO + MAP is ongoing in a phase II/III randomized efficacy study in newly diagnosed standard and high-risk patients using CABO dose of 35 mg/m 2 /day (max 60 mg), with delayed initiation of CABO in patients with port placement and early safety monitoring for wound-related events, as well as full study monitoring of dose delivery, wound complications and systemic toxicity. Clinical trial information: NCT05691478 .

10035 Background: Ewing sarcoma (EwS) is a rare malignancy of children, adolescents and young adults for which outcomes have progressively improved through intensification of conventional chemotherapy, including interval compression of cycles. Prior cooperative group reports of relapsed EwS included patients treated less intensively and with fewer treatment options at relapse. Here, we report overall survival (OS) and prognostic factors post-first recurrence in patients with EwS treated with frontline interval-compressed chemotherapy. Methods: We included patients treated on the last three phase 3 COG EwS studies treated with interval compressed chemotherapy, which accrued from 2001-2019. Patients with initially localized disease (L-EwS) were treated on AEWS0031 arm B and AEWS1031. Patients with initially metastatic disease (M-EwS) were treated on AEWS1221. The primary outcome was OS from first relapse. Demographic and clinical data from original diagnosis and from relapse were analyzed as potential prognostic factors. Kaplan-Meier survival curves were constructed and groups compared with log-rank tests. Results: 366 patients experienced disease recurrence as first event and were included in this analysis (AEWS0031 arm B, n = 69, AEWS1031, n = 115, for a total of 184 with L-EwS; AEWS1221, n = 182, all with M-EwS). Median age at relapse was 16 years. Median time from initial enrollment to first relapse was 1.52 years and was shorter for patients with M-EwS (Kruskall-Wallis, p < 0.001). First relapses were isolated local, isolated distant, and combined in 24%, 70%, and 6.4% of patients, respectively. Metastatic stage at initial diagnosis was associated with increased risk of post-first recurrence OS event (p < 0.0001). Two-year OS post-first recurrence (OS 2y ) was 25.6% for patients with M-EwS and 48.5% for patients with L-EwS. Time to first recurrence was also a predictor of post-recurrence survival (p < 0.0001): patients with initial L-EwS and relapse < 2 years from diagnosis had OS 2y of 31.4% vs. 70.8% for later relapses. Patients with initial M-EwS and relapse < 2 years from diagnosis had OS 2y of 18.9% vs. 71.2%. Patients with combined relapses had higher risk of post-relapse death compared to other patterns of failure (p = 0.003), an effect that was largely driven by the one seen in patients with initial L-EwS. Conclusions: Overall survival of patients with first recurrent EwS after having received modern era therapy with interval compressed chemotherapy on recent COG trials remains poor, particularly for M-EwS, early relapse and combined relapses. These data will inform the design of trials for this relapsed population and provide critical data to help counsel patients about goals of care at first relapse.

AbstractPatients with resectable Ewing sarcoma (ES) in select sites, such as the pelvis or chest wall, have a higher risk of positive microscopic margins following surgery. AEWS1031 was the first North American/Australasia ES cooperative group trial allowing standardized preoperative radiotherapy, intended to minimize the morbidity of combined modality local tumor control as well as improve the likelihood of clear surgical margins. In this study, we found that the use of low‐dose preoperative radiation to a smaller target volume resulted in a high rate of R0 resection. The robust pathologic response rate strengthens existing evidence illustrating the radiosensitivity of Ewing sarcoma.

Ewing sarcoma and osteosarcoma constitute 36% of all primary bone cancers. However, these 2 subtypes represent the most commonly diagnosed bone cancer types in the pediatric and adolescent population. Although still largely unknown, certain genetic mutations, rearrangements, and/or predisposition syndromes likely play a role in the pathogenesis of bone cancer. Osteosarcoma may also develop as a direct result of the long-term side effects of radiation therapy. With the implementation of a multimodality approach to treatment, including multiagent neoadjuvant and adjuvant chemotherapy regimens, targeted therapy options, surgery, and radiation, individuals with Ewing sarcoma and osteosarcoma are showing higher cure rates and improved overall survival. The NCCN Guidelines for Bone Cancer provide a consensus and evidence-based framework for the workup, management, and surveillance of local and recurrent/metastatic disease.

Trends in diagnostic biopsy sample collection approaches for primary bone sarcomas have shifted in the past 2 decades. Although open/incisional biopsies used to be the predominant approach to obtain diagnostic material for Ewing sarcoma and osteosarcoma, image-guided core needle biopsies have increased in frequency and are safe for patients. These procedures are less invasive and reduce recovery times but have potential limitations. The quantity and quality of tissue obtained through these procedures vary between institutions. Acquired viable tissue volumes can be low, limiting the conduct of downstream expanded clinical workup, molecular analyses, and research. Patients with advanced Ewing sarcoma and osteosarcoma continue to have overall poor outcomes despite dose-intensive cytotoxic chemotherapy. The biology of treatment resistance is not currently well understood, partly due to limited availability of relevant tissue to study. There is a need for access to quality tumor specimens for molecular and other analyses to identify high-risk tumor subsets and drive discovery to improve patient outcomes. Given broad variability in bone tumor tissue procurement and processing across member institutions, the Children’s Oncology Group Bone Tumor Committee convened a multidisciplinary group of experts to outline the current and near-future tissue needs for optimal clinical care and access to research platforms. The goal of this working group was to provide high-level guidance on biopsy practices that safely meet these evolving needs. Harmonizing tissue collection practices is paramount to improving the care of children, adolescents, and young adults diagnosed with Ewing sarcoma and osteosarcoma.

AbstractNon‐rhabdomyosarcoma soft tissue sarcoma (STS) comprises most STS in pediatric patients. It is a diverse set of over 30 histologic subtypes. Treatment is based on risk group determined by tumor size, grade, and the presence of metastases. Surgical resection is a cornerstone of therapy, as tumors are often resistant to chemotherapy or radiation. While patients with isolated tumors less than 5 cm may undergo upfront resection, strong consideration should be given to neoadjuvant chemoradiotherapy to ensure negative margins at surgical resection and optimal outcomes. Sentinel lymph node biopsy is strongly recommended for clear cell and epithelioid sarcomas. The most common metastatic site is the lung, and metastases should be resected at the end of therapy, when feasible. Unfortunately, many high‐risk patients progress on therapy, and alternative strategies including earlier metastatic control require investigation.

11529 Background: To evaluate clinical characteristics and patterns of treatment failure in patients with localized Ewing sarcoma (ES) treated on AEWS1031 according to local control (LC) strategies, tumor size, and tumor site. Methods: AEWS1031 was a phase 3 randomized trial comparing two interval compressed chemotherapy regimens. Patients who completed LC on AEWS1031 were analyzed. LC was with surgery alone (S), definitive radiation therapy (RT), or surgery plus radiation (S+RT), and determined by the treating investigator. Local failure (LF) and distant failure (DF) were defined as recurrence at primary tumor site or distant site, respectively. Fine and Gray method was used to estimate cumulative incidence of LF and DF from time LC was completed. P-values were calculated using logrank or Gray’s test, as appropriate. A two-sided p-value of ≤0.05 was considered significant. Results: 588 patients completed LC. Median age at enrollment was 13.0 years (range: 0.6- 33.9 years). Tumor sites were categorized as extremity (230; 39%), axial (142; 24%), extraosseous (110; 19%), and pelvis (106; 18%). At diagnosis, tumor volume (TV) was ≥200 mL in 170 patients (31%) and maximum tumor dimension (MTD) was ≥8 cm in 289 patients (52%). LC was with S in 320 patients (54%), RT in 160 (27%), and S+RT in 108 (18%). Eight patients received preoperative RT. Fifty-three patients (13.1%) who received S±RT had an R1 resection. LC with S was more likely for extremity (58%), RT for pelvis (38%) and S+ RT for axial (36%) and extraosseous (34%) primary tumors (p <0.01). With median follow up of 67.6 months from LC, the 5-year cumulative incidences of LF and DF for the entire cohort were 6.0% (95% CI, 4.3-8.3%) and 11.0% (95% CI, 8.6-13.9%), respectively. Eleven patients experienced simultaneous LF and DF. LF incidence was 5.0% for S, 8.4% for RT, and 5.6% for S+RT (p=0.47). DF incidence was 11.8% for S, 6.4% for RT, and 15.1% for S+RT (p=0.16). LF incidence by tumor site was 3.6% for extremity, 8.7% for pelvis, 7.3% for axial, and 6.8% for extraosseous (p=0.08). LF incidence was higher for primary tumors ≥200 mL (11.3%) compared to tumors < 200 mL (3.9%; p<0.01) and for tumors ≥8 cm (7.8%) compared to tumors < 8 cm (4.4%; p=0.02). Tumor size was associated with a higher LF incidence for S and RT, but not for S+RT (Table). LF incidence was 4.0% for R0, 7.5% for R1 with RT, and 16.7% for R1 without RT (p=0.02). Conclusions: We report the lowest LF incidence to date for prospective ES trials conducted. Both larger TV and MTD were associated with higher LF. Future investigations will aim to evaluate the impact of chemotherapy dose-intensity on LC and identify risk-stratification variables for improved LC. Five-year LF incidence by LC and tumor size. Clinical trial information: NCT01231906 . [Table: see text]

AbstractBackground and ObjectivesThe impact upon wound healing of targeted molecular therapies, when incorporated into neoadjuvant therapy of soft tissue sarcoma, is largely unknown. Here, we describe wound complications following addition of pazopanib, a tyrosine kinase inhibitor (TKI), to neoadjuvant radiotherapy (RT) +/− chemotherapy for soft tissue sarcoma.MethodsWound complications were evaluated on dose‐finding and randomized arms of ARST1321, a phase II/III study incorporating neoadjuvant RT, +/− pazopanib, +/− ifosfamide/doxorubicin (ID) for sarcoma therapy.ResultsOf 85 evaluable patients, 35 (41%) experienced postoperative wound complications. Most (57%) were grade III. Randomization to pazopanib + RT + ID carried a 50% wound complication rate (17/34, with 47% grade III), compared to 22% (5/23) with ID + RT alone. In nonchemotherapy study arms, pazopanib + RT resulted in a 59% wound complication rate versus 25% for those receiving RT alone. Grade III wound complications occurred among 26% (15/58) of all patients receiving pazopanib. Wound complications occurred a median of 35 days postoperatively. Some occurred following diagnostic biopsies and at remote surgical sites.ConclusionThe addition of pazopanib to neoadjuvant chemotherapy and RT resulted in a higher wound complication rate following therapy of soft tissue sarcoma. The rate of grade III complications remained comparable to that reported in contemporary literature.