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ABSTRACT Background Rhabdomyosarcoma is the most common soft tissue sarcoma in pediatrics and infants are reported to have inferior outcomes. ARST1431 recommended delayed primary excision (DPE) while discouraging radiation (RT) deviations. This analysis compared outcomes among very young and older patients in this study. Procedures Demographic and tumor characteristics were summarized using frequencies and percentages. Local failure (LF) frequency was summarized by age group, RT, and DPE status. Event‐free survival (EFS) and overall survival (OS) were estimated using the Kaplan–Meier method and compared between age groups using the log‐rank test. Results Of 296 patients, 48 (16.2%) were <24 months: 14 (4.7%) < 12 months, 34 (11.5%) 12–24 months–compared with 248 (83.8%) ≥24 months. DPE was performed in: 7 (50%), <12 months; 9 (26%), 12–24 months; 56 (22%), ≥24 months. RT was given to 9 (64%), 27 (79%), and 195 (79%) of <12, 12–24, and >24 months, respectively. LF in DPE+RT was 8.3% and 6.1%, < 24 months and ≥ 24 months, respectively, compared to 29.3% and 20.5% for RT without DPE. The 4‐year EFS did not vary: 56% (95% CI = 26.5, 86.0), 68% (95% CI = 51.2, 84.1), and 61% (95% CI = 54.2, 68.3) <12, 12–24, and >24 months old, respectively. Conclusions Outcomes in younger children are comparable to older children with local failure more common in those without DPE. Optimization of local control will be important for future studies. Trial Registration Number NCT02567435

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported. ARST1321 was a phase II study designed to compare the near complete pathologic response rate after preoperative chemoradiation with/without pazopanib in children and adults with intermediate-/high-risk chemotherapy-sensitive body wall/extremity non-Rhabdomyosarcoma Soft Tissue Sarcoma (ClinicalTrials.gov identifier: NCT02180867 ). Enrollment was stopped early following a predetermined interim analysis that found the rate of near complete pathologic response to be significantly greater with the addition of pazopanib. As a planned secondary aim of the study, the outcome data for this cohort were analyzed. Eight-five eligible patients were randomly assigned to receive (regimen A) or not receive (regimen B) pazopanib in combination with ifosfamide and doxorubicin + preoperative radiotherapy followed by primary resection at week 13 and then further chemotherapy at week 25. As of December 31, 2021, at a median survivor follow-up of 3.3 years (range, 0.1-5.8 years), the 3-year event-free survival for all patients in the intent-to-treat analysis was 52.5% (95% CI, 34.8 to 70.2) for regimen A and 50.6% (95% CI, 32 to 69.2) for regimen B ( P = .8677, log-rank test); the 3-year overall survival was 75.7% (95% CI, 59.7 to 91.7) for regimen A and 65.4% (95% CI, 48.1 to 82.7) for regimen B ( P = .1919, log-rank test). Although the rate of near complete pathologic response was significantly greater with the addition of pazopanib, outcomes were not statistically significantly different between the two regimens.

AbstractBackgroundPatients with alveolar rhabdomyosarcoma (ARMS) have inferior outcomes compared to patients with embryonal rhabdomyosarcoma (ERMS) and more effective chemotherapy options are needed for these patients. Vinorelbine is a semisynthetic vinca alkaloid that has clinical activity in relapsed rhabdomyosarcoma (RMS) when used alone or in combination with cyclophosphamide.AimsThe goal of our study was to evaluate whether RMS histology subtype influences response rate to vinorelbine alone or in combination.Materials & MethodsFive Phase 2 trials that enrolled RMS patients were included in the meta‐analysis. Two studies evaluated vinorelbine alone, two studies evaluated vinorelbine in combination with low dose oral cyclophosphamide, and one study evaluated vinorelbine and intravenous cyclophosphamide in combination with temsirolimus or bevacizumab. All RMS patients had relapsed or refractory disease and had received at least one prior therapy. Response was reported according to RECIST1.1 and was defined as a complete or partial response. Response data was obtained from published results or from trial principal investigator. RMS NOS patients were grouped with ERMS patients for this analysis. Summary estimates comparing differences between ARMS and ERMS response rates were generated using a random‐effects model to account for heterogeneity among the studies.ResultsOne hundred fifty‐six enrolled patients evaluable for response were included in the meta‐analysis, 85 ARMS, 64 ERMS and 7 RMS‐NOS. The combined effect generated from the random‐effects model demonstrated a 41% increase (p = 0.001, 95% CI; 0.21–0.60) in response to vinorelbine as a single agent or in combination in patients with ARMS compared to patients with ERMS. There was no significant difference in the rate of progressive disease between patients with ARMS compared to ERMS (p = 0.1, 95%CI; −0.26–0.02).DiscussionVinorelbine is an active agent for the treatment of relapsed or refractory RMS and a meta‐analysis of Phase 2 studies shows that radiographic responses in patients with ARMS were significantly higher than ERMS or RMS‐NOS.ConclusionThese data support further investigation of vinorelbine in newly diagnosed patients with RMS particularly those with alveolar histology.

Abstract Background To determine outcomes of children with rhabdomyosarcoma (RMS) with isolated lung metastases. Methods Data were analyzed for 428 patients with metastatic RMS treated on COG protocols. Categorical variables were compared using Chi‐square or Fisher's exact tests. Event‐free survival (EFS) and overall survival (OS) were estimated using Kaplan–Meier method and compared using the log‐rank test. Results Compared with patients with other metastatic sites ( n = 373), patients with lung‐only metastases ( n = 55) were more likely to be <10 years of age, have embryonal histology (embryonal rhabdomyosarcoma), have N0 disease, and less likely to have primary extremity tumors. Lung‐only patients had significantly better survival outcomes than patients with all other sites of metastatic disease ( p < .0001) with 5‐year EFS of 48.1 versus 18.8% and 5‐year OS of 64.1 versus 26.9%. Patients with lung‐only metastases, and those with a single extrapulmonary site of metastasis, had better survival compared with patients with two or more sites of metastatic disease ( p < .0001). In patients with ERMS and lung‐only metastases, there was no significant difference in survival between patients ≥10 years and 1–9 years (5‐year EFS: 58.3 vs. 68.2%, 5‐year OS: 66.7 vs. 67.7%). Conclusions With aggressive treatment, patients with ERMS and lung‐only metastatic disease have superior EFS and OS compared with patients with other sites of metastatic disease, even when older than 10 years of age. Consideration should be given to including patients ≥10 years with ERMS and lung‐only metastases in the same group as those <10 years in future risk stratification algorithms.

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.

11504 Background: Pazopanib is a multi-targeted tyrosine kinase inhibitor (TKI) with activity in advanced soft tissue sarcoma. ARST1321 was a phase II study designed to compare the near complete pathologic response rate (≥ 90% necrosis) following preoperative chemoradiation +/- pazopanib in children and adults with intermediate/high risk chemotherapy-sensitive body wall/extremity NRSTS. Enrollment was stopped early following a predetermined interim analysis that found the rate of near complete pathologic response to be significantly greater with the addition of pazopanib. As a planned secondary analysis of the study, we now report the outcome data for this cohort. Methods: ARST1321 was a jointly designed COG and NRG Oncology study open to enrollment July 2014-October 2018. Eligible adult (≥18 years) and pediatric (< 18 years) patients with newly-diagnosed unresected body wall/extremity NRSTS were enrolled into the Chemotherapy Cohort (> 5 cm, FNCLCC grade 2/3, protocol-designated chemotherapy-sensitive histology). Following a dose-finding phase, patients were randomized to receive (Regimen A) or not receive (Regimen B) pazopanib (< 18 years: 350 mg/m2/day; ≥ 18 years: 600 mg/day) in combination with ifosfamide (7.5 gm/m2/cycle) and doxorubicin (75 mg/m2/cycle) + 45 Gy preoperative RT followed by primary resection at week 13, then further chemotherapy to week 25. Results: Eighty-five eligible patients were enrolled in the Chemotherapy Cohort and randomized to receive or not receive pazopanib. Median age 22.1 years (range: 5.7-64.2 years); 30 patients < 18 years. Most common histologies were synovial sarcoma (n = 42) and undifferentiated pleomorphic sarcoma (n = 19). As of December 31, 2021, at a median survivor follow-up of 3.3 years (range: 0.1 – 5.8 years), the 3-year event-free survival (EFS) for all patients in the intent-to-treat analysis was 52.5% (95% CI: 34.8%-70.2%) for Regimen A and 50.6% (32%-69.2%) for Regimen B (p = 0.8677); 3-year overall survival (OS) was 75.7% (59.7%-91.7%) for Regimen A and 65.4% (48.1%-82.7%) for Regimen B (p = 0.1919). Conclusions: Although the rate of near complete pathologic response was significantly greater with the addition of pazopanib to preoperative chemoradiation in children and adults with intermediate/high risk body wall/extremity NRSTS, outcomes were not statistically significantly different between the two regimens. Pathologic response could be a TKI-related phenomenon and may not be a good surrogate marker of outcome in future studies. Clinical trial information: NCT02180867.

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 The Children's Oncology Group (COG) uses Clinical Group (CG) and modified Tumor Node Metastasis (TNM) stage to classify rhabdomyosarcoma (RMS). CG is based on surgicopathologic findings and is determined after the completion of initial surgical procedure(s) but prior to chemotherapy and/or radiation therapy. The modified TNM stage is based on clinical and radiographic findings and is assigned prior to any treatment. These systems have evolved over several decades. We review the history, evolution, and rationale behind the current CG and modified TNM classification systems used by COG for RMS. Data from the seven most recently completed and reported frontline COG trials (D9602, D9802, D9803, ARST0331, ARST0431, ARST0531, ARST08P1) were analyzed, and confirm that CG and modified TNM stage remain relevant and useful for predicting prognosis in RMS. We propose updates based on recent data and discuss factors warranting future study to further optimize these classification systems.

AbstractChildren and adolescents with rhabdomyosarcoma (RMS) comprise a heterogeneous population with variable overall survival rates ranging between approximately 6% and 100% depending on defined risk factors. Although the risk stratification of patients has been refined across five decades of collaborative group studies, molecular prognostic biomarkers beyond FOXO1 fusion status have yet to be incorporated prospectively in upfront risk‐based therapy assignments. This review describes the evolution of risk‐based therapy and the current risk stratification, defines a new risk stratification incorporating novel biomarkers, and provides the rationale for the current and upcoming Children's Oncology Group RMS studies.

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.