Siontis, Brittany L.

11531 Background: Conventional chondrosarcoma (cCS) is the 2nd most common primary bone tumor and is resistant to chemotherapy and radiation. IDH1/2 mutations (m) occur in 50% of cCS. Both IDHm and wild-type (wt) cCS harbor epigenetic dysregulation. In preclinical models of IDHm and wt cCS, combination treatment with HDAC and DNMT inhibitors (i) suppressed growth in vitro and in vivo by reversing the hypermethylated state and inducing tumor suppressors, interferon response genes and apoptosis (Sheikh T, Schwartz G. Mol Cancer Ther 2021;20). Methods: NCI 10330 is a single-arm, multicenter, phase 2 study evaluating the HDACi belinostat (B) with the DNMTi SGI-110 (S) or ASTX727 (A). A replaced S due to drug availability (pts were replaced). Pts had advanced cCS, ECOG PS ≤ 2 and could be treatment naïve. Progression was required for grade 1 cCS. Pts received B 1000mg/m2 IV + S 45mg/m2 SC both days 1-5 or B (same dosing) + A (cedazuridine 100mg/decitabine 35mg) PO both days 1-5, in 28-day cycles. 1° endpoint was objective response. A Simon 2-stage design was used. If ≥ 2/13 responses occurred in stage 1, the study would proceed to full accrual. Design had 85% power with α = 0.05 to test ORR 8% vs 28%. 2° endpoints included safety, PFS and OS. A safety lead-in was performed. Paired biopsies were collected. Results: Stage 1 is complete. 19 pts were treated: 6 on B+S and 13 on B+A. Median age was 50 and 67 years, respectively. All pts had prior surgery. 17% (B+S) and 38% (B+A) had prior radiation. 33% (B+S) and 55% (B+A) were IDHm. 67% (B+S) and 75% (B+A) were histologic grade ≥ 2. There were no objective responses. Best response (at 8 weeks) was stable disease (SD) in 4/6 pts (67%) on B+S and 6/10 pts (60%) on B+A. mPFS was 4.2 mos (95% CI 1.97-NR) for B+S and 3.8 mos (95% CI 2.17-NR) for B+A. mOS has not been reached. For B+A, mPFS for IDHm vs wt pts was 4.7 and 3.1 mos, respectively (p=0.21). One pt with IDHm grade 2 cCS who progressed on FT-2102 (IDH1i) remains on B+A > 1 year. There were no DLTs during either safety lead-in. Grade 3/4 treatment-related adverse events (TRAEs) occurred in 17% (B+S) and 69% (B+A). For B+A, the most common grade 3/4 TRAE was neutropenia (54%) and the most common all-grade TRAEs were nausea (69%), leukopenia (61%), neutropenia (54%), anemia (46%) and fatigue (46%). Paired tumor biopsies are being evaluated with whole exome sequencing, RNAseq, methylation array and multiplex IHC with results forthcoming. Conclusions: Combination HDACi + DNMTi was well-tolerated in advanced cCS. There were no objective responses; however, a subset of pts experienced prolonged SD with a trend towards improved mPFS in IDHm pts. Correlative work is ongoing with a focus on differential effects on IDHm tumors and whether modulation of the immune microenvironment might support combinations with immunotherapy. Support: UM1CA186689. Clinical trial information: NCT04340843 .

11507 Background: Single agent or combination chemotherapy, typically Dox- or gemcitabine-based, are standard 1st- and 2nd-line therapies in patients (pts) with metastatic LMS; however, objective response rates (ORR), progression-free, and overall survival (PFS/OS) remain inadequate. Lurbi (PharmaMar S.A. / Jazz Pharmaceuticals) binds to DNA inhibiting transcription and inducing double strand breaks leading to apoptosis and delaying S/G2 progression. In a prior pilot study, we showed Lurbi+Dox is well-tolerated, with signs of activity, particularly in LMS. We designed this phase 1b to optimize dosing to lead into a randomized (1:1) phase 2 trial of Dox+/-Lurbi in anthracycline-naïve LMS. Herein we provide updated efficacy and tolerability data for this Phase 1b cohort. Methods: Pts > 18 yrs with locally advanced/metastatic, unresectable non-GIST STS (Phase 1b only) w/o prior anthracycline or Lurbi/trabectedin, ECOG PS < 3, RECIST 1.1 measurable, and normal organ function were eligible. The phase 1b followed a 3+3 design. Dosing included fixed Lurbi (3.2 mg/m2 d1) with two Dox dose levels (DL; DL1: 25 mg/m2 d1; DL2 25 mg/m2 d1+8). All pts received GCSF prophylaxis. Tumor assessments were every 2 cycles. DL1 was chosen as RP2D and the phase 2 trial began accrual in Aug 2022 aiming to enroll 50 LMS pts randomized 1:1 (stratified by uterine LMS [uLMS]] v. other LMS) with PFS as primary endpoint. Pts progressing on Dox are allowed to cross to Lurbi monotherapy. Results: 10 patients were enrolled in Phase 1b. Histologies included 5 LMS (4 uLMS) and 1 each of myxofibrosarcoma (myxFS), undifferentiated pleomorphic sarcoma (UPS), dedifferentiated liposarcoma (DDLPS), endometrial stromal sarcoma (ESS), and solitary fibrous tumor (SFT). With a median follow-up of 344 days, 5/10 pts remain on treatment with median PFS of 357 days (95%CI 175-ND). 6 pts demonstrated partial response (PR; 5 confirmed), 3 with stable disease (SD), and 1 with progressive disease (PD, Table). Median time to PR was 81 days (range 46-207). Duration of response was over 132 days in all responders with 3 still on treatment. Treatment-related AEs were typical for Dox/Lurbi, including nausea, fatigue, and reversible LFT elevations/cytopenias. Updated safety and response data will be provided at the time of the meeting. Conclusions: Lurbi+Dox is well-tolerated with efficacy in STS including 6/10 pts achieving PR, 9/10 pts staying on treatment for >120d, and 6/10 pts >200d. The randomized phase 2 study is currently enrolling. Clinical trial information: NCT05099666 . [Table: see text]

11505 Background: Potentiation of chemotherapy, without increased toxicity, to improve outcome is an area of interest. Preclinical and clinical evidence shows simultaneous utilization of antiangiogenic agents and chemotherapy have a synergistic effect. We hypothesized that the dual targeting of VEGF and c-MET pathways with cabozantinib (CAB) would result in clinical benefit for patients with soft tissue sarcoma (STS) when combined with temozolomide (TMZ), an alkylating agent. Utilization of CAB/TMZ is anticipated to produce a synergistic antitumor effect worthwhile to explore in STS. Methods: A multicenter phase II study of CAB/TMZ in patients with unresectable/metastatic leiomyosarcoma (LMS) and other STS was conducted by the Midwest Sarcoma Trials Partnership. Age ≥ 18, adequate performance status, organ function, measurable disease (RECIST 1.1), and 0-5 prior chemotherapy regimens were required. CAB 40 mg PO daily plus TMZ 150-200 mg/m2 PO 1-5 days were given in 28-day cycles until disease progression or unacceptable toxicity. Patients enrolled in 2 cohorts: 1. Uterine and non-uterine LMS 2. Other STS. The first 14 subjects to be enrolled in the study in either cohort served as a safety lead in. The primary endpoint was progression-free rate (PFR) at 12 weeks for cohort 1. Secondary endpoints include overall response rate (ORR), clinical benefit rate, median progression-free survival (PFS), overall survival, and safety and tolerability. The exploratory endpoint was to estimate the correlation of PFR and OS to expression levels of VEGF, amongst others. A Simon 2-stage design was used. Results: A total of 42 patients were enrolled in Cohort 1, and 30 in Cohort 2, across 5 sites. For Cohort 1, median age was 59 years (range 35-86), 85.7% were non-Hispanic, 73.8% were female, 61.9% had ECOG of 0. The PFR at 12 weeks was 45.9% (for 37 evaluable patient) with a median PFS of 6.4 months (95% CI 4.6-6.7). Five PR were observed for an ORR of 13.5%. For Cohort 2, median age was 63 (20-86), 83.3% were non-Hispanic, 36.7% were female, 53.3% had ECOG of 0. The PFR at 12 weeks was 50% (for 28 evaluable patients) with a median PFS of 3.2 months (95% CI 1.4-4.6). One PR was observed. Reported grade 3-4 adverse events attributed to one or both intervention drugs affecting ≥10% of patients (n = 70) included hypertension (10%), decreased neutrophils (18.7%), decreased platelets (31%). Conclusions: The combination therapy of CAB/TMZ in patients with unresectable or metastatic LMS exceeded its primary endpoint with a PFR at 12 weeks > 39%. The PFS of 6.4 months in Cohort 1 exceeds rates achieved with second line tyrosine kinase inhibitors (TKIs) and alkylators in LMS patients. Treatment was feasible and did not reveal any previously unreported toxicities. The combination with CAB with TMZ demonstrated meaningful clinical benefit and is worth further exploration in LMS. Clinical trial information: NCT04200443 .

Abstract Purpose: To evaluate the impact of trimodality treatment versus monotherapy or dual therapy for radiation-associated angiosarcoma of the breast (RAASB) after prior breast cancer treatment. Experimental Design: With Institutional Review Board approval, we identified patients diagnosed with RAASB and abstracted data on disease presentation, treatment, and oncologic outcomes. Trimodality therapy included (i) taxane induction, (ii) concurrent taxane/radiation, and then (iii) surgical resection with wide margins. Results: A total of 38 patients (median age 69 years) met inclusion criteria. Sixteen received trimodality therapy and 22 monotherapy/dual therapy. Skin involvement and disease extent were similar in both groups. All trimodality patients required reconstructive procedures for wound closure/coverage, compared with 48% of monotherapy/dual therapy patients (P &lt; 0.001). Twelve of 16 (75%) patients receiving trimodality therapy had a pathologic complete response (pCR). With median follow-up of 5.6 years, none had local recurrence, 1 patient (6%) had distant recurrence, and no patients died. Among 22 patients in the monotherapy/dual therapy group, 10 (45%) had local recurrence, 8 (36%) had distant recurrence, and 7 (32%) died of disease. Trimodality therapy demonstrated significantly better 5-year recurrence-free survival [RFS; 93.8% vs. 42.9%; P = 0.004; HR, 7.6 (95% confidence interval, CI: 1.3–44.2)]. Combining all patients with RAASB regardless of treatment, local recurrence was associated with subsequent distant recurrence (HR, 9.0; P = 0.002); distant recurrence developed in 3 of 28 (11%) patients without local recurrence compared with 6 of 10 (60%) with local recurrence. The trimodality group had more surgical complications that required reoperation or prolonged healing. Conclusions: Trimodality therapy for RAASB was more toxic but is promising, with a high rate of pCR, durable local control, and improved RFS.

Abstract Background Extraskeletal Ewing sarcoma are rare tumors within the Ewing sarcoma family. Initial staging studies for extraskeletal Ewing sarcoma historically have included imaging and bone marrow aspiration and biopsy (BMAB). However, recent studies on Ewing sarcoma of bone have questioned the utility of BMAB in the initial staging of patients, but no studies of which we are aware have evaluated the role of BMAB in extraskeletal Ewing sarcoma. We suspected that BMAB was of low diagnostic yield in patients with extraskeletal Ewing sarcoma and exposed patients to potential morbidity without an impact on their clinical course. Question/purpose Is BMAB a useful test in the staging of extraskeletal Ewing sarcoma? Methods Between January 1996 and December 2021, our institution evaluated 109 patients with a listed diagnosis of extraskeletal Ewing sarcoma. Those patients were retrospectively reviewed for this study. Of those, we considered patients with biopsy-confirmed diagnosis of extraskeletal Ewing sarcoma. Biopsy was performed based on institutional protocols, with all diagnoses assigned by a board-certified pathologist. Based on that criteria, 96% (105 of 109) were eligible. An additional 18% (20 of 109) were excluded because records of their initial diagnostic and staging workup were not available. This left 78% (85 of 109) for analysis. Of those, 52% (44 of 85) were male. The average age was 32 ± 16 years. Primary tumor locations included extremities in 26% (22 of 85), paraspinal in 20% (17 of 85), chest in 19% (16 of 85), retroperitoneum in 13% (11 of 85), intraabdominal in 12% (10 of 85), intrapelvic in 7% (6 of 85), and head or neck in 4% (3 of 85). Initial diagnostic and staging information, including the use of PET-CT, bone scan, CT chest, and BMAB, was collected. Metastatic disease at the time of presentation or during follow-up was noted. The utility of BMAB was determined by the rate of positive tests in those undergoing BMAB during the initial staging process. Descriptive statistical analysis was sufficient to address the study question, and therefore no comparative statistics were performed. Results BMAB was obtained during the initial staging process in 64% (54 of 85) of patients. This BMAB was negative in all 54 patients, including those with known metastatic disease. Conclusion Diagnosing metastatic disease in extraskeletal Ewing sarcoma is important as the presence of metastases at diagnosis adversely affects prognosis. The routine use of BMAB in the staging process of extraskeletal Ewing sarcoma is of low diagnostic yield. BMAB is unlikely to diagnose metastatic involvement even in patients with known metastases to bone. We do not have enough data to suggest whether other modalities, such as PET-CT, might be more useful. Similar studies should be pursued to determine the utility of the remainder of staging modalities in patients with extraskeletal Ewing sarcoma to elucidate the most efficient and effective staging protocol. Level of Evidence Level III, diagnostic study

AbstractPurposeExtraskeletal Ewing sarcoma (EES), is a rare soft tissue sarcoma. Treatment for EES commonly involves chemotherapy and surgical resection (ST) or less commonly combined chemotherapy, surgery, and radiotherapy (ST + RT). The purpose of the current study was to evaluate our institutional experience treating EES.MethodsWe reviewed 36 (18 males:18 females) patients (mean age 30 years) with a nonretroperitoneal/visceral EES treated with either ST (n = 24, 67%) or ST + RT (n = 12, 33%). All patients were treated with chemotherapy, most commonly vincristine, doxorubicin, cyclophosphamide/ifosfamide and etoposide (VDC/IE, n = 23, 66%) Radiotherapy was mostly delivered preoperatively (n = 9). The mean follow‐up was 8 years.ResultsThe 10‐year disease specific survival for patients was 78%, with no difference in the survival between patients in the ST versus the ST + RT groups (83% vs. 71%, p = 0.86). There was no difference in the 10‐year local recurrence (91% vs. 100%, p = 0.29) or metastatic free survival (87% vs. 75%, p = 0.45) between the ST and ST + RT groups.ConclusionThe results of the current study highlight the ability to achieve excellent local control with chemotherapy and surgery for EES. We recommend for multidisciplinary management of patients with EES, including chemotherapy and surgery, with use of radiotherapy if there is concern for a potentially close margin of resection.

The treatment of sarcoma necessitates a collaborative approach, given its rarity and complex management. At a single institution, multidisciplinary teams of specialists determine and execute treatment plans involving surgical, radiation, and medical management. Treatment guidelines for systemic therapies in advanced or nonresectable soft tissue sarcoma have advanced in recent years as new immunotherapies and targeted therapies become available. Collaboration between institutions is necessary to facilitate accrual to clinical trials. Here, we describe the success of the Midwest Sarcoma Trials Partnership (MWSTP) in creating a network encompassing large academic centers and local community sites. We propose a new model utilizing online platforms to expand the reach of clinical expertise for the treatment of advanced soft tissue sarcoma.

ABSTRACT Primary pancreatic sarcomas are rare malignancies with an incidence of 0.1%. This case report is of a 48-year-old man who presented with this condition. The patient's treatment plan consisted of distal pancreatectomy and splenectomy with intraoperative immunohistochemistry and adjuvant chemotherapy. To correctly identify and treat undifferentiated pleomorphic sarcoma, a stepwise strategy involving cross-sectional imaging and extensive histopathology analysis is necessary.

AbstractBackgroundCompared to other sarcomas, myxoid liposarcoma (ML) is known to be radiosensitive, with improved oncologic outcomes. Although these tumors “shrink” following radiotherapy, there is a paucity of data examining the degree of radiosensitivity and oncologic outcome. The purpose of the study was to evaluate pre‐ and postradiotherapy tumor volume to determine if size reduction impacts outcome.MethodsWe reviewed 62 patients with ML undergoing surgical resection combined with preoperative radiotherapy, with pre‐ and postradiotherapy MRI. This included 34 (55%) males, with a mean age of 47 ± 14 years. All tumors were deep to the fascia, and 12 (19%) patients had tumors with a >5% round‐cell component.ResultsThe mean volume reduction was 54% ± 29%. Compared to patients with >25% volume reduction, patients with reduction ≤25% had worse 10‐year disease specific survival (86% vs. 37%, p < 0.01), in addition to an increased risk of metastatic disease (HR 4.63, p < 0.01) and death due to disease (HR 4.52, p < 0.01).ConclusionLack of volume reduction is a risk factor for metastatic disease and subsequent death due to disease in patients with extremity ML treated with combined preoperative radiotherapy and surgery. This data could be used to stratify patients for adjuvant therapies and follow‐up intervals.

AbstractBackgroundThis study was aimed at developing and validating a decision‐making tool predictive of overall survival (OS) for patients receiving stereotactic body radiation therapy (SBRT) for spinal metastases.MethodsThree hundred sixty‐one patients at one institution were used for the training set, and 182 at a second institution were used for external validation. Treatments most commonly involved one or three fractions of spine SBRT. Exclusion criteria included proton therapy and benign histologies.ResultsThe final model consisted of the following variables and scores: Spinal Instability Neoplastic Score (SINS) ≥ 6 (1), time from primary diagnosis < 21 months (1), Eastern Cooperative Oncology Group (ECOG) performance status = 1 (1) or ECOG performance status > 1 (2), and >1 organ system involved (1). Each variable was an independent predictor of OS (p < .001), and each 1‐point increase in the score was associated with a hazard ratio of 2.01 (95% confidence interval [CI], 1.79–2.25; p < .0001). The concordance value was 0.75 (95% CI, 0.71–0.78). The scores were discretized into three groups—favorable (score = 0–1), intermediate (score = 2), and poor survival (score = 3–5)—with 2‐year OS rates of 84% (95% CI, 79%–90%), 46% (95% CI, 36%–59%), and 21% (95% CI, 14%–32%), respectively (p < .0001 for each). In the external validation set (182 patients), the score was also predictive of OS (p < .0001). Increasing SINS<zaq;6> was predictive of decreased OS as a continuous variable (p < .0001).ConclusionsThis novel score is proposed as a decision‐making tool to help to optimize patient selection for spine SBRT. SINS may be an independent predictor of OS.