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Abstract BACKGROUND Radiation Therapy Oncology Group 9802 was a phase III trial for patients with centrally confirmed LGG (WHO grade II). Participants ³ 40 years or those with neurosurgeon defined less than gross total resection (GTR) were randomized to radiotherapy (RT) +/- PCV. In a separate cohort, adults age < 40 years with neurosurgeon defined GTR were observed by MRI every 6 months without adjuvant therapy. At last report, outcome for the observation cohort was immature with median follow-up of only 4.4 years. Here, we present mature outcomes for the observation arm. METHODS Eligible adults (as above) were observed by MRI every 6 months. OS and PFS were estimated by Kaplan-Meier method and estimated hazard ratios to characterize the prognostic variables. RESULTS There were 111 eligible patients (median age 30; median KPS = 100). Median follow-up was 16.1 years with 71 (64%) alive at the last follow-up. 79 patients (71%) had progressed with median PFS of 6.9 years. 5, 10, and 15 year-PFS and OS rates were 54%, 39%, 28% and 94%, 77%, and 65%. 1p19q status was codeleted in 32%, IDH1/2 mutant in 78% and MGMT promoter methylated in 39% of tested cases. Multivariate Cox analyses showed that preoperative tumor size ³ 4 cm (HR = 2.43 for PFS, p = 0.001; HR = 2.58 for death, p = 0.016) and residual disease on imaging ³ 1 cm (HR = 2.97 for PFS, P < 0.001; HR = 2.02 for death, p = 0.05) were associated with worse outcomes. Analyses based on molecular results will be presented. CONCLUSION A subset of low-grade gliomas can be observed after the initial resection based on younger age, smaller tumor size, and no residual disease on neuroimaging. This can likely be further refined by prognostic molecular markers. Patients with the most favorable prognostic factors can avoid or delay the acute and long-term side effects of RT and chemotherapy for several years.

2068 Background: There is a lack of effective therapy for recurrent high-grade meningiomas who relapsed after prior radiation therapy (RT). ETCTN 10186 is a phase I/II study to evaluate the feasibility and preliminary clinical efficacy of combining reirradiation using fractionated radiosurgery with nivolumab plus or minus ipilimumab for recurrent high-grade meningiomas. The preliminary results from the phase I portion are reported here. Methods: Recurrent grade II-III meningioma patients were treated with radiosurgery plus nivolumab with or without ipilimumab. Key eligibility criteria include age ≥ 18 years; ECOG score ≤ 2; tumor diameter 1-5 cm; prior radiation dose ≤ 70 Gy; normal organ function; no active autoimmunity. During the phase I portion, eligible patients were treated according to treatment-escalation schema following the modified 3+3 design (Table 1). The maximum tolerated combination (MTC) will be the regimen at which ≤ 1/6 patients experience dose-limiting toxicity (DLT) within 8 weeks of the start of study therapy. During the phase II portion, a total of 24 evaluable patients will be enrolled at the MTC using Simon’s MiniMax two-stage design. The primary endpoint of the phase I portion is to determine the MTC. Objective radiological responses (ORRs) are defined as per the Macdonald criteria. One cycle of immunotherapy is defined as 4 weeks of nivolumab with or without concurrent ipilimumab. Results: From 7/2019 to 3/2021, 13 patients were enrolled in the phase I, including 6 with regimen A and 7 with regimen B (Table). The median prior RT dose was 56 Gy (18-70) at a median interval of 2.8 years (1.3-13.3). There was no DLT in either cohort, so regimen B was deemed the MTC. The median cycles of immunotherapy completed were not significantly different between cohort A and B (11 vs. 6, p = 0.41, respectively). Three cohort A patients and 2 cohort B patients completed all planned doses of immunotherapy. Most patients stopped due to progression, and only one cohort B patient stopped due to treatment-related toxicity (grade 3 hypophysitis and encephalitis after 6 cycles of immunotherapy). After a median follow-up of 11.1 months, there have been 5 progressions and 4 deaths. The 6 month-PFS and 12 month-PFS rates are 62% and 54%, respectively. Two ORRs have been reported by institutional assessment, and central radiology review is ongoing and will be reported. Conclusions: Reirradiation using fractionated radiosurgery with nivolumab plus or minus ipilimumab are well tolerated for radiation-relapsed high-grade meningiomas. Phase II study of regimen B is currently enrolling. Clinical trial information: NCT03604978. [Table: see text]

2058 Background: Immunotherapies targeting the programmed cell death-1 (PD-1) pathway in recurrent glioblastoma (rGBM) have failed. We hypothesize that combining therapies targeting multiple immunosuppressive pathways with cytotoxic and antiangiogenic therapies will improve survival. Here, we evaluate the safety and efficacy of an anti-PD-1 monoclonal antibody (retifanlimab), hypofractionated radiotherapy (HFRT), and bevacizumab, with or without an oral IDO1 inhibitor (epacadostat), in patients with rGBM in a nonrandomized, noncomparative sequential two-arm Phase II study. Methods: This is an open-label Phase II study of 2 sequential cohorts (Table). Cohort A first examines retifanlimab + bevacizumab + HFRT in patients with IDH1/2-WT rGBM. After a toxicity monitoring period, Cohort B, which adds epacadostat, starts enrolling. Key inclusion criteria includes dexamethasone ≤ 4 mg/day at registration and candidacy for reirradiation. Previous bevacizumab use for radiation necrosis is permitted. The primary endpoint is OS probability at 9 months (OS-9). Secondary endpoints include PFS, OS, and toxicity. Exploratory endpoints include immunological phenotyping of blood and tissue. An increase of OS-9 from 38% (bevacizumab alone) to 60% is considered clinically relevant. Results: From 6/2020 to 12/2021, we have completed accrual for cohort A and the interim analysis results are presented here: 25 patients with rGBM enrolled, with 23 evaluable. Median age is 64.3 years (42.1-81.8), 30.4% female, 30.4% MGMT promotor methylated, median KPS 90 (range 70-100), baseline dexamethasone 0 mg (range 0-4) with 52.2% of patients on dexamethasone during the first 3 cycles, median baseline ALC 1,000 cells/µl (range 300-3,700). Patients received a median of 6 cycles to date (range 2-20). Median follow-up is 11.97 months per the reverse Kaplan-Meier method. Interim analysis shows a median PFS of 9.9 months (95%CI: 5.5 to not reached (NR)) and median OS of 12.2 months (95%CI 7.3-NR). Notably, Cohort A met the primary endpoint with an OS-9 of 71.4% (95%CI: 46.7% -86.1%). No dose limiting toxicities have been yet observed. Two treatment-related grade 3 toxicities have occurred (myositis, hypertension). Cohort B enrollment is ongoing, and correlative studies pending. Conclusions: Interim analysis suggests retifanlimab combined with HFRT and bevacizumab in patients with rGBM is well-tolerated and had encouraging OS and PFS at the time of data cutoff. Cohort B, which adds epacadostat, is currently enrolling. Clinical trial information: NCT03532295. [Table: see text]

Abstract BACKGROUND PCV+RT substantially prolongs survival in AO patients, but long-term CF and QOL implications are unclear. We compared CF and QOL by treatment arm in RTOG 9402 participants and evaluated the impact that baseline characteristics had on CF, QOL, and survival. METHODS CF and QOL were evaluated using the Mini Mental State Exam (MMSE) and Brain-Quality of Life (B-QOL) scale at baseline and annually. Scores were analyzed between treatment arms at each time point for patients with ≥ 10 years of follow-up data. Shared parameter models evaluated MMSE and B-QOL scores and survival for all patients. RESULTS 42/148 (28.4%) participants in PCV+RT and 20/143 (14%) in RT alone arms survived ≥ 10 years. 35/42 and 39/42 (PCV+RT) and 18/20 and 17/20 (RT) participants completed baseline B-QOL and MMSE assessments, respectively. B-QOL scores did not differ between treatment groups at any time-point. Among 16 patients (10 PCV+RT, 6 RT) who completed year 10 MMSE evaluations, mean MMSE score at 10 years was higher in the RT arm (29.83 [95% CI 22.1, 30.0] vs. 26.50 [95% CI 29.4, 30.0], P= 0.04). Change in MMSE and B-QOL scores from baseline did not differ significantly between treatment groups at any time. In shared parameter models including all patients with baseline assessments, MMSE and B-QOL scores decreased over time (MMSE P= 0.0189, B-QOL P= 0.0005), but this did not differ by treatment group (MMSE P= 0.5727, B-QOL P= 0.3592). Younger age and higher KPS predicted better scores (MMSE P < 0.0001, P = 0.0002; B-QOL P = 0.0043, P = 0.0007). PCV+RT predicted better survival in both models. CONCLUSIONS PCV+RT improves survival in AO. Shared parameter models show decrease in MMSE and B-QOL over time. However, relative to RT alone, the addition of PCV did not impact change in CF and QOL over time.

Background The indoleamine 2,3-dioxygenase (IDO) pathway is a key counter-regulatory mechanism that, in cancer, is exploited by tumors to evade antitumor immunity. Indoximod is a small-molecule IDO pathway inhibitor that reverses the immunosuppressive effects of low tryptophan (Trp) and high kynurenine (Kyn) that result from IDO activity. In this study, indoximod was used in combination with a checkpoint inhibitor (CPI) pembrolizumab for the treatment for advanced melanoma. Methods Patients with advanced melanoma were enrolled in a single-arm phase II clinical trial evaluating the addition of indoximod to standard of care CPI approved for melanoma. Investigators administered their choice of CPI including pembrolizumab (P), nivolumab (N), or ipilimumab (I). Indoximod was administered continuously (1200 mg orally two times per day), with concurrent CPI dosed per US Food and Drug Administration (FDA)-approved label. Results Between July 2014 and July 2017, 131 patients were enrolled. (P) was used more frequently (n=114, 87%) per investigator’s choice. The efficacy evaluable population consisted of 89 patients from the phase II cohort with non-ocular melanoma who received indoximod combined with (P). The objective response rate (ORR) for the evaluable population was 51% with confirmed complete response of 20% and disease control rate of 70%. Median progression-free survival was 12.4 months (95% CI 6.4 to 24.9). The ORR for Programmed Death-Ligand 1 (PD-L1)-positive patients was 70% compared with 46% for PD-L1-negative patients. The combination was well tolerated, and side effects were similar to what was expected from single agent (P). Conclusion In this study, the combination of indoximod and (P) was well tolerated and showed antitumor efficacy that is worth further evaluation in selected patients with advanced melanoma.

AbstractPurposeSevere adverse events (AEs), such as Guillain‐Barré syndrome (GBS) occur rarely after influenza vaccination. We identify highly associated AEs with GBS and develop prediction models for GBS using the US Vaccine Adverse Event Reporting System (VAERS) reports following trivalent influenza vaccination (FLU3).MethodsThis study analyzed 80 059 reports from the US VAERS between 1990 and 2017. Several AEs were identified as highly associated with GBS and were used to develop the prediction model. Some common and mild AEs that were suspected to be underreported when GBS occurred simultaneously were removed from the final model. The analyses were validated using European influenza vaccine AEs data from EudraVigilance.ResultsOf the 80 059 reports, 1185 (1.5%) were annotated as GBS related. Twenty‐four AEs were identified as having strong association with GBS. The full prediction model, using age, sex, and all 24 AEs achieved an area under the receiver operating characteristic (ROC) curve (AUC) of 85.4% (90% CI: [83.8%, 86.9%]). After excluding the nine (e.g., pruritus, rash, injection site pain) likely underreported AEs, the final AUC became 77.5% (90% CI: [75.5%, 79.6%]). Two hundred and one (0.25%) reports were predicted as of high risk of GBS (predicted probability >25%) and 84 actually developed GBS.ConclusionThe prediction performance demonstrated the potential of developing risk‐prediction models utilizing the VAERS cohort. Excluding the likely underreported AEs sacrificed some prediction power but made the model more interpretable and feasible. The high absolute risk of even a small number of AE combinations suggests the promise of GBS prediction within the VAERS dataset.

OBJECTIVE The internal high-dose volume varies widely for a given prescribed dose during stereotactic radiosurgery (SRS) to treat brain metastases (BMs). This may be altered during treatment planning, and the authors have previously shown that this improves local control (LC) for non–small cell lung cancer BMs without increasing toxicity. Here, they seek to identify potentially actionable dosimetric predictors of LC after SRS for melanoma BM. METHODS The records of patients with unresected melanoma BM treated with single-fraction Gamma Knife RS between 2006 and 2017 were reviewed. LC was assessed on a per-lesion basis, defined as stability or a decrease in lesion size. Outcome-oriented approaches were utilized to determine optimal dichotomization for dosimetric variables relative to LC. Univariable and multivariable Cox regression analysis was implemented to evaluate the impact of collected parameters on LC. RESULTS Two hundred eighty-seven melanoma BMs in 79 patients were identified. The median age was 56 years (range 31–86 years). The median follow-up was 7.6 months (range 0.5–81.6 months), and the median survival was 9.3 months (range 1.3–81.6 months). Lesions were optimally stratified by volume receiving at least 30 Gy (V30) greater than or equal to versus less than 25%. V30 was ≥ and < 25% in 147 and 140 lesions, respectively. For all patients, 1-year LC was 83% versus 66% for V30 ≥ and < 25%, respectively (p = 0.001). Stratifying by volume, lesions 2 cm or less (n = 215) had 1-year LC of 82% versus 70% (p = 0.013) for V30 ≥ and < 25%, respectively. Lesions > 2 to 3 cm (n = 32) had 1-year LC of 100% versus 43% (p = 0.214) for V30 ≥ and < 25%, respectively. V30 was still predictive of LC even after controlling for the use of immunotherapy and targeted therapy. Radionecrosis occurred in 2.8% of lesions and was not significantly associated with V30. CONCLUSIONS For a given prescription dose, an increased internal high-dose volume, as indicated by measures such as V30 ≥ 25%, is associated with improved LC but not increased toxicity in single-fraction SRS for melanoma BM. Internal dose escalation is an independent predictor of improved LC even in patients receiving immunotherapy and/or targeted therapy. This represents a dosimetric parameter that is actionable at the time of treatment planning and warrants further evaluation.

The NCCN Clinical Practice Guidelines in Oncology for Hodgkin Lymphoma (HL) provide recommendations for the management of adult patients with HL. The NCCN panel meets at least annually to review comments from reviewers within their institutions, examine relevant data, and reevaluate and update their recommendations. Current management of classic HL involves initial treatment with chemotherapy alone or combined modality therapy followed by restaging with PET/CT to assess treatment response. Overall, the introduction of less toxic and more effective regimens has significantly advanced HL cure rates. This portion of the NCCN Guidelines focuses on the management of classic HL.

Abstract PURPOSE: RTOG 0933 demonstrated benefits to memory following HA-WBRT, supporting the hypothesis of hippocampal radiosensitivity and associated memory specificity. However, some patients demonstrated cognitive decline, suggesting mechanisms outside hippocampal radiosensitivity playing a role. WMI has been implicated in RT-induced cognitive decline. This secondary analysis explored the relationship between pre-treatment WMI and memory following HA-WBRT. METHODS AND MATERIALS: 113 patients received HA-WBRT. Standardized cognitive assessments were performed at baseline, 2, 4, and 6 months. The primary endpoint was Hopkins Verbal Learning Test Delayed Recall (HVLT-DR) at 4 mos. Secondary endpoints included HVLT Total Recall (HVLT-TR) and Recognition (HVLT-Recog). Of 113 patients, 34 underwent pre-treatment and 4-month post-treatment HVLT testing and pre-treatment post-contrast volumetric T1 and axial T2/FLAIR MRI. Volumetric analysis of metastatic disease burden and disease-unrelated WMI was conducted on the pre-treatment MRI. Correlational analyses were performed examining the relationship between pre-treatment WMI and HVLT outcomes following HA-WBRT. RESULTS: Correlation was found between larger volumes of pre-treatment WMI and decline in HVLT-Recog (r=.54, p&lt; .05) and a correlational trend was observed between larger volume of pre-treatment WMI and decline in HVLT-DR (r=.31, p=.08). Patients with higher pre-treatment disease burden experienced a greater magnitude of stability or positive shift in HVLT-recall and –delayed recall following HA-WBRT. (r=-.36 and r=-.36, p’s &lt; .05), compared to the magnitude of stability/positive shift in those with lesser disease burden. CONCLUSION: In patients receiving HA-WBRT, pre-treatment-WMI predicts memory decline, suggesting white matter integrity pre-treatment contributes to the pathogenesis of post-WBRT cognitive toxicity independent of hippocampal stem cell radiosensitivity. Less decline or improvement in HVLT following HA-WBRT for patients with higher pre-treatment intracranial metastatic burden supports the importance of WBRT-induced intracranial control on cognition. These imaging biomarkers for cognitive toxicity will be further explored on NRG CC001 and CC003, phase III trials of WBRT with or without HA.