HLA-G 14bp ins/del Polymorphism, Plasma Level of Soluble HLA-G and Association with IL-6/IL-10 Ratio and Survival of Glioma Patients

HLA-G is an immune checkpoint molecule with immunosuppressive and anti-inflammatory activities, and its expression and level of its soluble form (sHLA-G) may play an important role in tumor prognosis. The HLA-G 14 bp ins/del polymorphism and the plasma level of soluble HLA-G (sHLA-G) were investigated by a polymerase chain reaction and ELISA, respectively, in 59 glioma patients. A significantly higher proportion of glioma patients had the 14 nt insert in both homozygous and heterozygous states compared to the control group. Glioma patients had also higher plasma levels of sHLA-G. Patients with methylated MGMT promoter had lower levels of sHLA-G than those with unmethylated MGMT promoter. Level of sHLA-G negatively correlated with the overall survival of patients. Glioblastoma patients who survived more than one year after diagnosis had lower levels of sHLA-G than those surviving less than one year. Patients with sHLA-G levels below the cut off value 40 U/mL survived significantly longer than patients with sHLA-G above 40 U/mL. The levels of sHLA-G also negatively correlated with the level of IL-6 (P=0.0004) and positively with IL-10/IL-6 (P=0.046). Conclusion: The presence of 14 nt insert in both homozygous and heterozygous states of the HLA-G 14 bp ins/del polymorphism is more frequent in glioma patients and the elevated plasma levels of sHLA-G are negatively associated with their survival.

CTIM-25. A RANDOMIZED PHASE 3 STUDY OF NIVOLUMAB OR PLACEBO COMBINED WITH RADIOTHERAPY PLUS TEMOZOLOMIDE IN PATIENTS WITH NEWLY DIAGNOSED GLIOBLASTOMA WITH METHYLATED MGMT PROMOTER: CHECKMATE 548

BACKGROUND Novel therapies are needed in newly diagnosed glioblastoma as nearly all patients experience recurrence following standard-of-care radiotherapy (RT) + temozolomide (TMZ), including patients with tumors with methylated MGMT promoter, a positive prognostic factor and predictor of benefit with TMZ. Here, we report the final analysis of progression-free survival (PFS), overall survival (OS), and safety from an international randomized, single-blind phase-3 study of nivolumab (NIVO)+RT+TMZ in patients with newly diagnosed glioblastoma with methylated/indeterminate MGMT promoter (CheckMate 548; NCT02667587). METHODS Patients (N=716) aged ≥ 18y were randomized 1:1 regardless of tumor PD-L1 expression to NIVO (240 mg Q2W×8, then 480 mg Q4W) + RT (60 Gy over 6 weeks) + TMZ (75 mg/m2 QD during RT, then 4-week break, then 150–200 mg/m2 QD on days 1–5 of every 28-day cycle for 6 cycles) or placebo (PBO)+RT+TMZ. The dual-primary endpoints were PFS by blinded independent central review and OS, both overall and without baseline corticosteroids. RESULTS As of December 22, 2020, median PFS was 10.6 months (95% CI, 8.9–11.8) with NIVO+RT+TMZ and 10.3 months (95% CI, 9.7–12.5) with PBO+RT+TMZ (HR, 1.06 [95% CI, 0.90–1.25]). Median OS was 28.9 months (95% CI, 24.4–31.6) with NIVO+RT+TMZ and 32.1 months (95% CI, 29.4–33.8) with PBO+RT+TMZ (HR, 1.10 [95% CI, 0.91–1.33]). Among patients without baseline corticosteroids, median OS was 31.3 months (95% CI, 28.6–34.8) with NIVO+RT+TMZ and 33.0 months (95% CI, 31.0–35.1) with PBO+RT+TMZ (HR, 1.12 [95% CI, 0.87–1.43]). Grade 3–4 treatment-related adverse events were 52.4% and 33.6% with NIVO+RT+TMZ and PBO+RT+TMZ, respectively. CONCLUSIONS NIVO added to RT+TMZ did not improve survival in patients with newly diagnosed glioblastoma with methylated/indeterminate MGMT promoter. No new safety signals were observed with NIVO. The role of immunotherapy in this treatment landscape remains an area for further investigation.

Does positive MGMT methylation outbalance the limitation of subtotal resection in glioblastoma IDH-wildtype patients?

Background The impact on survival of complete resection (CR) in patients with malignant glioma and MGMT promoter methylation on adjuvant therapy strategies has been proven in the past. However, it is not known whether a MGMT promoter methylation can compensate a subtotal resection. Therefore, we analyzed the progress of postoperative residual tumor tissue depending on the molecular tumor status. Methods We included all glioblastoma, IDH-wildtype (WHO grade IV) patients with postoperative residual tumor tissue, who were treated at our neurooncological department between 2010 and 2018. Correlation of molecular patterns with clinical data and survival times was performed. The results were compared to patients following CR. Results 267 patients with glioblastoma, IDH-wildtype (WHO grade IV) received surgery of whom 81 patients with residual tumor were included in the analysis. MGMT promoter was methylated in 31 patients (38.27%). Median OS and PFS were significantly increased in patients with methylated MGMT promoter (mOS: 16 M vs. 13 M, p = 0.009; mPFS: 13 M vs. 5 M, p = 0.003). In comparison to survival of patients following CR, OS was decreased in patients with residual tumor regardless MGMT methylation. Conclusion Our data confirm impact of MGMT promoter methylation in patients with glioblastoma, IDH-wildtype on OS and PFS. However, in comparison to patients after CR, a methylated MGMT promoter cannot compensate the disadvantage due to residual tumor volume. In terms of personalized medicine and quality of life as major goal in oncology, neuro-oncologists have to thoroughly discuss advantages and disadvantages of residual tumor volume versus possible neurological deficits in CR.

CBIO-14. ELUCIDATING THE MECHANISM OF TEMOZOLOMIDE-INDUCED ATR ACTIVATION IN MGMT-METHYLATED GLIOBLASTOMA MULTIFORME

Glioblastoma multiforme (GBM) is an aggressive, malignant brain tumor in adults. The current standard of care for GBM is surgical resection, radiation therapy and chemotherapy with temozolomide (TMZ). It is well established that GBM patients with a methylated MGMT promoter (MGMT-) who are treated with TMZ have a better overall survival than patients with an unmethylated MGMT promoter (MGMT+). The enzyme produced by the MGMT gene is responsible for removing cytotoxic O6-methylguanine (O6-meG) lesions formed by TMZ. In the MGMT- setting, the O6-meG lesion activates the mismatch repair (MMR) pathway which functions to remove the damage. Published work from our group reported differential activation of the ataxia telangiectasia and RAD3 related protein (ATR) in MGMT- and MGMT+ GBM cells in response to TMZ treatment, as demonstrated through the phosphorylation of CHK1. It is known that MMR proteins are involved in ATR activation, however, this project aims to unravel the specific MMR proteins required for ATR activation by TMZ-induced alkyl lesions. To accomplish this, we treated an shMSH2 MGMT- GBM cell line with TMZ and an ATR inhibitor (ATRi) compared to treatment in an MSH2-proficient MGMT- GBM cell line. We observed decreased cell death in the shMSH2 setting compared to the MSH2-proficient cells, suggesting that MSH2 is integral in the activation of ATR upon TMZ treatment in the MGMT- setting. This study elucidates a potential role for MSH2 in ATR activation. Mechanistic understanding of how the MMR system is involved in ATR activation by TMZ can ultimately be exploited for therapeutic gain in the treatment of patients with GBM.

TMIC-14. PD-L1 EXPRESSION IS NEGATIVELY CORRELATED TO OUTCOMES IN PATIENTS WITH MGMT METHYLATED PROMOTERS IN GBM

BACKGROUND Glioblastoma is a high-grade glioma and is considered the most aggressive primary brain tumor with a median overall survival of 11–15 months. Methylation of the promoter of the MGMT gene, which encodes a DNA repair protein, has been shown to be a good prognostic indicator for GBM survival. It is known that GBM has elevated expression of several immune checkpoint molecules that allow the tumor to evade anti-tumor immune response. Therefore, it is important to elucidate connections between prognostic factors like methylation status and immunologic markers in the tumor microenvironment (TME) that might lead to immunosuppression. METHODS Patients with resected GBM tumor samples were identified by pathology reports as having tumors with either methylated or unmethylated MGMT promoters. Corresponding patient tumor biopsy samples were embedded in paraffin, sectioned, and then stained using specific antibodies for known immune checkpoint molecules: PD-1, PD-L1, LAG-3, TIM-3, CSF1R, and IDO-1. RESULTS In our cohort of 34 patients, 17 had methylated MGMT promoter regions and 17 did not. We found no statistically significant difference between methylated and unmethylated MGMT promoter status for immune checkpoint expression. However, we did find a statistically significant negative correlation (P< 0.05) between the degree of PD-L1 expression in the TME and the progression free survival of patients with the MGMT promoter methylation phenotype. CONCLUSION Our study examined the relationship between immune checkpoint markers and methylation status of MGMT promoters in GBM. While there was no statistically significant difference between these two groups within the immunological framework of this study, there was a statistically significant negative correlation showing that increased PD-L1 expression in patients with methylated MGMT promoter tumors correlated to a worse progression free survival. Future studies are indicated to investigate the correlation between PD-L1 expression in relation to GBM treatment prognosis and its dependence on MGMT promoter methylation.

P14.29 Prediction of overall survival in patients with malignant glioma using dynamic O-(2-[18F]-fluoroethyl)-L-tyrosine PET

BACKGROUND Characterization of gliomas according to the revised World Health Organization (WHO) classification of 2016 has gained major importance regarding prognostication. The present study aimed at exploring the prognostic value of dynamic O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) PET in newly diagnosed and molecularly defined astrocytic high-grade glioma (HGG) of the WHO grades III or IV. MATERIAL AND METHODS Before initiation of treatment, dynamic FET PET imaging was performed in patients with newly diagnosed glioblastoma (GBM) and anaplastic astrocytoma (AA). Static FET PET parameters such as maximum and mean tumor/brain ratios (TBRmax/mean), as well as the dynamic FET PET parameters time-to-peak (TTP) and slope, were obtained. The predictive ability of FET PET parameters was evaluated with regard to the overall survival (OS). Using ROC analyses, threshold values for FET PET parameters were obtained. Subsequently, univariate Kaplan-Meier and multivariate Cox regression survival analyses were performed to assess their predictive power for OS. RESULTS Sixty patients (45 GBM, 15 AA) of two university centers were retrospectively identified. Patients with a methylated MGMT promoter as well as with an IDH mutation had a significantly longer OS (both P<0.001). Furthermore, ROC analysis revealed in IDH-wildtype HGG (n=45) that a TTP>25 minutes (AUC, 0.90; sensitivity, 90%; specificity, 87%; P<0.001) was highly prognostic for a longer OS (29 vs. 12 months; P<0.001). Besides a complete resection and a methylated MGMT promoter, TTP remained significant in the multivariate survival analysis (P=0.002, P=0.016, and P=0.003, respectively), indicating an independent predictor for OS. In contrast, both TBRmax and TBRmean were not prognostic (AUC, 0.37 and 0.32, respectively). CONCLUSION Data suggest that within the subgroup of patients with newly diagnosed and untreated IDH-wildtype GBM and AA, dynamic FET PET additionally allows the identification of patients with an improved OS.

Stratified monotherapy approach according to MGMT methylation status in elderly patients with glioblastoma.

2050 Background: The elderly patients with glioblastoma have an extremely poor prognosis. As they often have some degree of age-related vulnerability, it is especially important to minimize a risk of treatment-related adverse events by optimizing treatment intensity for this population. We conducted phaseⅡ clinical trial to investigate the efficacy of stratified monotherapy approach according to O6-methylguanine-DNA methyltransferase (MGMT) methylation status in elderly patients with glioblastoma. Methods: Patients aged 70 years or older with Karnofsky performance status (KPS) of at least 60 were eligible for this study. MGMT methylation status was quantitatively assessed by pyrosequencing based on the average methylation ratio of 16 CpG sites in the MGMT gene promoter. The patients with highly methylated MGMT promoter defined as an average methylation ratio with 30% or higher were treated with temozolomide (TMZ) monotherapy (standard 5/28 regimen), while the others with low or intermediate levels of MGMT promoter methylation were treated with radiation therapy (40Gy/15fr) alone. Results: Between April 2013 and December 2017, 70 patients were enrolled in this study. Median age was 78 years (70-91) and median KPS was 60 (60-100). Of 70 patients, 19 patients with highly methylated MGMT promoter received TMZ monotherapy, while the remaining 51 patients were treated with radiation therapy. Median progression-free survival (PFS) and median overall survival (OS) were 7.5 and 17.4 months in the TMZ group, respectively. Median PFS and median OS were 4.6 and 10.4 months in the radiotherapy group, respectively. Conclusions: For elderly glioblastoma patients with highly methylated MGMT promoter, TMZ monotherapy could be a treatment option. Clinical trial information: UMIN000012172.