Automated volumetry of meningiomas in contrast-enhanced T1-Weighted MRI using deep learning

BACKGROUND

Meningiomas are among the most common intracranial tumors. In these tumors, volumetric assessment is not only important for planning therapeutic intervention but also for follow-up examination.However, a highly accurate automated volumetric method for meningiomas using single-modality magnetic resonance imaging (MRI) has not yet been reported. Here, we aimed to develop a deep learning-based automated volumetry method for meningiomas in MRI and investigate its accuracy and potential clinical applications.

METHODS

For deep learning, we used MRI images of patients with meningioma who were referred to Osaka University Hospital between January 2007 and October 2020. Imaging data of eligible patients were divided into three non-overlapping groups: training, validation, and testing. The model was trained and tested using the leave-oneout cross-validation method. Dice index (DI) and root mean squared percentage error (RMSPE) were measured to evaluate the model accuracy. Result: A total of 178 patients (64.6 ± 12.3 years [standard deviation]; 147 women) were evaluated. Comparison of the deep learning model and manual segmentation revealed a mean DI of 0.923 ± 0.051 for tumor lesions. For total tumor volume, RMSPE was 9.5 ± 1.2%, and Mann-Whitney U test did not show a significant difference between manual and algorithm-based measurement of the tumor volume (p = 0.96).

CONCLUSION

The automatic tumor volumetry algorithm developed in this study provides a potential volume-based imaging biomarker for tumor evaluation in the field of neuroradiological imaging, which will contribute to the optimization and personalization of treatment for central nervous system tumors in the near future.

Qualitative MR features to identify non-enhancing tumors within glioblastoma's T2-FLAIR hyperintense lesions

PURPOSE

To identify qualitative MRI features of non-(contrast)-enhancing tumor (nCET) in glioblastoma's T2-FLAIR hyperintense lesion.

METHODS

Thirty-three histologically confirmed glioblastoma patients whose T1-, T2- and contrast-enhanced T1-weighted MRI and 11C-methionine positron emission tomography (Met-PET) were available were included in this study. Met-PET was utilized as a surrogate for tumor burden. Imaging features for identifying nCET were searched by qualitative examination of 156 targets. A new scoring system to identify nCET was established and validated by two independent observers.

RESULTS

Three imaging features were found helpful for identifying nCET; "Bulky gray matter involvement", "Around the rim of contrast-enhancement (Around-rim)," and "High-intensity on T1WI and low-intensity on T2WI (HighT1LowT2)" resulting in an nCET score = 2 × Bulky gray matter involvement - 2 × Around-rim + HighT1LowT2 + 2. The nCET score's classification performances of two independent observers measured by AUC were 0.78 and 0.80, with sensitivities and specificities using a threshold of four being 0.443 and 0.771, and 0.916 and 0.768, respectively. The weighted kappa coefficient for the nCET score was 0.946.

CONCLUSION

The current investigation demonstrated that qualitative assessments of glioblastoma's MRI might help identify nCET in T2/FLAIR high-intensity lesions. The novel nCET score is expected to aid in expanding treatment targets within the T2/FLAIR high-intensity lesions.

Subtyping of Group 3/4 medulloblastoma as a potential prognostic biomarker among patients treated with reduced dose of craniospinal irradiation: a Japanese Pediatric Molecular Neuro-Oncology Group study

BACKGROUND

One of the most significant challenges in patients with medulloblastoma is reducing the dose of craniospinal irradiation (CSI) to minimize neurological sequelae in survivors. Molecular characterization of patients receiving lower than standard dose of CSI therapy is important to facilitate further reduction of treatment burden.

METHODS

We conducted DNA methylation analysis using an Illumina Methylation EPIC array to investigate molecular prognostic markers in 38 patients with medulloblastoma who were registered in the Japan Pediatric Molecular Neuro-Oncology Group and treated with reduced-dose CSI.

RESULTS

Among the patients, 23 were classified as having a standard-risk and 15 as high-risk according to the classic classification based on tumor resection rate and presence of metastasis, respectively. The median follow-up period was 71.5 months (12.0-231.0). The median CSI dose was 18 Gy (15.0-24.0) in both groups, and 5 patients in the high-risk group received a CSI dose of 18.0 Gy. Molecular subgrouping revealed that the standard-risk cohort included 5 WNT, 2 SHH, and 16 Group 3/4 cases; all 15 patients in the high-risk cohort had Group 3/4 medulloblastoma. Among the patients with Group 3/4 medulloblastoma, 9 of the 31 Group 3/4 cases were subclassified as subclass II, III, and V, which were known to an association with poor prognosis according to the novel subtyping among the subgroups. Patients with poor prognostic subtype showed worse prognosis than that of others (5-year progression survival rate 90.4% vs. 22.2%; p < 0.0001). The result was replicated in the multivariate analysis (hazard ratio12.77, 95% confidence interval for hazard ratio 2.38-99.21, p value 0.0026 for progression-free survival, hazard ratio 5.02, 95% confidence interval for hazard ratio 1.03-29.11, p value 0.044 for overall survival).

CONCLUSION

Although these findings require validation in a larger cohort, the present findings suggest that novel subtyping of Group 3/4 medulloblastoma may be a promising prognostic biomarker even among patients treated with lower-dose CSI than standard treatment.

Surgical resection of glioblastoma in basal ganglia and utility of exoscope: Technical case reports

Background

Due to the presence of many perforating arteries and the deep location of basal ganglia tumors, dissection of the perforating arteries is critical during tumor resection. However, this is challenging as these arteries are deeply embedded in the cerebrum. Surgeons need to bend their heads for a long time using operative microscope and it is uncomfortable for the operating surgeon. A high-definition (4K-HD) 3D exoscope system can significantly improve the surgeon's posture during resection and widen the operating view field considerably by adjusting the camera angle.

Methods

We report two cases of glioblastoma (GBM) involving basal ganglia. We used a 4K-HD 3D exoscope system for resecting the tumor and analyzed the intraoperative visualization of the operative fields.

Results

We could approach the deeply located feeding arteries before successfully resecting the tumor using a 4K-HD 3D exoscope system which would have been difficult with the sole use of an operative microscope. The postoperative recoveries were uneventful in both cases. However, postoperative magnetic resonance imaging showed infarction around the caudate head and corona radiata in one of the cases.

Conclusion

This study has highlighted using a 4K-HD 3D exoscope system in dissecting GBM involving basal ganglia. Although postoperative infarction is a risk, we could successfully visualize and dissect the tumors with minimal neurological deficits.

WT1 Trio Peptide-Based Cancer Vaccine for Rare Cancers Expressing Shared Target WT1

No standard treatment has been established for most rare cancers. Here, we report a clinical trial of a biweekly WT1 tri-peptide-based vaccine for recurrent or advanced rare cancers. Due to the insufficient number of patients available for a traditional clinical trial, the trial was designed for rare cancers expressing shared target molecule WT1. The recruitment criteria included WT1-expressing tumors as well as HLA-A*24:02 or 02:01. The primary endpoints were immunoglobulin G (IgG) antibody (Ab) production against the WT1-235 cytotoxic T lymphocyte (CTL) epitope and delayed-type hypersensitivity (DTH) skin reactions to targeted WT1 CTL epitopes. The secondary endpoints were safety and clinical efficacy. Forty-five patients received WT1 Trio, and 25 (55.6%) completed the 3-month protocol treatment. WT1-235 IgG Ab was positive in 88.0% of patients treated with WT1 Trio at 3 months, significantly higher than 62.5% of the weekly WT1-235 CTL peptide vaccine. The DTH positivity rate in WT1 Trio was 62.9%, which was not significantly different from 60.7% in the WT1-235 CTL peptide vaccine. The WT1 Trio safety was confirmed without severe treatment-related adverse events, except grade 3 myasthenia gravis-like symptoms observed in a patient with thymic cancer. Fifteen (33.3%) patients achieved stable disease after 3 months of treatment. In conclusion, the biweekly WT1 Trio vaccine containing the WT1-332 helper T lymphocyte peptide induced more robust immune responses targeting WT1 than the weekly WT1-235 CTL peptide vaccine. Therefore, WT1-targeted immunotherapy may be a potential therapeutic strategy for rare cancers.

Optic nerve sheath meningioma presenting as progressive visual disturbance during pregnancy: A case report

Meningiomas are often reported to be sensitive to progesterone, but it is not clear how pregnancy and childbirth affect this. A 41-year-old woman experienced two pregnancies and two deliveries. During the first pregnancy, her right visual acuity was impaired, but it recovered after delivery. However, during the second pregnancy, the right visual acuity was impaired again and did not recover after the second delivery. The magnetic resonance imaging revealed a right optic nerve sheath meningioma (ONSM). Surgical resection of the intracranial extension of the tumor was performed to prevent tumor invasion of the left optic nerve and optic chiasm. Pathological examination diagnosed meningioma with positive immunostaining for progesterone receptor. The present study provided clinical features of ONSM associated with pregnancy. ONSM may present with increased tumor growth and impaired vision with pregnancy.

PEDT-10 PHASE II TRIAL OF PATHOLOGY-BASED THREE-GROUP TREATMENT STRATIFICATION FOR PATIENTS WITH CNS GERM CELL TUMORS: A LONG-TERM FOLLOW-UP STUDY

Background

Phase II clinical trial funded by Ministry of Health, Labour and Welfare from 1995 to 2003 evaluated efficacy of pathology-based three-group treatment stratification for CNS germ cell tumors (GCTs). We here present long-term follow-up results.

Methods

Total 228 cases were registered. Germinoma was treated with carboplatin+etoposide (CARE) and extended-local irradiation, local irradiation was added for intermediate-prognosis-group, and poor-prognosis-group was treated with ifosfamide+cisplatin+etoposide (ICE) and whole-brain or craniospinal irradiation.

Results

Mean/median ages at diagnosis were 16.8/16 years and female-to-male ratio was 40-188. Registry included 123 germinomas, 76 intermediate-prognosis-group cases (including 38 germinoma with STGC), 28 poor-prognosis-group cases and 1 mature teratoma. Median 222-months follow-up was conducted, and 56 recurrences and 39 deaths were recorded. 10 and 20-year recurrence-free survival (RFS) for germinoma, intermediate and poor-prognosis-groups were 84/79%, 83/76% and 59/59%, respectively, and overall survival (OS) for each were 97/91%, 92/85% and 57/53%, respectively. Prognosis for germinoma with or without STGC was the same. Basal ganglia germinoma showed significantly shorter RFS but OS was not different from other locations. Median age at death was 24 years, and ages were significantly different depending on causes, such as disease-related (14 years on average) and complications (29 years). OS after recurrence at 5/10/20 years were 64/62/48%.Hormonal supplementation was seen in 82% for neurohypophyseal cases and antidiuretic hormone supplementation was most frequent (82%). Among available cases, 20-out-of-155 cases showed neoplastic/vascular complications, among which cavernous malformation was the most (n=9). Median period until complication presentation was 235 months, and the rate at 20 years was 11%.

Conclusions

Germinoma and intermediate-prognosis-group cases showed long-term survival for approximately 90%, while more intensive treatment would be necessitated for poor-prognosis-group. Long-term survivors often required hormonal supplementation, and increasing frequency of treatment-related complications was observed. There is no end of outpatient follow-up for CNS GCT patients.

NI-3 FEASIBILITY OF MRI PERFUSION IN DISCRIMINATING BETWEEN EDEMA AND INFILTRATIVE AREAS IN THE PERI-GBM NON-CONTRAST T2 WEIGHTED HIGH AREA

Background

Glioblastomas are highly infiltrative tumors, and differentiating between infiltrating tumors and vasogenic edema occurring in the non-enhancing T2-weighted hyperintense area is challenging. Here, we differentiated between infiltrating tumors and edemas in glioblastomas using dynamic perfusion-weighted MR imaging.

Methods

Data were collected from 33 patients with glioblastomas and 15 with meningioma as controls, who underwent resection at our institution between January 2019 and March 2022. The MRI data included T2 weighted images and contrast-enhanced T1 weighted images, and dynamic perfusion-weighted MR imaging. Two neurosurgeons manually assigned regions of interest (ROIs) to infiltrating tumors and vasogenic edema based on a previous report using conventional MRI features. The ratio of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) in the ROIs to that contralateral normal regions were calculated. We also histological analysis using histological specimens obtained by stereotactic biopsy in each ROI.

Results

CBF and MTT ratios of infiltrating tumors and edemas differed significantly (p&lt;0.01), while CBF and MTT ratios of edemas and controls showed similarities. MTT values of controls and infiltrating tumors differed significantly (p=0.02). Receiver operating characteristic curve analysis revealed that CBF (area under the curve [AUC]=0.81) and MTT(AUC=0.95) were effective in distinguishing between infiltrating tumors and edemas. Pathological analysis revealed that cell density, MIB1-index, and microvessel density were higher in infiltrating tumors than in edemas.

Conclusions

Using dynamic perfusion-weighted MR imaging may prove useful in differentiating infiltrating tumors from edemas in the non-contrast T2 hyperintensity region of glioblastomas.

ACT-20 PHASE 1/2, PROSPECTIVE, INTERNATIONAL MULTI-CENTER STUDY TO ESTABLISH THE SAFETY AND FEASIBILITY OF BLOOD-BRAIN-BARRIER DISRUPTION COMBINED WITH CARBOPLATIN FOR RECURRENT GLIOBLASTOMA; FIRST CLINICAL EXPERIENCE IN JAPAN

The prognosis for glioblastoma is still very poor despite intensive treatment by surgery, radiation, and chemotherapy. One of the reasons for poor prognosis of glioblastoma is blood-brain-barrier (BBB), which limits the delivery of chemotherapeutic agents to the brain. Focused ultrasound (FUS) therapy is approved for essential tremor and Parkinson disease in Japan and preclinical studies suggest low-intensity focused ultrasound (LIFU) administered with microbubbles (MB) can disrupt BBB and can improve the delivery of chemotherapeutic agents. Thus, currently, focused ultrasound therapy has gained attention in neuro-oncology and a number of clinical trials using FUS for the treatment of glioblastoma are underway. Our institutions (Osaka University Hospital and Saito Yukoukai Hospital) are the first in Japan to join the international multicenter study to examine the safety and feasibility of BBB disruption by FUS and MB combined with intravenous carboplatin for the treatment of recurrent glioblastoma. We are planning to enroll one recurrent glioblastoma patient for this study soon. BBB disruption strategies using FUS and MB for the treatment of neuro-oncological disease has potentials to improve the outcome of patients and many clinical trials will be performed in future.

MNG-3 STRATIFICATION OF TUMOR GROWTH BY RISK FACTORS AND PREDICTED TUMOR VOLUME CURVES FOR SUPRATENTORIAL MENINGIOMAS

Background

The natural history of meningiomas is still unclear, and no guidelines have been established based on objective indices regarding the necessity and timing of therapeutic intervention.Objective: We attempted to provide statistics on the characteristics of tumor volume change, stratify tumor growth by risk factors, and generate a predictive tumor volume curve based on the statistics, with the aim of describing the natural history of meningiomas.

Methods

313 cases were included in the study, with the origin of meningioma being the circumflex and parasagittal sinus areas and the cerebral sickle region, and with multiple MRI scans performed at intervals of at least 3 months. Relative growth rate (RGR) and annual volume change (AVC) were calculated by measuring tumor volume, and the patients were classified into three groups according to the combination of gender, age, and MRI T2WI signal intensity, and compared.

Results

The median RGR and AVC of the entire cohort were 6.1% and 0.20 cm3/year, respectively, and there were significant differences between groups in gender (p=0.018) and MRI T2WI (p &lt; 0.001) for RGR and tumor location (p=0.025) and initial tumor volume (p &lt; 0.001)for AVC. The median RGR and AVC in the classification were 17.5% and 1.05 cm3/year for the very high growth group, 8.2% and 0.33 cm3/year for the high growth group, and 3.4% and 0.04 cm3/year for the low growth group, showing significant differences between the groups (p &lt; 0.001). The predicted tumor volume curve showed an average 2.24-fold or 5.24 cm3 increase in volume over 5 years in the very high-growth group, while little tumor volume change was observed in the low-growth group.

Conclusion

The combination of growth risk factors allowed stratification of tumor growth and provided a predictive tumor volume curve for each county. The results may assist in the treatment of meningiomas.

Identification of glioblastoma-specific antigens expressed in patient-derived tumor cells as candidate targets for chimeric antigen receptor T cell therapy

Background

New therapies for glioblastoma (GBM) are urgently needed because the disease prognosis is poor. Chimeric antigen receptor (CAR)-T cell therapy that targets GBM-specific cell surface antigens is a promising therapeutic strategy. However, extensive transcriptome analyses have uncovered few GBM-specific target antigens.

Methods

We established a library of monoclonal antibodies (mAbs) against a tumor cell line derived from a patient with GBM. We identified mAbs that reacted with tumor cell lines from patients with GBM but not with nonmalignant human brain cells. We then detected the antigens they recognized using expression cloning. CAR-T cells derived from a candidate mAb were generated and tested in vitro and in vivo.

Results

We detected 507 mAbs that bound to tumor cell lines from patients with GBM. Among them, E61 and A13 reacted with tumor cell lines from most patients with GBM, but not with nonmalignant human brain cells. We found that B7-H3 was the antigen recognized but E61. CAR-T cells were established using the antigen-recognition domain of E61-secreted cytokines and exerted cytotoxicity in co-culture with tumor cells from patients with GBM.

Conclusions

Cancer-specific targets for CAR-T cells were identified using a mAb library raised against primary GBM tumor cells from a patient. We identified a GBM-specific mAb and its antigen. More mAbs against various GBM samples and novel target antigens are expected to be identified using this strategy.

IMMU-19. IDENTIFICATION OF TARGET ANTIGENS FOR CHIMERIC ANTIGEN RECEPTOR T- CELL THERAPY AGAINST GLIOBLASTOMA USING A MONOCLONAL ANTIBODY LIBRARY RAISED AGAINST PATIENT-DERIVED TUMOR SPHERES

New therapies for GBM are urgently needed due to its poor prognosis and chimeric antigen receptor T (CAR-T) cell therapy is thought to be a promising strategy. To develop CAR-T cell therapy, cell surface targets that is highly specific for GBM cells are needed.Although extensive transcriptome analyses of GBM cells were performed, few transcripts highly specific for GBM cells have been identified. However, GBM cell-specific antigen epitopes formed by post-translational modifications of proteins may have been missed, and could still be discovered by thoroughly searching for cancer-specific monoclonal antibodies and characterizing the antigens they recognize. In this study, we applied this strategy to search for GBM-specific cell surface targets using patient derived tumor spheres. We identified two monoclonal antibodies E61 and A13 as those reacting with GBM cells but not with normal brain parenchymal cells. CAR-T cells derived from both monoclonal antibodies produced IL-2 and IFNɤ and exerted cytotoxicity to GBM cells by chromium 51 release assay. In addition, we identified B7-H3, which is frequently used for a CAR-T cell target against GBM, as the antigen recognized by B7-H3 by the expression cloning method. These results indicate that the strategy shown in this study is useful for identifying antigens that are expressed on patient-derived GBM cells and potentially useful as targets for CAR T cells.

[Neuroendoscopic Surgery for Pediatric Intraventricular Tumors]

Various tumors are found in ventricles and tissues surrounding the ventricles in children, adolescents, and young-adult patients. They cause cerebrospinal fluid pathway obstruction, resulting in hydrocephalus and isolated ventricles. In this paper we describe a neoplasm arising from the lateral and third ventricle. Intraventricular tumors are good candidates for neuroendoscopic surgery. Firstly, minimally invasive and established procedures, neuroendoscopic biopsy with flexible endoscopy or rigid endoscopy, are performed. These endoscopic biopsies can be performed concurrently with other procedures, such as third ventriculostomy or septostomy, to improve cerebrospinal fluid circulation. Neuroendoscopic biopsy for intraventricular tumor is associated with high diagnostic yield and relatively low incidence of morbidity and mortality, compared with open surgery. Endoscopic diagnostic procedure also can be applied in patients without ventricular dilatation, assisted by neuronavigation or echo-guided equipment. Secondly, neuroendoscopic cylinder surgery also makes it possible to remove intraventricular tumors with less damage. The two hands technique with rigid endoscopy helps debulking and hemostasis during tumor removal. Further developments in endoscopic equipment and training systems aimed at enhancing cooperation between the operator and assistant should be expected in the future. Neuroendoscopic resection appears to be a safe and reliable treatment option for patients with intraventricular tumors.

Growth risk classification and typical growth speed of convexity, parasagittal, and falx meningiomas: a retrospective cohort study

OBJECTIVE

Meningiomas are the most common primary intracranial tumors, and their clinical and biological characteristics vary by location. Convexity, parasagittal, and falx meningiomas account for approximately 50%-65% of intracranial meningiomas. Focusing only on these locations, the aim of this study was to determine the typical speed of tumor growth, to assess the growth risk, and to show the possible tumor volume that many lesions can reach after 5 years.

METHODS

Patients with radiologically suspected convexity, parasagittal, or falx meningiomas at the authors' institution were studied retrospectively. The relative growth rate (RGR) and annual volume change (AVC) were calculated from MRI at more than 3-month intervals. Based on sex, age, and signal intensity on T2-weighted MRI, the cases were classified into three groups: extremely high-growth, high-growth, and low-growth groups.

RESULTS

The data of 313 cases were analyzed. The median RGR and AVC for this entire cohort were 6.1% (interquartile range [IQR] 2.4%-16.0%) and 0.20 (IQR 0.04-1.18) cm3/year, respectively. There were significant differences in sex (p = 0.018) and T2-weighted MRI signal intensity (p < 0.001) for RGR, and T2-weighted MRI signal intensity (p < 0.001), tumor location (p = 0.025), and initial tumor volume (p < 0.001) for AVC. The median RGR and AVC were 17.5% (IQR 8.3%-44.1%) and 1.05 (IQR 0.18-3.53) cm3/year, 8.2% (IQR 2.9%-18.6%) and 0.33 (IQR 0.06-1.66) cm3/year, and 3.4% (IQR 1.2%-5.8%) and 0.04 (IQR 0.02-0.21) cm3/year for the extremely high-growth, high-growth, and low-growth groups, respectively, with a significant difference among the groups (p < 0.001). A 2.24-times, or 5.24 cm3, increase in tumor volume over 5 years was typical in the extremely high-growth group, whereas the low-growth group showed little change in tumor volume even over a 5-year follow-up period.

CONCLUSIONS

For the first time, the typical speed of tumor growth was calculated, focusing only on patients with convexity, parasagittal, and falx meningiomas. In addition, the possible tumor volume that many lesions in these locations can reach after 5 years was shown based on objective indicators. These results may allow clinicians to easily detect lesions that require frequent follow-up or early treatment by determining whether they deviate from the typical range of the growth rate, similar to a growth chart for children.

Cerebellopontine angle metastasis of a neuroendocrine tumor mimicking vestibular schwannoma: A case report

Background:

Neuroendocrine tumors (NETs) are uncommon neoplasms arising from neuroendocrine cells and are rarely associated with intracranial metastases.

Case Description:

We discuss the case of a 74-year-old woman with a right CPA tumor. She had a history of retroperitoneal NET, but was diagnosed with vestibular schwannoma due to a right-sided hearing loss and a right CPA tumor along the VII and VIII nerves. After a 3-year follow-up, she presented with repetitive vomiting, a 1-month history of gait instability, and a 3-month history of general fatigue. Brain imaging revealed tumor growth and edematous changes in the right cerebellum. She underwent retrosigmoid craniotomy and partial resection. Histopathological examination revealed metastatic NET. She underwent stereotactic radiosurgery for residual lesion and, at 11 months of follow-up, the lesion was confirmed to have shrunk on magnetic resonance imaging (MRI).

Conclusion:

This is the first case to report the natural course of cerebellopontine metastasis of a NET. The differential diagnosis of CPA tumors is diverse, and, in our case, we suspected a vestibular schwannoma because of the typical symptoms and imaging features. However, the tumor grew relatively faster than expected and showed intratumoral hemorrhage during the 3-year follow-up. Therefore, in patients with a history of a NET, a careful follow-up is advisable even for lesions highly suspected to be another benign tumor on MRI. Careful follow-up imaging and appropriate treatment strategies were useful to manage the brain metastasis. Although NETs metastasizing to the CPA are extremely rare, this possibility should be considered when patients with NETs have intracranial lesions.

GCT-21. Long-term outcome and follow up of intracranial germ cell tumors: Reduced-dose radiotherapy and intensified chemotherapy improves clinical outcome and quality of life for long-term survivors

BACKGROUND: Intracranial germ cell tumors (iGCT) are heterogeneous tumors with several histopathology. Chemoradiotherapy is effective and required for treatment against them, but optimal treatment intensity should be selected from the viewpoint of both improvement of clinical outcome and avoidance of late complications. We introduced a protocol with reduced-dose radiotherapy and intensified chemotherapy for iGCT. OBJECTIVE: We retrospectively analysed the clinical outcome, especially for non-germinomatous germ cell tumors and long-term clinical outcome of late complications, enrollment and employment, as indicators of quality of life (QOL). MATERIALS AND METHODS: Thirty-eight children and young adults (28 men and 10 women) with iGCTs treated in our institution from 1997 to 2013 were enrolled in this study. They consisted of 26 germinomas including HCG-producing cases and 12 non-germinomatous GCTs (NGGCT). Local irradiation was selected for all patients, and the dose of irradiation was 23.4-54 Gy. The whole-brain irradiation was made in patients who had intracranial dissemination, but any prophylactic irradiation to the whole brain and spinal cord was not performed. For NGGCT, high-dose chemotherapy and peripheral blood stem cell transplantation (PBSCT) were introduced. Second-look surgeries were performed for cases with residual tumors after induction chemotherapies. RESULTS: In germinoma group and NGGCT group, 10-year progression-free survival was 86% and 84%, 10-year overall survival was 93% and 91%, respectively. About late complications, endocrinological replacement (39%), cerebrovascular disease such as cavernous hemangioma and arterial stenosis (18%), secondary neoplasm (2.6%) were observed. Regarding QOL, enrollment and return to school rate was 92% and employment and the return rate was 89%, which were influenced by hemipararesis associated with basal ganglia lesion, intractable epilepsy and whole-brain irradiation. CONCLUSION: Reduced-dose radiotherapy and intensified chemotherapy for iGCT, especially NGGCT, improved the clinical outcome and QOL of long-term survivors, suppressing late complications. Further comprehensive follow-up and analysis are needed.

MEDB-30. Subclassification of Group 3/4 medulloblastoma as a potential prognostic biomarker to reduce the dose of craniospinal irradiation in patients with metastatic tumors: A Japanese Pediatric Molecular Neuro-Oncology Group study

BACKGROUND: In patients with medulloblastoma, one of the most significant challenges is to reduce the dose of craniospinal irradiation (CSI) to minimize neurological sequelae in survivors. Molecular characterization of patients treated using lower-dose CSI rather than standard therapy is important for further reducing the treatment burden. METHODS: We conducted DNA methylation analysis using an Illumina Methylation EPIC array to investigate molecular prognostic markers in 38 patients with medulloblastoma who were registered in the Japan Pediatric Molecular Neuro-Oncology Group and were treated using lower-dose CSI rather than standard-dose radiation therapy. RESULTS: Among the patients, 23 were classified as having a “standard-risk” and 15 as having a “high-risk” according to the classic classification based on tumor resection rate and presence of metastasis, respectively. The median follow-up period was 71.5 months. The median CSI dose was 18 Gy in both groups, and 10 patients in the “high-risk” group received a CSI dose of 23.4 Gy or 24 Gy. Molecular subgrouping revealed the “standard-risk” cohort included 5 WNT, 2 SHH, and 16 Group 3/4 cases; all 15 patients in the “high-risk” cohort had Group 3/4 medulloblastoma. Among the patients with Group 3/4 medulloblastoma, 13 of the 16 “standard-risk” patients were subclassified as subtypes I, IV, VI, and VII, which were associated with a good prognosis according to the novel sub-subclassification among Group 3/4 medulloblastomas. However, only 6 of the 15 “high-risk” patients were included in the subtypes. The good prognostic subtype cases among “high-risk” cohort were all survived without recurrence, in contrast to a worse prognosis (5-year progression free survival=33.3%; p=0.01) of the other cases. CONCLUSION: Although these findings require validation in a larger cohort, the present findings suggest that the novel sub-subclassification of Group 3/4 medulloblastoma may be a promising prognostic biomarker for reducing the dose of CSI in patients with metastatic medulloblastoma.

Successful separation of male pygopagus with anal canal and urethral reconstruction: a case report

Background

Pygopagus is a type of conjoined twin binding at the buttocks. Some cases of pygopagus involve the fusion of the gastrointestinal tract, urinary tract, and spinal cord. Few cases of male pygopagus have been reported; however, the prognosis after separation is unclear. Herein, we report a case of male pygopagus in which successful separation was performed with the reconstruction of the anal canal.

Case presentation

Twins with male pygopagus were born at 35 weeks by cesarean section. They shared a common anus, penis, and scrotum with four testes. The infants had normal defecation and urination after birth. The separation surgery was scheduled when they were 5 months. Two distinct anesthesia teams and four surgical teams (neurosurgery, pediatric urology, plastic surgery, and pediatric surgery) were involved in the multidisciplinary approach. After separating the spinal cord, we found that the anal canal and sphincter muscle complex were fused near the anal aperture, and we separated them. The fused penis and testis were separated and reconstructed using the same incisional line as the other separation, and the reconstructions of the anal canals with the sphincter muscle complex were completed. Both patients had an uneventful postoperative course. At 2 years of age, they could walk and defecate independently. In addition, they voided spontaneously without urinary incontinence at the time of 3 years and 11 months.

Conclusions

Separation of the spinal cord with anal canal and urethral reconstruction is important for male pygopagus patients as it allows them to preserve their independent function.

Prediction and Visualization of Non-Enhancing Tumor in Glioblastoma via T1w/T2w-Ratio Map

One of the challenges in glioblastoma (GBM) imaging is to visualize non-enhancing tumor (NET) lesions. The ratio of T1- and T2-weighted images (rT1/T2) is reported as a helpful imaging surrogate of microstructures of the brain. This research study investigated the possibility of using rT1/T2 as a surrogate for the T1- and T2-relaxation time of GBM to visualize NET effectively. The data of thirty-four histologically confirmed GBM patients whose T1-, T2- and contrast-enhanced T1-weighted MRI and ¹¹C-methionine positron emission tomography (Met-PET) were available were collected for analysis. Two of them also underwent MR relaxometry with rT1/T2 reconstructed for all cases. Met-PET was used as ground truth with T2-FLAIR hyperintense lesion, with >1.5 in tumor-to-normal tissue ratio being NET. rT1/T2 values were compared with MR relaxometry and Met-PET. rT1/T2 values significantly correlated with both T1- and T2-relaxation times in a logarithmic manner (p < 0.05 for both cases). The distributions of rT1/T2 from Met-PET high and low T2-FLAIR hyperintense lesions were different and a novel metric named Likeliness of Methionine PET high (LMPH) deriving from rT1/T2 was statistically significant for detecting Met-PET high T2-FLAIR hyperintense lesions (mean AUC = 0.556 ± 0.117; p = 0.01). In conclusion, this research study supported the hypothesis that rT1/T2 could be a promising imaging marker for NET identification.

How Much Tumor Volume Is Responsible for Development of Clinical Symptoms in Patients With Convexity, Parasagittal, and Falx Meningiomas?

Purpose: Meningiomas are the most common primary intracranial neoplasms and clinical symptom appearance depends on their volume and location. This study aimed to identify factors that influence clinical symptoms and to determine a specific threshold tumor volume for the prediction of symptomatic progression in patients with convexity, parasagittal, and falx meningiomas.

Materials and Methods: We retrospectively studied patients with radiologically suspected convexity, parasagittal, or falx meningiomas at our institution.

Results: The data of three hundred thirty-three patients were analyzed. We further divided patients into two groups based on clinical symptoms: an asymptomatic group (250 cases) and a symptomatic group (83 cases). Univariate analysis revealed significant differences between the groups in terms of sex (p = 0.002), age at the time of volumetric analysis (p < 0.001), hyperintense lesions on T2-weighted images (p = 0.029), peritumoral edema (p < 0.001), maximum tumor diameter (p < 0.001), and tumor volume (p < 0.001). Further multivariate analysis revealed significant differences between the groups in terms of age at the time of volumetric analysis (p = 0.002), peritumoral edema (p < 0.001), and tumor volume (p < 0.001). The receiver operating characteristic curve revealed a threshold tumor volume of 21.1 ml for predicting whether a patient would develop symptoms (sensitivity 0.843, specificity 0.880, an area under the curve 0.919 [95% confidence interval: 0.887–0.951]).

Conclusion: We identified factors predictive of clinical symptoms in patients with convexity, parasagittal, and falx meningiomas and determined the first-ever threshold tumor volume for predicting symptomatic progression in such patients.

COT-16 Development of automatic lesion extraction application using artificial intelligence for the purpose of simplifying tumor volume measurement of meningioma

BACKGROUND: With the widespread use of MRI equipment and brain scans, opportunities to perform follow-up examinations for meningiomas have increased. On the other hand, an objective evaluation index for meningiomas characterized by slow changes on imaging has not been established. To establish a volume-based evaluation index for meningoceles, we are developing an application for automatic lesion extraction using artificial intelligence as a highly reproducible tumor volume measurement technique that enables large volume image data processing. METHODS: In this study, 195 patients with meningioma who underwent contrast-enhanced MRI imaging at Osaka University Hospital were included. The images were manually extracted by three neurosurgeons and used as supervised data. deeplabV3 was used as the learning network. All the supervised data were randomly divided into training (80%) and testing (20%) data, and the application was constructed by deep learning and validation with 5-fold cross-validation. The matching rate of the area of the region automatically extracted by the device against the test data and the mean square error rate of the calculated tumor volume were used as indices of the product measurement performance. RESULTS: The matching rate using the automatic extraction application for the correct data(Dice index) was 91.5% on average. The mean squared error rate of the tumor volume calculated from these extracted regions was 8.84%. CONCLUSION: We consider that this application using artificial intelligence has a certain degree of validity in terms of the accuracy of extracted lesions. In the future, it is necessary not only to improve the performance of the equipment but also to clarify the clinical significance of the new imaging biomarkers based on tumor volume that can be obtained from these lesion extraction techniques.

TB-9 An attempt to establish a patient-derived brain tumor culture model by organoid culture method

Background: Molecular heterogeneity among and within tumors are one of the reasons for the poor survival rate of brain tumors even with the current standard therapy. However, monolayer culture and neuro-sphere culture (NS) use exogenous growth factors, so may not show the true nature of the tumor. And the culture establishment rate is low, especially low-grade tumors. Therefore, we used the glioblastoma organoid (GBO) culture method showed by Fadi to create culture models of various brain tumors and investigated their characteristics.

Methods: We examined the establishment rate in pathological and genotypic types of 56 patients who underwent brain tumor resection at our hospital between January 2020 and June 2021 and were cultured with GBO or NS. If tumor cells are increased visually at 1 month after culture, we defined establishment.

Results: There were 15 cases of glioblastoma, 7 cases of anaplastic astrocytoma, 7 cases of diffuse astrocytoma, 3 cases of diffuse midline glioma, 2 cases of anaplastic oligodendroglioma, 5 cases of oligodendroglioma, and 16 cases of others. The establishment rate was 76.5% by the GBO method and 40% by the N S method. By histological type, GBO: 80% in glioblastoma, NS: 58.3% in glioblastoma, GBO: 83.3% in AA, NS: 40% in AA, and GBO: 100% in DA. The IDH mutation and pTERT mutation were investigated in GBO: IDHwt/TERT+ 87.5%, IDHwt/TERT- 64.3%, IDHmt/TERT- 100%, and in NS: IDHwt/TERT+ 75%, IDHwt/TERT- 33.3%, IDHmt/ TERT- 20% in NS. In addition, establishment was observed in GBO 2 case in medulloblastoma, 1 case in ependymoma.

Discussion and Conclusion: This suggest that GBO can be used to establish culture models for low-grade tumors. In addition, GBO can establish culture earlier, so it is expected to be applicable to personalized therapies such as preclinical drug efficacy studies tailored to individual patients.

IM-7 Identification of novel glioblastoma specific antigen using patient derived tumor cell for CAR-T cell therapy

Chimeric antigen receptor T (CAR-T) cell therapy is a newly developed antitumor immunotherapy presenting remarkable clinical response with leukemia, and is expected to be applied to other malignant solid tumors including glioblastoma (GBM). However, for development of CAR-T therapy against GBM, identification of novel and suitable tumor specific antigen is required to expect higher therapeutic efficacy. Herein, we developed our original method to detect novel GBM specific antigen using patient derived GBM (PD-GBM) cells. First, BALB/c mice were immunized by footpad injection of PD-GBM cells. B cells were extracted from lymph nodes of the mice, fused with murine myeloma cells, and then cultured to produce monoclonal antibodies for GBM cells. About 500 GBM binding monoclonal antibody lines were established, and then each antibody was again analyzed by flow cytometry with multiple PD-GBM cells and human non-tumor brain cells to find out GBM specific antibodies. Consequently, two GBM specific antibody lines were selected and genetically analyzed to identify the recognized antigen. CAR-T cells targeting the detected antigens were successfully generated, and the cytotoxicity against GBM cells was confirmed by chromium releasing assay and bioluminescent cytokine assay. Remarkably, one of the identified tumor specific antigens proved to be B7-H3, which is known pan-cancer antigen expected to be one CAR-T therapeutic target for malignant solid tumors, also expressed in most GBM cells. This result confirms that our experimental method using murine antigen-antibody reaction is feasible for detecting antigen as a novel CAR-T therapeutic target for GBM. Moreover, this method can also detect antigens derived from post-translational conformational changes such as glycosylation, which might have been overlooked by conventional methods. In addition, these results suggest our method using PD-GBM cells can identify potential targets of CAR-T therapy for each GBM patients respectively, thus leading to precision immunotherapy for GBM.

MPC-6 Clinical significance of whole chromosomal aberration signatures in non-metastatic medulloblastomas treated with 18Gy of craniospinal irradiation

Background: One of the most significant challenges is a reduction in the dose of craniospinal irradiation (CSI) in patients with medulloblastoma to minimize neurological sequelae. However, a North American clinical trial failed to show the prognostic non-inferiority of lower-dose irradiation compared to that associated with standard-dose radiation therapy for non-metastatic medulloblastomas. A European retrospective study revealed that whole chromosomal aberration signatures (WCASs) are a potential prognostic factor in Group 3/4 medulloblastoma without metastasis, but whether the molecular signature has the same clinical impact in patients treated with lower-dose CSI remains unknown. Methods: We conducted DNA methylation analysis using an Illumina Infinium Human Methylation EPIC BeadChip array to investigate molecular prognostic markers in 23 medulloblastoma patients who were registered in the Japan Pediatric Molecular Neuro-Oncology Group and treated with lower-dose CSI relative to standard treatment. A WCAS was defined as the presence of at least two of three chromosomal changes as follows: chromosome (chr) 7 gain, chr 8 loss, and chr 11 gain.Results: All patients presented with no residue or a residual tumor smaller than 1.5 cm2 after surgery without metastasis. The median age at onset was 6.9 years, and the median follow-up period was 80.6 months. CSI was delivered at a median dose of 18.0 Gy. Regarding molecular subgrouping, there were 5 WNT, 2 SHH, 1 Group 3, and 15 Group 4 medulloblastomas. Seven patients with Group 3/4 medulloblastomas showed WCASs and had significantly better prognosis than those without the alteration (5-year progression-free survival 100% vs. 63%, p = 0.046). Two late relapses occurred at 89 and 115 months after diagnosis, respectively, and one of these patients presented with a WCAS.Conclusion: WCAS may be a molecular prognostic marker not only in patients with medulloblastoma treated with standard-dose CSI but also in those treated with lower-dose irradiation.

NI-14 estimation of property of MRI non-contrast enhanced lesion of Glioblastoma using T1/T2 ratio

Background: Tumor mass of glioblastoma is considered to exist beyond gadolinium-enhancing lesion into T2/FLAIR-high intensity lesions (T2/FL-HIL) on MRI. However, it is challenging to differentiate non-enhancing tumor region (NET) from pure brain edema for T2/FL-HIL. The T1/T2 ratio (rT1/T2) is an MRI metric considered to semi-quantify the tissue relaxation time on MRI. This research tested the hypothesis that rT1/T2 is useful for identifying NET within T2/FL-HIL by comparing it with 11C-methionine positron emission tomography (MET-PET). Method: Forty-six glioblastoma (GBM) patients at Osaka International Cancer Institute and Osaka University Hospital where T1-, T2- and contrast-enhanced T1-weighted MRI and MET-PET were available were included in this study. rT1/T2 maps were obtained after signal corrections were performed, as reported previously. Region-of-interests (ROIs) were defined within T2/FL-HILs beyond the gadolinium-enhanced lesion. MET-PET and rT1/T2 maps were co-registered to the same coordinate system, and the relationship between methionine uptake and rT1/T2 values was examined in a voxel-wise manner.ResultApproximately three million voxels were included for analysis. Lesions with methionine uptake higher than 5.0 on T/N showed 0.7 &lt rT1/T2 &lt 0.98. For those with methionine uptake higher than 3.0, rT1/T2 was between 0.70 and 1.04.DiscussionThis report suggested that rT1/T2 represents histological characteristics of the glioblastoma within T2/FL-HIL. It also indicated that rT1/T2 could be a useful biomarker for detecting NET within T2/FL-HIL for glioblastoma.

Safety and efficacy of depatuxizumab mafodotin in Japanese patients with malignant glioma: A nonrandomized, phase 1/2 trial

INTELLANCE‐J was a phase 1/2 study of a potent antibody‐drug conjugate targeting epidermal growth factor receptor (EGFR), depatuxizumab mafodotin (Depatux‐M), as a second‐ or first‐line therapy, alone or combined with chemotherapy or chemoradiotherapy in 53 Japanese patients with World Health Organization (WHO) grade III/IV glioma. In second‐line arms, patients with EGFR‐amplified recurrent WHO grade III/IV glioma received Depatux‐M plus chemotherapy (temozolomide) or Depatux‐M alone regardless of EGFR status. In first‐line arms, patients with newly diagnosed WHO grade III/IV glioma received Depatux‐M plus chemoradiotherapy. The study was halted following lack of survival benefit with first‐line Depatux‐M in the global trial INTELLANCE‐1. The primary endpoint was 6‐month progression‐free survival (PFS) in patients with EGFR‐amplified tumors receiving second‐line Depatux‐M plus chemotherapy. Common nonocular treatment‐emergent adverse events (TEAEs) with both second‐line and first‐line Depatux‐M included lymphopenia (42%, 33%, respectively), thrombocytopenia (39%, 47%), alanine aminotransferase increase (29%, 47%), and aspartate aminotransferase increase (24%, 60%); incidence of grade ≥3 TEAEs was 66% and 53%, respectively. Ocular side effects (OSEs) occurred in 93% of patients receiving second‐line Depatux‐M plus chemotherapy and all patients receiving second‐line Depatux‐M alone or first‐line Depatux‐M plus chemoradiotherapy. Most OSEs were manageable with dose modifications and concomitant medications. The 6‐month PFS estimate was 25.6% (95% confidence interval [CI] 11.4‒42.6), and median PFS was 2.1 months (95% CI 1.9‒3.9) with second‐line Depatux‐M plus chemotherapy in the EGFR‐amplified subgroup. This study showed acceptable safety profile of Depatux‐M alone or plus chemotherapy/chemoradiotherapy in Japanese patients with WHO grade III/IV glioma. The study was registered at ClinicalTrials.gov (NCT02590263).

Efficacy and safety of nivolumab in Japanese patients with first recurrence of glioblastoma: an open-label, non-comparative study

BACKGROUND

An open-label, non-comparative study assessed the efficacy and safety of nivolumab in Japanese patients with first recurrence glioblastoma.

METHODS

Patients with first recurrence of histologically confirmed World Health Organization Grade IV glioma, after treatment with temozolomide and radiotherapy, received nivolumab 3 mg/kg every 2 weeks until confirmed disease progression (Response Assessment in Neuro-Oncology criteria) or toxicity. Primary endpoint was 1-year overall survival rate assessed by Bayesian approach. The prespecified efficacy criterion was that the Bayesian posterior probability threshold for exceeding the 1-year overall survival of bevacizumab (34.5%) from the Japanese phase 2 study (JO22506) would be 93%.

RESULTS

Of the 50 enrolled patients, 44 (88.0%) had recurrent malignant glioma (glioblastoma, gliosarcoma), and of these, 26 (59.1%) had at least one measurable lesion at baseline. The Bayesian posterior mean 1-year overall survival (90% Bayesian credible intervals) with nivolumab was 54.4% (42.27-66.21), and the Bayesian posterior probability of exceeding the threshold of the 1-year overall survival rate of bevacizumab (34.5%) was 99.7%. Median (90% confidence interval) overall and progression-free survival was 13.1 (10.4-17.7) and 1.5 (1.4-1.5) months, respectively. One partial response was observed (objective response rate 1/26 evaluable patients [3.8%]). Treatment-related adverse event rates were 14.0% for Grade 3-4 and 2.0% for Grade 5; most adverse events resolved and were manageable.

CONCLUSIONS

The 1-year overall survival with nivolumab monotherapy in Japanese patients with glioblastoma met the prespecified efficacy criterion. The safety profile of nivolumab was consistent with that observed in other tumor types.

CLINICAL TRIAL REGISTRATION

JapicCTI-152967.

Distinct difference in tumor-infiltrating immune cells between Wilms' tumor gene 1 peptide vaccine and anti-programmed cell death-1 antibody therapies

Background

Wilms’ tumor gene 1 (WT1) peptide vaccine and anti-programmed cell death-1 (anti-PD-1) antibody are expected as immunotherapies to improve the clinical outcome of glioblastoma. The aims of this study were to clarify how each immunotherapy affects tumor-infiltrating immune cells (TIIs) and to determine whether the combination of these two therapies could synergistically work.

Methods

Mice were transplanted with WT1 and programmed cell death-ligand 1 doubly expressing glioblastoma cells into brain followed by treatment with WT1 peptide vaccine, anti-PD-1 antibody, or the combination of the two, and survival of each therapy was compared. CD45⁺ cells were positively selected as TIIs from the brains with tumors, and TIIs were compared between WT1 peptide vaccine and anti-PD-1 antibody therapies.

Results

Most mice seemed to be cured by the combination therapy with WT1 peptide vaccine and anti-PD-1 antibody, which was much better survival than each monotherapy. A large number of CD4⁺ T cells, CD8⁺ T cells, and NK cells including WT1-specific CD8⁺ and CD4⁺ T cells infiltrated into the glioblastoma in WT1 peptide vaccine-treated mice. On the other hand, the number of TIIs did not increase, but instead PD-1 molecule expression was decreased on the majority of the tumor-infiltrating CD8⁺ T cells in the anti-PD-1 antibody-treated mice.

Conclusion

Our results clearly demonstrated that WT1 peptide vaccine and anti-PD-1 antibody therapies worked in the different steps of cancer-immunity cycle and that the combination of the two therapies could work synergistically against glioblastoma.

Necessity for craniospinal irradiation of germinoma with positive cytology without spinal lesion on MR imaging-A controversy

Background

Cerebrospinal fluid (CSF) cytology and spinal MR imaging are routinely performed for staging before treatment of intracranial germinoma. However, the interpretation of the results of CSF cytology poses 2 unresolved clinical questions: (1) Does positive CSF cytology correlate with the presence of spinal lesion before treatment? and (2) Is craniospinal irradiation (CSI) necessary for patients with positive CSF cytology in the absence of spinal lesion?

Methods

Multicenter retrospective analyses were performed based on a questionnaire on clinical features, spinal MR imaging finding, results of CSF cytology, treatments, and outcomes which was sent to 86 neurosurgical and 35 pediatrics departments in Japan. Pretreatment frequencies of spinal lesion on MR imaging were compared between the patients with positive and negative cytology. Progression-free survival (PFS) rates were compared between patients with positive CSF cytology without spinal lesion on MR imaging treated with CSI and with whole brain or whole ventricular irradiation (non-CSI).

Results

A total of 92 germinoma patients from 45 institutes were evaluated by both CSF cytology and spinal MR images, but 26 patients were excluded because of tumor markers, the timing of CSF sampling or incomplete estimation of spinal lesion. Of the remaining 66 germinoma patients, spinal lesions were equally identified in patients with negative CSF cytology and positive cytology (4.9% and 8.0%, respectively). Eleven patients treated with non-CSI had excellent PFS comparable to 11 patients treated with CSI.

Conclusion

CSI is unnecessary for germinoma patients with positive CSF cytology without spinal lesions on MR imaging.

Determination of brain tumor recurrence using 11 C-methionine positron emission tomography after radiotherapy

We conducted a prospective multicenter trial to compare the usefulness of ¹¹C‐methionine (MET) and ¹⁸F‐fluorodeoxyglucose (FDG) positron emission tomography (PET) for identifying tumor recurrence. Patients with clinically suspected tumor recurrence after radiotherapy underwent both ¹¹C‐MET and ¹⁸F‐FDG PET. When a lesion showed a visually detected uptake of either tracer, it was surgically resected for histopathological analysis. Patients with a lesion negative to both tracers were revaluated by magnetic resonance imaging (MRI) at 3 months after the PET studies. The primary outcome measure was the sensitivity of each tracer in cases with histopathologically confirmed recurrence, as determined by the McNemar test. Sixty‐one cases were enrolled, and 56 cases could be evaluated. The 38 cases where the lesions showed uptake of either ¹¹C‐MET or ¹⁸F‐FDG underwent surgery; 32 of these cases were confirmed to be subject to recurrence. Eighteen cases where the lesions showed uptake of neither tracer received follow‐up MRI; the lesion size increased in one of these cases. Among the cases with histologically confirmed recurrence, the sensitivities of ¹¹C‐MET PET and ¹⁸F‐FDG PET were 0.97 (32/33, 95% confidence interval [CI]: 0.85‐0.99) and 0.48 (16/33, 95% CI: 0.33‐0.65), respectively, and the difference was statistically significant (P < .0001). The diagnostic accuracy of ¹¹C‐MET PET was significantly better than that of ¹⁸F‐FDG PET (87.5% vs. 69.6%, P = .033). No examination‐related adverse events were observed. The results of the study demonstrated that ¹¹C‐MET PET was superior to ¹⁸F‐FDG PET for discriminating between tumor recurrence and radiation‐induced necrosis.

Efficacy of endovascular intratumoral embolization for meningioma: assessment using dynamic susceptibility contrast-enhanced perfusion-weighted imaging

BACKGROUND

In preoperative embolization for intracranial meningioma, endovascular intratumoral embolization is considered to be more effective for the reduction of tumorous vascularity than proximal feeder occlusion. In this study, we aimed to reveal different efficacies for reducing tumor blood flow in meningiomas by comparing endovascular intratumoral embolization and proximal feeder occlusion using dynamic susceptibility contrast-enhanced perfusion-weighted imaging (DSC-PWI).

METHODS

28 consecutive patients were included. DSC-PWI was performed before and after embolization for intracranial meningiomas. Normalized tumor blood volume (nTBV) of voxels of interest of whole tumors were measured from the DSC-PWI data before and after embolization. ΔnTBV% was compared between the cases that received intratumoral embolization and proximal feeder occlusion.

RESULTS

ΔnTBV% in the intratumoral embolization group (42.4±29.8%) was higher than that of the proximal feeder occlusion group (15.3±14.3%, p=0.0039). We used three types of embolic materials and ΔnTBV% did not differ between treatments with or without the use of each material: 42.8±42.4% vs 28.7±20.1% for microspheres (p=0.12), 36.1±20.6% vs 28.1±41.1% for n-butyl cyanoacrylate (p=0.33), and 32.3±37.3% vs 34.1±19.0% for bare platinum coils (p=0.77).

CONCLUSIONS

The flow reduction effect of intratumoral embolization was superior to that of proximal feeder occlusion in preoperative embolization for intracranial meningioma in an assessment using DSC-PWI.

Successful neurosurgical separation of conjoined spinal cords in pygopagus twins: illustrative cases

BACKGROUND

Conjoined twins represent a rare congenital malformation. Pygopagus twins are fused at the sacrum and perineum, with union of the spine. The authors report a successful separation of a unique case of pygopagus twins sharing a U-shaped spinal cord, which the authors identified through aberrant nerves by intraoperative physiological spinal root examination.

OBSERVATIONS

The 6-month-old male pygopagus conjoined twins, who were diagnosed in the prenatal period, underwent separation. They had a single dural sac containing a U-shaped continuous spinal cord; their filum terminale appeared completely fused and the anatomical border of the spinal cord was not distinguishable. A triggered electromyogram (tEMG) was used on each nerve root to determine which belonged to one twin versus the other, to detect nerve cross, and to identify functional midline cleavage. Finally, the twins were separated after spinal division. Both twins recovered uneventfully with no lower limb neurological deficits or walking impairment for 16 months.

LESSONS

Pygopagus twins with a conjoined spinal cord are very rare, but a good long-term functional prognosis can be expected with successful separation. Intraoperative tEMG is useful in spinal separation surgery for twins with a conjoined spinal cord.

So-called bifocal tumors with diabetes insipidus and negative tumor markers: are they all germinoma?

BACKGROUND

The Delphi consensus statements on the management of germ cell tumors (GCTs) failed to reach agreements on the statement that the cases with (i) pineal and neurohypophyseal bifocal lesion, (ii) with diabetes insipidus, and (iii) with negative tumor markers can be diagnosed as germinoma without histological verification. To answer this, multicenter retrospective analysis was performed.

METHODS

A questionnaire on clinical findings, histological diagnosis, and details of surgical procedures was sent to 86 neurosurgical and 35 pediatrics departments in Japan.

RESULTS

Fifty-one institutes reported 132 cases that fulfilled the 3 criteria. Tissue sampling was performed in 91 cases from pineal (n = 44), neurohypophyseal (n = 32), both (n = 6), and distant (n = 9) lesions. Histological diagnosis was established in 89 cases: pure germinoma or germinoma with syncytiotrophoblastic giant cells in 82 (92.1%) cases, germinoma and mature teratoma in 2 cases, and granulomatous inflammation in 2 cases. Histological diagnosis was not established in 2 cases. Although no tumors other than GCTs were identified, 3 (3.4%) patients had non-germinomatous GCTs (NGGCTs). None of the patients developed permanent complications after endoscopic or stereotactic biopsy. Thirty-nine patients underwent simultaneous procedure for acute hydrocephalus without permanent complications, and hydrocephalus was controlled in 94.9% of them.

CONCLUSION

All patients who fulfilled the 3 criteria had GCTs or granulomatous inflammation, but not other types of tumors. However, no fewer than 3.4% of the patients had NGGCTs. Considering the safety and the effects of simultaneous procedures for acute hydrocephalus, biopsy was recommended in such patients.

Impact of Inversion Time for FLAIR Acquisition on the T2-FLAIR Mismatch Detectability for IDH-Mutant, Non-CODEL Astrocytomas

The current research tested the hypothesis that inversion time (TI) shorter than 2,400 ms under 3T for FLAIR can improve the diagnostic accuracy of the T2-FLAIR mismatch sign for identifying IDHmt, non-CODEL astrocytomas. We prepared three different cohorts; 94 MRI from 76 IDHmt, non-CODEL Lower-grade gliomas (LrGGs), 33 MRI from 31 LrGG under the restriction of FLAIR being acquired with TI < 2,400 ms for 3T or 2,016 ms for 1.5T, and 112 MRI from 112 patients from the TCIA/TCGA dataset for LrGG. The presence or absence of the “T2-FLAIR mismatch sign” was evaluated, and we compared diagnostic accuracies according to TI used for FLAIR acquisition. The T2-FLAIR mismatch sign was more frequently positive when TI was shorter than 2,400 ms under 3T for FLAIR acquisition (p = 0.0009, Fisher’s exact test). The T2-FLAIR mismatch sign was positive only for IDHmt, non-CODEL astrocytomas even if we confined the cohort with FLAIR acquired with shorter TI (p = 0.0001, Fisher’s exact test). TCIA/TCGA dataset validated that the sensitivity, specificity, PPV, and NPV of the T2-FLAIR mismatch sign to identify IDHmt, non-CODEL astrocytomas improved from 31, 90, 79, and 51% to 67, 94, 92, and 74%, respectively and the area under the curve of ROC improved from 0.63 to 0.87 when FLAIR was acquired with shorter TI. We revealed that TI for FLAIR impacts the T2-FLAIR mismatch sign’s diagnostic accuracy and that FLAIR scanned with TI < 2,400 ms in 3T is necessary for LrGG imaging.

GCT-69. VOLUMETRIC CHANGE BEFORE CHEMORADIOTHERAPY AND INFLUENCE OF DIAGNOSTIC RADIATION EXPOSURE IN INTRACRANIAL GERMINOMAS

BACKGROUND

Spontaneous regression in intracranial germ cell tumors has been reported in some literatures, but the mechanism has not been well known. We retrospectively measured the tumor volume before chemoradiotherapy and analyzed factors that influence reduction of tumor volume.

PATIENTS AND METHODS

Plural MRI scans were done before the first course of chemotherapy regimen in 27 patients with primary intracranial germinomas. Their age ranged from 8 to 31 years. 35 lesions from them were enrolled and included 13 pineal, 4 neurohypophyseal, 4 basal ganglia, 4 bifocal type, and 2 multiple lesions. All regions were verified as pure germinoma or HCG-producing germinoma by histopathological examination. Tumor volume of 35 lesions was analyzed by volumetric assessment based on MRI. Ratio of volumetric change between the first MRI and the scan immediately before chemotherapy was defined as shrinking rate (%). Period between disease onset and the first chemotherapy was 20 to 47 days. Diagnostic radiation dose was calculated in each case.

RESULTS

Initial tumor volume ranged from 0.962 to 72.356 cubic centimeters (mean: 8.27). Diagnostic radiation dose: 40.5 to 910.1 mGy. Shrinking rate ranged from -57.8 to 85.4% (mean: 30.8). In 10 regions, shrinking rate was within 30%. Shrinking rate was significant positively influenced by diagnostic radiation dose (p<0.05) and negatively influenced by initial volume (p<0.05). But, other factors such as age, sex, histopathological parameters did not influence tumor shrinkage.

CONCLUSION

This study shows that the volume of intracranial germ cell tumors is changing dynamically before chemoradiotherapy in many cases. Diagnostic exposure to low-dose radiation influences tumor shrinkage of intracranial germinomas.

QOL-44. ASSESSMENT OF NEUROCOGNITIVE FUNCTION AND MRI PARAMETERS IN LONG-TERM SURVIVORS WITH POSTERIOR FOSSA TUMORS: A COMPARISON BETWEEN MEDULLOBLASTOMAS TREATED BY REDUCED-DOSE CRANIOSPINAL IRRADIATION AND OTHER TUMORS

BACKGROUND

Children with medulloblastoma cannot avoid chemoradiotherapy including craniospinal radiation, although prognosis of medulloblastoma has improved and previous studies have reported a significant risk of intellectual disturbance by these treatments. We retrospectively analysed neurocognitive functions, clinical MRI parameters of patients with posterior fossa tumors, especially medulloblastomas.

MATERIALS AND METHODS

Twenty-two patients (12 medulloblastomas, 5 ependymomas, 5 astrocytomas) treated in our institution were enrolled in this study. Mean age was 7.8 years and 6.5 years, percentage of hydrocephalus at onset was 66.7% and 60%, respectively in medulloblastoma group and in other tumor group (ependymoma and astrocytoma). Postoperative chemoradiotherapy including reduced-dose craniospinal irradiation (18Gy) was done for medulloblastoma group and local radiation or operation only was done for other group. Version 3 or 4 of Wechsler Intelligent Scale for Children (WISC) was used by neurocognitive function analysis. Ventricular size, white matter volume and other parameters were also was estimated based on MRI. Follow-up duration was 6–17 years (mean: 10.5 years).

RESULTS

Evaluations of neurocognitive functions based on WISC pointed out lower performance IQ than verbal IQ in long term survivor of both group, especially working memory (P=0.05). Both hydrocephalus and cranial nerve complications was influenced lower scores of WISC, but age at onset did not influence WISC scores. Comparison between both group showed there was no significant difference about cognitive function and white matter volume.

ML-07 High expression of PD-L1 on tumor-associated macrophage is a predictive factor for favorable prognosis in PCNSL

PD-L1 and PD-L2 expression on tumor cells and tumor-infiltrating immune cells in primary central nervous system lymphoma (PCNSL) remains unclear. In the present study, we investigated the expressions of PD-L1 and PD-L2 in surgical specimens from needle biopsies and craniotomies to compare tumor tissue with surrounding tumor tissue (peritumoral tissue) and analyzed the correlation between expression of PD-L1/PD-L2 and survival in patients with PCNSL. We retrospectively analyzed the cases of 70 patients histologically diagnosed with PCNSL (diffuse large B-cell lymphoma). Immunohistochemistry for CD20, CD68, PD-L1, and PD-L2 was performed. In cases with specimens taken by craniotomy, the percentages of PD-L1- and PD-L2-positive macrophages were evaluated in both tumor and peritumoral tissue. The Kaplan-Meier method with log-rank test and Cox proportional hazard model were used for survival analysis. The tumor cells did not express very much PD-L1 and PD-L2, but macrophages expressed PD-L1 and PD-L2 in most of the patients. The median percentage of PD-L2-positive cells was significantly higher among peritumoral macrophages (32.5%; 95%CI: 0–94.6) than intratumoral macrophages (27.5%; 95%CI: 0–81.1, p=0.0014). There was a significant correlation between the percentages of PD-L2-positive intratumoral macrophages and PD-L2-positive peritumoral macrophages (p=0.0429), with very low coefficient correlation (ρ=0.098535). PD-L1 expression on macrophages was significantly associated with biological factors (intratumoral macrophages: better KPS, p=0.0008; better MSKCC score, p=0.0103; peritumoral macrophages: low proportion of LDH elevation, p=0.0064) and longer OS (for intratumoral macrophages: high PD-L1=60 months, 95%CI=30–132.6; low PD-L1=24 months, 95%CI=11–48; p=0.032; for peritumoral macrophages: high PD-L1=60 months, 95%CI=30.7-NR; low PD-L1=14 months, 95%CI=3–26). PD-L1 expression on peritumoral macrophages was strongly predictive of a favorable outcome (HR=0.30, 95%CI=0.12–0.77, p=0.0129). Macrophages in intratumoral and peritumoral tissue expressed PD-L1 and PD-L2 at a higher rate than tumor cells. PD-L1 expression, especially on peritumoral macrophages, seems to be an important prognostic factor in PCNSL.

STMO-03 Surgical resection for precentral gyrus glioma

Primary motor cortex glioma is usually considered unresectable because of its high risk for motor deficit. However, recent reports suggest that surgical resection for primary motor cortex brain tumor is feasible for selected patients. In this study, we analyzed the neurological outcomes for 27 patients who underwent surgical resections for precentral gyrus glioma. Glioma grades for 27 patients were Grade II in 6 cases, Grade III in 7 cases, and Grade IV in 13 cases. 11 patients were recurrent glioma cases and glioma grade for those patients were Grade II in 4 cases, Grade III in 3 cases, and Grade IV in 4 cases. Extent of resection for 27 patients was biopsy in 2 cases, partial resection in 16 cases, and more than 90% of resections in 9 cases. 6 patients underwent awake surgery and glioma grade for those patients were Grade II in 3 cases, Grade III in 2 cases, and Grade IV in 1 case. Median extent of resection for patients who underwent awake surgery was 90%. Transient neurological worsening was observed in 5 patients, however, no patient exhibited permanent neurological deficit. Surgical resections for primary motor cortex glioma were feasible in selected patients without severe neurological complication. Careful intraoperative awake mapping is desirable to achieve maximum resections.

ANGI-03 Functional roles of CD166/activated leukocyte cell adhesion molecule (CD166/ALCAM) for glioblastoma invasion

CD166/activated leukocyte cell adhesion molecule (CD166/ALCAM) is a transmembrane receptor, widely expressed in various tissues, and is involved in several functions such as cell adhesion, neurogenesis and angiogenesis. We have previously reported that CD166/ALCAM is expressed on glioblastoma progenitor cells and is involved in glioblastoma invasion. However, we only have analyzed the functional roles of ALCAM using glioblastoma cell lines, not using patient derived xenografts. In this study, we investigated the functional roles of CD166/ALCAM using patient derived xenografts. We established CD166/ALCAM knocked-down glioblastoma patient derived cell lines by shRNA. For in vitro analysis, we seeded control and CD166/ALCAM knocked-down glioblastoma cells on culture dishes and performed time lapse analysis to investigate cell motility. For in vivo analysis, we orthotopically injected control and CD166/ALCAM knocked-down glioblastoma cells into the immunodeficient mice. When the mice got sick due to the tumor, we dissected the mice and analyzed the difference in invasion by immunohistochemical analysis. We found that CD166/ALCAM knocked-down glioblastoma cells significantly decreased cell motility by time lapse analysis. In addition, CD166/ALCAM knocked-down glioblastoma cells suppressed cell invasion and leptomeningeal metastasis by immunohistochemical analysis from patient derived xenografts. Our results suggest that CD166/ALCAM is involved in glioblastoma invasion, thus future studies are necessary to investigate whether CD166/ALCAM could be a therapeutic target for glioblastoma.

NI-13 The effectiveness and limitation of survival prediction in primary glioblastoma using machine learning-based texture analysis

Introduction: Clinical application of survival prediction of primary glioblastoma (pGBM) using preoperative images remains challenging due to a lack of robustness and standardization of the method. This research focused on validating a machine learning-based texture analysis model for this purpose using internal and external cohorts. Method: We included all cases of IDH wild-type pGBM available of preoperative MRI (T1WI, T2WI, and Gd-T1WI) from the databases of Kansai Molecular Diagnosis Network for CNS tumors (KN) and The Cancer Genome Atlas (TCGA). Of 242 cases from KN, we assigned 137 cases as a training dataset (D1), and the remaining 105 cases as an internal validation dataset (D2). Furthermore, we extracted 96 cases from TCGA as an external validation dataset (D3). Preoperative MRI scans were semi-quantitatively analyzed, leading to the acquisition of 489 texture features as explanatory variables. Dichotomous overall survival (OS) with a 16.6 months cutoff was regarded as the response variable (short/long OS). We employed Lasso regression for feature selection, and a survival prediction model constructed for D1 via cross-validation (M1) was applied to D2 and D3 to ensure the model robustness. Results: The population of predicted short OS by M1 significantly showed poorer prognosis in D2 (median OS 11.1 vs. 19.4 months; log-rank test, p=0.03), while there was no significant difference in D3 (median OS 14.2 vs. 11.9 months; p=0.61). In the comparative analysis using t-SNE, there was little variation in the feature distribution among three datasets. Conclusion: We were able to validate the prediction model in the internal but not in the external cohort. The presented result supports the use of machine learning-based texture analysis for survival prediction of pGBM in a localized population or country. However, further consideration is required to achieve a universal prediction model for pGBM, irrespective of regional difference.

COT-18 Prognosis and problems about secondary intracranial neoplasm in childhood cancer survivors: a single-institution retrospective cohort study

Objective: As childhood cancer survivors gradually increased, late complications of treatment have been at issue and risk of secondary neoplasm is increasing cumulatively. We retrospectively analyzed clinical outcome and problems of treatment for secondary intracranial neoplasm. Patients and Methods: 497 patients (children, adolescents and young adults) with malignant central nervous system neoplasm were treated in our institution from 1971 to 2015. 188 cases (37.8%) were enrolled in this follow-up study. Diagnosis of primary neoplasm included low grade glioma (29%), embryonal tumor (23.5%), germ cell tumor (24.5%), ependymoma (8%), other (15%). Results: Fourteen cases of them were diagnosed as secondary intracranial neoplasm. Twelve cases were operated and histopathological diagnosis included 6 glioblastomas, 1 anaplastic astrocytoma, 1 anaplastic ependymoma, 4 meningiomas. In all cases, histopathological finding and molecular profile of secondary intracranial neoplasm differed from that of primary malignant brain tumors. Duration from the first operation of primary tumors to diagnosis of secondary intracranial neoplasm ranged from 5 to 36 years (average: 29.3). In malignant glioma cases except meningioma cases, origin of them was contained in high irradiation field (&gt;40Gy). In malignant glioma cases, Chemotherapies using temozolomide and bevacizumab were selected after tumor removal. In 3 cases of them, reirradiation was performed. Response for treatment was poor or transient in most cases, median survival time was 12 months. Of late complications, such as endocrinological problem needed replacement (55%), cerebrovascular event (15.9%), secondary neoplasm (7.4%), secondary neoplasm was importantly related with prognosis. Conclusion: It is difficult to plan therapeutic strategies against second malignant neoplasm because of lack of information in case of long-term survivors and restriction for first radiation. Clinical outcome of them is poor and new treatment targets should be developed. It is important to plan clinical trials to reduce treatment intensity and usable long-term follow-up system.

CBIO-02. COMPREHENSIVE ANALYSIS OF MECHANISMS AND MOLECULAR TARGETS FOR BREAST CANCER LEPTOMENINGEAL METASTASIS

Leptomeningeal metastasis from solid cancer is a devastating state for cancer patients. Leptomeningeal metastasis is diagnosed either by cerebrospinal fluid cytology and/or magnetic resonance imaging (MRI). However, it remains unclear as to whether tumor cells attached to leptomeninges are the same from floating tumor cells in cerebrospinal fluid (CSF). In this study, we aim to analyze the differences between tumor cells attached to leptomeninges and floating cells in CSF by xenograft models. We used breast cancer cell line, MDA-MB-231, labelled with green fluorescent protein (GFP) and luciferase. We injected those cells into right lateral ventricle of NOD/Shi-scid IL2Rγ KO mice. When the mice got any signs of tumor, we dissected spinal cord and got CSF from mice. We sorted tumor cells by flow cytometry and extracted RNA from the sorted tumor cells from spinal cord and CSF, respectively. We analyzed transcriptome differences between tumor cells from spinal cord and CSF by RNA sequencing. We found that extracellular matrix related proteins were highly upregulated while cell growth related proteins were downregulated in tumor cells from spinal cord compared with those from CSF. These results suggest that tumor cells attached to leptomeninges have different transcriptome profiles from floating tumor cells in CSF and extracellular matrix related proteins could be therapeutic targets for breast cancer leptomeningeal metastasis.

NIMG-11. IMPACT OF INVERSION TIME FOR FLAIR ACQUISITION ON THE T2-FLAIR MISMATCH DETECTABILITY FOR IDH-MUTANT, NON-CODEL ASTROCYTOMAS

PURPOSE

The current research tested the hypothesis that TI shorter than 2400 ms under 3T for FLAIR can improve the diagnostic accuracy of the T2-FLAIR mismatch sign for identifying IDHmt, non-CODEL astrocytomas.

EXPERIMENTAL DESIGN

We prepared three different cohorts; 94 MRI from 76 IDHmt, non-CODEL LrGGs, 33 MRI from 31 LrGG under the restriction of FLAIR being acquired with TI &lt; 2400 ms for 3T or 2016 ms for 1.5T, and 103 MRI from 103 patients from the TCIA/TCGA dataset for LrGG. The presence or absence of the “T2-FLAIR mismatch sign” was evaluated, and we compared diagnostic accuracies according to TI used for FLAIR acquisition.

RESULTS

The T2-FLAIR mismatch sign was more frequently positive when TI was shorter than 2400 ms under 3T for FLAIR acquisition (p = 0.0009, Fisher’s exact test). The T2-FLAIR mismatch sign was positive only for IDHmt, non-CODEL astrocytomas even if we confined the cohort with FLAIR acquired with shorter TI (p = 0.0001, Fisher’s exact test). TCIA/TCGA dataset validated that the sensitivity, specificity, PPV, and NPV of the T2-FLAIR mismatch sign to identify IDHmt, non-CODEL astrocytomas improved from 31%, 90%, 79%, and 51% to 67%, 94%, 92%, and 74%, respectively if we acquired FLAIR with TI shorter than 2400 ms.

CONCLUSIONS

We revealed that TI for FLAIR impacts diagnostic accuracy of the T2-FLAIR mismatch sign and that FLAIR scanned with TI &lt; 2400 ms in 3T is necessary for LrGG imaging.

Encouraging Clinical Evolution of a Pediatric Patient With Relapsed Diffuse Midline Glioma Who Underwent WT1-Targeting Immunotherapy: A Case Report and Literature Review

Diffuse midline glioma (DMG) in children is a highly aggressive, malignant brain tumor that is fatal when relapsed. Wilms tumor 1 (WT1) is a high-priority antigen target for cancer immunotherapy. We hereby report on a pediatric patient who had DMG that regrew after chemoradiotherapy and underwent WT1 peptide vaccination. A 13-year-old Japanese boy presented with vertigo, diplopia, and right hemiplegia at the initial visit to another hospital, where he was diagnosed with DMG by magnetic resonance imaging (MRI); DMG was categorized to histological grade IV glioma. The patient underwent radiotherapy and chemotherapy with temozolomide. After three cycles of chemotherapy, MRI revealed tumor regrowth that translated into deteriorated clinical manifestations. Immunohistochemically, the H3.3K27M mutation in the biopsy specimen was confirmed and the specimen was positive for WT1 protein. The patient underwent WT1-targeting immunotherapy with the WT1-specific peptide vaccine because of having HLA-A^*24:02. Consequently, his quality of life drastically improved so much as to the extent that the patient became capable of conducting nearly normal daily activities at weeks 8 to 12 of vaccination. MRI at week 8 of vaccination revealed an obvious reduction in the signal intensity of the tumor. Furthermore, betamethasone dose could be reduced successively (4, 1, and 0.5 mg/day at weeks 4, 5, and 7, respectively) without deteriorating clinical manifestations. Best response among responses assessed according to the Response Assessment in Neuro-Oncology criteria was stable disease. Overall survival was 6.5 months after vaccination onset and was 8.3 months after relapse; the latter was markedly longer than the reported median OS of 3.2 months for pediatric patients with relapsed DMG in the literature. Modified WT1 tetramer staining revealed the WT1 peptide vaccine-induced production of WT1-specific cytotoxic T cells, and the interferon-γ (IFN-γ) ELISpot assay of peripheral blood mononuclear cells disclosed the production of IFN-γ. Delayed-type hypersensitivity test became positive. Any treatment-emergent adverse events did not occur except injection site erythema. Our pediatric patient exhibited an encouraging clinical evolution as manifested by stable disease, improved clinical manifestations, steroid dose reductions, a WT1-specific immune response, and a good safety profile. Therefore, WT1-targeting immunotherapy warrants further investigation in pediatric patients with relapsed DMG.

PD-L1 and PD-L2 expression in the tumor microenvironment including peritumoral tissue in primary central nervous system lymphoma

Background

The prevalence of programmed death-ligand 1 (PD-L1) and PD-L2 expression on tumor cells and tumor-infiltrating immune cells in primary central nervous system lymphoma (PCNSL) remains unclear. In the present study, we analyzed needle biopsy and craniotomy specimens of patients with PCNSL to compare the PD-L1 and PD-L2 levels in the tumor and surrounding (peritumoral) tissue. We also assessed the correlation between biological factors and the prognostic significance of PD-L1 and PD-L2 expression.

Methods

We retrospectively analyzed the cases of 70 patients histologically diagnosed with PCNSL (diffuse large B-cell lymphoma). Immunohistochemistry for CD20, CD68, PD-L1, and PD-L2 was performed. In cases with specimens taken by craniotomy, the percentages of PD-L1- and PD-L2-positive macrophages were evaluated in both tumor and peritumoral tissue. The Kaplan-Meier method with log-rank test and Cox proportional hazard model were used for survival analysis.

Results

The tumor cells expressed little or no PD-L1 and PD-L2, but macrophages expressed PD-L1 and PD-L2 in most of the patients. The median percentage of PD-L2-positive cells was significantly higher among peritumoral macrophages (32.5%; 95% CI: 0–94.6) than intratumoral macrophages (27.5%; 95% CI: 0–81.1, p = 0.0014). There was a significant correlation between the percentages of PD-L2-positive intratumoral macrophages and PD-L2-positive peritumoral macrophages (p = 0.0429), with very low coefficient correlation (ρ = 0.098535). PD-L1 expression on macrophages was significantly associated with biological factors (intratumoral macrophages: better KPS, p = 0.0008; better MSKCC score, p = 0.0103; peritumoral macrophages: low proportion of LDH elevation, p = 0.0064) and longer OS (for intratumoral macrophages: high PD-L1 = 60 months, 95% CI = 30–132.6; low PD-L1 = 24 months, 95% CI = 11–48; p = 0.032; for peritumoral macrophages: high PD-L1 = 60 months, 95% CI = 30.7–NR; low PD-L1 = 14 months, 95% CI = 3–26). PD-L1 expression on peritumoral macrophages was strongly predictive of a favorable outcome (HR = 0.30, 95% CI = 0.12–0.77, p = 0.0129).

Conclusions

Macrophages in intratumoral and peritumoral tissue expressed PD-L1 and PD-L2 at a higher rate than tumor cells. PD-L1 expression, especially on peritumoral macrophages, seems to be an important prognostic factor in PCNSL. Future comprehensive analysis of checkpoint molecules in the tumor microenvironment, including the peritumoral tissue, is warranted.

STMO-10 SURGICAL RESECTION FOR PRIMARY MOTOR CORTEX GLIOMA, TWO CASE REPORTS

Primary motor cortex glioma is usually considered unresectable because of its high risk for motor deficit. However recent reports suggest that surgical resections for primary motor cortex brain tumor is feasible for selected patients. In this case report, we report two cases we can successfully resected primary motor cortex glioma by awake surgery without neurological worsening.

Case1 was 32 year-old woman with right primary motor cortex oligodendroglioma. We could only perform biopsy at initial surgery, however the patient got worsening of left hemiparesis which were gradually improved by rehabilitation. The patient underwent 50 Gy of radiation therapy and 6 courses of PCV chemotherapy. 60 months after the initial surgery, the tumor recurred and the she underwent 12 courses of temozolomide chemotherapy, but tumor continued to grow. She underwent second surgery 13 years after the initial biopsy. We resected primary motor cortex tumor by awake surgery without neurological complication.

Case2 was 31 year-old woman with left primary motor cortex oligodendroglioma. We could only perform biopsy at initial surgery, however the patient got mild right hemiparesis which were improved by rehabilitation. The patient underwent 4 courses of PAV chemotherapy and 54 Gy of Intensity Modulated Radiation Therapy (IMRT). 21 months after IMRT, the tumor recurred and the she underwent second surgery. We resected primary motor cortex tumor by awake motor mapping without severe neurological complication.

In conclusion, surgical resections for primary motor cortex glioma is feasible in selected patients without severe neurological complication. Neural plasticity is the reason for this, but careful intraoperative awake mapping is necessary to achieve maximum resections.

NI-07 VALIDATION OF MACHINE LEARNING BASED HIGH GRADE GLIOMA MR SEGMENTATION VIA METHIONINE PET

Treatment planning and lesion-follow up are generally conducted by contrast-enhanced MRI in glioma patient care. On the other hand, there are, however, substantial concerns whether MRI actually reflects the extension or activity of this neoplasm, which information should be fundamentally important at every step when treating this disease. As a matter of fact, the authors of this investigation have already shown that there is no difference in tumor cell density within areas with and without contrast enhancement (J Neurosurg. 2016,125(5):1136–1142.) and furthermore that the geometry of MRI based-radiation treatment planning is significantly altered when methionine PET is integrated for this purpose (J Neurosurg. 2018 published on-line). Regardless of these concerns, there is great interest in the research community to construct a machine learning based fully automated brain tumor segmentation tool specific for gliomas using MRI. The authors attempted to validate this method by comparing MRI-based automated brain tumor segmentation and methionine PET. Consecutively collected 45 high-grade gliomas (GBM-26, grade3-19) were analyzed. BraTumIA, an automated brain tumor segmentation tool, was used for machine learning based lesion segmentation. At the same time, lesions were segmented using various thresholds on methionine PET. The authors observed 40% of pseudo-positive and 90% of pseudo-negative error on BraTumIA based lesion segmentation when methionine PET was considered as ground truth with a cut-off of 1.3 in T/N ratio. Pseudo-negative error was as high as 60% even if the threshold was elevated to 2.0. Although machine learning based glioma segmentation is expected to expand in both research and clinical use, the observed results caution the use of MRI as ground truth of spatial extension of glioma and researchers should be reminded that this imaging modality may obscure the true behavior of the disease within the patient in some cases.

MNG-08 VOLUMETRIC STUDIES IN ASYMPTOMATIC MENINGIOMAS: SLOWDOWN CASES AND GROWTH ARREST CASES

BACKGROUND

The opportunity to follow up for asymptomatic meningiomas has increased. We have reported the risk of volume increase by individual continuous volume measurement of asymptomatic meningiomas. However, We have not reached fully understanding about natural history of meningiomas. Among cases are followed up over time, there are some cases that the volume increase rates slows down or almost stops are observed.

METHODS

We enrolled consecutive adult patients of asymptomatic meningiomas who follow-up for 2 years or more and 3 or more MRI scans. We performed sequential volumetric measurements on 95 patients (105 lesions) who met the criteria. We classified these transient volume curve of each lesion into three groups “Growing”, “Slowdown”, and “Growth arrest” for analysis.

RESULTS

The average age at the first visit was 62.8 years, the average follow-up period was 61.8 months, and the male-female ratio was 20:75 (male: female). There were 67 cases (73 lesions: 70.9%) that were in increasing trend, and 19 cases of those were received resection. Eleven cases (12 lesions: 11.7%) showed a tendency of “slow down” the increase rate, and one patient who became symptomatic led to surgical excision. In 18 cases (18 lesions: 17.4%) in which almost no volume change was observed during the observation period, no cases resulted in surgical treatment.

CONCLUSIONS

Among the meningiomas cases that have been followed for a long time, there are not a few those increase rate of tumor volume slows or does not change. Furthermore, most of these cases did not result in surgical treatment. The presence of these “Slowdown” and “Growth arrest” cases at a certain rate may have suggested the possibility of a Gompertz curve model as the natural course of meningiomas.

NI-13 PREDICTION OF PROGNOSIS IN NEWLY DIAGNOSED GLIOBLASTOMA USING MACHINE LEARNING-BASED TEXTURE ANALYSIS OF PREOPERATIVE MRI

INTRODUCTION

Preoperative magnetic resonance imaging (MRI) is a critical modality for the determination of glioblastoma (GBM) treatment strategy, as it is thought to reflect the biology of the tumor to some extent. The authors attempted to predict prognosis of newly diagnosed GBM (nGBM) using machine learning-based texture analysis of preoperative MRI in this study.

METHOD

A total of 160 nGBMs with determined overall survival were collected from Kansai Molecular Diagnosis Network for CNS tumors. Preoperative MRI scans (T1WI, T2WI, and Gd-T1WI) from all cases were semi-quantitatively analyzed leading to acquisition of 489 texture features as explanatory variables using Matlab-based in-house software. Dichotomous overall survival (OS) with a cutoff of 15 months was regarded as the response variable (short or long OS). Lasso regression was employed for feature selection to ensure robustness of the prediction model. One hundred patients were randomly assigned as training dataset (TR), followed by predictive model construction via 5-fold cross-validation. Subsequently, the constructed model was transferred to the remaining 60 patients, which was assigned as test dataset (TD). The survival distribution between populations with predicted short and long OS was compared using log-rank test.

RESULTS

Distributions of the analyzed data were as follows; 53 short OS cases in the TR (53.0%) and 27 cases in the TD (45.0%). As for the result of transfer analysis in TD, 38 cases out of 60 (63.3%) were predicted to be short OS (76.3 % of recall, 54.3% of precision, and 63.5% of F-measure). The population of predicted short OS significantly showed poorer prognosis (median OS 14.0 vs 19.1 months) (p=0.02, log-rank test).

CONCLUSION

Short OS was successfully identified from preoperative MRI with high recall rates with our algorithm. The presented result ensures the potential of machine learning-based texture analysis for prognostic stratification of nGBM.

IMT-07 CLINICAL TRIAL OF A COCKTAIL WILMS’ TUMOR 1 (WT1) VACCINATION USING TWO HLA CLASS I PEPTIDES AND ONE CLASS II PEPTIDE FOR RECURRENT MALIGNANT GLIOMAS

PURPOSE

Our clinical trials shows the safety and clinical efficacy of Wilms’ tumor 1 (WT1) human leukocyte antigen (HLA) class I (Izumoto S et al. J Neurosurg. 2008) and class II (Tsuboi A et al. Cancer Immunol Immunother. 2019) peptide vaccination for recurrent malignant gliomas have been established. We have developed a cocktail vaccine (WT1 trio) containing two class I peptides (HLA-A*24:02 and HLA-A*02:01) and one II class peptide to improve more effective immunological response and improve patient’s prognosis. Clinical trial of a cocktail vaccination using WT1 HLA class I and II peptides for recurrent malignant gliomas is planned to verify its safety, clinical efficacy and usefulness of surrogate markers.

PATIENTS AND METHODS

Twenty-three patients with recurrent malignant gliomas, which showed WT1-positive in tumor samples and HLA-A*24:02 or HLA-A*02:01-positive in blood sample, were enrolled. These patients (age: 26–72 years old, average: 49.4) included 15 cases of glioblastomas and 8 of anaplastic astrocytomas. Patients received a WT1 trio vaccine intradermally, 7 times at 2-week intervals during 3 months.WT1-DTH and WT1-IgG antibody were regularly measured. Vaccine-related adverse events, best clinical response and the transfer rate of long-term administration of WT1 trio vaccination were estimated.

RESULTS

WT1-DTH positive cases were 12, WT1-IgG antibody positive were in 11. In most patients, WT1 -DTH positiveness coincided with that of WT1-IgG antibody. 9 of 11 cases showed stable disease at 3 months and transferred long-term administration of WT1 trio vaccination. Transfer rate in GBM and AA of long-term administration was 33% and 25%, respectively. Grade1 skin eruption was observed at the injection sites in 15 cases, but no significant adverse events related with vaccination were shown.

CONCLUSION

the safety and clinical efficacy of WT1 trio vaccination was verified for recurrent malignant gliomas. WT1-DTH and WT1-IgG antibody may be useful surrogate markers.