Long-term outcome of surgically treated and conservatively managed Rathke cleft cysts

OBJECTIVE

Rathke cleft cysts (RCC) are benign lesions of the sellar region that require surgical treatment in case of visual deterioration or progression of the cyst. However, the natural course is often stable and asymptomatic. We aimed to investigate the characteristics of patients with cyst progression during follow-up (FU) and to compare the natural history of patients with RCC with patients who underwent surgery.

METHODS

Patients with an MR morphologic cystic sellar lesion classified as RCC between 04/2001 and 11/2020 were included. Functional outcomes, including ophthalmologic, endocrinologic, and MRI data, were retrospectively analyzed and compared between surgically treated patients, patients on a "watch and wait" strategy (WWS), and patients on a WWS who underwent secondary surgery due to cyst progression.

RESULTS

One hundred forty patients (median age 42.8 years) with RCC on MRI were identified. 52/140 (37.1%) underwent primary surgery. Of 88 patients (62.9%) with initial WWS, 21 (23.9%) underwent surgery for secondary cyst progression. Patients on the WWS had significantly smaller cyst volumes (p = 0.0001) and fewer visual disturbances (p = 0.0004), but a similar rate of hormone deficiencies (p = 0.99) compared with surgically treated patients preoperatively. Postoperatively patients suffered significantly more often from hormone deficiencies than WWS patients (p = 0.001). Patients who switched to the surgical group were significantly more likely to have preoperative T1 hyperintense signals on MRI (p = 0.0001) and visual disturbances (p = 0.001) than patients with continuous WWS. Postoperatively, these patients suffered more frequently from new hormonal deficiencies (p = 0.001). Endocrine and ophthalmologic outcomes in patients with primary and secondary surgery were comparable. Multivariate analysis showed that WWS patients were at a higher risk of requiring surgery for cyst progression when perimetric deficits (p = 0.006), hyperprolactinemia (p = 0.003), and corticotropic deficits (p = 0.005) were present.

CONCLUSION

Surgical treatment of RCC may cause new hormonal deficiencies, which are rare in the natural course. Therefore, the indication for surgery should be carefully evaluated. Hyperprolactinemia and corticotropic deficits were significant indicators for a secondary cyst progression in patients with RCC. However, a significant amount of almost 25% of initially conservatively managed cysts showed deterioration, necessary for surgical intervention.

Enhancing predictability of IDH mutation status in glioma patients at initial diagnosis: a comparative analysis of radiomics from MRI, [18F]FET PET, and TSPO PET

PURPOSE

According to the World Health Organization classification for tumors of the central nervous system, mutation status of the isocitrate dehydrogenase (IDH) genes has become a major diagnostic discriminator for gliomas. Therefore, imaging-based prediction of IDH mutation status is of high interest for individual patient management. We compared and evaluated the diagnostic value of radiomics derived from dual positron emission tomography (PET) and magnetic resonance imaging (MRI) data to predict the IDH mutation status non-invasively.

METHODS

Eighty-seven glioma patients at initial diagnosis who underwent PET targeting the translocator protein (TSPO) using [18F]GE-180, dynamic amino acid PET using [18F]FET, and T1-/T2-weighted MRI scans were examined. In addition to calculating tumor-to-background ratio (TBR) images for all modalities, parametric images quantifying dynamic [18F]FET PET information were generated. Radiomic features were extracted from TBR and parametric images. The area under the receiver operating characteristic curve (AUC) was employed to assess the performance of logistic regression (LR) classifiers. To report robust estimates, nested cross-validation with five folds and 50 repeats was applied.

RESULTS

TBRGE-180 features extracted from TSPO-positive volumes had the highest predictive power among TBR images (AUC 0.88, with age as co-factor 0.94). Dynamic [18F]FET PET reached a similarly high performance (0.94, with age 0.96). The highest LR coefficients in multimodal analyses included TBRGE-180 features, parameters from kinetic and early static [18F]FET PET images, age, and the features from TBRT2 images such as the kurtosis (0.97).

CONCLUSION

The findings suggest that incorporating TBRGE-180 features along with kinetic information from dynamic [18F]FET PET, kurtosis from TBRT2, and age can yield very high predictability of IDH mutation status, thus potentially improving early patient management.

Evaluation of surgical treatment strategies and outcome for cerebral arachnoid cysts in children and adults

OBJECTIVE

The best treatment strategies for cerebral arachnoid cysts (CAC) are still up for debate. In this study, we present CAC management, outcome data, and risk factors for recurrence after surgical treatment, focusing on microscopic/endoscopic approaches as compared to minimally invasive stereotactic procedures in children and adults.

METHODS

In our single-institution retrospective database, we identified all patients treated surgically for newly diagnosed CAC between 2000 and 2022. Microscopic/endoscopic surgery (ME) aimed for safe cyst wall fenestration. Stereotactic implantation of an internal shunt catheter (STX) to drain CAC into the ventricles and/or cisterns was used as an alternative procedure in patients aged ≥ 3 years. Treatment decisions in favor of ME vs. STX were made by interdisciplinary consensus. The primary study endpoint was time to CAC recurrence (TTR). Secondary endpoints were outcome metrics including clinical symptoms and MR-morphological analyses. Data analysis included subdivision of the total cohort into three distinct age groups (AG1, < 6 years; AG2, 6-18 years; AG3, ≥ 18 years).

RESULTS

Sixty-two patients (median age 26.5 years, range 0-82 years) were analyzed. AG1 included 15, AG2 10, and AG3 37 patients, respectively. The main presenting symptoms were headache and vertigo. In AG1 hygromas, an increase in head circumference and thinning of cranial calvaria were most frequent. Thirty-five patients underwent ME and 27 STX, respectively; frequency did not differ between AGs. There were two (22.2%) periprocedural venous complications in infants (4- and 10-month-old) during an attempt at prepontine fenestration of a complex CAC, one with fatal outcome in a 10-month-old boy. Other complications included postoperative bleeding (2, 22.2%), CSF leaks (4, 44.4%), and meningitis (1, 11.1%). Overall, clinical improvement and significant volume reduction (p = 0.008) were seen in all other patients; this did not differ between AGs. Median follow-up for all patients was 25.4 months (range, 3.1-87.1 months). Recurrent cysts were seen in 16.1%, independent of surgical procedure used (p = 0.7). In cases of recurrence, TTR was 7.9 ± 12.7 months. Preoperative ventricular expansion (p = 0.03), paresis (p = 0.008), and age under 6 years (p = 0.03) were significant risk factors for CAC recurrence in multivariate analysis.

CONCLUSIONS

In patients suffering from CAC, both ME and STX can improve clinical symptoms at low procedural risk, with equal extent of CAC volume reduction. However, in infants and young children, CAC are more often associated with severe clinical symptoms, stereotactic procedures have limited use, and microsurgery in the posterior fossa may bear the risk of severe venous bleeding.

Efficacy and safety of cysto-ventricular catheter implantation for space-occupying cysts arising from glioma and brain metastasis: a retrospective study

BACKGROUND

Cysto-ventricular catheters (CVC) have emerged as promising treatment option for cystic craniopharyngioma and arachnoid cysts, but their effectiveness in treating cysts originating from glioma or brain metastasis (BM) remains limited. This study aimed to analyze the efficacy of CVC in patients with glioma and BM as well as procedure-associated morbidity.

METHODS

This single-center retrospective study included all patients treated with CVC placement for acquired space-occupying cysts deriving from previously treated glioma or BMs between 1/2010 and 12/2021.

RESULTS

A total of 57 patients with a median age of 47 years (IQR 38-63) were identified. Focal neurological deficits were the predominant symptoms in 60% of patients (n = 34), followed by cephalgia in 14% (n = 8), and epileptic seizures in 21.1% (n = 12). Accurate CVC placement was achieved in all but one case requiring revision surgery due to malposition. Three months after CVC implantation, 70% of patients showed symptomatic improvement. Multivariate logistic regression analysis identified the development of space-occupying cysts later in the course of the disease (OR 1.014; p = 0.04) and a higher reduction of cyst-volume postoperatively (OR 1.055; p = 0.05) were significant predictors of postoperative symptomatic improvement following CVC placement. Local cyst recurrence was observed in three cases during follow-up MRI after an average time of 5 months (range 3-9 months). Further complications included secondary malresorptive hydrocephalus in three cases and meningeosis neoplastica in one patient.

CONCLUSIONS

Stereotactic implantation of CVC is an efficient treatment option for patients suffering from symptomatic space-occupying cysts from BMs or glioma, independently from their CNS WHO grade. However, a vigilant approach is crucial regarding potential complications and treatment failures.

Risk-benefit analysis of surgical treatment strategies for cystic craniopharyngioma in children and adolescents

Objective

Treatment strategies for craniopharyngiomas are still under debate particularly for the young population. We here present tumor control and functional outcome data after surgical treatment focusing on stereotactic and microsurgical procedures for cystic craniopharyngiomas in children and adolescents.

Methods

From our prospective institutional database, we identified all consecutive patients less than 18 years of age who were surgically treated for newly-diagnosed cystic craniopharyngioma between, 2000 and, 2022. Treatment decisions in favor of stereotactic treatment (STX) or microsurgery were made interdisciplinary. STX included aspiration and/or implantation of an internal shunt catheter for permanent cyst drainage. Microsurgery aimed for safe maximal tumor resections. Study endpoints were time to tumor recurrence (TTR) and functional outcome including ophthalmological/perimetric, endocrinological, and body-mass index (BMI) data.

Results

29 patients (median age 9.9 yrs, range 4-18 years) were analyzed. According to our interdisciplinary tumor board recommendation, 9 patients underwent stereotactic treatment, 10 patients microsurgical resection, and 10 patients the combination of both. Significant volume reduction was particularly achieved in the stereotactic (p=0.0019) and combined subgroups (p<0.001). Improvement of preoperative visual deficits was always achieved independent of the applied treatment modality. Microsurgery and the combinational treatment were associated with higher rates of postoperative endocrinological dysfunction (p<0.0001) including hypothalamic obesity (median BMI increase from 17.9kg/m2 to 24.1kg/m2, p=0.019). Median follow-up for all patients was 93.9 months (range 3.2-321.5 months). Recurrent tumors were seen in 48.3% and particularly concerned patients after initial combination of surgery and STX (p=0.004). In here, TTR was 35.1 ± 46.9 months. Additional radiation therapy was found indicated in 4 patients to achieve long-lasting tumor control.

Conclusion

In children and adolescents suffering from predominantly cystic craniopharyngiomas, stereotactic and microsurgical procedures can improve clinical symptoms at low procedural risk. Microsurgery, however, bears a higher risk of postoperative endocrine dysfunction. A risk-adapted surgical treatment concept may have to be applied repeatedly in order to achieve long-term tumor control even without additional irradiation.

Surgical management and outcome of newly diagnosed glioblastoma without contrast enhancement (low-grade appearance): a report of the RANO resect group

BACKGROUND

Resection of the contrast-enhancing (CE) tumor represents the standard of care in newly diagnosed glioblastoma. However, some tumors ultimately diagnosed as glioblastoma lack contrast enhancement and have a 'low-grade appearance' on imaging (non-CE glioblastoma). We aimed to (a) volumetrically define the value of non-CE tumor resection in the absence of contrast enhancement, and to (b) delineate outcome differences between glioblastoma patients with and without contrast enhancement.

METHODS

The RANO resect group retrospectively compiled a global, eight-center cohort of patients with newly diagnosed glioblastoma per WHO 2021 classification. The associations between postoperative tumor volumes and outcome were analyzed. Propensity score-matched analyses were constructed to compare glioblastomas with and without contrast enhancement.

RESULTS

Among 1323 newly diagnosed IDH-wildtype glioblastomas, we identified 98 patients (7.4%) without contrast enhancement. In such patients, smaller postoperative tumor volumes were associated with more favorable outcome. There was an exponential increase in risk for death with larger residual non-CE tumor. Accordingly, extensive resection was associated with improved survival compared to lesion biopsy. These findings were retained on a multivariable analysis adjusting for demographic and clinical markers. Compared to CE glioblastoma, patients with non-CE glioblastoma had a more favorable clinical profile and superior outcome as confirmed in propensity score analyses by matching the patients with non-CE glioblastoma to patients with CE glioblastoma using a large set of clinical variables.

CONCLUSIONS

The absence of contrast enhancement characterizes a less aggressive clinical phenotype of IDH-wildtype glioblastomas. Maximal resection of non-CE tumors has prognostic implications and translates into favorable outcome.

A prospective randomized comparison of functional and cosmetic outcomes of a coronal zigzag incision versus a conventional straight incision pattern for craniotomy

OBJECTIVE

Wound healing problems after neurosurgical procedures can lead to serious complications and may require complex revision or even reconstructive surgery. Therefore, optimal surgical management is critical to prevent complications. In a recent experimental study in animals, the authors demonstrated the superiority of a zigzag skin incision over a straight incision pattern. In this study, the authors applied these findings to clinical situations of neurosurgical patients with an indication for a coronal skin incision. The aim of this study was to objectively assess the functional and cosmetic outcomes between straight coronal and zigzag incisions in neurosurgical procedures.

METHODS

This prospective, randomized, controlled, single-center trial included adult patients undergoing frontal craniotomy for cerebrovascular or tumor pathologies. The study primarily included patients who were not expected to receive adjuvant radiation or chemotherapy. The zigzag incision was standardized using a template. A common straight skin incision behind the hairline served as a control. Complication rates, functional (2-point discrimination, width of the wound, Vancouver Scar Scale [VSS], and Patient and Observer Scar Assessment Scale [POSAS]), and cosmetic outcomes were assessed postoperatively and at 3-month follow-up evaluations. Additionally, all patients answered a wound-specific questionnaire and the SF-36 questionnaire.

RESULTS

Twenty-eight patients were randomized to the zigzag and 29 to the straight incision groups. Indications for surgery were cerebrovascular in 16 cases and tumors in 41 cases. Risk factors for wound healing were equally distributed in both groups. One patient in the zigzag group with poor postoperative compliance required surgery for secondary wound healing problems. Overall, the width of the scar was significantly smaller (p = 0.001) and local 2-point discrimination better (p = 0.005) in the zigzag group. Scores on the VSS (p = 0.003) and POSAS (p = 0.005) proved to be significantly superior in the zigzag group as well.

CONCLUSIONS

A zigzag coronal skin incision pattern leads to significantly superior functional and cosmetic outcome scores. For certain patient groups, these findings may prove to be practice-changing.

Minimally invasive third ventriculostomy with stereotactic internal shunt placement for the treatment of tumor-associated noncommunicating hydrocephalus

BACKGROUND

Intracranial tumors can cause obstructive hydrocephalus (OH). Most often, symptomatic treatment is pursued through ventriculoperitoneal shunt (VS) or endoscopic third ventriculostomy (ETV). In this study, we propose stereotactic third ventriculostomy with internal shunt placement (sTVIP) as an alternative treatment option and assess its safety and efficacy.

METHODS

In this single-center, retrospective analysis, clinical symptoms, procedure-related complications, and revision-free survival of all patients with OH due to tumor formations treated by sTVIP between January 2010 and December 2021 were evaluated.

RESULTS

Clinical records of thirty-eight patients (11 female, 27 male) with a mean age of 40 years (range 5-88) were analyzed. OH was predominantly (in 92% of patients) caused by primary brain tumors (with exception of 3 cases with metastases). Following sTVIP, 74.2% of patients experienced symptomatic improvement. Preoperative headache was a significant predictor of postoperative symptomatic improvement (OR 26.25; 95% CI 4.1-521.1; p = 0.0036). Asymptomatic hemorrhage was detected along the stereotactic trajectory in 2 cases (5.3%). One patient required local revision due to CSF fistula (2.6%); another patient had to undergo secondary surgery to connect the catheter to a valve/abdominal catheter due to CSF malabsorption. However, in the remaining 37 patients, shunt independence was maintained during a median follow-up period of 12 months (IQR 3-32 months). No surgery-related mortality was observed.

CONCLUSIONS

sTVIP led to a significant symptom control and was associated with low operative morbidity, along with a high rate of ventriculoperitoneal shunt independency during the follow-up period. Therefore, sTVIP constitutes a highly effective and minimally invasive treatment option for tumor-associated obstructive hydrocephalus, even in cases with a narrow prepontine interval.

Prognostic Value of TSPO PET Before Radiotherapy in Newly Diagnosed IDH-Wild-Type Glioblastoma

The 18-kDa translocator protein (TSPO) is gaining recognition as a relevant target in glioblastoma imaging. However, data on the potential prognostic value of TSPO PET imaging in glioblastoma are lacking. Therefore, we investigated the association of TSPO PET imaging results with survival outcome in a homogeneous cohort of glioblastoma patients. Methods: Patients were included who had newly diagnosed, histologically confirmed isocitrate dehydrogenase (IDH)-wild-type glioblastoma with available TSPO PET before either normofractionated radiotherapy combined with temozolomide or hypofractionated radiotherapy. SUVmax on TSPO PET, TSPO binding affinity status, tumor volumes on MRI, and further clinical data, such as O 6-alkylguanine DNA methyltransferase (MGMT) and telomerase reverse transcriptase (TERT) gene promoter mutation status, were correlated with patient survival. Results: Forty-five patients (median age, 63.3 y) were included. Median SUVmax was 2.2 (range, 1.0-4.7). A TSPO PET signal was associated with survival: High uptake intensity (SUVmax > 2.2) was related to significantly shorter overall survival (OS; 8.3 vs. 17.8 mo, P = 0.037). Besides SUVmax, prognostic factors for OS were age (P = 0.046), MGMT promoter methylation status (P = 0.032), and T2-weighted MRI volume (P = 0.031). In the multivariate survival analysis, SUVmax in TSPO PET remained an independent prognostic factor for OS (P = 0.023), with a hazard ratio of 2.212 (95% CI, 1.115-4.386) for death in cases with a high TSPO PET signal (SUVmax > 2.2). Conclusion: A high TSPO PET signal before radiotherapy is associated with significantly shorter survival in patients with newly diagnosed IDH-wild-type glioblastoma. TSPO PET seems to add prognostic insights beyond established clinical parameters and might serve as an informative tool as clinicians make survival predictions for patients with glioblastoma.

Translocator protein (18kDA) (TSPO) marks mesenchymal glioblastoma cell populations characterized by elevated numbers of tumor-associated macrophages

TSPO is a promising novel tracer target for positron-emission tomography (PET) imaging of brain tumors. However, due to the heterogeneity of cell populations that contribute to the TSPO-PET signal, imaging interpretation may be challenging. We therefore evaluated TSPO enrichment/expression in connection with its underlying histopathological and molecular features in gliomas. We analyzed TSPO expression and its regulatory mechanisms in large in silico datasets and by performing direct bisulfite sequencing of the TSPO promotor. In glioblastoma tissue samples of our TSPO-PET imaging study cohort, we dissected the association of TSPO tracer enrichment and protein labeling with the expression of cell lineage markers by immunohistochemistry and fluorescence multiplex stains. Furthermore, we identified relevant TSPO-associated signaling pathways by RNA sequencing.We found that TSPO expression is associated with prognostically unfavorable glioma phenotypes and that TSPO promotor hypermethylation is linked to IDH mutation. Careful histological analysis revealed that TSPO immunohistochemistry correlates with the TSPO-PET signal and that TSPO is expressed by diverse cell populations. While tumor core areas are the major contributor to the overall TSPO signal, TSPO signals in the tumor rim are mainly driven by CD68-positive microglia/macrophages. Molecularly, high TSPO expression marks prognostically unfavorable glioblastoma cell subpopulations characterized by an enrichment of mesenchymal gene sets and higher amounts of tumor-associated macrophages.In conclusion, our study improves the understanding of TSPO as an imaging marker in gliomas by unveiling IDH-dependent differences in TSPO expression/regulation, regional heterogeneity of the TSPO PET signal and functional implications of TSPO in terms of tumor immune cell interactions.

Stereotactic radiosurgery versus whole-brain radiotherapy in patients with 4-10 brain metastases: A nonrandomized controlled trial

BACKGROUND AND PURPOSE

There is no randomized evidence comparing whole-brain radiotherapy (WBRT) and stereotactic radiosurgery (SRS) in the treatment of multiple brain metastases. This prospective nonrandomized controlled single arm trial attempts to reduce the gap until prospective randomized controlled trial results are available.

MATERIAL AND METHODS

We included patients with 4-10 brain metastases and ECOG performance status ≤ 2 from all histologies except small-cell lung cancer, germ cell tumors, and lymphoma. The retrospective WBRT-cohort was selected 2:1 from consecutive patients treated within 2012-2017. Propensity-score matching was performed to adjust for confounding factors such as sex, age, primary tumor histology, dsGPA score, and systemic therapy. SRS was performed using a LINAC-based single-isocenter technique employing prescription doses from 15-20Gyx1 at the 80% isodose line. The historical control consisted of equivalent WBRT dose regimens of either 3Gyx10 or 2.5Gyx14.

RESULTS

Patients were recruited from 2017-2020, end of follow-up was July 1st, 2021. 40 patients were recruited to the SRS-cohort and 70 patients were eligible as controls in the WBRT-cohort. Median OS, and iPFS were 10.4 months (95%-CI 9.3-NA) and 7.1 months (95%-CI 3.9-14.2) for the SRS-cohort, and 6.5 months (95%-CI 4.9-10.4), and 5.9 months (95%-CI 4.1-8.8) for the WBRT-cohort, respectively. Differences were non-significant for OS (HR: 0.65; 95%-CI 0.40-1.05; P =.074) and iPFS (P =.28). No grade III toxicities were observed in the SRS-cohort.

CONCLUSION

This trial did not meet its primary endpoint as the OS-improvement of SRS compared to WBRT was non-significant and thus superiority could not be proven. Prospective randomized trials in the era of immunotherapy and targeted therapies are warranted.

Nuclear translocation of beta catenin in patients with Rathke cleft cysts-clinical and imaging characteristics and risk of recurrence

PURPOSE

Although Rathke cleft cysts (RCC) are benign lesions of the sellar region, recurrence is frequent after surgical treatment. Nuclear translocation of ß-catenin (NTßC), a key effector of the wnt-signaling pathway that is responsible for cell renewal, has been shown to act as a proto-oncogene and is considered to be a potential risk factor for increased recurrence in RCC. In this study, we analyzed a surgically treated cohort into patients with and without NTßC expression in order to identify clinical and imaging differences and further evaluate the risk of recurrence.

METHODS

Patients with resection of RCC between 04/2001 and 11/2020 were included. Histological specimens were immunohistochemically stained for ß-catenin. Study endpoints were time to cyst recurrence (TTR) and functional outcome. Functional outcome included ophthalmological and endocrinological data. Furthermore, MRI data were assessed.

RESULTS

Seventy-three patients (median age 42.3 years) with RCC underwent mainly transsphenoidal cyst resection (95.9%), 4.1% via transcranial approach. Immunohistochemical staining for ß-catenin was feasible in 61/73 (83.6%) patients, with nuclear translocation detected in 13/61 cases (21.3%). Patients with and without NTßC were equally likely to present with endocrine dysfunction before surgery (p = 0.49). Postoperative new hypopituitarism occurred in 14/73 (19.2%) patients. Preoperative visual impairment was equal in both groups (p = 0.52). Vision improved in 8/21 (33.3%) patients and visual field deficits in 22/34 (64.7%) after surgery. There was no difference in visual and perimetric outcome between patients with and without NTßC (p = 0.45 and p = 0.23, respectively). On preoperative MRI, cyst volume (9.9 vs. 8.2 cm3; p = 0.4) and evidence of hemorrhage (30.8% vs. 35.4%; p = 0.99) were equal and postoperative cyst volume decreased significantly in both groups (0.7 vs. 0.5 cm3; p < 0.0001 each). Cyst progression occurred in 13/73 (17.8%) patients after 39.3 ± 60.3 months. Cyst drainage with partial removal of the cyst wall resulted in improved recurrence-free survival without increasing the risk of complications compared with cyst fenestration alone. Patients with postoperative diabetes insipidus had an increased risk for recurrence according to multivariate analysis (p = 0.005). NTßC was evident in 4/15 patients (26.7%) and was not associated with a higher risk for recurrence (p = 0.67).

CONCLUSION

Transnasal transsphenoidal cyst drainage with partial removal of the cyst wall reduces the risk of recurrence without increasing the risk of complications compared with fenestration of the cyst alone. Patients with postoperative diabetes insipidus seem to have an increased risk for recurrence. In contrast, NTßC was not associated with a higher risk of recurrence and did not provide stratification for clinically distinct patients.

Perifocal Edema in Patients with Meningioma is Associated with Impaired Whole-Brain Connectivity as Detected by Resting-State fMRI

BACKGROUND AND PURPOSE

Meningiomas are intracranial tumors that usually carry a benign prognosis. Some meningiomas cause perifocal edema. Resting-state fMRI can be used to assess whole-brain functional connectivity, which can serve as a marker for disease severity. Here, we investigated whether the presence of perifocal edema in preoperative patients with meningiomas leads to impaired functional connectivity and if these changes are associated with cognitive function.

MATERIALS AND METHODS

Patients with suspected meningiomas were prospectively included, and resting-state fMRI scans were obtained. Impairment of functional connectivity was quantified on a whole-brain level using our recently published resting-state fMRI-based marker, called the dysconnectivity index. Using uni- and multivariate regression models, we investigated the association of the dysconnectivity index with edema and tumor volume as well as cognitive test scores.

RESULTS

Twenty-nine patients were included. In a multivariate regression analysis, there was a highly significant association of dysconnectivity index values and edema volume in the total sample and in a subsample of 14 patients with edema, when accounting for potential confounders like age and temporal SNR. There was no statistically significant association with tumor volume. Better neurocognitive performance was strongly associated with lower dysconnectivity index values.

CONCLUSIONS

Resting-state fMRI showed a significant association between impaired functional connectivity and perifocal edema, but not tumor volume, in patients with meningiomas. We demonstrated that better neurocognitive function was associated with less impairment of functional connectivity. This result shows that our resting-state fMRI marker indicates a detrimental influence of peritumoral brain edema on global functional connectivity in patients with meningiomas.

Treatment benefit in patients aged 80 years or older with biopsy-proven and non-resected glioblastoma is dependent on MGMT promoter methylation status

PURPOSE

Glioblastoma is associated with especially poor outcome in the elderly. It is unclear if patients aged ≥80 years benefit from tumor-specific therapy as opposed to receiving best supportive care (BSC) only.

METHODS

Patients with IDH-wildtype glioblastoma (WHO 2021), aged ≥80 years, and diagnosed by biopsy between 2010 and 2022 were included. Patient characteristics and clinical parameters were assessed. Uni- and multivariate analyses were performed.

RESULTS

76 patients with a median age of 82 (range 80-89) and a median initial KPS of 80 (range 50-90) were included. Tumor-specific therapy was initiated in 52 patients (68%). 22 patients (29%) received temozolomide monotherapy, 23 patients (30%) were treated with radiotherapy (RT) alone and 7 patients (9%) received combination therapies. In 24 patients (32%), tumor-specific therapy was omitted in lieu of BSC. Overall survival (OS) was longer in patients receiving tumor-specific therapy (5.4 vs. 3.3 months, p < 0.001). Molecular stratification showed that the survival benefit was owed to patients with MGMT promoter methylation (MGMTpos) who received tumor-specific therapy as opposed to BSC (6.2 vs. 2.6 months, p < 0.001), especially to those with better clinical status and no initial polypharmacy. Patients with unmethylated MGMT promoter (MGMTneg) did not benefit from tumor-specific therapy (3.6 vs. 3.7 months, p = 0.18). In multivariate analyses, better clinical status and MGMT promoter methylation were associated with prolonged survival (p < 0.01 and p = 0.01).

CONCLUSION

Benefit from tumor-specific treatment in patients with newly diagnosed glioblastoma aged ≥80 years might be restricted to MGMTpos patients, especially to those with good clinical status and no polypharmacy.

Interstitial Photodynamic Therapy of Glioblastomas: A Long-Term Follow-up Analysis of Survival and Volumetric MRI Data

BACKGROUND

The treatment of glioblastomas, the most common primary malignant brain tumors, with a devastating survival perspective, remains a major challenge in medicine. Among the recently explored therapeutic approaches, 5-aminolevulinic acid (5-ALA)-mediated interstitial photodynamic therapy (iPDT) has shown promising results.

METHODS

A total of 16 patients suffering from de novo glioblastomas and undergoing iPDT as their primary treatment were retrospectively analyzed regarding survival and the characteristic tissue regions discernible in the MRI data before treatment and during follow-up. These regions were segmented at different stages and were analyzed, especially regarding their relation to survival.

RESULTS

In comparison to the reference cohorts treated with other therapies, the iPDT cohort showed a significantly prolonged progression-free survival (PFS) and overall survival (OS). A total of 10 of 16 patients experienced prolonged OS (≥ 24 months). The dominant prognosis-affecting factor was the MGMT promoter methylation status (methylated: median PFS of 35.7 months and median OS of 43.9 months) (unmethylated: median PFS of 8.3 months and median OS of 15.0 months) (combined: median PFS of 16.4 months and median OS of 28.0 months). Several parameters with a known prognostic relevance to survival after standard treatment were not found to be relevant to this iPDT cohort, such as the necrosis-tumor ratio, tumor volume, and posttreatment contrast enhancement. After iPDT, a characteristic structure (iPDT remnant) appeared in the MRI data in the former tumor area.

CONCLUSIONS

In this study, iPDT showed its potential as a treatment option for glioblastomas, with a large fraction of patients having prolonged OS. Parameters of prognostic relevance could be derived from the patient characteristics and MRI data, but they may partially need to be interpreted differently compared to the standard of care.

High-Grade Glioma Radiation Therapy and Reirradiation Treatment Planning Using Translocator Protein Positron Emission Tomography With 18F-GE-180

Purpose

Translocator protein (TSPO) positron emission tomography (PET) using ¹⁸F-GE-180 shows high tumor-to-brain contrast in high-grade glioma (HGG), even in areas without magnetic resonance imaging (MRI) contrast enhancement. Until now, the benefit of ¹⁸F-GE-180 PET in primary radiation therapy (RT) and reirradiation (reRT) treatment planning for patients with HGG has not been assessed.

Methods and Materials

The possible benefit of ¹⁸F-GE-180 PET in RT and reRT planning was retrospectively evaluated through post hoc spatial correlations of PET-based biological tumor volumes (BTVs) with conventional MRI-based consensus gross tumor volumes (cGTVs). To find the ideal threshold for BTV definition in RT and reRT treatment planning, tumor-to-background activity thresholds of 1.6, 1.8, and 2.0 were applied. Spatial overlap of PET- and MRI-based tumor volumes was measured by the Sørensen-Dice coefficient (SDC) and the conformity index (CI). Additionally, the minimal margin to include the entire BTV into the expanded cGTV was determined.

Results

Thirty-five primary RT and 16 reRT cases were examined. BTV1.6, BTV1.8, and BTV2.0 were significantly larger than corresponding cGTV volumes in primary RT (median volumes: 67.4, 50.7, and 39.1, respectively, vs 22.6 cm³; P < .001, P < .001, and P = .017, respectively; Wilcoxon test) and reRT cases (median volumes: 80.5, 55.0, and 41.6, respectively, vs 22.7 cm³; P = .001, P = .005, and P = .144, respectively; Wilcoxon test). BTV1.6, BTV1.8, and BTV2.0 showed low but increasing conformity with cGTVs in the primary RT (SDC: 0.51, 0.55, and 0.58, respectively; CI: 0.35, 0.38, and 0.41, respectively) and reRT setting (SDC: 0.38, 0.40, and 0.40, respectively; CI: 0.24, 0.25, and 0.25, respectively). The minimal margin required to include the BTV within the cGTV was significantly smaller in the RT versus the reRT setting for thresholds 1.6 and 1.8 but not significantly different for threshold 2.0 (median margin: 16, 12, and 10, respectively, vs 21.5, 17.5, and 13 mm, respectively; P = .007, P = .031, and P = .093, respectively; Mann-Whitney U test).

Conclusions

¹⁸F-GE-180 PET provides valuable information in RT treatment planning for patients with HGG. ¹⁸F-GE-180-based BTVs with a threshold of 2.0 were most consistent in primary and reRT.

Interstitial photodynamic therapy for newly diagnosed glioblastoma

PURPOSE

Innovative, efficient treatments are desperately needed for people with glioblastoma (GBM).

METHODS

Sixteen patients (median age 65.8 years) with newly diagnosed, small-sized, not safely resectable supratentorial GBM underwent interstitial photodynamic therapy (iPDT) as upfront eradicating local therapy followed by standard chemoradiation. 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX was used as the photosensitizer. The tumors were irradiated with light at 635 nm wavelength via stereotactically implanted cylindrical diffuser fibers. Outcome after iPDT was retrospectively compared with a positively-selected in-house patient cohort (n = 110) who underwent complete tumor resection followed by chemoradiation.

RESULTS

Median progression-free survival (PFS) was 16.4 months, and median overall survival (OS) was 28.0 months. Seven patients (43.8%) experienced long-term PFS > 24 months. Median follow-up was 113.9 months for the survivors. Univariate regression revealed MGMT-promoter methylation but not age as a prognostic factor for both OS (p = 0.04 and p = 0.07) and PFS (p = 0.04 and p = 0.67). Permanent iPDT-associated morbidity was seen in one iPDT patient (6.3%). Patients treated with iPDT experienced superior PFS and OS compared to patients who underwent complete tumor removal (p < 0.01 and p = 0.01, respectively). The rate of long-term PFS was higher in iPDT-treated patients (43.8% vs. 8.9%, p < 0.01).

CONCLUSION

iPDT is a feasible treatment concept and might be associated with long-term PFS in a subgroup of GBM patients, potentially via induction of so far unknown immunological tumor-controlling processes.

Frequency and Prognostic Relevance of Volumetric MRI Changes in Contrast- and Non-Contrast-Enhancing Tumor Compartments between Surgery and Radiotherapy of IDHwt Glioblastoma

In newly diagnosed IDH-wildtype glioblastoma, the frequency and prognostic relevance of tumor regrowth between resection and the initiation of adjuvant radiochemotherapy are unclear. In this retrospective single-center study we included 64 consecutive cases, for whom magnetic resonance imaging (MRI) was available for both the volumetric assessment of the extent of resection immediately after surgery as well as the volumetric target delineation before the initiation of adjuvant radiochemotherapy (time interval: 15.5 ± 1.9 days). Overall, a median new contrast-enhancement volume was seen in 21/64 individuals (33%, 1.5 ± 1.5 cm3), and new non-contrast lesion volume in 18/64 patients (28%, 5.0 ± 2.3 cm3). A multidisciplinary in-depth review revealed that new contrast-enhancement was either due to (I) the progression of contrast-enhancing tumor remnants in 6/21 patients or (II) distant contrast-enhancing foci or breakdown of the blood–brain barrier in previously non-contrast-enhancing tumor remnants in 5/21 patients, whereas it was unspecific or due to ischemia in 10/21 patients. For non-contrast-enhancing lesions, three of eighteen had progression of non-contrast-enhancing tumor remnants and fifteen of eighteen had unspecific changes or changes due to ischemia. There was no significant association between findings consistent with tumor regrowth and a less favorable outcome (overall survival: 14 vs. 19 months; p = 0.423). These findings support the rationale that analysis of the postsurgical remaining tumor-volume for prognostic stratification should be carried out on immediate postoperative MRI (<72 h), as unspecific changes are common. However, tumor regrowth including distant foci may occur in a subset of IDH-wildtype glioblastoma patients diagnosed per WHO 2021 classification. Thus, MRI imaging prior to radiotherapy should be obtained to adjust radiotherapy planning accordingly.

Neurosurgical Interventions for Cerebral Metastases of Solid Tumors

BACKGROUND

Metastases are the most common malignant tumors affecting the central nervous system and occur in 20-40 percent of patients with solid systemic tumors. The aim of this review is to discuss the role of neurosurgical procedures in a modern, multidisciplinary treatment approach.

METHODS

An expert panel of neurosurgeons, neurologists, and radio-oncologists conducted a selective literature review on neurosurgical interventions for the diagnosis and treatment of cerebral metastases. Original articles, meta-analyses, and systematic reviews were included.

RESULTS

There is a lack of prospective randomized studies. Based on retrospective case series, international guidelines recommend the harvesting (if required, stereotactically guided) of tissue for histological and molecular diagnosis in cases of unknown or possibly competing underlying systemic malignant diseases, in cases of suspected tumor recurrence, and with regard to the evaluation of targeted therapies taking into account molecular heterogeneity of primary and secondary tumors. Surgical resection is particularly valuable for the treatment of up to three space-occupying cerebral metastases, especially to achieve clinical stabilization to allow further non-surgical treatment For cystic metastasis, a combination of stereotactic puncture and radiotherapy may be useful. Meningeal carcinomatosis can be treated with intrathecal medication via an intraventricular catheter system. Ventriculo-peritoneal shunts represents an effective treatment option for patients with tumorassociated hydrocephalus.

CONCLUSION

Neurosurgical procedures are of central importance in the multimodal treatment of cerebral metastases. The indications for neurosurgical interventions will be refined in the light of more effective radiation techniques and systemic treatments with new targeted therapeutic approaches and immunotherapies on the horizon.

Shunt dependency in supratentorial intraventricular tumors depends on the extent of tumor resection

BACKGROUND

Supratentorial intraventricular tumors (SIVTs) are rare lesions of various entities characteristically presenting with hydrocephalus and often posing a surgical challenge due to their deep-seated localization. We aimed to elaborate on shunt dependency after tumor resection, clinical characteristics, and perioperative morbidity.

METHODS

We retrospectively searched the institutional database for patients with supratentorial intraventricular tumors treated at the Department of Neurosurgery of the Ludwig-Maximilians-University in Munich, Germany, between 2014 and 2022.

RESULTS

We identified 59 patients with over 20 different SIVT entities, most often subependymoma (8/59 patients, 14%). Mean age at diagnosis was 41 ± 3 years. Hydrocephalus and visual symptoms were observed in 37/59 (63%) and 10/59 (17%) patients, respectively. Microsurgical tumor resection was provided in 46/59 patients (78%) with complete resection in 33/46 patients (72%). Persistent postoperative neurological deficits were encountered in 3/46 patients (7%) and generally mild in nature. Complete tumor resection was associated with less permanent shunting in comparison to incomplete tumor resection, irrespective of tumor histology (6% versus 31%, p = 0.025). Stereotactic biopsy was utilized in 13/59 patients (22%), including 5 patients who received synchronous internal shunt implantation for symptomatic hydrocephalus. Median overall survival was not reached and did not differ between patients with or without open resection.

CONCLUSIONS

SIVT patients display a high risk of developing hydrocephalus and visual symptoms. Complete resection of SIVTs can often be achieved, preventing the need for long-term shunting. Stereotactic biopsy along with internal shunting represents an effective approach to establish diagnosis and ameliorate symptoms if resection cannot be safely performed. Due to the rather benign histology, the outcome appears excellent when adjuvant therapy is provided.

In vivo dynamics and anti-tumor effects of EpCAM-directed CAR T-cells against brain metastases from lung cancer

Lung cancer patients are at risk for brain metastases and often succumb to their intracranial disease. Chimeric Antigen Receptor (CAR) T-cells emerged as a powerful cell-based immunotherapy for hematological malignancies; however, it remains unclear whether CAR T-cells represent a viable therapy for brain metastases. Here, we established a syngeneic orthotopic cerebral metastasis model in mice by combining a chronic cranial window with repetitive intracerebral two-photon laser scanning-microscopy. This approach enabled in vivo-characterization of fluorescent CAR T-cells and tumor cells on a single-cell level over weeks. Intraparenchymal injection of Lewis lung carcinoma cells (expressing the tumor cell-antigen EpCAM) was performed, and EpCAM-directed CAR T-cells were injected either intravenously or into the adjacent brain parenchyma. In mice receiving EpCAM-directed CAR T-cells intravenously, we neither observed substantial CAR T-cell accumulation within the tumor nor relevant anti-tumor effects. Local CAR T-cell injection, however, resulted in intratumoral CAR T-cell accumulation compared to controls treated with T-cells lacking a CAR. This finding was accompanied by reduced tumorous growth as determined per in vivo-microscopy and immunofluorescence of excised brains and also translated into prolonged survival. However, the intratumoral number of EpCAM-directed CAR T-cells decreased during the observation period, pointing toward insufficient persistence. No CNS-specific or systemic toxicities of EpCAM-directed CAR T-cells were observed in our fully immunocompetent model. Collectively, our findings indicate that locally (but not intravenously) injected CAR T-cells may safely induce relevant anti-tumor effects in brain metastases from lung cancer. Strategies improving the intratumoral CAR T-cell persistence may further boost the therapeutic success.

Significance of molecular diagnostics for therapeutic decision-making in recurrent glioma

Background

Targeted therapies have substantially improved survival in cancer patients with malignancies outside the brain. Whether in-depth analysis for molecular alterations may also offer therapeutic avenues in primary brain tumors remains unclear. We herein present our institutional experience for glioma patients discussed in our interdisciplinary molecular tumor board (MTB) implemented at the Comprehensive Cancer Center Munich (LMU).

Methods

We retrospectively searched the database of the MTB for all recurrent glioma patients after previous therapy. Recommendations were based on next-generation sequencing results of individual patient's tumor tissue. Clinical and molecular information, previous therapy regimens, and outcome parameters were collected.

Results

Overall, 73 consecutive recurrent glioma patients were identified. In the median, advanced molecular testing was initiated with the third tumor recurrence. The median turnaround time between initiation of molecular profiling and MTB case discussion was 48 ± 75 days (range: 32-536 days). Targetable mutations were found for 50 recurrent glioma patients (68.5%). IDH1 mutation (27/73; 37%), epidermal growth factor receptor amplification (19/73; 26%), and NF1 mutation (8/73; 11%) were the most detected alterations and a molecular-based treatment recommendation could be made for all of them. Therapeutic recommendations were implemented in 12 cases (24%) and one-third of these heavily pretreated patients experienced clinical benefit with at least disease stabilization.

Conclusions

In-depth molecular analysis of tumor tissue may guide targeted therapy also in brain tumor patients and considerable antitumor effects might be observed in selected cases. However, future studies to corroborate our results are needed.

The value of stereotactic biopsy of primary and recurrent brain metastases in the era of precision medicine

Background

Brain metastases (BM) represent the most frequent intracranial tumors with increasing incidence. Many primary tumors are currently treated in protocols that incorporate targeted therapies either upfront or for progressive metastatic disease. Hence, molecular markers are gaining increasing importance in the diagnostic framework of BM. In cases with diagnostic uncertainty, both in newly diagnosed or recurrent BM, stereotactic biopsy serves as an alternative to microsurgical resection particularly whenever resection is not deemed to be safe or feasible. This retrospective study aimed to analyze both diagnostic yield and safety of an image-guided frame based stereotactic biopsy technique (STX).

Material and methods

Our institutional neurosurgical data base was searched for any surgical procedure for suspected brain metastases between January 2016 and March 2021. Of these, only patients with STX were included. Clinical parameters, procedural complications, and tissue histology and concomitant molecular signature were assessed.

Results

Overall, 467 patients were identified including 234 (50%) with STX. Median age at biopsy was 64 years (range 29 - 87 years). MRI was used for frame-based trajectory planning in every case with additional PET-guidance in 38 cases (16%). In total, serial tumor probes provided a definite diagnosis in 230 procedures (98%). In 4 cases (1.7%), the pathological tissue did not allow a definitive neuropathological diagnosis. 24 cases had to be excluded due to non-metastatic histology, leaving 206 cases for further analyses. 114 patients (49%) exhibited newly diagnosed BM, while 46 patients (20%) displayed progressive BM. Pseudoprogression was seen in 46 patients, a median of 12 months after prior therapy. Pseudoprogression was always confirmed by clinical course. Metastatic tissue was found most frequently from lung cancer (40%), followed by breast cancer (9%), and malignant melanoma (7%). Other entities included gastrointestinal cancer, squamous cell cancer, renal cell carcinoma, and thyroid cancer, respectively. In 9 cases (4%), the tumor origin could not be identified (cancer of unknown primary). Molecular genetic analyses were successful in 137 out of 144 analyzed cases (95%). Additional next-generation sequencing revealed conclusive results in 12/18 (67%) cases. Relevant peri-procedural complications were observed in 5 cases (2.4%), which were all transient. No permanent morbidity or mortality was noted.

Conclusion

In patients with BM, frame-based stereotactic biopsy constitutes a safe procedure with a high diagnostic yield. Importantly, this extended to discerning pseudoprogression from tumor relapse after prior therapy. Thus, comprehensive molecular characterization based on minimal-invasive stereotactic biopsies lays the foundation for precision medicine approaches in the treatment of primary and recurrent BM.

SURG-39. SURGICAL RESULTS AND LONG-TERM OUTCOME IN SUPRATENTORIAL INTRAVENTRICULAR TUMORS

BACKGROUND

Intraventricular tumors (IVTs) are rare lesions of various entities, which pose a surgical challenge. We aimed to elaborate on surgical approaches and outcomes, postoperative morbidity, and elucidate whether preoperative hydrocephalus necessitates shunting despite surgical resection.

METHODS

We retrospectively searched the institutional database for patients with supratentorial intraventricular tumours that were treated in the Department of Neurosurgery of the Ludwig-Maximilians-University Munich, Germany between 2014 and 2022.

RESULTS

We identified 59 patients with supratentorial intraventricular tumors comprising over 15 different tumor entities, most often subependymoma (8/59 patients, 14%). Median age at diagnosis was 41.4 years (range 0-86 years) with 31 male patients (53%) and 28 female patients (48%). Microsurgical tumor resection was completed in 46/59 patients (78%) with incomplete tumor resection (≥ 1ml postoperative tumor volume) in 13/46 patients (28%) and complete tumor resection (&lt; 1ml postoperative tumor volume) in 33/46 patients (72%). In cases where neurosurgical tumor resection was not feasible, stereotactic biopsy was provided in 13/59 patients (22%), often combined with stereotactic internal shunt implantation (5/59 patients, 8%). Mean follow-up was 24 months; median overall survival was not reached. Postoperative persistent hydrocephalus necessitating ventriculoperitoneal shunt placement was rare (5/59 patients, 8%). Ventriculocisternostomy was performed in one patient. New postoperative focal neurological deficits – mostly transient – were encountered in 16/59 patients (27%) at discharge with mild to moderate permanent focal neurological deficits at 3 months in 3/59 patients (5%).

CONCLUSION

Complete resection of IVT can often be achieved and forms the basis for favourable outcome. Permanent neurological deficits are rare, and hydrocephalus can almost always be alleviated which prevents the need for long-term shunting. If microsurgical resection is not feasible, stereotactic biopsy along with internal shunting represents an effective approach to establish diagnosis and ameliorate symptoms.

NIMG-26. UPTAKE OF [18F]GE-180 IN TSPO PET IS ASSOCIATED WITH SURVIVAL IN PATIENTS WITH RECURRENT GLIOMA

OBJECTIVE

The 18 kDa translocator protein (TSPO) is expressed in both activated microglia and glioma cells. Elevated expression of TSPO has been reported to be associated with higher WHO grade. Here we analyze whether TSPO positron emission tomography (PET) signal using the tracer [18F]GE-180 is correlated with clinical outcome in a cohort of patients with recurrent glioma.

METHODS

Patients with suspected glioma recurrence received a [18F]GE-180 TSPO PET. All recurrent tumors were confirmed either by stereotactic biopsy or resection. Maximum standard uptake value SUVmax as well as tumor volume in MRI and, if available, in [18F]FET PET were evaluated together with patient characteristics (age, sex, Karnofsky-Performance score) and neuropathological features (WHO grade, IDH-mutation status). Uni- and multivariate Cox regression and Kaplan-Meier survival analyses were performed to identify prognostic factors for post-recurrence survival (PRS) and time to treatment failure (TTF).

RESULTS

88 consecutive patients were evaluated. TSPO tracer uptake correlated with tumor grade at recurrence (p&lt; 0.05), with no significant differences between IDH-wildtype and IDH-mutant tumors. Within the subgroup of IDH-mutant glioma (n= 46), patients with low SUVmax (median split, ≤ 1.60) had a significantly longer PRS (median 41.6 vs. 25.3 months, p= 0.031) and TTF (32.2 vs 8.7 months, p= 0.001). Also among IDH-wildtype tumors (n= 42), patients with low SUVmax (≤ 1.89) had a significantly longer PRS (median not reached vs 8.2 months, p= 0.002). SUVmax remained an independent prognostic factor for PRS in a multivariate analysis including WHO grade, IDH status and age. Tumor volume defined by [18F]FET PET or contrast-enhanced MRI correlated weakly with TSPO tracer uptake. Treatment regimen did not differ between the subgroups.

CONCLUSION

Our data suggest that uptake of [18F]GE-180 in TSPO PET can add prognostic information in patients with recurrent glioma even in molecular defined subgroups and might serve as an imaging biomarker.

EXTH-02. ANTI-TUMOR EFFECTS AND IN VIVO DYNAMICS OF EPCAM-DIRECTED CAR T-CELLS FOR BRAIN METASTASES FROM LUNG CANCER

BACKGROUND

Lung cancer patients are at a high risk for brain metastases, and affected patients frequently succumb to their intracranial disease. Chimeric Antigen Receptor (CAR) T-cells emerged as a powerful cell-based immunotherapy for hematological malignancies; however, it remains unclear whether CAR T-cells represent a viable therapeutic avenue for brain metastases.

METHODS

A fully immunocompetent, orthotopic cerebral metastasis model was established in mice by combining a chronic cranial window with repetitive intracerebral two-photon laser scanning microscopy. This approach enabled the in vivo-characterization of fluorescent CAR T-cells and tumor cells on a single-cell level over weeks. Intraparenchymal injection of EpCAM-expressing Lewis lung carcinoma cells was performed, and EpCAM-directed CAR T-cells (EpCAMCAR T-cells) were injected into the adjacent brain parenchyma after brain tumor formation.

RESULTS

All mice had visible tumor take with rapidly growing lesions following intracranial tumor cell injection. In mice treated with EpCAMCAR T-cells, we observed substantial CAR T-cell accumulation within the tumor compared to controls treated with undirected T-cells. This was paralleled by lower velocities of EpCAMCAR T-cells, characterizing antitumor cytotoxicity due to ‘immune cell’-‘tumor cell’ contacts. Consequently, treatment with EpCAMCAR T-cells resulted in reduced tumorous growth as determined per in vivo-microscopy (median tumor area on day 10: 1.8 versus 10.8 mm2; p=0.001) and immunohistochemistry of excised brains. However, the number of intratumoral EpCAMCAR T-cells within the tumor markedly decreased during the observation period, pointing towards insufficient persistence. Accordingly, survival was prolonged in mice receiving EpCAMCAR T-cells but long-lasting remission was rare (median survival: 15 versus 13 days; p=0.012). No CNS-specific or systemic toxicities of EpCAMCAR T-cells were encountered.

CONCLUSION

Our findings indicate that EpCAMCAR T-cells injected into the cerebral parenchyma may safely induce relevant anti-tumor effects in brain metastases from lung cancer. Strategies improving the CAR T-cell persistence within brain metastases are warranted to further boost the therapeutic success.

NIMG-66. CANNY EDGE DETECTION ALGORITHM FOR QUANTITATIVE DIFFERENTIATION BETWEEN DIFFUSE AND CIRCUMSCRIPT GLIOMA GROWTH PATTERNS ON MRI

BACKGROUND

Lower grade gliomas show heterogenous appearance on T2-weighted MRI. Some tumors grow diffusely along axonal structures whereas others distort adjacent brain tissue through local mass effect. The diagnostic, therapeutic and prognostic implication of differential growth patterns on MRI remain unknown and are difficult to assess quantitatively.

METHODS

A web-based application allowing for image preprocessing and providing a comprehensive edge detection tool by means of quantifying tumor border delineation on T2-weighted images based on the canny edge detection algorithm was developed. A sigma value between 1 and 100 determined the threshold where tumor borders where not detected anymore, with 1 equating to the lowest threshold and thus detection of all edges contained in the image. Two experienced faculty members assigned sigma values to axial T2 images of a random sample of 20 WHO grade 2 astrocytomas, IDH-mutant and 1p/19q-non-codeleted. The sigma values were then compared with a binary, subjective rating by the same faculty staff according to the perceived predominant growth pattern (diffuse versus circumscript) of each glioma.

RESULTS

When subjectively categorizing tumors binarily (diffuse versus circumscript), there was moderate interrater variability between observers (cohen’s kappa=0.6). Raters agreed in 16 of 20 cases, terming 7 gliomas unanimously diffuse and 9 gliomas circumscript. In 4 cases, the raters opinions diverged. The sigma values differed significantly between diffuse and circumscript tumors in both raters (rater 1, p=0.002; rater 2, p=0.018). For rater 1, the mean sigma difference between diffuse and circumscript tumors was 10.7 and 9.3 for rater 2. The mean overall sigma value was 13.3 for rater 1 and 18.7 for rater 2 (p=0.005).

CONCLUSION

Edge detection algorithms can be efficiently applied on MRI scans and are highly accurate in differentiating diffuse from circumscript gliomas. Objectification demands defining imaging criteria for diffuse and circumscript appearance of lower grade gliomas on MRI.

CTNI-55. INITIAL TEMOZOLOMIDE MONOTHERAPY WITHOUT RADIOTHERAPY MIGHT BE OF LIMITED BENEFIT IN THE TREATMENT OF ASTROCYTOMA, IDH-MUTANT, CNS WHO GRADE 2 AND 3

QUESTION

The role of temozolomide chemotherapy alone in isocitrate dehydrogenase (IDH)-mutant astrocytomas has not been conclusively determined. Recent studies have linked temozolomide therapy with induction of hypermutation and poor clinical course in some IDH-mutant gliomas.

METHODS

In this retrospective, single-center study, 183 patients with astrocytoma, IDH-mutant, CNS WHO grade 2 or 3 diagnosed between 2003 and 2019 were included. Patients initially monitored by means of a wait-and-scan strategy, or treated with radiotherapy alone, or receiving temozolomide alone, after histological sampling through biopsy or tumor resection, were studied. Progression-free and overall survival was analysed. A matched-pair analysis accounting for post-surgical tumor volume was conducted.

RESULTS

Initial T2 tumor volume and WHO grade were associated with survival in univariate analyses (p &lt; 0.01). The proportion of WHO grade 2 gliomas was highest in the wait-and-scan cohort (p &lt; 0.01). Tumor volumes were largest in the temozolomide cohort (p &lt; 0.01). Radiotherapy was associated with longer progression-free survival than temozolomide (6.2 vs 3.4 years, p = 0.02) and wait-and-scan strategies (6.2 vs 4 years, p = 0.03). Patients treated with radiotherapy showed longer overall survival than patients treated with temozolomide (14.4 vs 10.7 years, p = 0.02). Survival was longer in patients initially monitored by means of a wait-and-scan strategy than in patients treated with temozolomide (not reached vs 10.7 years, p &lt; 0.0001). The same association was seen in a subgroup analysis of WHO grade 2 astrocytomas (p = 0.02) and by trend in a matched pair analysis (p = 0.09).

CONCLUSION

The results suggest superiority for progression-free survival of radiotherapy alone over temozolomide alone or wait-and-scan strategies and for overall survival of radiotherapy alone and wait-and-scan therapies over temozolomide in IDH-mutant WHO grade 2 and 3. Recent study results indicating that temozolomide might compromise prognosis in some patients with IDH-mutant gliomas might be supported by our data.

Limited efficacy of temozolomide alone for astrocytoma, IDH-mutant, CNS WHO grades 2 or 3

Purpose

The role of temozolomide chemotherapy alone in isocitrate dehydrogenase (IDH)-mutant astrocytomas has not been conclusively determined. Radiotherapy might be superior to temozolomide. Recent studies have linked temozolomide with induction of hypermutation and poor clinical course in some IDH-mutant gliomas.

Methods

In this retrospective study, 183 patients with astrocytoma, IDH-mutant, CNS WHO grade 2 or 3 and diagnosed between 2001 and 2019 were included. Patients initially monitored by wait-and-scan strategies or treated with radiotherapy or temozolomide alone were studied. Patient data were correlated with outcome. Matched pair and subgroup analyses were conducted.

Results

Radiotherapy was associated with longer progression-free survival than temozolomide (6.2 vs 3.4 years, p = 0.02) and wait-and-scan strategies (6.2 vs 4 years, p = 0.03). Patients treated with radiotherapy lived longer than patients treated with temozolomide (14.4 vs 10.7 years, p = 0.02). Survival was longer in the wait-and-scan cohort than in the temozolomide cohort (not reached vs 10.7 years, p < 0.01). Patients from the wait-and-scan cohort receiving temozolomide at first progression had significantly shorter survival times than patients treated with any other therapy at first progression (p < 0.01). Post-surgical T2 tumor volume, contrast enhancement on MRI and WHO grade were associated with overall survival in univariate analyses (p < 0.01).

Conclusion

The results suggest superiority of radiotherapy over temozolomide and wait-and-scan strategies regarding progression-free survival and superiority of radiotherapy over temozolomide regarding overall survival. Our results are consistent with the notion that early temozolomide might compromise outcome in some patients.

P15.09.A Canny edge detection algorithm for quantitative differentiation between diffuse and circumscript glioma growth patterns on MRI

Background

Lower grade gliomas show heterogenous appearance on T2-weighted MRI. Some tumors grow diffusely along axonal structures whereas others distort adjacent brain tissue through local mass effect. The diagnostic, therapeutic and prognostic implication of differential growth patterns on MRI remain unknown and are difficult to assess quantitatively.

Material and Methods

A web-based application allowing for image preprocessing and providing a comprehensive edge detection tool by means of quantifying tumor border delineation on T2-weighted images based on the canny edge detection algorithm was developed. A sigma value between 1 and 100 determined the threshold where tumor borders where not detected by the algorithm anymore, with 1 equating to the lowest threshold and thus detection of all edges contained in the image. Two experienced faculty members assigned sigma values to axial T2 images of a random sample of 20 WHO grade 2 astrocytomas, IDH-mutant and 1p/19q-non-codeleted. The sigma values were then compared with a binary, subjective rating by the same faculty staff according to the perceived predominant growth pattern (diffuse versus circumscript) of each glioma.

Results

When subjectively categorizing tumors binarily (diffuse versus circumscript), there was moderate interrater variability between observers (cohen’s kappa=0.6). Raters agreed in 16 of 20 cases, terming 7 gliomas unanimously diffuse and 9 gliomas circumscript. In 4 cases, the raters opinions diverged. The sigma values differed significantly between diffuse and circumscript tumors in both raters (rater 1, p=0.002; rater 2, p=0.018). For rater 1, the mean sigma difference between diffuse and circumscript tumors was 10.7 and 9.3 for rater 2.

Conclusion

Edge detection algorithms can be efficiently applied on MRI scans and are highly accurate in differentiating diffuse from circumscript gliomas. Objectification demands defining imaging criteria for diffuse and circumscript appearance of lower grade gliomas on MRI.

OS03.4.A In vivo dynamics and anti-tumor effects of EpCAM-directed CAR T-cells against brain metastases from lung cancer

Background

Lung cancer patients are at a particularly high risk for brain metastases, and a considerable number of affected patients succumb due to their intracranial disease. Chimeric Antigen Receptor (CAR) T-cells emerged as a powerful class of cell-based immunotherapy for hematological malignancies. However, it remains unclear whether CAR T-cells also represent a safe and effective therapeutic option for brain metastases.

Material and Methods

A fully syngeneic orthotopic cerebral metastasis model in mice was established by combining a chronic cranial window with repetitive intracerebral two-photon laser scanning microscopy. This approach enabled the in vivo characterization of red fluorescent CAR T-cells and tumor cells on a single-cell level over weeks. Intraparenchymal injection of Lewis lung carcinoma cells (expressing the tumor cell-antigen EpCAM) was performed, and CAR T-cells directed against EpCAM (EpCAMCAR T-cells) were injected into the adjacent brain parenchyma after solid brain tumors have formed.

Results

All mice had visible tumor take four days after the intracranial tumor cell injection, and rapid growth of solitary lesions was seen in the following days. No toxicities mediated by intracranially injected EpCAMCAR T-cells were encountered. In mice treated with EpCAMCAR T-cells, we initially observed substantial CAR T-cell accumulation within the tumor compared to controls (median number: 1700 versus 939 cells/mm2; p = 0.007). This was paralleled by lower velocities of EpCAMCAR T-cells, characterizing T-cell receptor (TCR)-mediated antitumor cytotoxicity due to long-lasting contacts between effector immune cells and tumor cells. Consequently, treatment with EpCAMCAR T-cells resulted in reduced tumorous growth as determined per in vivo microscopy (median tumor area on day 10: 1.8 versus 10.8 mm2; p = 0.001) and immunohistochemistry of excised brains (median tumor volume on day 10: 3.6 versus 33.2 mm3; p = 0.001). However, the number of EpCAM-directed CAR T-cells within the tumor markedly decreased during the observation period, pointing towards insufficient persistence of EpCAM-directed CAR T-cells. In line with these findings, survival was prolonged in mice receiving EpCAMCAR T-cells but long-lasting remission was rare (median survival: 15 versus 13 days; p = 0.012).

Conclusion

Our findings indicate that CAR T-cells injected into the cerebral parenchyma may induce relevant anti-tumor effects in brain metastases from lung cancer. Due to the translational nature of our study, prospective clinical cohorts appear warranted. Strategies improving the intratumoral persistence of CAR T-cells in brain metastases may be utilized to further boost the success of such promising therapy.

P11.51.B Initial temozolomide monotherapy without radiotherapy might be of limited benefit in the treatment of astrocytoma, IDH-mutant, CNS WHO grade 2 and 3

Background

The role of temozolomide chemotherapy alone in isocitrate dehydrogenase (IDH-) mutant astrocytomas has not been conclusively determined. Radiotherapy might be superior to temozolomide alone. Recent studies have linked temozolomide therapy with poor clinical course and induction of hypermutation in IDH-mutant gliomas.

Material and Methods

In this retrospective, single-center study, 183 patients with astrocytoma, IDH-mutant, CNS WHO grade 2 or 3 according to WHO 2021 and diagnosed between 2000 and 2019 were included. Patients initially monitored by means of a wait-and-scan strategy, or treated with radiotherapy alone, or receiving temozolomide alone after histological sampling through biopsy or tumor resection were studied. Patient-related, clinical and imaging data were correlated with progression-free and overall survival. A matched-pair analysis accounting for post-surgical tumor volume was conducted.

Results

No significant differences in median age and clinical status at diagnosis was seen. WHO grades were balanced between patients treated with radiotherapy and temozolomide, but the proportion of WHO grade 2 gliomas was higher in the wait-and-scan cohort. Radiotherapy was associated with significantly longer overall survival than temozolomide (in years, 14.4 vs 10.7; p=0.02) and longer progression-free survival than temozolomide (in years, 6.2 vs 3.4, p=0.02) and wait-and-scan strategies (in years, 6.2 vs 4; p=0.03). Comparing wait-and-scan with temozolomide, survival was significantly longer in the wait-and-scan cohort (in years, not reached vs 10.7, p&lt;0.0001). An analysis of WHO grade 2 astrocytomas only also showed superior survival in the wait-and-scan cohort as compared to temozolomide (p=0.02). Of note PFS was similar overall and in WHO grade 2 astrocytomas.

Conclusion

The results suggest superiority of radiotherapy alone over temozolomide alone or wait-and-scan strategies in IDH-mutant WHO grade 2 and 3. Recent study results indicating that temozolomide might compromise prognosis in some IDH-mutant gliomas might be supported by our data, although caution in interpretation of retrospective data is required. The potential negative effects may only be apparent in the long-term.

Physician Health: Results and Caveats from Surveys in Austria, Switzerland and Germany

Background: Surveys assessing alcohol use among physicians most commonly employed the Alcohol Use Disorders Identification Test (AUDIT) or the AUDIT-C. As with other screeners, prevalence estimation is dependent on the accuracy of the test as well as choice of the cut-off value. The aim of the current study is to use samples from various countries derive more precise prevalence estimates of alcohol problems in physicians by correcting for false positive and false negative results using samples from various countries Method: At the Congress of the German Association of Psychiatry, Psychotherapy and Psychosomatics, 2005 in Berlin, 1800 questionnaires, which included the AUDIT-C were distributed among the attending participants. 936 questionnaires (52%) were returned. Also, the data are compared to a second study, performed in Salzburg, Austria to further elucidate the situation. The screening results will be presented and compared to the values when using a correction- formula using data from a general population sample on sensitivity and specificity of the AUDIT-C. Results: Based on the results of AUDIT-C and using a cut-off of 5 for both sexes, 24.1% of the sample of 887 physicians of the German sample are problematic drinkers (14.7% in female and 32 % in male physicians). Using a correction formula leads to markedly lower rates: 6.1% (all), 3.7% (female), 8.1% (male). Discussion: In this large sample, findings clearly confirm that uncorrected screening results lead to severe over-estimation of the prevalence of problematic drinking in physicians. The corrected prevalence rates are lower than in the general population.

Finding the Optimal Surgical Incision Pattern-A Biomechanical Study

The closure of wounds and subsequent optimal wound healing is essential to any successful surgical intervention. Especially on parts of the body with limited possibilities for local reconstruction, optimal distribution of load is essential. The aim of the present study was therefore to examine three different incision patterns, conventional straight, Lazy-S and Zigzag, with regard to their biomechanical stability and mode of failure on a porcine skin model. Our results demonstrate the superior biomechanical stability of Lazy-S and Zigzag incision patterns with perpendicular suture placement. This holds true, in particular, for Zigzag incisions, which showed the highest values for all parameters assessed. Moreover, the observed superior stability of Lazy-S and Zigzag incision patterns was diminished when sutures were placed in tensile direction. The conventional straight incision represents the standard access for a large number of surgical procedures. However, we were able to demonstrate the superior biomechanical stability of alternative incision patterns, in particular the Zigzag incision. This is most likely caused by an improved distribution of tensile force across the wound due to the perpendicular placement of sutures. Moreover, this technique offers additional advantages, such as a better overview of the operated area as well as several cosmetic improvements. We therefore advocate that the surgeon should consider the use of a Zigzag incision over a conventional straight incision pattern.

MRI-based contrast clearance analysis shows high differentiation accuracy between radiation-induced reactions and progressive disease after cranial radiotherapy

Background

Pseudoprogression (PsP) or radiation necrosis (RN) may frequently occur after cranial radiotherapy and show a similar imaging pattern compared with progressive disease (PD). We aimed to evaluate the diagnostic accuracy of magnetic resonance imaging-based contrast clearance analysis (CCA) in this clinical setting.

Patients and methods

Patients with equivocal imaging findings after cranial radiotherapy were consecutively included into this monocentric prospective study. CCA was carried out by software-based automated subtraction of imaging features in late versus early T1-weighted sequences after contrast agent application. Two experienced neuroradiologists evaluated CCA with respect to PsP/RN and PD being blinded for histological findings. The radiological assessment was compared with the histopathological results, and its accuracy was calculated statistically.

Results

A total of 33 patients were included; 16 (48.5%) were treated because of a primary brain tumor (BT), and 17 (51.1%) because of a secondary BT. In one patient, CCA was technically infeasible. The accuracy of CCA in predicting the histological result was 0.84 [95% confidence interval (CI) 0.67-0.95; one-sided P = 0.051; n = 32]. Sensitivity and specificity of CCA were 0.93 (95% CI 0.66-1.00) and 0.78 (95% CI 0.52-0.94), respectively. The accuracy in patients with secondary BTs was 0.94 (95% CI 0.71-1.00) and nonsignificantly higher compared with patients with primary BT with an accuracy of 0.73 (95% CI 0.45-0.92), P = 0.16.

Conclusions

In this study, CCA was a highly accurate, easy, and helpful method for distinguishing PsP or RN from PD after cranial radiotherapy, especially in patients with secondary tumors after radiosurgical treatment.

•

CCA is accurate in distinguishing treatment reactions from true PD.

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CCA was more accurate for irradiated metastases than primary BTs.

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CCA is not feasible for lesions with no contrast media uptake.

Diagnostic Yield and Complication Rate of Stereotactic Biopsies in Precision Medicine of Gliomas

Background

An integrated diagnosis consisting of histology and molecular markers is the basis of the current WHO classification system of gliomas. In patients with suspected newly diagnosed or recurrent glioma, stereotactic biopsy is an alternative in cases in which microsurgical resection is deemed to not be safely feasible or indicated. In this retrospective study, we aimed to analyze both the diagnostic yield and the safety of a standardized biopsy technique.

Material and Methods

The institutional database was screened for frame-based biopsy procedures (January 2016 until March 2021). Only patients with a suspected diagnosis of glioma based on imaging were included. All tumors were classified according to the current WHO grading system. The clinical parameters, procedural complications, histology, and molecular signature of the tissues obtained were assessed.

Results

Between January 2016 and March 2021, 1,214 patients underwent a stereotactic biopsy: 617 (50.8%) for a newly diagnosed lesion and 597 (49.2%) for a suspected recurrence. The median age was 56.9 years (range 5 months−94.4 years). Magnetic resonance imaging (MRI)-guidance was used in 99.3% of cases and additional positron emission tomography (PET)-guidance in 34.3% of cases. In total, stereotactic serial biopsy provided an integrated diagnosis in 96.3% of all procedures. The most frequent diagnoses were isocitrate dehydrogenase (IDH) wildtype glioblastoma (n = 596; 49.2%), oligodendroglioma grade 2 (n = 109; 9%), astrocytoma grade 3 (n = 108; 8.9%), oligodendroglioma grade 3 (n = 76; 6.3%), and astrocytoma grade 2 (n = 66; 5.4%). A detailed determination was successful for IDH 1/2 mutation in 99.4% of cases, for 1p/19q codeletion in 97.4% of cases, for TERT mutation in 98.9% of cases, and for MGMT promoter methylation in 99.1% of cases. Next-generation sequencing was evaluable in 64/67 (95.5%) of cases and DNA methylome analysis in 41/44 (93.2%) of cases. Thirteen (1.1%) cases showed glial tumors that could not be further specified. Seventy-three tumors were different non-glioma entities, e.g., of infectious or inflammatory nature. Seventy-five out of 597 suspected recurrences turned out to be post-therapeutic changes only. The rate of post-procedural complications with clinical symptoms of the Common Terminology Criteria for Adverse Events (CTCAE) grade 3 or higher was 1.2% in overall patients and 2.6% in the subgroup of brainstem biopsies. There was no fatal outcome in the entire series.

Conclusion

Image-guided stereotactic serial biopsy enables obtaining reliable histopathological and molecular diagnoses with a very low complication rate even in tumors with critical localization. Thus, in patients not undergoing microsurgical resection, this is a valuable tool for precision medicine of patients with glioma.

Phase I/II trial of meclofenamate in progressive MGMT-methylated glioblastoma under temozolomide second-line therapy-the MecMeth/NOA-24 trial

Background

Glioblastoma is the most frequent and malignant primary brain tumor. Even in the subgroup with O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation and favorable response to first-line therapy, survival after relapse is short (12 months). Standard therapy for recurrent MGMT-methylated glioblastoma is not standardized and may consist of re-resection, re-irradiation, and chemotherapy with temozolomide (TMZ), lomustine (CCNU), or a combination thereof. Preclinical results show that meclofenamate (MFA), originally developed as a nonsteroidal anti-inflammatory drug (NSAID) and registered in the USA, sensitizes glioblastoma cells to temozolomide-induced toxicity via inhibition of gap junction-mediated intercellular cytosolic traffic and demolishment of tumor microtube (TM)-based network morphology.

Methods

In this study, combined MFA/TMZ therapy will be administered (orally) in patients with first relapse of MGMT-methylated glioblastoma. A phase I component (6–12 patients, 2 dose levels of MFA + standard dose TMZ) evaluates safety and feasibility and determines the dose for the randomized phase II component (2 × 30 patients) with progression-free survival as the primary endpoint.

Discussion

This study is set up to assess toxicity and first indications of efficacy of MFA repurposed in the setting of a very difficult-to-treat recurrent tumor. The trial is a logical next step after the identification of the role of resistance-providing TMs in glioblastoma, and results will be crucial for further trials targeting TMs. In case of favorable results, MFA may constitute the first clinically feasible TM-targeted drug and therefore might bridge the idea of a TM-targeted therapeutic approach from basic insights into clinical reality.

Trial registration

EudraCT 2021-000708-39. Registered on 08 February 2021

Liquid biopsy in gliomas: A RANO review and proposals for clinical applications

BACKGROUND

There is an extensive literature highlighting the utility of blood-based liquid biopsies in several extracranial tumors for diagnosis and monitoring.

METHODS

The RANO (Response Assessment in Neuro-Oncology) group developed a multidisciplinary international Task Force to review the English literature on liquid biopsy in gliomas focusing on the most frequently used techniques, that is circulating tumor DNA, circulating tumor cells, and extracellular vesicles in blood and CSF.

RESULTS

ctDNA has a higher sensitivity and capacity to represent the spatial and temporal heterogeneity in comparison to circulating tumor cells. Exosomes have the advantages to cross an intact blood-brain barrier and carry also RNA, miRNA, and proteins. Several clinical applications of liquid biopsies are suggested: to establish a diagnosis when tissue is not available, monitor the residual disease after surgery, distinguish progression from pseudoprogression, and predict the outcome.

CONCLUSIONS

There is a need for standardization of biofluid collection, choice of an analyte, and detection strategies along with rigorous testing in future clinical trials to validate findings and enable entry into clinical practice.

Differential Spatial Distribution of TSPO or Amino Acid PET Signal and MRI Contrast Enhancement in Gliomas

Simple Summary

Radiotracers targeting the translocator protein (TSPO) have recently gained substantial interest, since TSPO is overexpressed in malignant gliomas, where it correlates inversely with patient’s survival. The high-affinity TSPO PET ligand [¹⁸F]GE180 was found to depict tumor areas with a remarkably high contrast and has been shown to provide non-invasive information on histological tumor grades. Yet, its significance was questioned with the argument, that the high contrast may solely arise from nonspecific accumulation in tissue supplied by leaky vessels. This study aimed to address this question by providing a detailed evaluation of spatial associations between TSPO and amino acid PET with relative contrast enhancement in T1-weighted MRI. The results show that [¹⁸F]GE180 contrast does not reflect a disrupted blood–brain barrier (BBB) only and that multi-modal imaging generates complementary information, which may better depict spatial heterogeneity of tumor biology and may be used to individualize the therapy for each patient.

Abstract

In this study, dual PET and contrast enhanced MRI were combined to investigate their correlation per voxel in patients at initial diagnosis with suspected glioblastoma. Correlation with contrast enhancement (CE) as an indicator of BBB leakage was further used to evaluate whether PET signal is likely caused by BBB disruption alone, or rather attributable to specific binding after BBB passage. PET images with [¹⁸F]GE180 and the amino acid [¹⁸F]FET were acquired and normalized to healthy background (tumor-to-background ratio, TBR). Contrast enhanced images were normalized voxel by voxel with the pre-contrast T1-weighted MRI to generate relative CE values (rCE). Voxel-wise analysis revealed a high PET signal even within the sub-volumes without detectable CE. No to moderate correlation of rCE with TBR voxel-values and a small overlap as well as a larger distance of the hotspots delineated in rCE and TBR-PET images were detected. In contrast, voxel-wise correlation between both PET modalities was strong for most patients and hotspots showed a moderate overlap and distance. The high PET signal in tumor sub-volumes without CE observed in voxel-wise analysis as well as the discordant hotspots emphasize the specificity of the PET signals and the relevance of combined differential information from dual PET and MRI images.

Extent, pattern, and prognostic value of MGMT promotor methylation: does it differ between glioblastoma and IDH-wildtype/TERT-mutated astrocytoma?

Introduction

The cIMPACT-NOW update 6 first introduced glioblastoma diagnosis based on the combination of IDH-wildtype (IDHwt) status and TERT promotor mutation (pTERTmut). In glioblastoma as defined by histopathology according to the WHO 2016 classification, MGMT promotor status is associated with outcome. Whether this is also true in glioblastoma defined by molecular markers is yet unclear.

Methods

We searched the institutional database for patients with: (1) glioblastoma defined by histopathology; and (2) IDHwt astrocytoma with pTERTmut. MGMT promotor methylation was analysed using methylation-specific PCR and Sanger sequencing of CpG sites within the MGMT promotor region.

Results

We identified 224 patients with glioblastoma diagnosed based on histopathology, and 54 patients with IDHwt astrocytoma with pTERTmut (19 astrocytomas WHO grade II and 38 astrocytomas WHO grade III). There was no difference in the number of MGMT methylated tumors between the two cohorts as determined per PCR, and also neither the number nor the pattern of methylated CpG sites differed as determined per Sanger sequencing. Progression-free (PFS) and overall survival (OS) was similar between the two cohorts when treated with radio- or chemotherapy. In both cohorts, higher numbers of methylated CpG sites were associated with favourable outcome.

Conclusions

Extent and pattern of methylated CpG sites are similar in glioblastoma and IDHwt astrocytoma with pTERTmut. In both tumor entities, higher numbers of methylated CpG sites appear associated with more favourable outcome. Evaluation in larger prospective cohorts is warranted.

Clinical Reasoning: A 64-Year-Old Man With History of Meningitis Presenting With Proximal Weakness of the Arms

A 64-year-old man presented for evaluation of proximally pronounced weakness of the arms with preserved facial and lower extremity strength. Symptoms slowly developed over the last two years, and the patient's history was notable for severe Listeria monocytogenes meningitis four years prior to presentation, which was adequately treated with antibiotics. On examination, symptoms clinically reassembled 'man-in-the-barrel' syndrome and localized to the cervicothoracic central cord. Blood analysis was unremarkable, and CSF analysis showed no recurrent or persistent infection. Spinal MRI revealed pockets of sequestered CSF from C3 to C4 and areas of CSF space effacement from C3 to T12. MRI findings were interpreted as cord tethering suggestive of adhesive arachnoiditis. CT myelogram showed insufficient contrast agent migration above T10 and contour irregularities of the conus medullaris, confirming the postulated pathomechanism of cord tethering. Final diagnosis was therefore cervicothoracic central cord damage due to cord tethering in the setting of postinfectious adhesive arachnoiditis following bacterial meningitis. The patient failed a course of pulsed methylprednisolone therapy, and symptoms progressed. Best supportive care was provided. The clinical presentation of adhesive arachnoiditis is variable, and advanced imaging techniques and invasive studies such as CT myelogram may be required to establish the diagnosis. Timely diagnosis is warranted as early surgical or medical therapy can improve symptoms.

TAMI-02. DEPLETION OF INTRATUMORAL TUMOR-ASSOCIATED MACROPHAGES AND MICROGLIA (TAM/M) IMPROVES CHECKPOINT-INHIBITION THERAPY FOR BRAIN METASTASIS FROM LUNG CANCER

BACKGROUND

Brain metastases dramatically limit prognosis of lung cancer patients. Unlike systemic disease, brain metastases from lung cancer poorly respond to checkpoint-inhibition therapy. Targeting the immunosuppressive tumor-associated macrophages and microglia (TAM/M) and their receptor CSF1R may increase efficacy of checkpoint-inhibitors.

METHODS

Cranial windows were prepared in fully immunocompetent, transgenic CX3CR1GFP/wt-mice with green-fluorescent TAM/M. Intracranial injection of red-fluorescent Lewis Lung Carcinoma-cells was performed, and mice received one of the following three treatments: PD1-inhibition only (n = 8); PD1-inhibition combined with an anti-CSF1R-antibody (exhibiting limited blood-brain-barrier permeability under physiologic conditions, n = 8); or PD1-inhibition combined with a small molecular CSF1R-inhibitor (exhibiting high blood-brain-barrier permeability, n = 7). Tumor growth and TAM/M were followed by repetitive two-photon laser-scanning-microscopy over weeks.

RESULTS

Following intracranial injection, metastases were detected in all three treatment groups within eight days. In mice receiving PD1-inhibition only, metastases showed exponential growth which was paralleled by intra- and peritumoral accumulation of TAM/M. Treatment with an anti-CSF1R-antibody resulted in significantly lower numbers of intratumoral TAM/M given increased tumoral blood-brain-barrier permeability, but did not substantially affect peritumoral TAM/M or TAM/M localized in the healthy contralateral hemisphere. In contrast, treatment with a small molecular CSF1R-inhibitor not only reduced the number of intratumoral TAM/M, but also of peritumoral and contralateral TAM/M. Compared to PD1-inhibition only, the addition of either an anti-CSF1R-antibody or a small molecular CSF1R-inhibitor resulted in decreased tumor growth (tumor size on day 12: 8.3 mm2 (PD1-inhibition only) versus 0.9 mm2 (PD1-inhibition + anti-CSF1R-antibody) versus 2.5 mm2 (PD1-inhibition + small molecular CSF1R-inhibitor)) (p = 0.01). The beneficial effects of the small molecular CSF1R-inhibitor in reducing tumor growth were similar to those of the anti-CSF1R-antibody.

CONCLUSION

Targeting intratumoral TAM/M using CSF1-inhibition may increase the efficacy of checkpoint-inhibition therapy for cerebral lung cancer metastases. This approach warrants further evaluation in preclinical and clinical studies.

PATH-32. EXTENT, PATTERN, AND PROGNOSTIC VALUE OF MGMT PROMOTOR METHYLATION: DOES IT DIFFER BETWEEN GLIOBLASTOMA AND IDH-WILDTYPE/TERT-MUTATED ASTROCYTOMA?

INTRODUCTION

The cIMPACT-NOW update 6 introduced glioblastoma diagnosis based on the combination of IDH-wildtype (IDHwt) status and TERT promotor mutation (pTERTmut). In glioblastoma as defined by histopathology according to the WHO 2016 classification, MGMT promotor status is associated with outcome. Whether this is also true in glioblastoma defined by molecular markers is yet unclear.

METHODS

We searched the institutional database for patients with: 1.) glioblastoma defined by histopathology; and 2.) IDHwt astrocytoma with pTERTmut. MGMT promotor methylation was analysed using methylation-specific PCR and Sanger sequencing of CpG sites within the MGMT promotor region.

RESULTS

We identified 224 patients with glioblastoma diagnosed based on histopathology, and 71 patients with IDHwt astrocytoma with pTERTmut (32 astrocytomas WHO grade II and 39 astrocytomas WHO grade III). There was no difference in the number of MGMT methylated tumors between the two groups as determined per PCR, and also neither the number nor the pattern of methylated CpG sites differed as determined per Sanger sequencing. Progression-free (PFS) and overall survival (OS) was similar between the two groups. Surgery was associated with improved overall survival in IDHwt astrocytoma with pTERTmut. In patients treated with radiochemotherapy or radiotherapy, higher numbers of methylated CpG sites were associated with favourable outcome in both groups.

CONCLUSION

Extent and pattern of methylated CpG sites are similar in glioblastoma and IDHwt astrocytoma with pTERTmut. In both groups, higher numbers of methylated CpG sites are associated with favourable outcome when radio/chemotherapy is administered. Surgery may form the basis for favourable outcome.

NIMG-65. RESTING-STATE FUNCTIONAL MRI DEMONSTRATES DAMAGE TO FUNCTIONAL CONNECTIVITY IN MENINGIOMA PATIENTS WITH PERIFOCAL EDEMA

BACKGROUND

Meningiomas are common intracranial tumors which usually carry a benign prognosis. Some meningiomas cause perifocal edema which might indicate that this subset could interfere with normal brain function. Resting-state functional MRI (rsfMRI) can be used to assess whole brain functional connectivity (fc) which can be used as a marker for disease severity in patients with intracranial tumors, as was recently shown by our group in a cohort of glioma patients. In this study, we investigated whether the presence of perifocal edema in preoperative patients with meningioma leads to fc.

METHODS

Patients with suspected meningioma were prospectively included and functional resting state MRI scans were obtained. The resulting data was processed according to our recently published method and abnormality of fc was quantified for each individual patient. Abnormality of fc was then correlated with tumor and edema volume as well as WHO grade.

RESULTS

26 patients (23 WHO grade I, 3 WHO grade II) were included. 13 patients had perifocal edema. There was a highly significant correlation between edema volume and higher abnormality of fc both in the lesional and the contra-lesional hemisphere (r=0.51, p=0.008 and r=0.61, p=0.001). Patients with no perifocal edema showed only very low abnormality of fc. Tumor volume was not correlated with abnormal fc in both the lesional and the contralesional hemispheres (r=0.23, p=0.27 and r=0.28, p=0.17). There was also no significant correlation between WHO grade and abnormality of fc.

CONCLUSION

RsfMRI showed significant abnormal fc in meningioma patients with perifocal edema in contrast to patients without edema, independent of tumor volume. This demonstrates that the presence of edema but not the tumor volume is relevant for disturbances of fc.

Trabectedin for recurrent WHO grade 2 or 3 meningioma: a randomized phase 2 study of the EORTC Brain Tumor Group (EORTC-1320-BTG)

BACKGROUND

No systemic treatment has been established for meningioma progressing after local therapies.

METHODS

This randomized, multicenter, open-label, phase 2 study included adult patients with recurrent WHO grade 2 or 3 meningioma. Patients were 2:1 randomly assigned to intravenous trabectedin (1.5 mg/m 2 every three weeks) or local standard of care (LOC). The primary endpoint was progression-free survival (PFS). Secondary endpoints comprised overall survival (OS), objective radiological response, safety, quality of life (QoL) assessment using the QLQ-C30 and QLQ-BN20 questionnaires, and we performed tissue-based exploratory molecular analyses.

RESULTS

Ninety patients were randomized (n=29 in LOC, n=61 in trabectedin arm). With 71 events, median PFS was 4.17 months in the LOC and 2.43 months in the trabectedin arm (hazard ratio [HR]=1.42; 80% CI, 1.00-2.03; p=0.294) with a PFS-6 rate of 29.1% (95% CI, 11.9%-48.8%) and 21.1% (95% CI, 11.3%-32.9%), respectively. Median OS was 10.61 months in the LOC and 11.37 months in the trabectedin arm (HR=0.98; 95% CI, 0.54-1.76; p=0.94). Grade ≥3 adverse events occurred in 44.4% patients in the LOC and 59% of patients in the trabectedin arm. Enrolled patients had impeded global QoL and overall functionality and high fatigue before initiation of systemic therapy. DNA methylation class, performance status, presence of a relevant co-morbidity, steroid use, and right hemisphere involvement at baseline were independently associated with OS.

CONCLUSIONS

Trabectedin did not improve PFS and OS and was associated with higher toxicity than LOC treatment in patients with non-benign meningioma. Tumour DNA methylation class is an independent prognostic factor for OS.

Subventricular zone involvement is associated with worse outcome in glioma WHO grade 2 depending on molecular markers

Neural stem cells within the subventricular zone were identified as cells of origin driving growth of high-grade gliomas, and anatomical involvement of the subventricular zone has been associated with an inferior clinical outcome. Whether the association between poor outcome and subventricular zone involvement also applies to glioma of lower grades is unclear. We therefore analysed a retrospective cohort of 182 patients with glioma grade 2 (according to the WHO 2016 classification) including 78 individuals (43%) with subventricular zone involvement. Patients with and without subventricular zone involvement did not differ in regard to demographics, histopathology, and molecular markers. Notably, subventricular zone involvement was a negative prognostic marker for malignant progression and overall survival on uni- and multivariate analysis. When patients were stratified according to the cIMPACT-NOW update 6, subventricular zone involvement was negatively associated with outcome in IDH-wildtype astrocytomas and 1p19q-codeleted oligodendrogliomas but not in IDH-mutant astrocytomas. Collectively, subventricular zone involvement may represent a risk factor for worse outcome in glioma WHO grade 2 depending on the molecular tumor signature. The present data confirm the relevance of molecular glioma classifications as proposed by the cIMPACT-NOW update 6. These findings warrant evaluation in prospective cohorts.

In vivo two-photon characterization of tumor-associated macrophages and microglia (TAM/M) and CX3CR1 during different steps of brain metastasis formation from lung cancer

Brain metastases frequently occur in lung cancer and dramatically limit prognosis of affected patients. The influence of tumor-associated macrophages and microglia (TAM/M) and their receptor CX3CR1 on different steps of brain metastasis formation from lung cancer is poorly characterized. We established a syngeneic orthotopic cerebral metastasis model in mice by combining a chronic cranial window with repetitive intravital 2-photon laser scanning microscopy. This allowed in vivo tracking of fluorescence-expressing tumor cells and TAM/M on a single-cell level over weeks. Intracarotid injection of red tdTomato-fluorescent Lewis lung carcinoma cell was performed in transgenic mice either proficient or deficient for CX3CR1. After intracarotid cell injection, intravascular tumor cells extravasated into the brain parenchyma and formed micro- and mature macrometastases. We observed potential phagocytosis of extravasated tumor cells by TAM/M. However, during later steps of metastasis formation, these anti-tumor effects diminished and were paralleled by TAM/M accumulation and activation. Although CX3CR1 deficiency resulted in a lower number of extravasated tumor cells, progression of these extravasated cells into micro metastases was more efficient. Overall, this resulted in a comparable number of mature macrometastases in CX3CR1-deficient and -proficient mice. Our findings indicate that unspecific inhibition of CX3CR1 might not be a suitable therapeutic option to prevent dissemination of lung cancer cells to the brain. Given the close interaction between TAM/M and tumor cells during metastasis formation, other therapeutic approaches targeting TAM/M function may warrant further evaluation. The herein established orthotopic mouse model may be a useful tool to evaluate such concepts in vivo.