Petr Pospíšil

Why and how to spare the hippocampus during brain radiotherapy: the developing role of hippocampal avoidance in cranial radiotherapy

The goal of this review is to summarize the rationale for and feasibility of hippocampal sparing techniques during brain irradiation. Radiotherapy is the most effective non-surgical treatment of brain tumors and with the improvement in overall survival for these patients over the last few decades, there is an effort to minimize potential adverse effects leading to possible worsening in quality of life, especially worsening of neurocognitive function. The hippocampus and associated limbic system have long been known to be important in memory formation and pre-clinical models show loss of hippocampal stem cells with radiation as well as changes in architecture and function of mature neurons. Cognitive outcomes in clinical studies are beginning to provide evidence of cognitive effects associated with hippocampal dose and the cognitive benefits of hippocampal sparing. Numerous feasibility planning studies support the feasibility of using modern radiotherapy systems for hippocampal sparing during brain irradiation. Although results of the ongoing phase II and phase III studies are needed to confirm the benefit of hippocampal sparing brain radiotherapy on neurocognitive function, it is now technically and dosimetrically feasible to create hippocampal sparing treatment plans with appropriate irradiation of target volumes. The purpose of this review is to provide a brief overview of studies that provide a rationale for hippocampal avoidance and provide summary of published feasibility studies in order to help clinicians prepare for clinical usage of these complex and challenging techniques.

Advanced MRI increases the diagnostic accuracy of recurrent glioblastoma: Single institution thresholds and validation of MR spectroscopy and diffusion weighted MR imaging

The accurate identification of glioblastoma progression remains an unmet clinical need. The aim of this prospective single-institutional study is to determine and validate thresholds for the main metabolite concentrations obtained by MR spectroscopy (MRS) and the values of the apparent diffusion coefficient (ADC) to enable distinguishing tumor recurrence from pseudoprogression. Thirty-nine patients after the standard treatment of a glioblastoma underwent advanced imaging by MRS and ADC at the time of suspected recurrence — median time to progression was 6.7 months. The highest significant sensitivity and specificity to call the glioblastoma recurrence was observed for the total choline (tCho) to total N-acetylaspartate (tNAA) concentration ratio with the threshold ≥ 1.3 (sensitivity 100.0% and specificity 94.7%). The ADCmean value higher than 1313 × 10− 6 mm2/s was associated with the pseudoprogression (sensitivity 98.3%, specificity 100.0%). The combination of MRS focused on the tCho/tNAA concentration ratio and the ADCmean value represents imaging methods applicable to early non-invasive differentiation between a glioblastoma recurrence and a pseudoprogression. However, the institutional definition and validation of thresholds for differential diagnostics is needed for the elimination of setup errors before implementation of these multimodal imaging techniques into clinical practice, as well as into clinical trials.

Post-WBRT cognitive impairment and hippocampal neuronal depletion measured by in vivo metabolic MR spectroscopy: Results of prospective investigational study

BACKGROUND AND PURPOSE The aim of this prospective study is to evaluate post-whole brain radiotherapy (WBRT) changes in hippocampal concentration of N-acetylaspartate (h-tNAA) as a marker of neuronal loss and to correlate those changes to neurocognitive function. MATERIAL AND METHODS Thirty-five patients with brain metastases underwent baseline single slice multi-voxel MR spectroscopy (MRS) examination for measurement of hippocampal h-tNAA together with baseline battery of neurocognitive tests focused on memory (Auditory Verbal Learning Test and Brief Visuospatial Memory Test - Revised) as well as quality of life questionnaires (EORTC QLQ-C30 a EORTC QLQ-BN20). Eighteen patients completed follow-up evaluation four months after standard WBRT (2 laterolateral fields, 10×3.0Gy, 6MV photons) and were included in this analysis. MRS and cognitive examinations were repeated and compared to baseline measurements. RESULTS Statistically significant decreases in h-tNAA were observed in the right (8.52-7.42mM; -12.9%, 95%CI: -7.6 to -16.4%) as well as in the left hippocampus (8.64-7.60mM; -12%, 95%CI: -7.9 to -16.2%). Statistically significant decline was observed in all AVLT and BVMT-R subtests with exception of AVLT_Recognition. Quality of life declined after WBRT (mean Δ -14.1±20.3 points in transformed 0-100 point scale; p=0.018) with no correlation to changes in hippocampal metabolite concentrations. Moderate positive correlation was observed between left h-tNAA concentration decrease and AVLT_TR decline (r=+0.32; p=0.24) as well as with AVLT_DR (r=+0.33; p=0.22) decline. Changes in right h-tNAA/Cr negatively correlated with AVLT_DR (r=-0.48; p=0.061). No correlation between right hippocampus h-tNAA and memory decline (AVLT) was observed. CONCLUSIONS Our results suggest hippocampal NAA concentrations decline after WBRT and MRS may be a useful biomarker for monitoring neuronal loss after radiotherapy.

Whole brain radiotherapy: Consequences for personalized medicine

Several studies focusing on brain irradiation are in progress. Reflecting updates of relevant outcomes in palliative treatment of patients suffering from brain metastases, the primary objective of these studies is the evaluation of neurocognitive function and quality of life. Improvements of technology in radiation oncology allows us to spare the hippocampal region while appropriately irradiating other parts of brain tissue. Irradiation of the hippocampus region is likely to lead to manifestations of adverse events with a subsequent impact on patients quality of life, which is in fact an improper approach in palliative medicine. Ongoing studies evaluate results of hippocampus avoiding radiotherapy compared to standard whole brain radiotherapy. Incorporation of neurocognitive function assessment may result in the confirmation of superiority of sparing the region of hippocampus and thus change current style of providing brain irradiation.

Volumetric modulated arc therapy for hippocampal-sparing radiotherapy in transformed low-grade glioma: A treatment planning case report

Timing of radiotherapy for low-grade gliomas is still controversial due to concerns of possible adverse late effects. Prevention of possible late cognitive sequelae by hippocampal avoidance has shown promise in phase II trials. A patient with progressive low-grade glioma with gradual dedifferentiation into anaplastic astrocytoma is presented along with description of radiotherapy planning process attempting to spare the hippocampus. To our knowledge, this is the first described case using volumetric modulated arc technique to spare hippocampus during transformed low-grade glioma radiotherapy. Using modern intensity-modulated radiotherapy systems it is possible to selectively spare hippocampus together with other standard organs at risk. For selected patients, an attempt to spare hippocampus can be considered as long as other dose characteristics are not significantly compromised compared to standard treatment plan created without any effort to avoid hippocampus.

Patterns of failure after brain metastases radiotherapy: reflections on the importance for treatment and clinical trials reporting

In many ongoing clinical trials, new strategies for radiotherapy of brain metastases are currently being investigated. A post surgical focal cavity stereotactic radiosurgery and the developing role of a hippocampal-sparing whole brain radiotherapy are of the highest importance. The evaluation of spatial patterns of metastases failure after radiotherapy is a powerful tool for assessing the potential benefit of new different radiotherapy approaches, which enables to identify possible directions leading to better radiotherapy techniques and to modify general management for newly diagnosed brain metastases. The purpose of this article is to present a mix between trial data and philosophical point of view for discussion about the importance of systematic evaluation of spatial patterns of failure in all ongoing trials investigating new approaches in local brain metastases treatment.

Radiotherapy of glioblastoma 15 years after the landmark Stupp’s trial: more controversies than standards?

Abstract Background The current standard of care of glioblastoma, the most common primary brain tumor in adults, has remained unchanged for over a decade. Nevertheless, some improvements in patient outcomes have occurred as a consequence of modern surgery, improved radiotherapy and up-to-date management of toxicity. Patients from control arms (receiving standard concurrent chemoradiotherapy and adjuvant chemotherapy with temozolomide) of recent clinical trials achieve better outcomes compared to the median survival of 14.6 months reported in Stupp’s landmark clinical trial in 2005. The approach to radiotherapy that emerged from Stupp’s trial, which continues to be a basis for the current standard of care, is no longer applicable and there is a need to develop updated guidelines for radiotherapy within the daily clinical practice that address or at least acknowledge existing controversies in the planning of radiotherapy. The goal of this review is to provoke critical thinking about potentially controversial aspects in the radiotherapy of glioblastoma, including among others the issue of target definitions, simultaneously integrated boost technique, and hippocampal sparing. Conclusions In conjunction with new treatment approaches such as tumor-treating fields (TTF) and immunotherapy, the role of adjuvant radiotherapy will be further defined. The personalized approach in daily radiotherapy practice is enabled with modern radiotherapy systems.

The Role of Chemotherapy in the Treatment of Low-grade Gliomas

BACKGROUND The standard postsurgical options for low-grade gliomas include watchful waiting or radiotherapy depending on the risk factors for recurrence. The use of chemotherapy for the treatment of this disease is generally controversial, although the recently published results of the first of two large randomized phase III clinical trials (RTOG 9802 a EORTC 22033-26033), focusing on the evaluation of chemotherapy for the upfront treatment of newly diagnosed low-grade gliomas, are reassuring in this respect. The long-term results of a RTOG 9802 comparing radiotherapy alone with radiotherapy and six cycles of adjuvant PCV chemotherapy (procarbazine, lomustine, vincristine) in patients with high-risk low-grade gliomas will probably have an impact on daily clinical practice. The increase in median overall survival from 7.8 years to 13.3 years, mainly for patients with oligodendrogliomas, is unprecedented, but the toxicity of PCV is too high and molecular marker analysis remains inadequate. It is still unclear whether less toxic temozolomide can replace PCV and whether temozolomide can be used upfront alone instead of with radiotherapy. This question is addressed by the ongoing EORTC 22033-26033 study. The preliminary results show no significant difference in progression-free survival between patients receiving radiotherapy and those receiving temozolomide alone. Treatment with temozolomide was not associated with an improvement in cognitive function compared with treatment with radiotherapy. Despite limited follow-up, the study clearly confirmed the importance of molecular characterization of low-grade gliomas, as currently defined in the new 2016 WHO Classification of Tumors of the Central Nervous System. AIM The aim of the review is to summarize available information from listed key clinical trials of chemotherapy for low-grade gliomas and draw attention to unresolved issues concerning the use of chemotherapy for the treatment of this disease.Key words: glioma - astrocytoma - chemotherapy - PCV - temozolomide - RTOG 9802 This work was supported by MH CZ - RVO (MMCI, 00209805) and by project of the Ministry of Education, Youths and Sports of the Czech Republic CEITEC 2020 (LQ1601). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 21. 2. 2017Accepted: 20. 3. 2017.

Controversy in the Postoperative Treatment of Low-grade Gliomas

BACKGROUND The optimal treatment for low-grade gliomas remains controversial. Neurosurgery, radiotherapy, and chemotherapy are the main treatment options. Despite advances in oncology, there are still a lot of uncertainties, and the optimal sequences, combinations, and timings of these procedures have not yet been optimized. It is still unclear whether temozolomide can replace effective, but toxic PCV chemotherapy (procarbazine, lomustine, vincristine) and whether temozolomide can be used upfront alone instead of radiotherapy alone. Mature results from phase III trials (CODEL, EORTC 22033-26033) will provide answers to these questions. Correlative analyses of survival data and molecular marker findings (1p/19q codeletion, IDH1/2 mutation, and MGMT promoter methylation status) are essential. Due to slow progressive nature of the disease, all clinical trials with low-grade gliomas are complicated by the need for long-term follow-up to obtain valid mature data, which makes any new treatment procedures or developments in basic research developed during the course of closed clinical trials difficult to apply in daily clinical practice. An example is the recently published RTOG 9802 study evaluating the role of adjuvant PCV in combination with radiotherapy for the treatment of high-risk low-grade glioma patients where the recruitment of patients was initiated almost two decades ago. Health-related quality of life after treatment of patients with expected long-term survival is also very important and its maintenance is currently the focus of considerable interest. AIM The main objective of the present review is to summarize the results of key clinical trials and highlight controversial issues that could have an impact on future daily practice. Another aim is to discuss these issues in the light of newly established molecular markers from the new 2016 WHO Classification of Tumors of the Central Nervous System.Key words: glioma - astrocytoma - radiotherapy - temozolomide - PCV - cognition This work was supported by MH CZ - RVO (MMCI, 00209805) and by project of the Ministry of Education, Youths and Sports of the Czech Republic CEITEC 2020 (LQ1601). The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 21. 2. 2017Accepted: 20. 3. 2017.

P16.15DEVELOPING ROLE OF ADVANCED MRI TECHNIQUES FOR DIAGNOSIS OF HIGH-GRADE GLIOMA RELAPSE AFTER COMPLEX ONCOLOGY TREATMENT

PURPOSE/OBJECTIVES: High-grade gliomas (HGG) are the most common primary brain tumors of adults. Despite a multidisciplinary approach, HGGs frequently recur as a new gadolinium-enhanced MRI lesion at or near the site of the original tumor; thus, at the site of high-dose target volume for radiotherapy. An early differentiation between HGG relapse and changes in connection with oncology treatment (pseudoprogression or radionecrosis) is still problematic by commonly used diagnostic imaging techniques. The goal of our project is to verify whether a combination of diffusion-weighted MR imaging (DWI) and proton magnetic resonance spectroscopy (MRS) increase specificity of the conventional structural MRI with gadolinium for early non-invasive differentiation between of HGG relapse and pseudoprogression or radionecrosis. MATERIALS/METHODS: Patients (n= 26) with HGG and structural progression on MRI after neurosurgical resection and radiotherapy with concurrent administration of temozolomide underwent DWI expressed as ADC map and MRS focused on concentration of N-acetylaspartate (NAA), choline (Cho), creatine (Cr), lactate (Lac), and lipids (Lip). An etiology of the lesion was then established by a finding on a subsequent MRI or by a biopsy and correlated with results of the investigated MR techniques. RESULTS: Compared to the pseudoprogression or radionecrosis, the relapse of HGG was characterized by significantly lower ADC values, lower NAA concentration, appearance of Lac+Lip spectra, as well as by non-significant increase in Cho. We found very high sensitivity and specificity of ADC median value (≤1220 × 10−6 mm2/sec) and Cho/NAA ratio (≥1.7) to designate the MRI lesion with gadolinium uptake as the HGG relapse. CONCLUSION: It can be concluded that DWI (ADC value) and MRS (mainly Cho/NAA ratio) have the ability for early non-invasive differentiation of the HGG relapse from the pseudoprogression or radionecrosis after the oncology treatment. The project is supported by grants IGA MZC R NT/14120 and NT/14600 and the European Regional Development Fund Project FNUSA-IC RC (No. CZ.1.05/1.1.00/02.0123).