Combination of peptide receptor radionuclide therapy with fractionated external beam radiotherapy for treatment of advanced symptomatic meningioma

Joint EANM/EANO/RANO/SNMMI practice guideline/procedure standards for diagnostics and therapy (theranostics) of meningiomas using radiolabeled somatostatin receptor ligands: version 1.0

PURPOSE

To provide practice guideline/procedure standards for diagnostics and therapy (theranostics) of meningiomas using radiolabeled somatostatin receptor (SSTR) ligands.

METHODS

This joint practice guideline/procedure standard was collaboratively developed by the European Association of Nuclear Medicine (EANM), the Society of Nuclear Medicine and Molecular Imaging (SNMMI), the European Association of Neurooncology (EANO), and the PET task force of the Response Assessment in Neurooncology Working Group (PET/RANO).

RESULTS

Positron emission tomography (PET) using somatostatin receptor (SSTR) ligands can detect meningioma tissue with high sensitivity and specificity and may provide clinically relevant information beyond that obtained from structural magnetic resonance imaging (MRI) or computed tomography (CT) imaging alone. SSTR-directed PET imaging can be particularly useful for differential diagnosis, delineation of meningioma extent, detection of osseous involvement, and the differentiation between posttherapeutic scar tissue and tumour recurrence. Moreover, SSTR-peptide receptor radionuclide therapy (PRRT) is an emerging investigational treatment approach for meningioma.

CONCLUSION

These practice guidelines will define procedure standards for the application of PET imaging in patients with meningiomas and related SSTR-targeted PRRTs in routine practice and clinical trials and will help to harmonize data acquisition and interpretation across centers, facilitate comparability of studies, and to collect larger databases. The current document provides additional information to the evidence-based recommendations from the PET/RANO Working Group regarding the utilization of PET imaging in meningiomas Galldiks (Neuro Oncol. 2017;19(12):1576-87). The information provided should be considered in the context of local conditions and regulations.

Combination Strategies and Targeted Radionuclide Therapies

Combination models utilising treatments from two or more therapeutic classes are well established in cancer care. In the new era of theranostic (theragnostic) medicine there is an ongoing need to identify and refine novel combination strategies to optimise multidisciplinary care for conditions commonly encountered in nuclear medicine such as neuroendocrine neoplasms (NEN), prostate cancer (PCa), and thyroid cancer, along with seeking advancements in molecular imaging and therapy techniques for other tumour streams. This concise review explores the background of theranostic monotherapy, established approaches to combination strategies in theranostics, and emerging targeted radionuclide therapies in use or under active investigation, with a focus on Australian-led studies.

Peptide radionuclide radiation therapy with Lutathera in multirecurrent nonanaplastic meningiomas: antitumoral activity study by growth rate analysis

PURPOSE

Several retrospective studies and meta-analyses of Peptide Radionuclide Radiation Therapy in meningiomas suggest six-month progression-free survival improvement for WHO grade 1 and 2 meningiomas. In the present study, we aimed to evaluate the impact of such treatment on three-dimensional volume growth rate (3DVGR) in nonanaplastic meningiomas.

METHODS

The authors performed a retrospective study including eight patients treated with Lutathera®. Millimetric 3D T1-weighted with gadolinium enhancement magnetic resonance imaging sequences were requested for volume measurement. Then, tumor growth rate was classified following a previously described 3DVGR classification (Graillon et al.).

RESULTS

Patients harbored seven WHO grade 2 meningiomas and one aggressive WHO grade 1. All patients, except one, underwent four treatment cycles. 3DVGR significantly decreased at 3, 6, and 12 months after treatment initiation analyzing each lesion separately. Mean and median 3DVGR from all patients were respectively at 29.5% and 44.5%/6 months before treatment initiation, then at 16.5% and 25%/6 months at three months post-treatment initiation, 9.5% and 4.5%/6 months after 6 months, as well as 9.5% and 10.5%/6 months after 12 months. At 3, 6, and 12 months after treatment initiation, 4/8, 6/7, and 5/6 patients were class 2 (stabilization or severe 3DVGR slowdown), respectively. No patient was class 1 at 6 and 12 months, suggesting a lack of drug response.

CONCLUSION

In nonanaplastic meningiomas, Lutathera®'s antitumoral activity appeared delayed and more likely observed at six months, while no major response was observed under treatment. Moreover, its antitumoral activity persisted for 12-18 months following treatment initiation.

Radiolabeled Somatostatin Receptor Antagonist Versus Agonist for Peptide Receptor Radionuclide Therapy in Patients with Therapy-Resistant Meningioma: PROMENADE Phase 0 Study

Our primary aim was to compare the therapeutic index (tumor-to-bone marrow and tumor-to-kidney absorbed-dose ratios) of the new radiolabeled somatostatin receptor antagonist [177Lu]Lu-DOTA-JR11 with the established radiolabeled somatostatin receptor agonist [177Lu]Lu-DOTATOC in the same patients with progressive, standard therapy-refractory meningioma. Methods: In this prospective, single-center, open-label phase 0 study (NCT04997317), 6 consecutive patients were included: 3 men and 3 women (mean age, 63.5 y). Patients received 6.9-7.3 GBq (standard injected radioactivity) of [177Lu]Lu-DOTATOC followed by 3.3-4.9 GBq (2 GBq/m2 × body surface area) of [177Lu]Lu-DOTA-JR11 at an interval of 10 ± 1 wk. In total, 1 [177Lu]Lu-DOTATOC and 2-3 [177Lu]Lu-DOTA-JR11 treatment cycles were performed. Quantitative SPECT/CT was done at approximately 24, 48, and 168 h after injection of both radiopharmaceuticals to calculate meningioma and organ absorbed doses as well as tumor-to-organ absorbed-dose ratios (3-dimensional segmentation approach for meningioma, kidneys, liver, bone marrow, and spleen). Results: The median of the meningioma absorbed dose of 1 treatment cycle was 3.4 Gy (range, 0.8-10.2 Gy) for [177Lu]Lu-DOTATOC and 11.5 Gy (range, 4.7-22.7 Gy) for [177Lu]Lu-DOTA-JR11. The median bone marrow and kidney absorbed doses after 1 treatment cycle were 0.11 Gy (range, 0.05-0.17 Gy) and 2.7 Gy (range, 1.3-5.3 Gy) for [177Lu]Lu-DOTATOC and 0.29 Gy (range, 0.16-0.39 Gy) and 3.3 Gy (range, 1.6-5.9 Gy) for [177Lu]Lu-DOTA-JR11, resulting in a 1.4 (range, 0.9-1.9) times higher median tumor-to-bone marrow absorbed-dose ratio and a 2.9 (range, 2.0-4.8) times higher median tumor-to-kidney absorbed-dose ratio with [177Lu]Lu-DOTA-JR11. According to the Common Terminology Criteria for Adverse Events version 5.0, 2 patients developed reversible grade 2 lymphopenia after 1 cycle of [177Lu]Lu-DOTATOC. Afterward, 2 patients developed reversible grade 3 lymphopenia and 1 patient developed reversible grade 3 lymphopenia and neutropenia after 2-3 cycles of [177Lu]Lu-DOTA-JR11. No grade 4 or 5 adverse events were observed at 15 mo or more after the start of therapy. The disease control rate was 83% (95% CI, 53%-100%) at 12 mo or more after inclusion. Conclusion: Treatment with 1 cycle of [177Lu]Lu-DOTA-JR11 showed 2.2-5.7 times higher meningioma absorbed doses and a favorable therapeutic index compared with [177Lu]Lu-DOTATOC after injection of 1.4-2.1 times lower activities. The first efficacy results demonstrated a high disease control rate with an acceptable safety profile in the standard therapy for refractory meningioma patients. Therefore, larger studies with [177Lu]Lu-DOTA-JR11 are warranted in meningioma patients.

Minimally Invasive Approaches in the Surgical Treatment of Intracranial Meningiomas: An Analysis of 54 Cases

BACKGROUND

Intracranial meningiomas, being a fairly common disease in the population, often require surgical treatment, which, in turn, can completely heal the patient. The localization of meningiomas often influences treatment even if they are asymptomatic. By modernizing approaches to surgical treatment, it is possible to minimize intra- and postoperative risks, while achieving complete removal of the tumor. One of these methods is minimally invasive neurosurgery, the development of which in recent years allows it to compete with standard surgical methods. The purpose of this study was the objectification of minimally invasive approaches, such as the calculation of the craniotomy area and the ratio of craniotomy area to the resected tumor volume.

METHODS

The retrospective study consisted of a group of 54 consecutive patients who were operated on in our neurosurgery clinic specialized on minimally invasive neurosurgery. Preoperative planning was carried out using the Surgical Theater visualization platform. Using this system, the tumor volume and craniotomy surface area were calculated. During the analysis, the symptoms before and after the surgery, classification of tumors, postoperative complications, further treatment and follow-up results were assessed.

RESULTS

Twelve (22.2%) patients were men and 42 (77.8%) were women. The mean age of the group was 64.2 years (median 67.5). The craniotomy area ranged from 202 to 2,108 mm² (mean 631 mm²). Tumor volume ranged from 0.85 to 110.1 cm3 (mean 21.6 cm3). The craniotomy size of minimally invasive approaches to the skull base was 3-5 times smaller than standard approaches. Skull base meningiomas accounted for 19 cases (35.2%), convexity meningiomas for 26 cases (48.1%), and falx and tentorium meningiomas for 9 cases (16.7%). Three complications were reported: postoperative hemorrhage, CSF leakage, and ophthalmoplegia. Relapse was detected in 2 patients with a mean follow-up of 26.3 months (median 20).

CONCLUSION

Minimally invasive approaches in the surgical treatment of intracranial meningiomas reduce the possibility of operating trauma by several times; they are safe and sufficient for complete removal of the tumor.

Theranostics in Neurooncology: Heading Toward New Horizons

Therapeutic approaches to brain tumors remain a challenge, with considerable limitations regarding delivery of drugs. There has been renewed and increasing interest in translating the popular theranostic approach well known from prostate and neuroendocrine cancer to neurooncology. Although far from perfect, some of these approaches show encouraging preliminary results, such as for meningioma and leptomeningeal spread of certain pediatric brain tumors. In brain metastases and gliomas, clinical results have failed to impress. Perspectives on these theranostic approaches regarding meningiomas, brain metastases, gliomas, and common pediatric brain tumors will be discussed. For each tumor entity, the general context, an overview of the literature, and future perspectives will be provided. Ongoing studies will be discussed in the supplemental materials. As most theranostic agents are unlikely to cross the blood-brain barrier, the delivery of these agents will be dependent on the successful development and clinical implementation of techniques enhancing permeability and retention. Moreover, the international community should strive toward sufficiently large and randomized studies to generate high-level evidence on theranostic approaches with radioligand therapies for central nervous system tumors.

[Combination of internal and external beam radiotherapy]

External beam radiation therapy and internal vectorized radiation therapy are two types of radiotherapy that can be used to treat cancer. They differ in the way they are administered, and the type of radiation used. Although they can be effective in treating cancer, they each have their own advantages and disadvantages, and their combination could be synergistic. Preclinical studies on combined internal and external beam radiation therapy have mainly used radiolabelled antibodies, whose bone marrow toxicity remains the limiting factor in increasing the administered activities. The use of small radioligands in clinical trials has shown to be better tolerated and more effective, which explains their rapid development. The results of preclinical studies on combined internal and external beam radiation therapy appear heterogeneous, making it impossible to determine an ideal therapeutic sequencing scheme, and complicating the transposition to clinical studies. The few clinical studies on combined internal and external beam radiation therapy available to date have demonstrated feasibility and tolerability. More work remains to be done in the fields of dosimetry and radiobiology, as well as in the sequencing of these two irradiation modalities to optimize their combination.

Application of nano-radiosensitizers in combination cancer therapy

Radiosensitizers are compounds or nanostructures, which can improve the efficiency of ionizing radiation to kill cells. Radiosensitization increases the susceptibility of cancer cells to radiation-induced killing, while simultaneously reducing the potentially damaging effect on the cellular structure and function of the surrounding healthy tissues. Therefore, radiosensitizers are therapeutic agents used to boost the effectiveness of radiation treatment. The complexity and heterogeneity of cancer, and the multifactorial nature of its pathophysiology has led to many approaches to treatment. The effectiveness of each approach has been proven to some extent, but no definitive treatment to eradicate cancer has been discovered. The current review discusses a broad range of nano-radiosensitizers, summarizing possible combinations of radiosensitizing NPs with several other types of cancer therapy options, focusing on the benefits and drawbacks, challenges, and future prospects.

Lutathera® Orphans: State of the Art and Future Application of Radioligand Therapy with 177Lu-DOTATATE

Lutathera® is the first EMA- and FDA-approved radiopharmaceutical for radioligand therapy (RLT). Currently, on the legacy of the NETTER1 trial, only adult patients with progressive unresectable somatostatin receptor (SSTR) positive gastroenteropancreatic (GEP) neuroendocrine neoplasms (NET) can be treated with Lutathera®. Conversely, patients with SSTR-positive disease arising from outside the gastroenteric region do not currently have access to Lutathera® treatment despite several papers in the literature reporting the effectiveness and safety of RLT in these settings. Moreover, patients with well-differentiated G3 GEP-NET are also still “Lutathera orphans”, and retreatment with RLT in patients with disease relapse is currently not approved. The aim of this critical review is to summarize current literature evidence assessing the role of Lutathera® outside the approved indications. Moreover, ongoing clinical trials evaluating new possible applications of Lutathera® will be considered and discussed to provide an updated picture of future investigations.

Tolerability of concurrent external beam radiotherapy and [177Lu]Lu-PSMA-617 for node-positive prostate cancer in treatment naïve patients, phase I study (PROQURE-I trial)

BACKGROUND

Prostate cancer patients with locoregional lymph node disease at diagnosis (N1M0) still have a limited prognosis despite the improvements provided by aggressive curative intent multimodal locoregional external beam radiation therapy (EBRT) with systemic androgen deprivation therapy (ADT). Although some patients can be cured and the majority of patients have a long survival, the 5-year biochemical failure rate is currently 29-47%. [¹⁷⁷Lu]Lu-PSMA-617 has shown impressive clinical and biochemical responses with low toxicity in salvage setting in metastatic castration-resistant prostate cancer. This study aims to explore the combination of standard EBRT and ADT complemented with a single administration of [¹⁷⁷Lu]Lu-PSMA-617 in curative intent treatment for N1M0 prostate cancer. Hypothetically, this combined approach will enhance EBRT to better control macroscopic tumour localizations, and treat undetected microscopic disease locations inside and outside EBRT fields.

METHODS

The PROQURE-I study is a multicenter prospective phase I study investigating standard of care treatment (7 weeks EBRT and 3 years ADT) complemented with one concurrent cycle (three, six, or nine GBq) of systemic [¹⁷⁷Lu]Lu-PSMA-617 administered in week two of EBRT. A maximum of 18 patients with PSMA-positive N1M0 prostate cancer will be included. The tolerability of adding [¹⁷⁷Lu]Lu-PSMA-617 will be evaluated using a Bayesian Optimal Interval (BOIN) dose-escalation design. The primary objective is to determine the maximum tolerated dose (MTD) of a single cycle [¹⁷⁷Lu]Lu-PSMA-617 when given concurrent with EBRT + ADT, defined as the occurrence of Common Terminology Criteria for Adverse Events (CTCAE) v 5.0 grade three or higher acute toxicity. Secondary objectives include: late toxicity at 6 months, dosimetric assessment, preliminary biochemical efficacy at 6 months, quality of life questionnaires, and pharmacokinetic modelling of [¹⁷⁷Lu]Lu-PSMA-617.

DISCUSSION

This is the first prospective study to combine EBRT and ADT with [¹⁷⁷Lu]Lu-PSMA-617 in treatment naïve men with N1M0 prostate cancer, and thereby explores the novel application of [¹⁷⁷Lu]Lu-PSMA-617 in curative intent treatment. It is considered likely that this study will confirm tolerability as the combined toxicity of these treatments is expected to be limited. Increased efficacy is considered likely since both individual treatments have proven high anti-tumour effect as mono-treatments.

TRIAL REGISTRATION

ClinicalTrials, NCT05162573 . Registered 7 October 2021.

Efficacy and safety of peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE in 15 patients with progressive treatment-refractory meningioma

PURPOSE

There is no evidence-based systemic therapy for patients with progressive meningiomas for whom surgery or external radiotherapy is no longer an option. In this study, the efficacy and safety of peptide receptor radionuclide therapy (PRRT) in patients with progressive, treatment-refractory meningiomas were evaluated.

METHODS

Retrospective analysis of all meningioma patients treated with [¹⁷⁷Lu]Lu-DOTA-TATE from 2000 to 2020 in our centre. Primary outcomes were response according to RANO bidimensional and volumetric criteria and progression-free survival (PFS). Overall survival (OS) and tumour growth rate (TGR) were secondary endpoints. TGR was calculated as the percentage change in surface or volume per month.

RESULTS

Fifteen meningioma patients received [¹⁷⁷Lu]Lu-DOTA-TATE (7.5-29.6 GBq). Prior to PRRT, all patients had received external radiotherapy, and 14 patients had undergone surgery. All WHO grades were included WHO 1 (n=3), WHO 2 (n=5), and WHO 3 (n=6). After PRRT, stable disease was observed in six (40%) patients. The median PFS was 7.8 months with a 6-month PFS rate of 60%. The median OS was 13.6 months with a 12-month OS rate of 60%. All patients had progressive disease prior to PRRT, with an average TGR of 4.6% increase in surface and 14.8% increase in volume per month. After PRRT, TGR declined to 3.1% in surface (p=0.016) and 5.0% in volume (p=0.013) per month.

CONCLUSION

In this cohort of meningioma patients with exhaustion of surgical and radiotherapeutic options and progressive disease, it was shown that PRRT plays a role in controlling tumour growth.

Imaging Characteristics of Meningiomas

Contemporary neuroimaging of meningiomas has largely relied on computed tomography, and more recently magnetic resonance imaging. While these modalities are frequently used in nearly all clinical settings where meningiomas are treated for the routine diagnosis and follow-up of these tumors, advances in neuroimaging have provided novel opportunities for prognostication and treatment planning (including both surgical planning and radiotherapy planning). These include perfusion MRIs, and positron emission tomography (PET) imaging modalities. Here we will summarize the contemporary uses for neuroimaging in meningiomas, and future applications of novel, cutting edge imaging techniques that may be routinely implemented in the future to enable more precise treatment of these challenging tumors.

The Complementary Role of 68Ga-DOTATATE PET/CT in Diagnosis of Recurrent Meningioma

Introduction: Contrast-enhanced brain MRI is the choice of imaging modality in diagnosis and posttreatment evaluation, its role is limited in distinguishing recurrent lesion from postoperative change. 68Ga-DOTATATE is a somatostatin analog PET tracer which has high affinity to meningioma expressing somatostatin receptor. Methods and subjects: In this case series review, we described 8 patients with brain MRI suspected of recurrent meningioma who underwent focused 68Ga-DOTATATE PET/CT scan for radiation treatment planning. Results: The combined brain MRI and PET/CT allowed improved conspicuity of the lesions and aided radiation treatment planning. The time from the initial surgery to PET/CT scans varied widely ranging from 1 year to 12 years. Three patients had PET/CT shortly after the initial surgery (1-3 years) and underwent targeted radiation therapy. Subsequent imaging showed no evidence of recurrence. Four patients had prolonged time between the PET/CT and the initial surgery (7-12 years) which showed extensive tumor burden. All four patients expired shortly after the last PET/CT scan. Conclusion: 68Ga-DOTATATE PET shows promising complementary role in detection and treatment planning of recurrent meningioma.

Somatostatin Receptor Theranostics for Refractory Meningiomas

Somatostatin receptor (SSTR)-targeted peptide receptor radionuclide therapy (PRRT) represents a promising approach for treatment-refractory meningiomas progressing after surgery and radiotherapy. The aim of this study was to provide outcomes of patients harboring refractory meningiomas treated by 177Lu-DOTATATE and an overall analysis of progression-free survival at 6 months (PFS-6) of the same relevant studies in the literature. Eight patients with recurrent and progressive WHO grade II meningiomas were treated after multimodal pretreatment with 177Lu-DOTATATE between 2019 and 2022. Primary and secondarily endpoints were progression-free survival at 6-months (PFS-6) and toxicity, respectively. PFS-6 analysis of our case series was compared with other similar relevant studies that included 86 patients treated with either 177Lu-DOTATATE or 90Y-DOTATOC. Our retrospective study showed a PFS-6 of 85.7% for WHO grade II progressive refractory meningiomas. Treatment was clinically and biologically well tolerated. The overall analysis of the previous relevant studies showed a PFS-6 of 89.7% for WHO grade I meningiomas (n = 29); 57.1% for WHO grade II (n = 21); and 0 % for WHO grade III (n = 12). For all grades (n = 86), including unknown grades, PFS-6 was 58.1%. SSTR-targeted PRRT allowed us to achieve prolonged PFS-6 in patients with WHO grade I and II progressive refractory meningiomas, except the most aggressive WHO grade II tumors. Large scale randomized trials are warranted for the better integration of PRRT in the treatment of refractory meningioma into clinical practice guidelines.

Management of a Patient With Metastatic Gastrointestinal Neuroendocrine Tumor and Meningioma Submitted to Peptide Receptor Radionuclide Therapy With 177Lu-DOTATATE

ABSTRACT

A 76-year-old woman affected by pancreatic neuroendocrine tumor previously subjected to surgery with progressive liver disease and a concomitant mild symptomatic meningioma of the left pontocerebellar angle underwent 4 cycles of peptide receptor radionuclide therapy with 177Lu-DOTATATE. A prophylactic therapy with corticosteroids was carried out before each treatment cycle, and the neurosurgery unit was alerted in case of cerebral edema and related neurologic symptoms. A 68Ga-DOTATOC PET/CT scan performed after the completion of the 4 cycles' treatment documented a hepatic partial response and a substantial stability of the brain mass. No neurological complications occurred during treatment and follow-up.

The Current Role of Peptide Receptor Radionuclide Therapy in Meningiomas

Meningiomas are the most common primary intracranial tumors. The majority of patients can be cured by surgery, or tumor growth can be stabilized by radiation. However, the management of recurrent and more aggressive tumors remains difficult because no established alternative treatment options exist. Therefore, innovative therapeutic approaches are needed. Studies have shown that meningiomas express somatostatin receptors. It is well known from treating neuroendocrine tumors that peptide radioreceptor therapy that targets somatostatin receptors can be effective. As yet, this therapy has been used for treating meningiomas only within individual curative trials. However, small case series and studies have demonstrated stabilization of the disease. Therefore, we see potential for optimizing this therapeutic option through the development of new substances and specific adaptations to the different meningioma subtypes. The current review provides an overview of this topic.

Theragnostic in neuroendocrine tumors

In the last few decades, the incidence and prevalence of neuroendocrine tumors has been increasing. The theragnostic approach, that allows the diagnosis and treatment of different neoplasms with the same ligand, is a typical nuclear medicine tool. Applied for years, is also pivotal in neuroendocrine tumors (NETs) where it has improved the diagnostic accuracy and the therapeutic efficacy with impact on patient's survival. Theragnostic also allows the identification of important prognostic factors such as tumor location and burden, presence of liver metastases and intensity of somatostatin receptors (SSTR) expression to consider in new and possibly combined studies to ameliorate patient's outcome. Moreover, the possibility to evaluate receptor expression even in non-NET malignancies has de facto widened the possible indications for PRRT. We believe that this innovative therapeutic approach will be implemented in next years by radiomics and biological tumors characterization to better address PRRT applications.

[Treatment Planning and Dose Verification for Combined Internal and External Radiotherapy (CIERT)]

AIM

The combined internal and external radiotherapy (CIERT) take advantage of the benefits from radionuclide therapy and external beam irradiation. These include steep dose gradients and a low toxicity to normal tissue due to the use of unsealed radioisotopes as well as homogeneous dose distribution within the tumor due to external beam irradiation. For a combined irradiation planning, an infrastructure has to be developed that takes into account the dose contributions from both modalities. A physical verification of the absorbed dose distribution should follow by measurements using OSL detectors.

METHOD

Internal irradiation was performed using Re-188 in a cylindrical phantom with three inserts. SPECT images were acquired to calculate the internal dose using the software STRATOS. The dose distribution was exported as DICOM-RT data and imported in the software Pinnacle. Based on the internal dose distribution the external irradiation using 6 MV photons was planned. The dose contributions of both modalities separately as well as for combined irradiation was measured using OSL detectors made out of Beryllium oxide.

RESULTS

The planed doses of combined irradiation (1 Gy, 2 Gy, 4 Gy) could be verified within the uncertainty of the detectors. The mean energy response to Re-188 was (88.6 ± 2.4) % with respect to the calibration with 200 kV X-ray irradiation. The energy response to 6 MV photons was (146.0 ± 4.9) %.

CONCLUSION

A workflow for the treatment planning of combined internal and external radiotherapy has been developed and tested. Measurements verified the calculated doses. Therefore, the physical and technical basis for the dosimetry of combined irradiation were worked out.

Combining External Beam Radiation and Radionuclide Therapies: Rationale, Radiobiology, Results and Roadblocks

The emergence of effective radionuclide therapeutics, such as radium-223 dichloride, [¹⁷⁷Lu]Lu-DOTA-TATE and [¹⁷⁷Lu]Lu-PSMA ligands, over the last 10 years is driving a rapid expansion in molecular radiotherapy (MRT) research. Clinical trials that are underway will help to define optimal dosing protocols and identify groups of patients who are likely to benefit from this form of treatment. Clinical investigations are also being conducted to combine new MRT agents with other anticancer drugs, with particular emphasis on DNA repair inhibitors and immunotherapeutics. In this review, the case is presented for combining MRT with external beam radiotherapy (EBRT). The technical and dosimetric challenges of combining two radiotherapeutic modalities have impeded progress in the past. However, the need for research into the specific radiobiological effects of radionuclide therapy, which has lagged behind that for EBRT, has been recognised. This, together with innovations in imaging technology, MRT dosimetry tools and EBRT hardware, will facilitate the future use of this important combination of treatments.

Uncovering an Optic Nerve Sheath Meningioma Using 68Ga-DOTATATE PET/CT

ABSTRACT

A 56-year-old woman was initially diagnosed with optic neuritis. However, several "red flags" were present: older age at presentation, no multiple sclerosis suspicious findings on MRI, and negative oligoclonal bands. 68Ga-DOTATATE PET/CT confirmed the differential diagnosis of an optic sheath meningioma. Our case stresses the value of the somatostatin receptor ligand PET/CT in patients with suspected optic neuritis if the diagnostic workup does not support immune-mediated pathogenesis.

Theranostics in oncology: What radiologists want to know

Combination of radioligand imaging and therapy, so called radiotheranostics, is a novel tool of precision oncology with proven clinical value. In-depth knowledge of functional imaging nuances is critically needed for precise prognostication and guidance of management. Here, we review theranostic applications with up to Phase III type evidence for outcome improvement: Imaging and therapy of neuroendocrine neoplasms (NEN) exploiting high levels of somatostatin receptor (SSTR) expression and radiotheranostics of prostate cancer targeting the prostate specific membrane antigen (PSMA). This narrative review focusses on these two applications and elucidates patient selection and response assessment by radioligand scintigraphy and/or positron emission tomography. Furthermore, we provide a brief outlook on future applications for novel targets outside of NEN and prostate cancer.

Current experimental therapies for atypical and malignant meningiomas

INTRODUCTION

Atypical (WHO grade II) and malignant meningiomas (WHO Grade III) are a rare subset of primary intracranial tumors. Given their relatively high recurrence rate after surgical resection and radiotherapy, there has been a recent push to explore other adjuvant treatment options for these treatment-refractory tumors. Recent advances in molecular sequencing of tumors have elucidated new pathways and drug targets which are currently being studied. This article provides a thorough overview of novel investigational therapeutics including targeted therapy, immunotherapy, and new technological modalities for atypical and malignant meningiomas.

METHODS

We performed a comprehensive review of the available literature regarding preclinical and clinical evidence for emerging treatments for high grade meningiomas from 1980 to 2020 including contemporaneous clinical trials.

RESULTS

There is encouraging preclinical evidence regarding the efficacy of the emerging treatments discussed in this article. Several clinical trials are currently recruiting patients to translate targeted molecular therapy for meningiomas. Several clinical studies have suggested a clinical benefit of combinatorial treatment for these treatment-refractory tumors.

CONCLUSION

With numerous active clinical trials for high grade meningiomas, a meaningful improvement in the outcomes for these tumors may be on the horizon.

Differences in the expression of SSTR1-5 in meningiomas and its therapeutic potential

Beyond microsurgical resection and radiation therapy, there are currently no established treatment alternatives for meningioma patients. In selected cases, peptide radio receptor therapy (PRRT) can be implemented. For this purpose, a radionuclide is bound to a substance targeting specific receptors in meningiomas. One of them is somatostatin receptor 2, which can be found in most meningiomas. However, other somatostatin receptors (SSTR) exist, but their expressions have only been described in small case series. In this study, we analyzed the expression of SSTR1, 2A, 3, 4, and 5 in a large cohort of meningiomas in order to enable further refinement of this innovative treatment option. Overall, 726 tumor samples were processed into tissue microarrays and stained for SSTR1, 2A, 3, 4, and 5 immunohistochemically. Microscopic evaluation was done with an established semiquantitative score regarding percentual quantification and staining intensity, and results were correlated with clinical data. There was a significant lower rate of SSTR1 expression in meningiomas of male patients. Older age was associated with higher expression of SSTR1, 2A, and 5 and lower scores for SSTR3 and 4. Tumors treated with radiotherapy before resection showed lower rates of SSTR1 and 5 expression, while recurrent meningiomas had lower SSTR1 scores. Tumor tissue from patients suffering from neurofibromatosis type 2 had lower expression scores for SSTR1, 2, and 5. For SSTR3 and 4, NF2 patients showed higher scores than sporadic tumors. Spinal meningiomas had higher scores for SSTR1, 4, and 5 compared tumor location of the skull base and convexity/falx. Overall, higher WHO grade was associated with lower SSTR scores. While all SSTRs were expressed, there are marked differences of SSTR expression between meningioma subgroups. This has the potential to drive the development of more selective PRRT substances with higher treatment efficacy.

Improved Detection of Postoperative Residual Meningioma with [68Ga]Ga-DOTA-TOC PET Imaging Using a High-resolution Research Tomograph PET Scanner

PURPOSE

PET with somatostatin receptor ligand [⁶⁸Ga]Ga-DOTA-D-Phe¹-Tyr³-octreotide ([⁶⁸Ga]Ga-DOTA-TOC) is an established method in radiotherapy planning because of the improved detection and delineation of meningioma tissue. We investigated the diagnostic accuracy of supplementary [⁶⁸Ga]Ga-DOTA-TOC PET in patients with a 3-month postoperative MRI reporting gross-total resection (GTR).

EXPERIMENTAL DESIGN

Thirty-seven patients with a histologically proven meningioma and GTR on postoperative MRI were prospectively referred to [⁶⁸Ga]Ga-DOTA-TOC PET. Detection and volume measurements of [⁶⁸Ga]Ga-DOTA-TOC-avid lesions in relation to the primary tumor site were recorded. Residual tumor in suspicious lesions suggested by [⁶⁸Ga]Ga-DOTA-TOC PET was verified by (i) tumor recurrence/progression on subsequent MRI scans according to the Response Assessment of Neuro-Oncology criteria, (ii) subsequent histology, and (iii) follow-up [⁶⁸Ga]Ga-DOTA-TOC PET scan.

RESULTS

Twenty-three PET scans demonstrated [⁶⁸Ga]Ga-DOTA-TOC-avid lesions suspicious of residual meningioma, where 18 could be verified by (i) tumor progression on subsequent MRI scans (n = 6), (ii) histologic confirmation (n = 3), and (iii) follow-up [⁶⁸Ga]Ga-DOTA-TOC PET scans confirming the initial PET findings (n = 9) after an overall median follow-up time of 17 months (range, 9-35 months). In contrast, disease recurrence was seen in only 2 of 14 patients without [⁶⁸Ga]Ga-DOTA-TOC-avid lesions (P < 0.0001). The sensitivity, specificity, and diagnostic accuracy of [⁶⁸Ga]Ga-DOTA-TOC PET in detecting meningioma residue was 90% [95% confidence interval (CI), 67-99], 92% (95% CI, 62-100), and 90% (95% CI, 74-98; P < 0.0001), respectively.

CONCLUSIONS

The majority of patients with GTR on 3-month postoperative MRI may have small unrecognized meningioma residues that can be detected using [⁶⁸Ga]Ga-DOTA-TOC PET.

Recent Advances in Radiometals for Combined Imaging and Therapy in Cancer

Nuclear medicine is defined as the use of radionuclides for diagnostic and therapeutic applications. The imaging modalities positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are based on γ-emissions of specific energies. The therapeutic technologies are based on β^- -particle-, α-particle-, and Auger electron emitters. In oncology, PET and SPECT are used to detect cancer lesions, to determine dosimetry, and to monitor therapy effectiveness. In contrast, radiotherapy is designed to irreparably damage tumor cells in order to eradicate or control the disease's progression. Radiometals are being explored for the development of diagnostic and therapeutic radiopharmaceuticals. Strategies that combine both modalities (diagnostic and therapeutic), referred to as theranostics, are promising candidates for clinical applications. This review provides an overview of the basic concepts behind therapeutic and diagnostic radiopharmaceuticals and their significance in contemporary oncology. Select radiometals that significantly impact current and upcoming cancer treatment strategies are grouped as clinically suitable theranostics pairs. The most important physical and chemical properties are discussed. Standard production methods and current radionuclide availability are provided to indicate whether a cost-efficient use in a clinical routine is feasible. Recent preclinical and clinical developments and outline perspectives for the radiometals are highlighted in each section.

Somatostatin Receptor-Targeted Radiopeptide Therapy in Treatment-Refractory Meningioma: Individual Patient Data Meta-analysis

Somatostatin receptor (SSTR)-targeted peptide receptor radionuclide therapy (PRRT) represents a promising approach for treatment-refractory meningiomas. Methods: We performed an individual patient data meta-analysis, including all published data on meningioma patients treated with SSTR-targeted PRRT. The main outcomes were toxicity, response to treatment, progression-free survival (PFS), and overall survival (OS). We applied the Kaplan-Meier method to estimate survival probabilities and report incidence rates per 100 person-years. We applied Cox proportional hazards models to determine the effect of covariates. Results: We screened 537 papers and identified 6 eligible cohort studies. We included a total of 111 patients who had treatment-refractory meningioma and received SSTR-targeted PRRT. Disease control was achieved in 63% of patients. The 6-mo PFS rates were 94%, 48%, and 0% for World Health Organization grades I, II, and III, respectively. The risk of disease progression decreased by 13% per 1,000-MBq increase in the total applied activity. The 1-y OS rates were 88%, 71%, and 52% for World Health Organization grades I, II, and III, respectively. The risk of death decreased by 17% per 1,000-MBq increase in the total applied activity. The main side effects comprised transient hematotoxicity, such as anemia in 22% of patients, leukopenia in 13%, lymphocytopenia in 24%, and thrombocytopenia in 17%. Conclusion: To our knowledge, this individual patient data meta-analysis represents the most comprehensive analysis of the benefits of and adverse events associated with SSTR-targeted PRRT for treatment-refractory meningioma. The treatment was well tolerated, achieved disease control in most cases, and showed promising results regarding PFS and OS.

Clinical Significance of Somatostatin Receptor (SSTR) 2 in Meningioma

Somatostatin receptor (SSTR) 2, widely expressed in meningioma, is a G-protein-coupled receptor and can be activated by somatostatin or its synthetic analogs. SSTR2 is therefore extensively studied as a marker and target for the diagnosis and treatment of meningioma. Accumulating studies have revealed the crucial clinical significance of SSTR2 in meningioma. Summarizing the progress of these studies is urgently needed as it may not only provide novel and better management for patients with meningioma but also indicate the direction of future research. Pertinent literature is reviewed to summarize the recent collective knowledge and understanding of SSTR2’s clinical significance in meningioma in this review. SSTR2 offers novel ideas and approaches in the diagnosis, treatment, and prognostic prediction for meningioma, but more and further studies are required.

Response assessment of somatostatin receptor targeted radioligand therapies for progressive intracranial meningioma

BACKGROUND

 In somatostatin receptor (SSTR) expressing progressive meningioma, peptide receptor radionuclide therapy (PRRT) has shown effect in small clinical series. However, standardized treatment and response assessment protocols are lacking. We present our experience on PPRT with 177Lu-DOTATATE in progressive meningioma with a special emphasis on state-of-the-art response assessment.

METHODS

 Retrospective analysis on PRRT with 177Lu-DOTATATE from 2015 to 2019. Pre- and post-therapy imaging was performed using MRI and 68Ga-DOTATATE-PET for standard bidimensional and volumetric analyses, respectively, following novel RANO guidelines.

RESULTS

 Seven patients with progressive intracranial meningioma (median age 73 years, interquartile range 60-76; 5 WHO II, 2 WHO I; 5 multifocal) received a median of 4 cycles 2 3 4 of PRRT with 177Lu-DOTATATE in eight-week intervals. Three patients did not undergo post-therapy 68Ga-DOTATATE-PET due to early symptomatic progression and subsequent cessation of PRRT. After completion of 4 PRRT cycles volumetric PET imaging showed stable disease in two of four patients. According to bidimensional MRI response assessment, only one patient was stable. Progression free survival at six months was 42.9 %.

CONCLUSION

 In this heterogeneous collective of seven patients with progressive meningioma, 177Lu-DOTATATE therapies showed heterogeneous effectiveness. PET-based volumetric assessment should be used for response assessment in PRRT additionally to bidimensional imaging.

Long-term results of multimodal peptide receptor radionuclide therapy and fractionated external beam radiotherapy for treatment of advanced symptomatic meningioma

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Combination of PRRT and EBRT is feasible and safe in meningioma.

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Combined therapy resulted in disease stabilization in 7 of 10 patients.

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Future prospective validation of this new approach in larger cohorts is warranted.

Background

The combination of somatostatin receptor-directed peptide receptor radionuclide therapy (PRRT) in combination with external beam radiotherapy (EBRT) might prove a feasible treatment option in patients with advanced meningioma.

Patients and methods

From May 2010 to May 2011, 10 patients with unresectable meningioma (6 × WHO grade I, 2 × WHO grade II, 2 × WHO grading not available) were treated with one cycle of PRRT followed by EBRT. Long-term toxicity and efficacy were assessed according to Common Terminology Criteria for Adverse Events version 5.0 and magnetic resonance imaging-based Response Assessment in Neuro-Oncology Working Group criteria, respectively.

Results

During long-term follow-up of a median of 105.0 months (range, 38.2–111.4 m), combined PRRT and EBRT was well-tolerated with no severe acute or chronic toxicity. Kidney or bone marrow function was not affected in any patient. Combination of PRRT and EBRT resulted in disease stabilization in 7 of the 10 patients with a median progression-free survival of 107.7 months (range, 47.2–111.4 m) vs. 26.2 months (range, 13.8–75.9 m) for the patients with meningioma progression.

Conclusions

The combination of PRRT and EBRT is a feasible and safe therapeutic option in meningioma patients. In this pilot cohort, the multimodality treatment demonstrated good disease stabilization.

Theranostics: Leveraging Molecular Imaging and Therapy to Impact Patient Management and Secure the Future of Nuclear Medicine

Nuclear medicine is experiencing a renaissance, with U.S. Food and Drug Administration approval recently being obtained for theranostic agents and a wide variety of such agents soon to impact patient care significantly in the era of precision medicine. The NETTER-1 trial demonstrated the therapeutic effect of a theranostic agent in markedly improving progression-free survival in patients with metastatic gastroenteropancreatic neuroendocrine tumors. Predominantly retrospective studies have demonstrated a significant response to ¹⁷⁷Lu-labeled agents targeting prostate-specific membrane antigen (PSMA) in patients with prostate cancer. At least 2 prospective clinical trials involving ¹⁷⁷Lu-PSMA agents are under way that will likely pave the way for Food and Drug Administration approval in the United States. A significant upside to theranostics is that patients tend to tolerate these agents better than chemotherapy. Theranostic compounds are likely to impact many cancers in the near future, not only through improvements in quality of life but also in terms of survival. This article provides an overview of already approved agents as well as those on the horizon. It is important that as these agents are clinically onboarded, nuclear medicine physicians have the expertise to deploy theranostics safely and efficiently, ensuring that these agents attain and maintain their position as leading lines of therapy in managing patients with cancer as well as becoming an important aspect of nuclear medicine practice in the future.

Theragnostic Use of Radiolabelled Dota-Peptides in Meningioma: From Clinical Demand to Future Applications

Meningiomas account for approximately 30% of all new diagnoses of intracranial masses. The 2016 World Health Organization's (WHO) classification currently represents the clinical standard for meningioma's grading and prognostic stratification. However, watchful waiting is frequently the chosen treatment option, although this means the absence of a certain histological diagnosis. Consequently, MRI (or less frequently CT) brain imaging currently represents the unique available tool to define diagnosis, grading, and treatment planning in many cases. Nonetheless, these neuroimaging modalities show some limitations, particularly in the evaluation of skull base lesions. The emerging evidence supporting the use of radiolabelled somatostatin receptor analogues (such as dota-peptides) to provide molecular imaging of meningiomas might at least partially overcome these limitations. Moreover, their potential therapeutic usage might enrich the current clinical offering for these patients. Starting from the strengths and weaknesses of structural and functional neuroimaging in meningiomas, in the present article we systematically reviewed the published studies regarding the use of radiolabelled dota-peptides in surgery and radiotherapy planning, in the restaging of treated patients, as well as in peptide-receptor radionuclide therapy of meningioma.

Combination of Proton Therapy and Radionuclide Therapy in Mice: Preclinical Pilot Study at the Paul Scherrer Institute

Proton therapy (PT) is a treatment with high dose conformality that delivers a highly-focused radiation dose to solid tumors. Targeted radionuclide therapy (TRT), on the other hand, is a systemic radiation therapy, which makes use of intravenously-applied radioconjugates. In this project, it was aimed to perform an initial dose-searching study for the combination of these treatment modalities in a preclinical setting. Therapy studies were performed with xenograft mouse models of folate receptor (FR)-positive KB and prostate-specific membrane antigen (PSMA)-positive PC-3 PIP tumors, respectively. PT and TRT using ¹⁷⁷Lu-folate and ¹⁷⁷Lu-PSMA-617, respectively, were applied either as single treatments or in combination. Monitoring of the mice over nine weeks revealed a similar tumor growth delay after PT and TRT, respectively, when equal tumor doses were delivered either by protons or by β¯-particles, respectively. Combining the methodologies to provide half-dose by either therapy approach resulted in equal (PC-3 PIP tumor model) or even slightly better therapy outcomes (KB tumor model). In separate experiments, preclinical positron emission tomography (PET) was performed to investigate tissue activation after proton irradiation of the tumor. The high-precision radiation delivery of PT was confirmed by the resulting PET images that accurately visualized the irradiated tumor tissue. In this study, the combination of PT and TRT resulted in an additive effect or a trend of synergistic effects, depending on the type of tumor xenograft. This study laid the foundation for future research regarding therapy options in the situation of metastasized solid tumors, where surgery or PT alone are not a solution but may profit from combination with systemic radiation therapy.

Will 177Lu-DOTATATE Treatment Become More Effective in Salvage Meningioma Patients, When Boosting Somatostatin Receptor Saturation? A Promising Case on Intra-arterial Administration

Somatostatin receptor subtype 2 upregulation is very common in meningiomas, and the use of peptide receptor radionuclide therapy (PRRT) is recognized in recent European guidelines, with long-term stable disease and a long overall survival. Treatment efficacy of radionuclide treatments is correlated with tumour radiation absorbed dose. Meningioma patients with low tumour uptake might benefit less from treatment. Thus, a method to increase tumour uptake in these patients is needed. We describe a case treated with both intravenous and intra-arterial PRRT. Tumour uptake after intravenous PRRT was disappointing, and after intra-arterial administration significantly increased tumour uptake was seen. Patient had a partial response on imaging and reduction in tumour-related complaints. Potentially, intra-arterial administration of PRRT could increase treatment efficacy in meningioma patients.Level of Evidence 5 (case report).

Whole-Body Staging of Metastatic Atypical Meningioma Using 68Ga-DOTATATE PET/CT

A 43-year-old woman with suspected recurrence of atypical meningioma World Health Organization grade II presented extensive intracranial lesions with high Ga-DOTATATE uptake. Moreover, numerous Ga-DOTATATE-positive bone, lung, and liver lesions were seen. For final diagnosis, biopsies taken from a lung lesion revealed distant metastases of the atypical meningioma. This case underlines the high diagnostic power of Ga-DOTATATE PET/CT for the staging of meningioma even beyond cerebral or spinal lesions; in case of distant lesions in patients with known meningioma, differential diagnosis should also contain metastases despite their rare occurrence. Moreover, this case emphasizes radioligand therapy especially in metastatic meningioma.

Treatment planning algorithm for peptide receptor radionuclide therapy considering multiple tumor lesions and organs at risk

PURPOSE

Peptide receptor radionuclide therapy (PRRT) has shown promising results in the treatment of tumors with high expression of somatostatin receptors such as neuroendocrine tumors (NETs) and meningioma. However, PRRT potentially produces high renal and red marrow (RM) toxicity, the kidneys usually being the dose-limiting organ. Previously, it was shown that an improved therapeutic index can be achieved by choosing an optimal combination of injected activity and peptide molar amount. The aim of this work was to develop a clinically applicable algorithm for treatment planning in PRRT. To demonstrate the applicability and possible advantages of the algorithm thus developed, an in silico clinical trial applying the algorithm to 177 Lu-DOTATATE therapy in nine virtual patients was conducted.

METHODS

An algorithm for treatment planning in PRRT was developed, which simultaneously considers multiple tumor lesions, maximum tolerated biologically effective doses (BEDs) for multiple organs at risk (OARs) and a maximum achievable molar activity. The algorithm, subject to the abovementioned constraints, aims at maximizing the total number of killed tumor cells in the considered lesions/metastases. An in silico clinical trial was conducted with nine virtual patients. For each virtual patient, simulations increasing the molar dose of 177 Lu-DOTATATE from 2 to 2048 nmol by factors of 25 were performed. Maximum tolerated BEDs per cycle for the kidneys (10 Gy2.5 ) and for the RM (0.5 Gy15 ) were defined based on a planned total treatment of four cycles. A maximum achievable molar activity of 420 MBq/nmol was assumed. Optimal combinations of molar dose and activity were determined by applying the developed algorithm. For comparison, simulations for a typical plan with 177 Lu-DOTATATE (7.4 GBq, 265 nmol) were performed and BEDs for the OARs and for individual tumor lesions were calculated. Furthermore, to determine treatment efficacy, overall tumor control probability (oTCP) values after a four-cycle treatment were estimated for the optimal and typical plans.

RESULTS

The conducted in silico clinical trial yielded optimal molar doses and activities ranging from 24 to 512 nmol and from 6 to 30 GBq, respectively. Tumor BEDs ranged from 2 to 107 Gy10 and from 1 to 65 Gy10 for the optimal and typical plans, respectively. The estimated oTCP values showed that the optimal plans may produce adequate tumor control in six of the nine virtual patients after four cycles of 177 Lu-DOTATATE while the typical plan may be sufficient in only two virtual patients.

CONCLUSIONS

The algorithm presented can derive plans with higher tumor control than the typically delivered plan. Therefore, we propose this algorithm for clinical validation and possibly future implementation in treatment planning in molecular radiotherapy.

Lung Metastases of Intracranial Atypical Meningioma Diagnosed on Posttherapeutic Imaging After 177Lu-DOTATATE Therapy

Meningiomas are typically benign solitary intracranial tumors. Atypical (World Health Organization [WHO] grade II) or malignant/anaplastic (WHO grade III) meningiomas are seldom, and distant metastases occur only in rare exceptions. We present a case of a 54-year-old male patient with atypical (WHO grade II) meningioma who underwent 1 cycle of peptide receptor radionuclide therapy. Previous imaging studies were confined to the head, but posttherapeutic whole-body Lu-DOTATATE scintigraphy revealed thoracic uptake arising from previously undetected pulmonic meningioma metastases. The case highlights the importance of consideration of rare/untypical metastatic sides and the value of radiotracer whole-body imaging in identifying these.

Combined Yttrium-90 microsphere selective internal radiation therapy and external beam radiotherapy in patients with hepatocellular carcinoma: From clinical aspects to dosimetry

Purpose

Selective internal radiation therapy (SIRT) is an effective treatment strategy for unresectable hepatocellular carcinoma (HCC) patients. However, the prognoses of patients with portal vein thrombosis, extra-hepatic metastases, or residual tumors remain poor when treated with SIRT alone. In these patients, sequential external beam radiotherapy (EBRT) may offer a chance of salvage. Here, we reported the clinical outcomes and the detailed dosimetry analysis of 22 patients treated with combination therapy.

Methods

Between October 2011 and May 2015, 22 consecutive patients who underwent EBRT after yttrium-90 (⁹⁰Y) SIRT were included in this study. The post-SIRT ⁹⁰Y bremsstrahlung SPECT/CT of each patient was transferred to dose distribution by adopting the local deposition hypothesis. The patient-specific 3-dimensional biological effective dose distribution of combined SIRT and EBRT was generated. The overall survival and safety were evaluated. The relationship between dosimetric parameters and liver toxicity was analyzed.

Results

The mean administered activity of SIRT was 1.50 GBq (range: 0.5–2.8). The mean prescribed dose of EBRT was 42.3 Gy (range: 15–63) in 14 fractions (range: 5–15) and was targeted to the residual liver tumor in 12 patients (55%), portal vein thrombosis in 11 patients (50%), and perihilar lymphadenopathies in 4 patients (18%). The overall 1-, 2-, and 3-year survival rates were 59.8%, 47.9%, and 47.9%, respectively. Overall, 8 patients (36%) developed > grade 2 liver toxicities, and the Child-Pugh score prior to EBRT strongly affected the toxicity risk. A dosimetry analysis restricted to 18 Child-Pugh A/B patients showed that the V100 (The fraction of normal liver exposed to more than 100 Gy) to V140 significance differed between patients who did or did not experience hepatotoxicity. The V110 was the strongest predictor of hepatotoxicity (18.6±11.6% vs 29.5±5.8%; P = 0.030).

Conclusion

Combined therapy is feasible and safe if patients are carefully selected. Specifically, 3-dimensional dosimetry is crucial for the evaluation of efficacy and toxicity. The normal liver V100 to V140 values of the combined dose should be as low as possible to minimize the risk of liver toxicity.

Cancer Radiosensitizers

Radiotherapy (RT) is a mainstay treatment for many types of cancer, although it is still a large challenge to enhance radiation damage to tumor tissue and reduce side effects to healthy tissue. Radiosensitizers are promising agents that enhance injury to tumor tissue by accelerating DNA damage and producing free radicals. Several strategies have been exploited to develop highly effective and low-toxicity radiosensitizers. In this review, we highlight recent progress on radiosensitizers, including small molecules, macromolecules, and nanomaterials. First, small molecules are reviewed based on free radicals, pseudosubstrates, and other mechanisms. Second, nanomaterials, such as nanometallic materials, especially gold-based materials that have flexible surface engineering and favorable kinetic properties, have emerged as promising radiosensitizers. Finally, emerging macromolecules have shown significant advantages in RT because these molecules can be combined with biological therapy as well as drug delivery. Further research on the mechanisms of radioresistance and multidisciplinary approaches will accelerate the development of radiosensitizers.

PET imaging in patients with meningioma-report of the RANO/PET Group

Meningiomas are the most frequent nonglial primary brain tumors and represent about 30% of brain tumors. Usually, diagnosis and treatment planning are based on neuroimaging using mainly MRI or, rarely, CT. Most common treatment options are neurosurgical resection and radiotherapy (eg, radiosurgery, external fractionated radiotherapy). For follow-up after treatment, a structural imaging technique such as MRI or CT is used. However, these structural imaging modalities have limitations, particularly in terms of tumor delineation as well as diagnosis of posttherapeutic reactive changes. Molecular imaging techniques such as PET can characterize specific metabolic and cellular features which may provide clinically relevant information beyond that obtained from structural MR or CT imaging alone. Currently, the use of PET in meningioma patients is steadily increasing. In the present article, we provide recommendations for the use of PET imaging in the clinical management of meningiomas based on evidence generated from studies being validated by histology or clinical course.

Targeted radionuclide therapy in combined-modality regimens

Targeted radionuclide therapy (TRT) is a branch of cancer medicine concerned with the use of radioisotopes, radiolabelled molecules, nanoparticles, or microparticles that either naturally accumulate in or are designed to target tumours. TRT combines the specificity of molecular and sometimes physical targeting with the potent cytotoxicity of ionising radiation. Targeting vectors for TRT include antibodies, antibody fragments, proteins, peptides, and small molecules. The diversity of available carrier molecules, together with the large panel of suitable radioisotopes with unique physicochemical properties, allows vector-radionuclide pairings to be matched to the molecular, pathological, and physical characteristics of a tumour. Some pairings are designed for dual therapeutic and diagnostic applications. Use of TRT is increasing with the adoption into practice of radium-223 dichloride for the treatment of bone metastases and with the ongoing clinical development of, among others, 177Lu-dodecanetetraacetic acid tyrosine-3-octreotate (DOTATATE) for the treatment of neuroendocrine tumours and 90Y-microspheres for the treatment of hepatic tumours. The increasing use of TRT raises the question of how best to integrate TRT into multimodality protocols. Achievements in this area and the future prospects of TRT are evaluated in this Review.

Out-of-field doses in radiotherapy: Input to epidemiological studies and dose-risk models

Out-of-field doses in radiotherapy have been increasingly studied in recent years because of the generally improved survival of patients who have received radiotherapy as part of their treatment for cancer and their subsequent risk of a second malignancy. This short article attempts to identify some current problems, challenges and opportunities for dosimetry developments in this field. Out-of-field doses and derived risk estimates contribute to general knowledge about radiation effects on humans as well as contributing to risk-benefit considerations for the individual patient. It is suggested that for input into epidemiological studies, the complete dose description (i.e. the synthesis of therapy and imaging doses from all the treatment and imaging modalities) is ideally required, although there is currently no common dosimetry framework which easily covers all modalities. A general strategy for out-of-field dose estimation requires development and improvement in several areas including (i) dosimetry in regions of steep dose gradient close to the field edge (ii) experimentally verified analytical and Monte Carlo models for out-of-field doses (iii) the validity of treatment planning system algorithms outside the field edge (iv) dosimetry of critical sub-structures in organs at risk (v) mixed field (including neutron) dosimetry in proton and ion radiotherapy and photoneutron production in high energy photon beams (vi) the most appropriate quantities to use in neutron dosimetry in a radiotherapy context and (vii) simplification of measurement methods in regions distant from the target volume.

EANO guidelines for the diagnosis and treatment of meningiomas

Although meningiomas are the most common intracranial tumours, the level of evidence to provide recommendations for the diagnosis and treatment of meningiomas is low compared with other tumours such as high-grade gliomas. The meningioma task force of the European Association of Neuro-Oncology (EANO) assessed the scientific literature and composed a framework of the best possible evidence-based recommendations for health professionals. The provisional diagnosis of meningioma is mainly made by MRI. Definitive diagnosis, including histological classification, grading, and molecular profiling, requires a surgical procedure to obtain tumour tissue. Therefore, in many elderly patients, observation is the best therapeutic option. If therapy is deemed necessary, the standard treatment is gross total surgical resection including the involved dura. As an alternative, radiosurgery can be done for small tumours, or fractionated radiotherapy in large or previously treated tumours. Treatment concepts combining surgery and radiosurgery or fractionated radiotherapy, which enable treatment of the complete tumour volume with low morbidity, are being developed. Pharmacotherapy for meningiomas has remained largely experimental. However, antiangiogenic drugs, peptide receptor radionuclide therapy, and targeted agents are promising candidates for future pharmacological approaches to treat refractory meningiomas across all WHO grades.