Cerebral radiation necrosis

Cerebral radiation‐induced injury ranges from acute reversible edema to late irreversible radiation necrosis (RN). Cerebral RN is poorly responsive to treatment, is associated with permanent neurological deficits and occasionally progresses to death. We review the literature regarding cerebral RN after radiotherapy for various brain and head and neck lesions and discuss its clinical features, imaging characteristics, pathophysiology and treatment. For new enhancing lesions on computed tomography or magnetic resonance imaging, apart from tumor progression or recurrence, RN needs to be considered in the differential diagnosis. Further studies are required to design chemoradiotherapy protocols that are effective in treating tumors while minimizing risk of RN. Current available treatments for RN, steroid and surgery, only relieve the mass effect. None of the experimental treatments to date have consistently been shown to reverse the pathologic process of RN.     

Reevaluating the imaging definition of tumor progression: perfusion MRI quantifies recurrent glioblastoma tumor fraction, pseudoprogression, and radiation necrosis to predict survival

INTRODUCTION: Contrast-enhanced MRI (CE-MRI) represents the current mainstay for monitoring treatment response in glioblastoma multiforme (GBM), based on the premise that enlarging lesions reflect increasing tumor burden, treatment failure, and poor prognosis. Unfortunately, irradiating such tumors can induce changes in CE-MRI that mimic tumor recurrence, so called post treatment radiation effect (PTRE), and in fact, both PTRE and tumor re-growth can occur together. Because PTRE represents treatment success, the relative histologic fraction of tumor growth versus PTRE affects survival. Studies suggest that Perfusion MRI (pMRI)–based measures of relative cerebral blood volume (rCBV) can noninvasively estimate histologic tumor fraction to predict clinical outcome. There are several proposed pMRI-based analytic methods, although none have been correlated with overall survival (OS). This study compares how well histologic tumor fraction and OS correlate with several pMRI-based metrics. METHODS: We recruited previously treated patients with GBM undergoing surgical re-resection for suspected tumor recurrence and calculated preoperative pMRI-based metrics within CE-MRI enhancing lesions: rCBV mean, mode, maximum, width, and a new thresholding metric called pMRI–fractional tumor burden (pMRI-FTB). We correlated all pMRI-based metrics with histologic tumor fraction and OS. RESULTS: Among 25 recurrent patients with GBM, histologic tumor fraction correlated most strongly with pMRI-FTB (r = 0.82; P < .0001), which was the only imaging metric that correlated with OS (P<.02). CONCLUSION: The pMRI-FTB metric reliably estimates histologic tumor fraction (i.e., tumor burden) and correlates with OS in the context of recurrent GBM. This technique may offer a promising biomarker of tumor progression and clinical outcome for future clinical trials.     

Disease progression or pseudoprogression after concomitant radiochemotherapy treatment: pitfalls in neurooncology

Although radionecrosis has been exhaustively described in depth in the neurooncological literature, its diagnosis is still a challenging issue because its radiological pattern is frequently indistinguishable from that of tumor recurrence. This review discusses the causes of radionecrosis and the potential effect of adjuvant chemotherapy concomitant with radiotherapy on its rate and onset. The potential pitfalls in clinical studies attempting to make a differential diagnosis between radionecrosis and disease progression are also discussed.     

磁共振灌注成像鉴别诊断高级别脑胶质瘤复发与假性进展

目的 探讨磁共振灌注成像(magnetic resonance perfusion weighted imaging,MR-PWI)鉴别诊断高级别脑胶质瘤综合治疗后复发与假性进展的价值.方法 纳入56例经手术切除后行术后同步放化疗的高级别脑胶质瘤患者,在MRI复查时行3.0T MR-PWI及常规T1加权增强(T1-weighted imaging,T1WI)检查,对术区新强化病灶行相对脑血容量(relative cerebral blood volume,rCBV)值的灌注分析,并行立体定向活检进行病理诊断.使用ROC评估rCBV值在鉴别诊断高级别脑胶质瘤复发与假性进展中的最佳临界值、敏感性和特异性.结果 56例患者,经病理证实30例为胶质瘤复发,26例为假性进展.胶质瘤复发组的rCBV值为2.81±1.26,假性进展组rCBV值为0.53±0.15,差异有统计学意义(P＜0.01).ROC曲线分析显示,以rCBV＞2.15作为判断胶质瘤复发的临界值,其鉴别诊断复发与假性进展的敏感性和特异性分别为84.5％、100.0％.结论 MR-PWI可以较准确区分高级别脑胶质瘤复发还是假性进展,为疾病的诊治提供客观依据.     

Pseudoprogression in patients with glioblastoma: clinical relevance despite low incidence

Background

According to the Response Assessment in Neuro-Oncology criteria, new enhancement within the radiation field on contrast enhanced T1-weighted images within 12 weeks after completion of radiotherapy should not qualify for progressive disease, since up to 50% of these cases may be pseudoprogression (PsP). To validate this concept, we assessed incidence and overall survival (OS) of patients with suspected and confirmed PsP dependent on different time intervals and definitions of PsP.

Methods

Patients with newly diagnosed glioblastoma and an enhancement increase of at least 25% after completion of standard radiochemotherapy at month 1, 4, 7, or 10 were eligible. Based on the development of the enhancement in follow-up examinations, patients were categorized as either PsP (subgrouped as complete resolution/decrease >50% and decrease <50%/stable) or true progression.

Results

Out of 548 patients, 79 fulfilled the inclusion criteria. Of these 79 patients, 9 (11.4%) showed PsP (6/45 patients at 1 month, 2/17 at 4 months, 1/9 at 7 months, and 0/8 at 10 months). Complete resolution of the enhancement was found in 1, decrease >50% in 3, decrease <50% in 2, and stable enhancement in 3 patients with PsP. Patients with PsP showed a significantly longer OS (P < .012). No difference in OS was found among PsP subgroups.

Conclusions

This series challenges the current concept of PsP. Even though we could confirm a prolonged OS of patients with PsP, the incidence of PsP was lower than reported previously and extended beyond 12 weeks.     

High-grade glioma management and response assessment—recent advances and current challenges

The management of high-grade gliomas (hggs) is complex and ever-evolving. The standard of care for the treatment of hggs consists of surgery, chemotherapy, and radiotherapy. However, treatment options are influenced by multiple factors such as patient age and performance status, extent of tumour resection, biomarker profile, and tumour histology and grade. Follow-up cranial magnetic resonance imaging (mri) to differentiate treatment response from treatment effect can be challenging and affects clinical decision-making. An assortment of advanced radiologic techniques—including perfusion imaging with dynamic susceptibility contrast mri, dynamic contrast-enhanced mri, diffusion-weighted imaging, proton spectroscopy, mri subtraction imaging, and amino acid radiotracer imaging—can now incorporate novel physiologic data, providing new methods to help characterize tumour progression, pseudoprogression, and pseudoresponse. In the present review, we provide an overview of current treatment options for hgg and summarize recent advances and challenges in imaging technology.