Intraoperative MRI to guide the resection of primary supratentorial glioblastoma multiforme--a quantitative radiological analysis

Transoperative Magnetic Resonance Imaging in Awake Glioma Surgery: Experience in a Latin American Tertiary-Level Center

OBJECTIVE

Analyze the usefulness, efficacy, and safety of transoperative magnetic resonance imaging (tMRI) in glioma surgery in awake patients.

METHODS

Retrospective, single-center, analytical study of a cohort of patients who underwent awake surgery for gliomas by the same surgeon in a third-level Argentine center, in the period between 2012 and 2022. Only patients with pathology-confirmed gliomas, with 6-month follow-up, who had preoperative and postoperative volumetric magnetic resonance imaging, were included in this sample. Subsequently, we analyzed which patients received surgery with the tMRI protocol and the results using multivariate regression analysis.

RESULTS

A total of 71 patients were included. A tMRI study was performed on 22 (31%) of these patients. The use of tMRI increased the percentage of resection by 20% (P = 0.03), thereby increasing the possibility of gross total resection. However, using tMRI significantly extended surgical time by 84 minutes (P < 0.001). In 55% of the patients in whom tMRI was performed, the resection was continued after it. The use of tMRI did not increase the rate of infections or the development of surgically associated neurological deficits in the long term, despite the fact that 47% of the patients showed the development of a new deficit or worsening of a previous one during the intraoperative period.

CONCLUSIONS

The use of tMRI in awake glioma surgery proved to be a safe tool that contributes to increasing the degree of tumor resection, compared to the use of neurophysiological mapping and neuronavigation, at the expense of increased surgical times and costs. We consider tMRI in awake glioma surgery should be used in properly selected cases.

Intraoperative use of ultra-low-field, portable magnetic resonance imaging - first report

Background

Intraoperative use of portable magnetic resonance imaging (pMRI) has become a valuable tool in a surgeon's arsenal since its inception. It allows intraoperative localization of tumor extent and identification of residual disease, hence maximizing tumor resection. Its utility has been widespread in high-income countries for the past 20 years, but in lower-middle-income countries (LMIC), it is still not widely available due to several reasons, including cost constraints. The use of intraoperative pMRI may be a cost-effective and efficient substitute for conventional MRI machines. The authors present a case where a pMRI device was used intraoperatively in an LMIC setting.

Case Description

The authors performed a microscopic transsphenoidal resection of a sellar lesion with intraoperative imaging using the pMRI system on a 45-year-old man with a nonfunctioning pituitary macroadenoma. Without the need for an MRI suite or other MRI-compatible equipment, the scan was conducted within the confinements of a standard operating room. Low-field MRI showed some residual disease and postsurgical changes, comparable to postoperative high-field MRI.

Conclusion

To the best of our knowledge, our report provides the first documented successful intraoperative transsphenoidal resection of a pituitary adenoma using an ultra-low-field pMRI device. The device can potentially enhance neurosurgical capacity in resource-constrained settings and improve patient outcomes in developing country.

Timing of Early Postoperative MRI following Primary Glioblastoma Surgery-A Retrospective Study of Contrast Enhancements in 311 Patients

An early postoperative MRI is recommended following Glioblastoma surgery. This retrospective, observational study aimed to investigate the timing of an early postoperative MRI among 311 patients. The patterns of the contrast enhancement (thin linear, thick linear, nodular, and diffuse) and time from surgery to the early postoperative MRI were recorded. The primary endpoint was the frequencies of the different contrast enhancements within and beyond the 48-h from surgery. The time dependence of the resection status and the clinical parameters were analysed as well. The frequency of the thin linear contrast enhancements significantly increased from 99/183 (50.8%) within 48-h post-surgery to 56/81 (69.1%) beyond 48-h post-surgery. Similarly, MRI scans with no contrast enhancements significantly declined from 41/183 (22.4%) within 48-h post-surgery to 7/81 (8.6%) beyond 48-h post-surgery. No significant differences were found for the other types of contrast enhancements and the results were robust in relation to the choice of categorisation of the postoperative periods. Both the resection status and the clinical parameters were not statistically different in patients with an MRI performed before and after 48 h. The findings suggest that surgically induced contrast enhancements are less frequent when an early postoperative MRI is performed earlier than 48-h, supporting the recommendation of a 48-h window for an early postoperative MRI.

Low-field MRI: Clinical promise and challenges

Modern MRI scanners have trended toward higher field strengths to maximize signal and resolution while minimizing scan time. However, high-field devices remain expensive to install and operate, making them scarce outside of high-income countries and major population centers. Low-field strength scanners have drawn renewed academic, industry, and philanthropic interest due to advantages that could dramatically increase imaging access, including lower cost and portability. Nevertheless, low-field MRI still faces inherent limitations in image quality that come with decreased signal. In this article, we review advantages and disadvantages of low-field MRI scanners, describe hardware and software innovations that accentuate advantages and mitigate disadvantages, and consider clinical applications for a new generation of low-field devices. In our review, we explore how these devices are being or could be used for high acuity brain imaging, outpatient neuroimaging, MRI-guided procedures, pediatric imaging, and musculoskeletal imaging. Challenges for their successful clinical translation include selecting and validating appropriate use cases, integrating with standards of care in high resource settings, expanding options with actionable information in low resource settings, and facilitating health care providers and clinical practice in new ways. By embracing both the promise and challenges of low-field MRI, clinicians and researchers have an opportunity to transform medical care for patients around the world. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY: Stage 6.

Updates in intraoperative strategies for enhancing intra-axial brain tumor control

To ensure excellent postoperative clinical outcomes while preserving critical neurologic function, neurosurgeons who manage patients with intra-axial brain tumors can use intraoperative technologies and tools to achieve maximal safe resection. Neurosurgical oncology revolves around safe and optimal extent of resection, which further dictates subsequent treatment regimens and patient outcomes. Various methods can be adapted for treating both primary and secondary intra-axial brain lesions. We present a review of recent advances and published research centered on different innovative tools and techniques, including fluorescence-guided surgery, new methods of drug delivery, and minimally invasive procedural options.

Evaluation of a Navigated 3D Ultrasound Integration for Brain Tumor Surgery: First Results of an Ongoing Prospective Study

The aim of the study was to assess the quality, accuracy and benefit of navigated 2D and 3D ultrasound for intra-axial tumor surgery in a prospective study. Patients intended for gross total resection were consecutively enrolled. Intraoperatively, a 2D and 3D iUS-based resection was performed. During surgery, the image quality, clinical benefit and navigation accuracy were recorded based on a standardized protocol using Likert’s scales. A total of 16 consecutive patients were included. Mean ratings of image quality in 2D iUS were significantly higher than in 3D iUS (p < 0.001). There was no relevant decrease in rating during the surgery in 2D and 3D iUS (p > 0.46). The benefit was rated 2.2 in 2D iUS and 2.6 in 3D iUS (p = 0.08). The benefit remained stable in 2D, while there was a slight decrease in the benefit in 3D after complete tumor resection (p = 0.09). The accuracy was similar in both (mean 2.2 p = 0.88). Seven patients had a small tumor remnant in intraoperative MRT (mean 0.98 cm3) that was not appreciated with iUS. Crucially, 3D iUS allows for an accurate intraoperative update of imaging with slightly lower image quality than 2D iUS. Our preliminary data suggest that the benefit and accuracy of 2D and 3D iUS navigation do not undergo significant variations during tumor resection.

Use of intraoperative MRI for resection of intracranial tumors: A nationwide analysis of short-term outcomes

OBJECTIVE

Recent evidence supports the use of intraoperative MRI (iMRI) during resection of intracranial tumors due to its demonstrated efficacy and clinical benefit. Though many single-center investigations have been conducted, larger nationwide outcomes have yet to be characterized.

METHODS

We used the American College of Surgeons National Surgical Quality Improvement Program database to examine baseline characteristics and 30-day postoperative outcomes among patients undergoing craniotomy for tumor resection with and without iMRI. Comparisons between outcomes were accomplished after propensity matching using chi-square tests for categorical variables and Welch two-sample t-tests for continuous variables.

RESULTS

A total of 38,003 patients met inclusion criteria. Of this population, 54 (0.1%) received iMRI, while 37,949 (99.9%) did not receive iMRI. After propensity score matching, the resulting groups consisted of an iMRI group (n = 54) and a matched non-iMRI group (n = 54). Procedures involving iMRI were associated with significantly increased operation length compared to those without (p < 0.01). Length of hospital stay was higher in patients without iMRI, with this difference trending towards significance (p = 0.05) in the unmatched comparison. Patients undergoing craniotomy without iMRI had a higher rate of readmission (p = 0.04). There was no significant difference in occurrence of other adverse events between the two patient groups.

CONCLUSION

Despite increasing operative length, iMRI is not associated with higher infection rate and may have a clinical benefit associated with reducing readmissions and a trend towards reducing inpatient length of stay. Additional nationwide analyses including more iMRI patients would provide further insight into the strength of these findings.

The value of intraoperative MRI in recurrent intracranial tumor surgery

OBJECTIVE

Identifying tumor remnants in previously operated tumor lesions remains a challenge. Intraoperative MRI (ioMRI) helps the neurosurgeon to reorient and update image guidance during surgery. The purpose of this study was to analyze whether ioMRI is more efficient in detecting tumor remnants in the surgery of recurrent lesions compared with primary surgery.

METHODS

All consecutive patients undergoing elective intracranial tumor surgery between 2013 and 2018 at the authors’ institution were included in this retrospective cohort study. The cohort was divided into two groups: re-craniotomy and primary craniotomy. In contrast-enhancing tumors, tumor suspicion in ioMRI was defined as contrast enhancement in T1-weighted imaging. In non–contrast-enhancing tumors, tumor suspicion was defined as hypointensity in T1-weighted imaging and hyperintensity in T2-weighted imaging and FLAIR. In cases in which the ioMRI tumor suspicion was a false positive and not confirmed during in situ inspection by the neurosurgeon, the signal was defined as a tumor-imitating ioMRI signal (TIM). Descriptive statistics were performed.

RESULTS

A total of 214 tumor surgeries met the inclusion criteria. The re-craniotomy group included 89 surgeries, and the primary craniotomy group included 123 surgeries. Initial complete resection after ioMRI was less frequent in the re-craniotomy group than in the primary craniotomy group, but this was not a statistically significant difference. Radiological suspicion of tumor remnants in ioMRI was present in 78% of re-craniotomy surgeries and 69% of primary craniotomy surgeries. The incidence of false-positive TIMs was significantly higher in the re-craniotomy group (n = 11, 12%) compared with the primary craniotomy group (n = 5, 4%; p = 0.015), and in contrast-enhancing tumors was related to hemorrhages in situ (n = 9).

CONCLUSIONS

A history of previous surgery in contrast-enhancing tumors made correct identification of tumor remnants in ioMRI more difficult, with a higher rate of false-positive ioMRI signals in the re-craniotomy group. The majority of TIMs were associated with the inability to distinguish contrast enhancement from hyperacute hemorrhage. The addition of a specific sequence in ioMRI to further differentiate both should be investigated in future studies.

Surgically Induced Contrast Enhancements on Intraoperative and Early Postoperative MRI Following High-Grade Glioma Surgery: A Systematic Review

For the radiological assessment of resection of high-grade gliomas, a 72-h diagnostic window is recommended to limit surgically induced contrast enhancements. However, such enhancements may occur earlier than 72 h post-surgery. This systematic review aimed to assess the evidence on the timing of the postsurgical MRI. PubMed, Embase, Web of Science and Cochrane were searched following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only original research articles describing surgically induced contrast enhancements on MRI after resection for high-grade gliomas were included and analysed. The frequency of different contrast enhancement patterns on intraoperative MRI (iMRI) and early postoperative MRI (epMRI) was recorded. The search resulted in 1443 studies after removing duplicates, and a total of 12 studies were chosen for final review. Surgically induced contrast enhancements were reported at all time points after surgery, including on iMRI, but their type and frequency vary. Thin linear contrast enhancements were commonly found to be surgically induced and were less frequently recorded on postoperative days 1 and 2. This suggests that the optimal time to scan may be at or before this time. However, the evidence is limited, and higher-quality studies using larger and consecutively sampled populations are needed.

Endoscope-assisted fluorescence-guided resection allowing supratotal removal in glioblastoma surgery

OBJECTIVE

Several studies have proven the benefits of a wide extent of resection (EOR) of contrast-enhancing tumor in terms of progression-free survival (PFS) and overall survival (OS) in patients with glioblastoma (GBM). Thus, gross-total resection (GTR) is the main surgical goal in noneloquently located GBMs. Complete tumor removal can be almost doubled by microscopic fluorescence guidance. Recently, a study has shown that an endoscope with a light source capable of inducing fluorescence allows visualization of remnant fluorescent tumor tissue even after complete microscopic fluorescence-guided (FG) resection, thereby increasing the rate of GTR. Since tumor infiltration spreads beyond the borders of contrast enhancement on MRI, the aim of this study was to determine via volumetric analyses of the EOR whether endoscope-assisted FG resection enables supratotal resection beyond the borders of contrast enhancement.

METHODS

The authors conducted a retrospective single-center analysis of a consecutive series of patients with primary GBM presumed to be noneloquently located and routinely operated on at their institution between January 2015 and February 2018 using a combined microscopic and endoscopic FG resection. A 20-mg/kg dose of 5-aminolevulinic acid (5-ALA) was administered 4 hours before surgery. After complete microscopic FG resection, the resection cavity was scanned using the endoscope. Detected residual fluorescent tissue was resected and embedded separately for histopathological examination. Nonenhanced and contrast-enhanced 3D T1-weighted MR images acquired before and within 48 hours after tumor resection were analyzed using 3D Slicer. Bias field-corrected data were used to segment brain parenchyma, contrast-enhancing tumor, and the resection cavity for volume definition. The difference between the pre- and postoperative brain parenchyma volume was considered to be equivalent to the resected nonenhancing but fluorescent tumor tissue. The volume of resected tumor tissue was calculated from the sum of resected contrast-enhancing tumor tissue and resected nonenhancing tumor tissue.

RESULTS

Twelve patients with GBM were operated on using endoscopic after complete microscopic FG resection. In all cases, residual fluorescent tissue not visualized with the microscope was detected. Histopathological examination confirmed residual tumor tissue in all specimens. The mean preoperative volume of brain parenchyma without contrast-enhancing tumor was 1213.2 cm3. The mean postoperative volume of brain parenchyma without the resection cavity was 1151.2 cm3, accounting for a mean volume of nonenhancing but fluorescent tumor tissue of 62.0 cm3. The mean relative rate of the overall resected volume compared to the contrast-enhancing tumor volume was 244.7% (p < 0.001).

CONCLUSIONS

Combined microscopic and endoscopic FG resection of GBM significantly increases the EOR and allows the surgeon to achieve a supratotal resection beyond the borders of contrast enhancement in noneloquently located GBM.

Frequency and Evolution of New Postoperative Enhancement on 3 Tesla Intraoperative and Early Postoperative Magnetic Resonance Imaging

BACKGROUND

Intraoperative magnetic resonance imaging (IO-MRI) provides real-time assessment of extent of resection of brain tumor. Development of new enhancement during IO-MRI can confound interpretation of residual enhancing tumor, although the incidence of this finding is unknown.

OBJECTIVE

To determine the frequency of new enhancement during brain tumor resection on intraoperative 3 Tesla (3T) MRI. To optimize the postoperative imaging window after brain tumor resection using 1.5 and 3T MRI.

METHODS

We retrospectively evaluated 64 IO-MRI performed for patients with enhancing brain lesions referred for biopsy or resection as well as a subset with an early postoperative MRI (EP-MRI) within 72 h of surgery (N = 42), and a subset with a late postoperative MRI (LP-MRI) performed between 120 h and 8 wk postsurgery (N = 34). Three radiologists assessed for new enhancement on IO-MRI, and change in enhancement on available EP-MRI and LP-MRI. Consensus was determined by majority response. Inter-rater agreement was assessed using percentage agreement.

RESULTS

A total of 10 out of 64 (16%) of the IO-MRI demonstrated new enhancement. Seven of 10 patients with available EP-MRI demonstrated decreased/resolved enhancement. One out of 42 (2%) of the EP-MRI demonstrated new enhancement, which decreased on LP-MRI. Agreement was 74% for the assessment of new enhancement on IO-MRI and 81% for the assessment of new enhancement on the EP-MRI.

CONCLUSION

New enhancement occurs in intraoperative 3T MRI in 16% of patients after brain tumor resection, which decreases or resolves on subsequent MRI within 72 h of surgery. Our findings indicate the opportunity for further study to optimize the postoperative imaging window.

Fluorescence Guidance and Intraoperative Adjuvants to Maximize Extent of Resection

Safely maximizing extent of resection has become the central goal in glioma surgery. Especially in eloquent cortex, the goal of maximal resection is balanced with neurological risk. As new technologies emerge in the field of neurosurgery, the standards for maximal safe resection have been elevated. Fluorescence-guided surgery, intraoperative magnetic resonance imaging, and microscopic imaging methods are among the most well-validated tools available to enhance the level of accuracy and safety in glioma surgery. Each technology uses a different characteristic of glioma tissue to identify and differentiate tumor tissue from normal brain and is most effective in the context of anatomic, connectomic, and neurophysiologic context. While each tool is able to enhance resection, multiple modalities are often used in conjunction to achieve maximal safe resection. This paper reviews the mechanism and utility of the major adjuncts available for use in glioma surgery, especially in tumors within eloquent areas, and puts forth the foundation for a unified approach to how leverage currently available technology to ensure maximal safe resection.

Impact of Extent of Resection on Incidence of Postoperative Complications in Patients With Glioblastoma

BACKGROUND

Extent of resection (EOR) is well established as correlating with overall survival in patients with glioblastoma (GBM). The impact of EOR on reported quality metrics such as patient safety indicators (PSIs) and hospital-acquired conditions (HACs) is unknown.

OBJECTIVE

To perform a retrospective study to evaluate possible associations between EOR and the incidence of PSIs and HACs.

METHODS

We queried all patients diagnosed with GBM who underwent surgical resection at our institution between January 2011 and May 2017. Pre- and postoperative magnetic resonance images were analyzed for EOR. Each chart was reviewed to determine the incidence of PSIs and HACs.

RESULTS

A total of 284 patients met the inclusion criteria. EOR ranged from 39.00 to 100%, with a median of 99.84% and a mean of 95.7%. There were 16 PSI, and 13 HAC, events. There were no significant differences in the rates of PSIs or HACs when compared between patients stratified by gross total resection (EOR ≥ 95%) and subtotal resection (EOR < 95%). The odds of encountering a PSI or HAC were 2.5 times more likely in the subtotal resection group compared to the gross total resection group (P = .58). After adjusting for confounders, the odds of encountering a PSI or HAC in the subtotal resection group were 3.9 times greater than for the gross total resection group (P < .05).

CONCLUSION

Gross total resection of GBM is associated with a decreased incidence of PSIs and HACs, as compared to subtotal resection.

Importance and Evidence of Extent of Resection in Glioblastoma

Maximal safe resection is an essential part of the multidisciplinary care of patients with glioblastoma. A growing body of data shows that gross total resection is an independent prognostic factor associated with improved clinical outcome. The relationship between extent of glioblastoma (GB) resection and clinical benefit depends critically on the balance between cytoreduction and avoiding neurologic morbidity. The definition of the extent of tumor resection, how this is best measured pre- and postoperatively, and its relation to volume of residual tumor is still discussed. We review the literature supporting extent of resection in GB, highlighting the importance of a standardized definition and measurement of extent of resection to allow greater collaboration in research projects and trials. Recent developments in neurosurgical techniques and technologies focused on maximizing extent of resection and safety are discussed.

A new application of ultrasound-magnetic resonance multimodal fusion virtual navigation in glioma surgery

Background

Long-term survival and high-quality life of patients with gliomas depends on the extent of resection (EOR) and the protection of functional white matter fibers. The navigation system provides precise positioning for surgery based on preoperative magnetic resonance imaging (MRI) but the precision decreases when intraoperative brain drift occurs. Ultrasound (US) can support real-time imaging and correct brain shift. The real-time US-MRI multimodal fusion virtual navigation system (UMNS) is a new technique for glioma surgery. In order to obtain a maximum EOR and functional protection, this study aimed to explore the feasibility, efficiency, and safety of real-time UMNS for glioma surgery, and to evaluate the benefit of the new application by UMNS presetting markers between the tumor and functional white matter fiber surgery.

Methods

A retrospective analysis included 45 patients who underwent glioma surgery, 19 patients with only intraoperative US, and 26 patients with UMNS. A preoperative plan was made by 3D-slicer software based on preoperative MRI. This was combined with a reconstruction of diffusion tensor imaging (DTI) that designed the important locations as "warning points" between functional white matter fibers and tumor. Following patient registration, markers were injected into preset "warning points" under image-guided UMNS in order to give us a warning during surgery in case of postoperative function deficits. The operating time, volumetric assessment in glioma resection, and postoperative complications were evaluated and used to compared those surgeries using intraoperative US (iUS) with those surgeries using intraoperate MRI (iMRI) navigation.

Results

A total of 45 patients underwent glioma surgery. Gross total removal (GTR) of iUS alone was achieved in 6 of 19 cases, while this was achieved in 22 of 26 cases with UMNS alone, demonstrating an improvement in rate of GTR from 31.58% to 84.62%, respectively. This may be attributable to the superior US image quality provided by UMNS. In 13 of 26 cases, there was improved image quality (from poor/moderate to moderate/good) with the aid of UMNS. In addition, the consistency of EOR of postoperative MRI evaluated by UMNS (92.31%) was higher than when using iUS alone (42.11%). The whole process of intraoperative scanning time and marker injection did not lead to a significant delay of the operating time compared to using iUS alone, and has been reported to be shorter than with iMRI as well. Furthermore, the percentage of postoperative morbidity in the UMNS group was lower than that in the iUS group (motor deficit: 11.54% vs. 42.11%; aphasia: P =3.85% vs. 31.58%, respectively).

Conclusions

Real-time UMNS is an effective, timesaving technology that offers high quality intraoperative imaging. Injection markers between functional white matter fibers and tumor by UMNS can help to obtain a maximum EOR of glioma and functional protection postoperatively. The integration of iUS into the neuronavigation system offered quick and helpful intra-operative images.

Intraoperative MRI and FLAIR Analysis: Implications for low-grade glioma surgery

PURPOSE

Intraoperative MRI (iMRI) offers the possibility of acquiring intraoperatively real-time images that will guide neurosurgeons when removing brain tumors. The objective of this study was to report the existence of FLAIR abnormalities on iMRI that may occur on the margin of a brain resection and may lead to misdiagnosis of residual tumor.

METHODS

We retrospectively analyzed intraoperative MRI (iMRI) in 21 consecutive patients who underwent surgery for a low-grade glioma. Two readers independently reviewed iMRI images to search for the presence of a FLAIR hyperintensity surrounding the surgical cavity. For each patient, they were instructed to characterize FLAIR abnormalities on the margins of the resected area as (1) no FLAIR abnormality; (2) "linear FLAIR hyperintensity (LFH)", when a<5mm linear FLAIR hyperintensity was present; or (3) "nodular FLAIR hyperintensity (NFH)", in the case of a thick and nodular FLAIR hyperintensity.

RESULTS

LFH were present on at least one surgical margin of one third of the patients analyzed with iMRI, and vanished on follow-up MRI, confirming its transient condition; whereas NFH were linked to persistence of pre-surgical abnormalities, such as residual tumor as confirmed or by histopathological analysis of a second surgery or by its remnant on follow-up MRI.

CONCLUSION

Linear FLAIR hyperintensities can be present on surgical margins analyzed by iMRI and should not be mistaken for residual tumor.

Evaluation of the extent of resection and detection of ischemic lesions with intraoperative MRI in glioma surgery: is intraoperative MRI superior to early postoperative MRI?

OBJECTIVE

MRI scans obtained within 48-72 hours (early postoperative MRI [epMRI]), prior to any postoperative reactive changes, are recommended for the accurate assessment of the extent of resection (EOR) after glioma surgery. Diffusion-weighted imaging (DWI) enables ischemic lesions to be detected and distinguished from the residual tumor. Prior studies, however, revealed that postoperative reactive changes were often present, even in epMRI. Although intraoperative MRI (iMRI) is widely used to maximize safe resection during glioma surgery, it is unclear whether iMRI is superior to epMRI when evaluating the EOR, because it theoretically shows fewer postoperative reactive changes. In addition, the ability to detect ischemic lesions using iMRI has not been investigated.

METHODS

The authors retrospectively analyzed prospectively collected data in 30 patients with glioma (22 and 8 patients with enhancing and nonenhancing lesions, respectively) who underwent tumor resection. These patients had received preoperative MRI within 24 hours prior to surgery, postresection radiological evaluation with iMRI during surgery, and epMRI within 24 hours after surgery, with all neuroimaging performed using identical 1.5T MRI scanners. The authors compared iMRI or epMRI with preoperative MRI, and defined a postoperative reactive change as a new postoperative enhancement or T2 high-intensity area (HIA), if this lesion was outside of the preoperative original tumor location. In addition, postoperative ischemia was evaluated on DWI. The iMRI and epMRI findings were compared in terms of 1) postoperative reactive changes, 2) evaluation of the EOR, and 3) presence of ischemic lesion on DWI.

RESULTS

In patients with enhancing lesions, a new enhancement was seen in 8 of 22 patients (36.4%) on iMRI and in 12 of 22 patients (54.5%) on epMRI. In patients with nonenhancing lesions, a new T2 HIA was seen in 4 of 8 patients (50.0%) on iMRI and in 7 of 8 patients (87.5%) on epMRI. A discrepancy between the EOR measured on iMRI and epMRI was noted in 5 of the 22 patients (22.7%) with enhancing lesions, and in 3 of the 8 patients (37.5%) with nonenhancing lesions. The occurrence of ischemic lesions on DWI was found in 5 of 30 patients (16.7%) on iMRI, whereas it was found in 16 of 30 patients (53.3%) on epMRI (p = 0.003); ischemic lesions were underestimated on iMRI in 11 patients.

CONCLUSIONS

Overall, given the lower incidence of postoperative reactive changes on iMRI, it was superior to epMRI in evaluating the EOR in patients with glioma, both with enhancing and nonenhancing lesions. However, because ischemic lesions can be overlooked on iMRI, the authors recommend only the additional DWI scan during the early postoperative period. Clinicians need to be mindful about not overestimating the presence of residual tumor on epMRI due to the high incidence of postoperative reactive changes.

Which Parameter Is More Important for the Prognosis of New-Onset Adult Glioblastoma: Residual Tumor Volume or Extent of Resection?

BACKGROUND

The extent of resection (EOR) and residual tumor volume (RTV) are 2 pivotal predictors influencing the survival of patients with new-onset adult glioblastoma. Which of these 2 factors is more important remains unclear, however. The present aimed to evaluate and compare the accuracy of EOR and RTV, based on contrast-enhancing (CE) T1-weighted magnetic resonance imaging (MRI) and T2-weighted/fluid-attenuated inversion recovery (F) MRI, as prognostic factors in these patients.

METHODS

In this retrospective study, data were extracted from the databases of 2 hospitals between January 1, 2013, and December 31, 2015. The subjects were divided into 2 groups, the total resection group and the partial resection group. The analysis comprised EOR and RTV. Statistical analysis was performed after controlling for other relevant factors.

RESULTS

We analyzed 292 patients with new-onset glioblastoma who met the inclusion criteria. In the partial resection group, univariate analysis revealed that CE-EOR, CE-RTV, F-EOR, and F-RTV were correlated with progression-free survival (PFS) and overall survival (OS), but multivariate analysis identified no correlation between CE-EOR or F-EOR and PFS or OS. In the total resection group, F-EOR and F-RTV were correlated with PFS and OS in univariate analysis, but F-EOR was not correlated in multivariate analysis.

CONCLUSIONS

Regardless of total or partial CE tumor resection, EOR might not be an independent prognostic factor. In contrast, RTV has the potential to offer greater predictive power for the prognosis of new-onset adult glioblastoma. Further investigations of the correlations of RTV and EOR with survival in patients with new-onset glioblastoma are needed.

Intraoperative imaging techniques for glioma surgery

Gliomas are CNS neoplasms that infiltrate the surrounding brain parenchyma, complicating their treatment. Tools that increase extent of resection while preventing neurological deficit are essential to improve prognosis of patients diagnosed with gliomas. Tools such as intraoperative MRI, ultrasound and fluorescence-guided microsurgery have been used in the surgical resection of CNS gliomas with the goal of maximizing extent of resection to improve patient outcomes. In addition, emerging experimental techniques, for example, optical coherence tomography and Raman spectroscopy are promising techniques which could 1 day add to the increasing armamentarium used in the surgical resection of CNS gliomas. Here, we present the potential advantages and limitations of these imaging techniques for the purposes of identifying gliomas in the operating room.

Intraoperative MRI for the management of brain lesions adjacent to eloquent areas

BACKGROUND

The aim of our study was to report the usefulness of intraoperative MRI guidance in the resection of brain lesions adjacent to eloquent areas.

PATIENTS AND METHODS

A single center prospective series of gliomas amenable to optimized resection with intraoperative MRI between September 2014 and December 2015.

RESULTS

The study included 56 patients. The median duration of the first intraoperative MRI was 38min, interquartile range (IQR 30-46). Fourteen patients (40%) underwent a second intraoperative MRI, which had a median duration of 26min (IQR, 18-30). The median total operative time was 265min (IQR, 242-337). After the first intraoperative MRI, the median residual glioma volume of the 35 gliomas adjacent to eloquent areas was 7.04cm³ (IQR, 2.22-13.8), which did not significantly differ from the other gliomas (P=0.07). After the second intraoperative MRI, the median residual glioma volume was 3.86cm³ (IQR, 0.82-6.99), which did not significantly differ from the other patients (P=0.700). On the postoperative MRI, the median extent of the glioma resections adjacent to eloquent areas was 99.78% (IQR, 88.9-100), which was not significantly different from the rest of the population (P=0.290). At 6 months after surgery, the median Karnofsky Performance Score was 90, and 2.8% of the patients presented a permanent new neurological deficit.

CONCLUSION

Our results suggest that intraoperative MRI is an effective and safe technique to improve the extent of brain lesion resections close to eloquent areas.

Theranostic Application of Mixed Gold and Superparamagnetic Iron Oxide Nanoparticle Micelles in Glioblastoma Multiforme

The treatment of glioblastoma multiforme, the most prevalent and lethal form of brain cancer in humans, has been limited in part by poor delivery of drugs through the blood-brain barrier and by unclear delineation of the extent of infiltrating tumor margins. Nanoparticles, which selectively accumulate in tumor tissue due to their leaky vasculature and the enhanced permeability and retention effect, have shown promise as both therapeutic and diagnostic agents for brain tumors. In particular, superparamagnetic iron oxide nanoparticles (SPIONs) have been leveraged as T2-weighted MRI contrast agents for tumor detection and imaging; and gold nanoparticles (AuNP) have been demonstrated as radiosensitizers capable of propagating electron and free radical-induced radiation damage to tumor cells. In this study, we investigated the potential applications of novel gold and SPION-loaded micelles (GSMs) coated by polyethylene glycol-polycaprolactone (PEG-PCL) polymer. By quantifying gh2ax DNA damage foci in glioblastoma cell lines, we tested the radiosensitizing efficacy of these GSMs, and found that GSM administration in conjunction with radiation therapy (RT) led to ~2-fold increase in density of double-stranded DNA breaks. For imaging, we used GSMs as a contrast agent for both computed tomography (CT) and magnetic resonance imaging (MRI) studies of stereotactically implanted GBM tumors in a mouse model, and found that MRI but not CT was sufficiently sensitive to detect and delineate tumor borders after administration and accumulation of GSMs. These results suggest that with further development and testing, GSMs may potentially be integrated into both imaging and treatment of brain tumors, serving a theranostic purpose as both an MRI-based contrast agent and a radiosensitizer.

Perspectives in Intraoperative Diagnostics of Human Gliomas

Amongst large a variety of oncological diseases, malignant gliomas represent one of the most severe types of tumors. They are also the most common type of the brain tumors and account for over half of the astrocytic tumors. According to different sources, the average life expectancy of patients with various glioblastomas varies between 10 and 12 months and that of patients with anaplastic astrocytic tumors between 20 and 24 months. Therefore, studies of the physiology of transformed glial cells are critical for the development of treatment methods. Modern medical approaches offer complex procedures, including the microsurgical tumor removal, radiotherapy, and chemotherapy, supplemented with photodynamic therapy and immunotherapy. The most radical of them is surgical resection, which allows removing the largest part of the tumor, reduces the intracranial hypertension, and minimizes the degree of neurological deficit. However, complete removal of the tumor remains impossible. The main limitations are insufficient visualization of glioma boundaries, due to its infiltrative growth, and the necessity to preserve healthy tissue. This review is devoted to the description of advantages and disadvantages of modern intraoperative diagnostics of human gliomas and highlights potential perspectives for development of their treatment.

Misleading FLAIR imaging pattern after glioma surgery with intraoperative MRI

Intraoperative MRI (iMRI) allows a more detailed appreciation of the extent of resection than does conventional neurosurgery and results in longer overall survival in patients with malignant glioma. However, it is unknown whether the intraoperative application of contrast agent influences the early postsurgical MRI. The preceding iMRI could alter the signals of MR sequences in the early postsurgical MRI, especially in sequences influenced by T1 contrast. Hereby, we investigate such iMRI-induced influences on the fluid-attenuated inversion recovery (FLAIR) sequence. We retrospectively analyzed postsurgical T2w, T1w, and FLAIR images by visual inspection and by signal measurements in 46 patients with malignant gliomas after tumor resection. Of these, n = 25 patients were operated with conventional microsurgery, and n = 21 patients were operated with contrast-enhanced iMRI-guided microsurgery. We measured signal intensity in the resection cavity, in the cerebrospinal fluid (CSF) of the ventricles, and in the normal brain tissue contralateral to the tumor-bearing hemisphere on axial FLAIR images and T1-weighted and T2-weighted images. In 18 patients, the FLAIR sequence revealed hyperintense signal changes of the CSF in the subarachnoid or ventricular spaces. Seventeen of these 18 patients had received intraoperative MRI. In both FLAIR and T1-weighted images, the signal of the CSF in the ventricles was significantly higher in patients with iMRI than in patients without iMRI. The intraoperative application of contrast agent that is used for iMRI significantly influences postsurgical MRI within the first 72 h. We found hyperintense signal changes of the CSF in the FLAIR sequence in the subarachnoid and intraventricular spaces mimicking subarachnoid hemorrhage. The findings may result in a misdiagnosis of subarachnoid hemorrhage (SAH) in these patients.

Stereotactic laser ablation of high-grade gliomas

Evolving research has demonstrated that surgical cytoreduction of a high-grade glial neoplasm is an important factor in improving the prognosis of these difficult tumors. Recent advances in intraoperative imaging have spurred the use of stereotactic laser ablation (laser interstitial thermal therapy [LITT]) for intracranial lesions. Among other targets, laser ablation has been used in the focal treatment of high-grade gliomas (HGGs). The revived application of laser ablation for gliomas parallels major advancements in intraoperative adjuvants and groundbreaking molecular advances in neuro-oncology. The authors review the research on stereotactic LITT for the treatment of HGGs and provide a potential management algorithm for HGGs that incorporates LITT in clinical practice.

Intraoperative Magnetic Resonance Imaging in Intracranial Glioma Resection: A Single-Center, Retrospective Blinded Volumetric Study

BACKGROUND

Intraoperative magnetic resonance imaging (IoMRI) was devised to overcome brain shifts during craniotomies. Yet, the acceptance of IoMRI is limited.

OBJECTIVE

To evaluate impact of IoMRI on intracranial glioma resection outcome including overall patient survival.

METHODS

A retrospective review of records was performed on a cohort of 164 consecutive patients who underwent resection surgery for newly diagnosed intracranial gliomas either with or without IoMRI technology performed by 2 neurosurgeons in our center. Patient follow-up was at least 5 years. Extent of resection (EOR) was calculated using pre- and postoperative contrast-enhanced and T2-weighted MR-images. Adjusted analysis was performed to compare gross total resection (GTR), EOR, permanent surgery-associated neurologic deficit, and overall survival between the 2 groups.

RESULTS

Overall median EOR was 92.1%, and 97.45% with IoMRI use and 89.9% without IoMRI, with crude (unadjusted) P < 0.005. GTR was achieved in 49.3% of IoMRI cases, versus in only 21.4% of no-IoMRI cases, P < 0.001. GTR achieved was more with the use of IoMRI among gliomas located in both eloquent and noneloquent brain areas, P = 0.017 and <0.001, respectively. Permanent surgery-associated neurologic deficit was not (statistically) more significant with no-IoMRI, P = 0.284 (13.8% vs. 6.7%). In addition, the IoMRI group had better 5-year overall survival, P < 0.001.

CONCLUSION

This study shows that the use of IoMRI was associated with greater rates of EOR and GTR, and better overall 5-year survival in both eloquent brain areas located and non-eloquent brain areas located gliomas, with no increased risk of neurologic complication.

Advances in the Surgical Management of Low-Grade Glioma

Over the past 2 decades, extent of resection has emerged as a significant prognostic factor in patients with low-grade gliomas (LGGs). Greater extent of resection has been shown to improve overall survival, progression-free survival, and time to malignant transformation. The operative goal in most LGG cases is to maximize extent of resection, while avoiding postoperative neurologic deficits. Several advanced surgical techniques have been developed in an attempt to better achieve maximal safe resection. Intraoperative magnetic resonance imaging, fluorescence-guided surgery, intraoperative functional pathway mapping, and neuronavigation are some of the most commonly used techniques with multiple studies to support their efficacy in glioma surgery. By using these techniques either alone or in combination, patients harboring LGGs have a better prognosis with less surgical morbidity following tumor resection.

Use of high-field intraoperative magnetic resonance imaging to enhance the extent of resection of enhancing and nonenhancing gliomas

BACKGROUND

Intraoperative magnetic resonance imaging (IoMRI) is used to improve the extent of resection of brain tumors. Most previous studies evaluating the utility of IoMRI have focused on enhancing tumors.

OBJECTIVE

To report our experience with the use of high-field IoMRI (1.5 T) for both enhancing and nonenhancing gliomas.

METHODS

An institutional review board-approved retrospective review was performed of 102 consecutive glioma patients (104 surgeries, 2010-2012). Pre-, intra-, and postoperative tumor volumes were assessed. Analysis was performed with the use of volumetric T2 images in 43 nonenhancing and 13 minimally enhancing tumors and with postcontrast volumetric magnetization-prepared rapid gradient-echo images in 48 enhancing tumors.

RESULTS

In 58 cases, preoperative imaging showed tumors likely to be amenable to complete resection. Intraoperative electrocorticography was performed in 32 surgeries, and 14 cases resulted in intended subtotal resection of tumors due to involvement of deep functional structures. No further resection (complete resection before IoMRI) was required in 25 surgeries, and IoMRI showed residual tumor in 79 patients. Of these, 25 surgeries did not proceed to further resection (9 due to electrocorticography findings, 14 due to tumor in deep functional areas, and 2 due to surgeon choice). Additional resection that was performed in 54 patients resulted in a final median residual tumor volume of 0.21 mL (0.6%). In 79 patients amenable to complete resection, the intraoperative median residual tumor volume for the T2 group was higher than for the magnetization-prepared rapid gradient-echo group (1.088 mL vs 0.437 mL; P = .049), whereas the postoperative median residual tumor volume was not statistically significantly different between groups.

CONCLUSION

IoMRI enhances the extent of resection, particularly for nonenhancing gliomas.

Awake craniotomy for gliomas in a high-field intraoperative magnetic resonance imaging suite: analysis of 42 cases

OBJECTIVES

The object of this study was to describe the experience of combining awake craniotomy techniques with high-field (1.5 T) intraoperative MRI (iMRI) for tumors adjacent to eloquent cortex.

METHODS

From a prospective database the authors obtained and evaluated the records of all patients who had undergone awake craniotomy procedures with cortical and subcortical mapping in the iMRI suite. The integration of these two modalities was assessed with respect to safety, operative times, workflow, extent of resection (EOR), and neurological outcome.

RESULTS

Between February 2010 and December 2011, 42 awake craniotomy procedures using iMRI were performed in 41 patients for the removal of intraaxial tumors. There were 31 left-sided and 11 right-sided tumors. In half of the cases (21 [50%] of 42), the patient was kept awake for both motor and speech mapping. The mean duration of surgery overall was 7.3 hours (range 4.0-13.9 hours). The median EOR overall was 90%, and gross-total resection (EOR ≥ 95%) was achieved in 17 cases (40.5%). After viewing the first MR images after initial resection, further resection was performed in 17 cases (40.5%); the mean EOR in these cases increased from 56% to 67% after further resection. No deficits were observed preoperatively in 33 cases (78.5%), and worsening neurological deficits were noted immediately after surgery in 11 cases (26.2%). At 1 month after surgery, however, worsened neurological function was observed in only 1 case (2.3%).

CONCLUSIONS

There was a learning curve with regard to patient positioning and setup times, although it did not adversely affect patient outcomes. Awake craniotomy can be safely performed in a high-field (1.5 T) iMRI suite to maximize tumor resection in eloquent brain areas with an acceptable morbidity profile at 1 month.

Principles of surgery for malignant astrocytomas

Malignant astrocytomas constitute the most aggressive and common primary tumors of the central nervous system. The standard treatment protocol for these tumors involves maximum safe surgical resection with adjuvant chemoradiotherapy. Despite numerous advances in surgical techniques and adjuncts, as well as the ongoing renaissance in the genetic and molecular characterization of these tumors, malignant astrocytomas continue to be associated with poor prognosis, with median overall survival averaging 15 months for grade IV astrocytomas after standard-of-care treatment. In this article, the goals, principles, techniques, prognostic factors, and modern outcomes of malignant astrocytoma surgery are reviewed. Particular attention is paid to contemporary methods of neuronavigation and functional mapping, the prognostic significance of the extent of resection, surgically delivered adjunctive therapies, and future avenues of research.

3-Dimensional magnetic resonance spectroscopic imaging at 3 Tesla for early response assessment of glioblastoma patients during external beam radiation therapy

PURPOSE

To evaluate the utility of 3-dimensional magnetic resonance (3D-MR) proton spectroscopic imaging for treatment planning and its implications for early response assessment in glioblastoma multiforme.

METHODS AND MATERIALS

Eighteen patients with newly diagnosed, histologically confirmed glioblastoma had 3D-MR proton spectroscopic imaging (MRSI) along with T2 and T1 gadolinium-enhanced MR images at simulation and at boost treatment planning after 17 to 20 fractions of radiation therapy. All patients received standard radiation therapy (RT) with concurrent temozolomide followed by adjuvant temozolomide. Imaging for response assessment consisted of MR scans every 2 months. Progression-free survival was defined by the criteria of MacDonald et al. MRSI images obtained at initial simulation were analyzed for choline/N-acetylaspartate ratios (Cho/NAA) on a voxel-by-voxel basis with abnormal activity defined as Cho/NAA ≥2. These images were compared on anatomically matched MRSI data collected after 3 weeks of RT. Changes in Cho/NAA between pretherapy and third-week RT scans were tested using Wilcoxon matched-pairs signed rank tests and correlated with progression-free survival, radiation dose and location of recurrence using Cox proportional hazards regression.

RESULTS

After a median follow-up time of 8.6 months, 50% of patients had experienced progression based on imaging. Patients with a decreased or stable mean or median Cho/NAA values had less risk of progression (P<.01). Patients with an increase in mean or median Cho/NAA values at the third-week RT scan had a significantly greater chance of early progression (P<.01). An increased Cho/NAA at the third-week MRSI scan carried a hazard ratio of 2.72 (95% confidence interval, 1.10-6.71; P=.03). Most patients received the prescription dose of RT to the Cho/NAA ≥2 volume, where recurrence most often occurred.

CONCLUSION

Change in mean and median Cho/NAA detected at 3 weeks was a significant predictor of early progression. The potential impact for risk-adaptive therapy based on early spectroscopic findings is suggested.

Neurosurgical oncology: advances in operative technologies and adjuncts

Modern glioma surgery has evolved around the central tenet of safely maximizing resection. Recent surgical adjuncts have focused on increasing the maximum extent of resection while minimizing risk to functional brain. Technologies such as cortical and subcortical stimulation mapping, intraoperative magnetic resonance imaging, functional neuronavigation, navigable intraoperative ultrasound, neuroendoscopy, and fluorescence-guided resection have been developed to augment the identification of tumor while preserving brain anatomy and function. However, whether these technologies offer additional long-term benefits to glioma patients remains to be determined. Here we review advances over the past decade in operative technologies that have offered the most promising benefits for glioblastoma patients.

Impact of fluorescence-guided surgery on the improvement of clinical outcomes in glioblastoma patients

Background

To evaluate the clinical impact of fluorescence-guided surgery (FGS) in glioblastoma, we analyzed the clinical data of 80 consecutive patients operated on by a single surgeon with or without 5-aminolevulinic acid (5-ALA).

Methods

We compared 3-dimensional volumetric extent of resection and clinical outcomes between 40 consecutive patients undergoing resection using a white-light (WL) microscope and 40 subsequent consecutive patients undergoing resection using FGS with 5ALA.

Results

By introducing FGS, there was a significant difference in the mean volumetric extent of the resection rate of T1-enhancing lesions (84.7% in the white-light group and 97.0% in the 5-ALA group, P = .002). The complete resection rate was improved from 43% to 80%, and the proportion of resections that were <80% was reduced from 26% to 4% by FGS. The median progression-free survival was significantly better in the 5-ALA group (18.0 months vs. 6.0 months; P = .001). Although the immediate postoperative functional status was slightly worse in the 5-ALA group, this trend had reversed itself by 3 months postoperatively.

Conclusions

The present study adds practical evidence of the clinical impact of 5-ALA FGS on glioblastomas from the surgeon's standpoint.

Intraoperative magnetic resonance imaging versus standard neuronavigation for the neurosurgical treatment of glioblastoma: A randomized controlled trial

BACKGROUND

Although the added value of increasing extent of glioblastoma resection is still debated, multiple technologies can assist neurosurgeons in attempting to achieve this goal. Intraoperative magnetic resonance imaging (iMRI) might be helpful in this context, but to date only one randomized trial exists.

METHODS

We included 14 adults with a supratentorial tumor suspect for glioblastoma and an indication for gross total resection in this randomized controlled trial of which the interim analysis is presented here. Participants were assigned to either ultra-low-field strength iMRI-guided surgery (0.15 Tesla) or to conventional neuronavigation-guided surgery (cNN). Primary endpoint was residual tumor volume (RTV) percentage. Secondary endpoints were clinical performance, health-related quality of life (HRQOL) and survival.

RESULTS

Median RTV in the cNN group is 6.5% with an interquartile range of 2.5-14.75%. Median RTV in the iMRI group is 13% with an interquartile range of 3.75-27.75%. A Mann-Whitney test showed no statistically significant difference between these groups (P =0.28). Median survival in the cNN group is 472 days, with an interquartile range of 244-619 days. Median survival in the iMRI group is 396 days, with an interquartile range of 191-599 days (P =0.81). Clinical performance did not differ either. For HRQOL only descriptive statistics were applied due to a limited sample size.

CONCLUSION

This interim analysis of a randomized trial on iMRI-guided glioblastoma resection compared with cNN-guided glioblastoma resection does not show an advantage with respect to extent of resection, clinical performance, and survival for the iMRI group. Ultra-low-field strength iMRI does not seem to be cost-effective compared with cNN, although the lack of a valid endpoint for neurosurgical studies evaluating extent of glioblastoma resection is a limitation of our study and previous volumetry-based studies on this topic.

Role of surgical resection in low- and high-grade gliomas

OPINION STATEMENT

Central nervous system tumors are a major cause of morbidity and mortality in the United States. Outside of brain metastasis, low- and high-grade gliomas are the most common intrinsic brain tumors. Low-grade gliomas have a 5- and 10-year survival rate of 97 % and 91 %, respectively, when extent of resection is greater than 90 %. High-grade gliomas are extremely aggressive with the vast majority of patients experiencing recurrence and a median survival of 1 to 3 years. Survival of patients with both low- and high-grade gliomas is enhanced with maximal tumor resection. The pursuit of more aggressive extent of resection must be balanced with preservation of functional pathways. Several innovations in neurosurgical oncology have expanded our understanding of individualized patient neuroanatomy, physiology, and function. Emerging imaging technologies as well as intraoperative techniques have expanded our ability to resect maximal amounts of tumor while preserving essential function. Stimulation mapping of language and motor pathways is well-established for the safe resection of intrinsic brain lesions. Additional techniques including neuro-navigation, fluorescence-guided microsurgery using 5-aminolevulinic acid, intraoperative magnetic resonance imaging, and high-frequency ultrasonography can all be used to improve extent of resection in glioma patients.

Establishing percent resection and residual volume thresholds affecting survival and recurrence for patients with newly diagnosed intracranial glioblastoma

INTRODUCTION

Surgery is first-line therapy for glioblastoma, and there is evidence that gross total resection is associated with improved survival. Gross total resection, however, is not always possible, and relationships among extent (percent) of resection (EOR), residual volume (RV), and survival are unknown. The goals were to evaluate whether there is an association between EOR and RV with survival and recurrence and to establish minimum EOR and maximum RV thresholds.

METHODS

Adult patients who underwent primary glioblastoma surgery from 2007 to 2011 were retrospectively reviewed. Three-dimensional volumetric tumor measurements were made. Multivariate proportional hazards regression analysis was used to evaluate the relationship between EOR and RV with survival and recurrence.

RESULTS

Of 259 patients, 203 (78%) died and 156 (60%) had tumor recurrence. The median survival and progression-free survival were 13.4 and 8.9 months, respectively. The median (interquartile range) pre- and postoperative tumor volumes were 32.2 (14.0-56.3) and 2.1 (0.0-7.9) cm(3), respectively. EOR was independently associated with survival (hazard ratio [HR], 0.995; 95% confidence interval [CI]: 0.990-0.998; P = .008) and recurrence (HR [95% CI], 0.992 [0.983-0.998], P = .005). The minimum EOR threshold for survival (P = .0006) and recurrence (P = .005) was 70%. RV was also associated with survival (HR [95% CI], 1.019 [1.006-1.030], P = .004) and recurrence (HR [95% CI], 1.024 [1.001-1.044], P = .03). The maximum RV threshold for survival (P = .01) and recurrence (P = .01) was 5 cm(3).

CONCLUSION

This study shows for the first time that both EOR and RV are significantly associated with survival and recurrence, where the thresholds are 70% and 5 cm(3), respectively. These findings may help guide surgical and adjuvant therapies aimed at optimizing outcomes for glioblastoma patients.

Using intraoperative dynamic contrast-enhanced T1-weighted MRI to identify residual tumor in glioblastoma surgery

OBJECT

The goal of surgery in high-grade gliomas is to maximize the resection of contrast-enhancing tumor without causing additional neurological deficits. Intraoperative MRI improves surgical results. However, when using contrast material intraoperatively, it may be difficult to differentiate between surgically induced enhancement and residual tumor. The purpose of this study was to assess the usefulness of intraoperative dynamic contrast-enhanced T1-weighted MRI to guide this differential diagnosis and test it against tissue histopathology.

METHODS

Preoperative and intraoperative dynamic contrast-enhanced MRI was performed in 21 patients with histopathologically confirmed WHO Grade IV gliomas using intraoperative 3-T MRI. Standardized regions of interest (ROIs) were placed manually at 2 separate contrast-enhancing areas at the resection border for each patient. Time-intensity curves (TICs) were generated for each ROI. All ROIs were biopsied and the TIC types were compared with histopathological results. Pharmacokinetic modeling was performed in the last 10 patients to confirm nonparametric TIC analysis findings.

RESULTS

Of the 42 manually selected ROIs in 21 patients, 25 (59.5%) contained solid tumor tissue and 17 (40.5%) retained the brain parenchymal architecture but contained infiltrating tumor cells. Time-intensity curves generated from residual contrast-enhancing tumor and their preoperative counterparts were comparable and showed a quick and persistently increasing slope ("climbing type"). All 17 TICs obtained from regions that did not contain solid tumor tissue were undulating and low in amplitude, compared with those obtained from residual tumors ("low-amplitude type"). Pharmacokinetic findings using the transfer constant, extravascular extracellular volume fraction, rate constant, and initial area under the curve parameters were significantly different for the tumor mass, nontumoral regions, and surgically induced contrast-enhancing areas.

CONCLUSIONS

Intraoperative dynamic contrast-enhanced MRI provides quick, reproducible, high-quality, and simply interpreted dynamic MR images in the intraoperative setting and can aid in differentiating surgically induced enhancement from residual tumor.