The impact of tumour volume and surgery on the outcome of adults with supratentorial WHO grade II astrocytomas and oligoastrocytomas

Evaluation of a nnU-Net type automated clinical volumetric tumor segmentation tool for diffuse low-grade glioma follow-up

BACKGROUND AND PURPOSE

Diffuse low-grade gliomas (DLGG) are characterized by a slow and continuous growth and always evolve towards an aggressive grade. Accurate prediction of the malignant transformation is essential as it requires immediate therapeutic intervention. One of its most precise predictors is the velocity of diameter expansion (VDE). Currently, the VDE is estimated either by linear measurements or by manual delineation of the DLGG on T2 FLAIR acquisitions. However, because of the DLGG's infiltrative nature and its blurred contours, manual measures are challenging and variable, even for experts. Therefore we propose an automated segmentation algorithm using a 2D nnU-Net, to 1) gain time and 2) standardize VDE assessment.

MATERIALS AND METHODS

The 2D nnU-Net was trained on 318 acquisitions (T2 FLAIR & 3DT1 longitudinal follow-up of 30 patients, including pre- & post-surgery acquisitions, different scanners, vendors, imaging parameters…). Automated vs. manual segmentation performance was evaluated on 167 acquisitions, and its clinical interest was validated by quantifying the amount of manual correction required after automated segmentation of 98 novel acquisitions.

RESULTS

Automated segmentation showed a good performance with a mean Dice Similarity Coefficient (DSC) of 0.82±0.13 with manual segmentation and a substantial concordance between VDE calculations. Major manual corrections (i.e., DSC<0.7) were necessary only in 3/98 cases and 81% of the cases had a DSC>0.9.

CONCLUSION

The proposed automated segmentation algorithm can successfully segment DLGG on highly variable MRI data. Although manual corrections are sometimes necessary, it provides a reliable, standardized and time-winning support for VDE extraction to asses DLGG growth.

Molecular MRI-Based Monitoring of Cancer Immunotherapy Treatment Response

Immunotherapy constitutes a paradigm shift in cancer treatment. Its FDA approval for several indications has yielded improved prognosis for cases where traditional therapy has shown limited efficiency. However, many patients still fail to benefit from this treatment modality, and the exact mechanisms responsible for tumor response are unknown. Noninvasive treatment monitoring is crucial for longitudinal tumor characterization and the early detection of non-responders. While various medical imaging techniques can provide a morphological picture of the lesion and its surrounding tissue, a molecular-oriented imaging approach holds the key to unraveling biological effects that occur much earlier in the immunotherapy timeline. Magnetic resonance imaging (MRI) is a highly versatile imaging modality, where the image contrast can be tailored to emphasize a particular biophysical property of interest using advanced engineering of the imaging pipeline. In this review, recent advances in molecular-MRI based cancer immunotherapy monitoring are described. Next, the presentation of the underlying physics, computational, and biological features are complemented by a critical analysis of the results obtained in preclinical and clinical studies. Finally, emerging artificial intelligence (AI)-based strategies to further distill, quantify, and interpret the image-based molecular MRI information are discussed in terms of perspectives for the future.

Contemporary assessment of extent of resection in molecularly defined categories of diffuse low-grade glioma: a volumetric analysis

OBJECTIVE

While the effect of increased extent of resection (EOR) on survival in diffuse infiltrating low-grade glioma (LGG) patients is well established, there is still uncertainty about the influence of the new WHO molecular subtypes. The authors designed a retrospective analysis to assess the interplay between EOR and molecular classes.

METHODS

The authors retrospectively reviewed the records of 326 patients treated surgically for hemispheric WHO grade II LGG at Brigham and Women's Hospital and Massachusetts General Hospital (2000-2017). EOR was calculated volumetrically and Cox proportional hazards models were built to assess for predictive factors of overall survival (OS), progression-free survival (PFS), and malignant progression-free survival (MPFS).

RESULTS

There were 43 deaths (13.2%; median follow-up 5.4 years) among 326 LGG patients. Median preoperative tumor volume was 31.2 cm3 (IQR 12.9-66.0), and median postoperative residual tumor volume was 5.8 cm3 (IQR 1.1-20.5). On multivariable Cox regression, increasing postoperative volume was associated with worse OS (HR 1.02 per cm3; 95% CI 1.00-1.03; p = 0.016), PFS (HR 1.01 per cm3; 95% CI 1.00-1.02; p = 0.001), and MPFS (HR 1.01 per cm3; 95% CI 1.00-1.02; p = 0.035). This result was more pronounced in the worse prognosis subtypes of IDH-mutant and IDH-wildtype astrocytoma, for which differences in survival manifested in cases with residual tumor volume of only 1 cm3. In oligodendroglioma patients, postoperative residuals impacted survival when exceeding 8 cm3. Other significant predictors of OS were age at diagnosis, IDH-mutant and IDH-wildtype astrocytoma classes, adjuvant radiotherapy, and increasing preoperative volume.

CONCLUSIONS

The results corroborate the role of EOR in survival and malignant transformation across all molecular subtypes of diffuse LGG. IDH-mutant and IDH-wildtype astrocytomas are affected even by minimal postoperative residuals and patients could potentially benefit from a more aggressive surgical approach.

Preoperative Two-Dimensional Size of Glioblastoma is Associated with Patient Survival

BACKGROUND

Although tumor size affects survival of patients with lower-grade glioma, a prognostic effect on patients with glioblastoma remains to be established.

METHODS

We performed a retrospective analysis of 61 patients using volumetric data of tumor compartments of 61 patients obtained by preoperative magnetic resonance images using the visual ABC/2 method. Preoperative enhancing, nonenhancing, necrosis, and edema volume, the preoperative tumor area (TA) as a product of the 2 largest tumor diameters perpendicular to each other on axial T1-weighted postcontrast images, as well as postoperative enhancing residual volumes, were measured. Multivariable Cox proportional hazard models were used to associate these parameters with overall survival, adjusting for potential confounders.

RESULTS

The median preoperative enhancing tumor volume was 18.2 mL (interquartile range, 8.2-41.7 mL); the median remnant tumor volume was 1.3% (interquartile range, 0.0%-42.9%). During follow-up, 59 patients (92%) died; median survival time and median follow-up time were both 404 days. We found a statistically significant multiplicative effect of TA on survival: the hazard ratio (HR) was increased by 1.096 per unit increase of 200 mm² (95% confidence interval [CI], 1.027-1.170; P < 0.01). The effect of remnant tumor on HR increased multiplicatively by 1.013 (95% CI, 1.001-1.026; P = 0.04) per unit increase of 1 log (day) and 1% in tumor remnant. HR associated with age at surgery increased by 1.503 per 5 years of age (95% CI, 1.243-1.817; P < 0.01).

CONCLUSIONS

Preoperative TA proved to be the only glioblastoma size parameter that affects patient survival.

Comparative volumetric analysis of the extent of resection of molecularly and histologically distinct low grade gliomas and its role on survival

The authors investigate the role of extent of resection (EOR) and genetic markers on patient outcome and survival for LGGs. We conducted a retrospective cohort between 2005 and 2015, of 109 adult patients who underwent surgery for a LGG by a single surgeon. Volumetric computations of MRI studies were conducted to evaluate the EOR, and genetic markers (IDH1, 1p/19q co-deletion, and p53) were assessed and their effects on survival and neurological outcome were evaluated. The median EOR was 88.1%. Permanent postoperative neurological deficits were seen in 4.6% of patients. EOR was a significant predictor for both overall survival (OS) (hazard ratio [HR] = 0.979, 95% CI 0.961-0.980, p = 0.029) and progression free survival (PFS) (HR = 0.982, 95% CI 0.968-0.997, p = 0.018). Malignant progression free survival (MPFS) was predicted by the 1p/19q co-deletion (HR = 0.148, 95% CI 0.019-1.148, p = 0.048). Patients with EOR of 100% had a significantly better OS than EOR less than 90% (p = 0.038). Patients with an EOR of at least 76% had a better OS than EOR less than 76% (p = 0.025). Patients with an EOR of at least 71% had a better PFS than EOR less than 71% (p = 0.030). Preoperative tumor volume was found to have significant association with EOR (R² = 0.049, p = 0.031). Increased EOR is associated with improved OS and PFS survival outcomes, while 1p/19q co-deletion provides improved MPFS. Understanding both surgical resections and molecular markers of the tumor are important for effective management of LGG patients.

Stereotactic interstitial brachytherapy for the treatment of oligodendroglial brain tumors

PURPOSE

We evaluated the treatment of oligodendroglial brain tumors with interstitial brachytherapy (IBT) using (125)iodine seeds ((125)I) and analyzed prognostic factors.

PATIENTS AND METHODS

Between January 1991 and December 2010, 63 patients (median age 43.3 years, range 20.8-63.4 years) suffering from oligodendroglial brain tumors were treated with (125)I IBT either as primary, adjuvantly after incomplete resection, or as salvage therapy after tumor recurrence. Possible prognostic factors influencing disease progression and survival were retrospectively investigated.

RESULTS

The actuarial 2-, 5-, and 10-year overall and progression-free survival rates after IBT for WHO II tumors were 96.9, 96.9, 89.8 % and 96.9, 93.8, 47.3 %; for WHO III tumors 90.3, 77, 54.9 % and 80.6, 58.4, 45.9 %, respectively. Magnetic resonance imaging demonstrated complete remission in 2 patients, partial remission in 13 patients, stable disease in 17 patients and tumor progression in 31 patients. Median time to progression for WHO II tumors was 87.6 months and for WHO III tumors 27.8 months. Neurological status improved in 10 patients and remained stable in 20 patients, while 9 patients deteriorated. There was no treatment-related mortality. Treatment-related morbidity was transient in 11 patients. WHO II, KPS ≥ 90 %, frontal location, and tumor surface dose > 50 Gy were associated with increased overall survival (p ≤ 0.05). Oligodendroglioma and frontal location were associated with a prolonged progression-free survival (p ≤ 0.05).

CONCLUSION

Our study indicates that IBT achieves local control rates comparable to surgery and radio-/chemotherapy treatment, is minimally invasive, and safe. Due to the low rate of side effects, IBT may represent an attractive option as part of a multimodal treatment schedule, being supplementary to microsurgery or as a salvage therapy after chemotherapy and conventional irradiation.

IDH/MGMT-driven molecular classification of low-grade glioma is a strong predictor for long-term survival

BACKGROUND

Low-grade gliomas (LGGs) are rare brain neoplasms, with survival spanning up to a few decades. Thus, accurate evaluations on how biomarkers impact survival among patients with LGG require long-term studies on samples prospectively collected over a long period.

METHODS

The 210 adult LGGs collected in our databank were screened for IDH1 and IDH2 mutations (IDHmut), MGMT gene promoter methylation (MGMTmet), 1p/19q loss of heterozygosity (1p19qloh), and nuclear TP53 immunopositivity (TP53pos). Multivariate survival analyses with multiple imputation of missing data were performed using either histopathology or molecular markers. Both models were compared using Akaike's information criterion (AIC). The molecular model was reduced by stepwise model selection to filter out the most critical predictors. A third model was generated to assess for various marker combinations.

RESULTS

Molecular parameters were better survival predictors than histology (ΔAIC = 12.5, P< .001). Forty-five percent of studied patients died. MGMTmet was positively associated with IDHmut (P< .001). In the molecular model with marker combinations, IDHmut/MGMTmet combined status had a favorable impact on overall survival, compared with IDHwt (hazard ratio [HR] = 0.33, P< .01), and even more so the triple combination, IDHmut/MGMTmet/1p19qloh (HR = 0.18, P< .001). Furthermore, IDHmut/MGMTmet/TP53pos triple combination was a significant risk factor for malignant transformation (HR = 2.75, P< .05).

CONCLUSION

By integrating networks of activated molecular glioma pathways, the model based on genotype better predicts prognosis than histology and, therefore, provides a more reliable tool for standardizing future treatment strategies.

Low-grade astrocytoma: surgical outcomes in eloquent versus non-eloquent brain areas

A retrospective study of 81 patients with low-grade astrocytoma (LGA) comparing the efficacy of aggressive versus less aggressive surgery in eloquent and non-eloquent brain areas was conducted. Extent of surgical resection was analyzed to assess overall survival (OS) and progression- free survival (PFS). Degree of tumor resection was classified as gross total resection (GTR), subtotal resection (STR) or biopsy. GTR, STR and biopsy in patients with tumors in non-eloquent areas were performed in 31, 48 and 21% subjects, whereas in patients with tumors in eloquent areas resections were 22.5, 35 and 42.5%. Overall survival was 4.7 and 1.9 years in patients with tumors in non-eloquent brain areas submitted to GTR/STR and biopsy (p=0.013), whereas overall survival among patients with tumors in eloquent area was 4.5 and 2.1 years (p=0.33). Improved outcome for adult patients with LGA is predicted by more aggressive surgery in both eloquent and non-eloquent brain areas.

Current treatment of low grade astrocytoma: a review

Through a comprehensive review of the current literature, the present article investigates several aspects of low grade astrocytomas (LGA), including prognostic factors, treatment strategies and follow-up regimes. LGA are in general relatively slow-growing primary brain tumours, but they have a very heterogeneous clinical behaviour. Several factors affect prognosis, and these include age, histological subtype, and Karnofsky Performance Score (KPS) prior to surgery. Furthermore, a number of different molecular genetic alterations have been shown to affect both the prognosis as well as the course of disease. The current literature seems to support the idea that treatment with radical tumour resection, where possible, yields better long term outcome for patients with LGA. However, adjuvant therapy is often necessary. Administering early postoperative radiotherapy to patients with partially resected LGA yields a longer period of progression-free survival, whereas patients with radically resected tumours should receive radiotherapy at the time of progression. Regarding chemotherapy, we found evidence to suggest that patients respond to both temozolomide (TMZ) and the combination of procarbazine, lomustine and vincristine (PCV). However, the response rates in patients receiving PCV seem superior to those of patients receiving TMZ. In follow-up PET scans, the tracers (18)F-FDG and MET provide high sensitivities for detection of new suspicious lesions and these tracers are furthermore effective in discriminating between tumour progression and radiation necrosis. The research into biomarkers is currently limited with regards to their applications in LGA diagnostics, and therefore further studies including larger patient populations are needed.

Brain tumors

For most cancers, PET is essentially a diagnostic tool. For brain tumors, PET has got its main contribution at the level of the therapeutic management. Indeed, specific reasons render the therapeutic management of brain tumors, especially gliomas, a real challenge. Although some gliomas may appear well-delineated on conventional neuroimaging such as CT and MRI, they are by nature infiltrating neoplasms and the interface between tumor and normal brain tissue may not be accurately defined. Moreover, gliomas may present as ill-defined lesions for which various MRI sequences combination does not provide a unique contour for tumor delineation. Also, gliomas are often histologically heterogeneous with anaplastic areas evolving within a low-grade tumor, and contrast-enhancement on CT or MRI does not represent a good marker for anaplastic tissue detection. Finally, assessment of tumor residue, recurrence, or progression, may be altered by different signals related to inflammation or adjuvant therapies, and contrast enhancement on CT and MRI is not an appropriate marker at the postoperative or posttherapeutic stage. These limitations of conventional neuroimaging in detecting tumor tissue, delineating tumor extent and evidencing anaplastic changes, lead to potential inaccuracy in lesion targeting at different steps of the management (diagnostic, surgical, postoperative, and posttherapeutic stages). Molecular information provided by PET has proved helpful to supplement morphological imaging data in this context. F-18 FDG and amino-acid tracers such as C-11 methionine (C-11 MET) provide complementary metabolic data that are independent from the anatomical MR information. These tracers help in the definition of glioma extension, detection of anaplastic areas, and postoperative follow-up. Additionally, PET data have a prognostic value independently of histology. To take advantage of PET data in glioma treatment, PET might be integrated in the planning of image-guided biopsy, resection, and radiosurgery.

Molecular genetics, imaging and treatment of oligodendroglial tumours

The discovery of a genetic signature of chemosensitivity and prognosis in oligodendroglial tumours prompted a new optimism in glioma management. After more than a decade since the initial reports, where do we stand in the current management of oligodendroglial tumours? This review focuses on the latest molecular genetics, imaging characteristics, and recent trials of treatment paradigms for these tumours.

Intraoperative mapping for tumor resection

This article describes the rationale, indications, and modality for intraoperative brain mapping for safe and effective surgical removal of tumors located within functional brain areas.

Present day's standards in microsurgery of low-grade gliomas

Low-grade gliomas are slow growing intrinsic lesions that induces a progressive functional reshaping of the brain. Surgical removal of these lesions requires the combined efforts of a multidiscipinary team of neurosurgeon, neuroradiologist, neuropsychologist, neurophysiologist, and neurooncologists that all together contribute in the definition of the location, extension, and extent of functional involvement that a specific lesion has induced in a particular patient. Each tumor has induced particular and specific changes of the functional network, that varies among patients. This requires that each treatment plan should be tailored to the tumor and to the patient. When this is reached, surgery should be accomplished according to functional and anatomical boundaries, and has to aim to the maximal resection with the maximal patient functional preservation. This can be reached at the time of the initial surgery, depending on the functional organization of the brain, or may require additional surgeries, eventually intermingled with adjuvant treatments. The use of so called brain mapping techniques extend surgical indications, improve extent of resection with greater oncological impact, minimization of morbidity and increase in quality of life. To achieve the goal of a satisfactory tumor resection associated with the full preservation of the patients abilities, a series of neuropsychological, neurophysiological, neuroradiological and intraoperative investigations have to be performed. In this chapter, we will describe the rationale, the indications and the modality for performing a safe and rewarding surgical removal of low-grade gliomas by using these techniques, as well as the functional and oncological results.

Intraoperative mapping and monitoring of brain functions for the resection of low-grade gliomas: technical considerations

Low-grade gliomas ([LGGs] WHO Grade II) are slow-growing intrinsic cerebral lesions that diffusely infiltrate the brain parenchyma along white matter tracts and almost invariably show a progression toward malignancy. The treatment of these tumors forces the neurosurgeon to face uncommon difficulties and is still a subject of debate. At the authors' institution, resection is the first option in the treatment of LGGs. It requires the combined efforts of a multidisciplinary team of neurosurgeons, neuroradiologists, neuropsychologists, and neurophysiologists, who together contribute to the definition of the location, extension, and extent of functional involvement that a specific lesion has caused in a particular patient. In fact, each tumor induces specific modifications of the brain functional network, with high interindividual variability. This requires that each treatment plan is tailored to the characteristics of the tumor and of the patient. Consequently, surgery is performed according to functional and anatomical boundaries to achieve the maximal resection with maximal functional preservation. The identification of eloquent cerebral areas, which are involved in motor, language, memory, and visuospatial functions and have to be preserved during surgery, is performed through the intraoperative use of brain mapping techniques. The use of these techniques extends surgical indications and improves the extent of resection, while minimizing the postoperative morbidity and safeguarding the patient's quality of life. In this paper the authors present their paradigm for the surgical treatment of LGGs, focusing on the intraoperative neurophysiological monitoring protocol as well as on the brain mapping technique. They briefly discuss the results that have been obtained at their institution since 2005 as well as the main critical points they have encountered when using this approach.

POSITRON EMISSION TOMOGRAPHY-GUIDED VOLUMETRIC RESECTION OF SUPRATENTORIAL HIGH-GRADE GLIOMAS

OBJECTIVE

Integrating positron emission tomographic (PET) images into the image-guided resection of high-grade gliomas (HGG) has shown that metabolic information on tumor heterogeneity and distribution are useful for planning surgery, improve tumor delineation, and provide a final target contour different from that obtained with magnetic resonance imaging (MRI) alone in about 80% of the procedures. Moreover, PET guidance helps to increase the amount of tumor removed and to target image-guided resection to anaplastic tissue areas. The present study aims to evaluate whether PET-guided volumetric resection (VR) in supratentorial HGG might add benefit to the patient's outcome.

METHODS

PET images using [18F]fluorodeoxyglucose (n=23) and [11C]methionine (n=43) were combined with MRI scans in the planning of VR procedures performed at the initial stage in 66 consecutive patients (43 M/23 F) with supratentorial HGG according to the technique previously described. In all cases (35 anaplastic gliomas [20 astrocytomas, 10 oligoastrocytomas, 5 oligodendrogliomas] and 31 glioblastomas [GBM]), level and distribution of PET tracer uptake were analyzed to define a PET contour projected on MRI scans to define a final target contour for VR. Maximal tumor resection was accomplished in each case, with the intention to remove the entire abnormal metabolic area comprised in the surgical planning. Early postoperative MRI and PET assessed tumor resection. Survival analysis was performed separately in anaplastic gliomas and glioblastoma multiforme according to the presence or absence of residual tracer uptake on postoperative PET and according to the presence or absence of residual contrast enhancement on postoperative MRI.

RESULTS

Preoperatively, metabolic information helped the surgical planning. In all procedures, PET contributed to define a final target contour different from that obtained with MRI alone. Postoperatively, 46 of 66 patients had no residual PET tracer uptake (total PET resection), 23 of 66 had no residual MRI contrast enhancement. No additional neurological morbidity due to the technique was reported. A total PET tracer uptake resection was associated with a significantly longer survival in anaplastic gliomas (P = 0.0071) and in glioblastoma multiforme (P = 0.0001), respectively. A total MRI contrast enhancement resection was not correlated with a significantly better survival, neither in anaplastic gliomas (P = 0.6089) nor in glioblastoma multiforme (P = 0.6806).

CONCLUSIONS

Complete resection of the increased PET tracer uptake prolongs the survival of HGG patients. Because PET information represents a more specific marker than MRI enhancement for detecting anaplastic tumor tissue, PET-guidance increases the amount of anaplastic tissue removed in HGG.

Three-dimensional Gaussian model to define brain metastasis limits on 11C-methionine PET

PURPOSE

Since 11C-methionine (MET) heavily accumulates in brain tumors, PET with MET (MET-PET) is proposed for the image-guided planning of their targeted therapy. Determination of bulk tumor limits is therefore a crucial component of MET-PET image analysis. We aimed at validating a Gaussian model of tumor delineation on MET-PET. We choose MET-PET and MRI data obtained in brain metastases to adjust the model. Indeed, MRI limits of these non-infiltrative hypermetabolic brain lesions are efficiently used for their curative treatment.

METHODS AND MATERIALS

We developed a three-dimensional (3D) Gaussian model that relates the tumor-limit-defining threshold to maximum and mean count values in the defined tumor volume and to mean count values in a reference region. To adjust the model to experimental data, we selected 25 brain metastases following these criteria: (i) no surgery or classical radiotherapy within 6 months, (ii) no previous radiosurgery, (iii) MET-PET and MRI acquired within a 48-h interval, (vi) necrosis representing less than 25% of tumor volume on MRI. We applied a progressive thresholding procedure on MET-PET so as to match tumor limits on contrast-enhanced co-registered MRI.

RESULTS

In 22 tumors, a match could be reached between tumor margins on MET-PET and MRI. The relation between mean, maximum and threshold values closely fits the 3D-Gaussian model function. We found a quadratic relation between the mean-to-threshold ratio and the maximum-to-cerebellum activity ratio.

CONCLUSIONS

A 3D-Gaussian model may describe the limits of MET uptake distribution within brain metastases, providing a simple method for metabolic tumor delineation.

Role of Extent of Resection in the Long-Term Outcome of Low-Grade Hemispheric Gliomas

Purpose

The prognostic role of extent of resection (EOR) of low-grade gliomas (LGGs) is a major controversy. We designed a retrospective study to assess the influence of EOR on long-term outcomes of LGGs.

Patients and Methods

The study population (N = 216) included adults undergoing initial resection of hemispheric LGG. Region-of-interest analysis was performed to measure tumor volumes based on fluid-attenuated inversion-recovery (FLAIR) imaging.

Results

Median preoperative and postoperative tumor volumes and EOR were 36.6 cm3 (range, 0.7 to 246.1 cm3), 3.7 cm3 (range, 0 to 197.8 cm3) and 88.0% (range, 5% to 100%), respectively. There was no operative mortality. New postoperative deficits were noted in 36 patients (17%); however, all but four had complete recovery. There were 34 deaths (16%; median follow-up, 4.4 years). Progression and malignant progression were identified in 95 (44%) and 44 (20%) cases, respectively. Patients with at least 90% EOR had 5- and 8-year overall survival (OS) rates of 97% and 91%, respectively, whereas patients with less than 90% EOR had 5- and 8-year OS rates of 76% and 60%, respectively. After adjusting each measure of tumor burden for age, Karnofsky performance score (KPS), tumor location, and tumor subtype, OS was predicted by EOR (hazard ratio [HR] = 0.972; 95% CI, 0.960 to 0.983; P < .001), log preoperative tumor volume (HR = 4.442; 95% CI, 1.601 to 12.320; P = .004), and postoperative tumor volume (HR = 1.010; 95% CI, 1.001 to 1.019; P = .03), progression-free survival was predicted by log preoperative tumor volume (HR = 2.711; 95% CI, 1.590 to 4.623; P ≤ .001) and postoperative tumor volume (HR = 1.007; 95% CI, 1.001 to 1.014; P = .035), and malignant progression-free survival was predicted by EOR (HR = 0.983; 95% CI, 0.972 to 0.995; P = .005) and log preoperative tumor volume (HR = 3.826; 95% CI, 1.632 to 8.969; P = .002).

Conclusion

Improved outcome among adult patients with hemispheric LGG is predicted by greater EOR.

Molecular imaging-guided gene therapy of gliomas

Gene therapy of patients with glioblastoma using viral and non-viral vectors, which are applied by direct injection or convection-enhanced delivery (CED), appear to be satisfactorily safe. Up to date, only single patients show a significant therapeutic benefit as deduced from single long-term survivors. Non-invasive imaging by PET for the identification of viable target tissue and for assessment of transduction efficiency shall help to identify patients which might benefit from gene therapy, while non-invasive follow-up on treatment responses allows early and dynamic adaptations of treatment options. Therefore, molecular imaging has a critical impact on the development of standardised gene therapy protocols and on efficient and safe vector applications in humans.

Surgery Insight: the role of surgery in the management of low-grade gliomas

The benefits of surgery for the management of low-grade gliomas have been difficult to determine from the literature. This difficulty might be explained by the inconsistency of the published data, and also by advances in both neuroimaging and neurosurgical techniques, which have made surgical intervention a safer and more viable option than it has been in the past, making the earlier studies less applicable to modern care. In this article, we critically analyze the utility of surgery in the management of low-grade gliomas, including the value of observation without surgical intervention, the relative risks and benefits of biopsy versus craniotomy and resection, and recent advances that have made surgery safer and gross total resection a more realistic proposition. As we will discuss, the literature provides modest evidence that surgery leads to improved outcomes through a reduction in tumor burden. As a result of advances in surgical techniques, the time might now be right to effectively and accurately assess the influence of aggressive surgical resection on the prognosis of low-grade gliomas.

Prognostic significance of loss of O6-methylguanine-DNA methyltransferase expression in supratentorial diffuse low-grade astrocytoma

BACKGROUND

O(6)-Methylguanine-DNA methyltransferase is a DNA repair protein. Epigenetic silencing of MGMT function by its promoter hypermethylation is considered to contribute to carcinogenesis. If loss of function in MGMT is related to tumor progression, the immunohistochemical method may predict the malignant change of gliomas.

METHOD

We investigated the expression of MGMT by immunohistochemical method in 28 supratentorial hemispheric diffuse astrocytomas. The prognostic significance of MGMT expression, proliferation index (MIB-1), and various clinical factors was evaluated.

RESULTS

There were 19 MGMT-positive and 9 MGMT-negative astrocytomas. Their rates of malignant transformation at 5 years were 12.3% and 51.4%, respectively. The difference was significant in the univariate (P = .004) and multivariate analyses (P = .044). Age, sex, extent of surgery, MIB-1 value, and radiation therapy at initial treatment did not correlate with the malignant progression. The 10-year overall survival rates were 71.8% and 58.3% in the patients with MGMT-positive and MGMT-negative tumors, respectively, and were not significantly different between these 2 groups (P = .079). Two long-term survivors with MGMT-negative tumor responded well to nitrosourea-based chemotherapy and lived more than 8 years after malignant transformation. The patients' age (P = .0047) and the degree of surgical removal (P = .0082) affected the overall survival in the univariate analysis. In the multivariate analysis, none of these factors reached significance.

CONCLUSION

Although the status of MGMT did not affect the overall survival, immunohistochemical evaluation of MGMT expression may be a good marker for tumor progression.

Brain tumor imaging and cancer management: the neuro-oncologists perspective

Brain tumors remain a significant cause of morbidity and mortality and are often refractory to treatment. Neuroimaging, in particular magnetic resonance imaging (MRI) and associated techniques, has become an important tool for the neuro-oncologist in the management of brain tumors. Magnetic resonance imaging is the most sensitive method to demonstrate the presence of a mass in the brain and can often narrow the differential diagnosis with nonneoplastic lesions such as cerebral abscess and subacute infarction. Once the diagnosis has been confirmed, MRI is essential for initial treatment planning, including surgical resection and radiation therapy. In selected patients, serial MRI will also be necessary to evaluate for response during adjuvant chemotherapy and to monitor for treatment-induced toxicity. New magnetic resonance techniques such as magnetic resonance spectroscopy, diffusion-weighted imaging, and perfusion-based imaging methods will also be discussed where applicable.

Loss of heterozygosity 1p36 and 19q13 is a prognostic factor for overall survival in patients with diffuse WHO grade 2 gliomas treated without chemotherapy

PURPOSE

This study was conducted to elucidate the impact of loss of heterozygosity (LOH) for chromosomes 1p36 and 19q13 on the overall survival of patients with diffusely infiltrating WHO grade 2 gliomas treated without chemotherapy.

PATIENTS AND METHODS

We assessed the LOH status of tumors from patients harboring WHO grade 2 gliomas diagnosed between 1991 and 2000. Patients were either followed after initial biopsy or treated by surgery and/or radiation therapy (RT). Overall survival, time to malignant transformation, and progression-free survival were last updated as of March 2005.

RESULTS

Of a total of 79 patients, LOH 1p36 and LOH 19q13 could be assessed in 67 and 66 patients, respectively. The median follow-up after diagnosis was 6 years. Loss of either 1p or 19q, in particular codeletion(s) at both loci, was found to positively impact on both overall survival (log-rank P < .01), progression-free survival, and survival without malignant transformation (P < .05). Tumor volume (P < .0001), neurologic deficits at diagnosis (P < .01), involvement of more than one lobe (P < .01), and absence of an oligodendroglial component (P < .05) were also predictors of shorter overall survival. The extent of surgery was similar in patients with or without LOH 1p and/or 19q; RT was more frequently resorted to for patients without than for patients with LOH 1p/19q (30% v 60%).

CONCLUSION

The presence of LOH on either 1p36 or 19q13, and in particular codeletion of both loci is a strong, nontreatment-related, prognostic factor for overall survival in patients with diffusely infiltrating WHO grade 2 gliomas.

Integrated positron emission tomography and magnetic resonance imaging–guided resection of brain tumors: a report of 103 consecutive procedures

Object

The aim of this study was to evaluate the integration of positron emission tomography (PET) scanning data into the image-guided resection of brain tumors.

Methods

Positron emission tomography scans obtained using fluorine-18 fluorodeoxyglucose (FDG) and l-[methyl-11C]methionine (MET) were combined with magnetic resonance (MR) images in the navigational planning of 103 resections of brain tumors (63 low-grade gliomas [LGGs] and 40 high-grade gliomas [HGGs]). These procedures were performed in 91 patients (57 males and 34 females) in whom tumor boundaries could not be accurately identified on MR images for navigation-based resection. The level and distribution of PET tracer uptake in the tumor were analyzed to define the lesion contours, which in turn yielded a PET volume. The PET scanning–demonstrated lesion volume was subsequently projected onto MR images and compared with MR imaging data (MR volume) to define a final target volume for navigation-based resection—the tumor contours were displayed in the microscope’s eyepiece. Maximal tumor resection was accomplished in each case, with the intention of removing the entire area of abnormal metabolic activity visualized during surgical planning. Early postoperative MR imaging and PET scanning studies were performed to assess the quality of tumor resection. Both pre- and postoperative analyses of MR and PET images revealed whether integrating PET data into the navigational planning contributed to improved tumor volume definition and tumor resection.

Metabolic information on tumor heterogeneity or extent was useful in planning the surgery. In 83 (80%) of 103 procedures, PET studies contributed to defining a final target volume different from that obtained with MR imaging alone. Furthermore, FDG-PET scanning, which was performed in a majority of HGG cases, showed that PET volume was less extended than the MR volume in 16 of 21 cases and contributed to targeting the resection to the hypermetabolic (anaplastic) area in 11 (69%) of 16 cases. Performed in 59 LGG cases and 23 HGG cases, MET-PET demonstrated that the PET volume did not match the MR volume and improved the tumor volume definition in 52 (88%) of 59 and 18 (78%) of 23, respectively. Total resection of the area of increased PET tracer uptake was achieved in 54 (52%) of 103 procedures.

Conclusions

Imaging guidance with PET scanning provided independent and complementary information that helped to assess tumor extent and plan tumor resection better than with MR imaging guidance alone. The PET scanning guidance could help increase the amount of tumor removed and target image-guided resection to tumor portions that represent the highest evolving potential.

Imaging in neurooncology

Imaging in patients with brain tumors aims toward the determination of the localization, extend, type, and malignancy of the tumor. Imaging is being used for primary diagnosis, planning of treatment including placement of stereotaxic biopsy, resection, radiation, guided application of experimental therapeutics, and delineation of tumor from functionally important neuronal tissue. After treatment, imaging is being used to quantify the treatment response and the extent of residual tumor. At follow-up, imaging helps to determine tumor progression and to differentiate recurrent tumor growth from treatment-induced tissue changes, such as radiation necrosis. A variety of complementary imaging methods are currently being used to obtain all the information necessary to achieve the above mentioned goals. Computed tomography and magnetic resonance imaging (MRI) reveal mostly anatomical information on the tumor, whereas magnetic resonance spectroscopy and positron emission tomography (PET) give important information on the metabolic state and molecular events within the tumor. Functional MRI and functional PET, in combination with electrophysiological methods like transcranial magnetic stimulation, are being used to delineate functionally important neuronal tissue, which has to be preserved from treatment-induced damage, as well as to gather information on tumor-induced brain plasticity. In addition, optical imaging devices have been implemented in the past few years for the development of new therapeutics, especially in experimental glioma models. In summary, imaging in patients with brain tumors plays a central role in the management of the disease and in the development of improved imaging-guided therapies.