Low grade gliomas treated with adjuvant radiation therapy in the modern imaging era

How Histopathologic Tumor Extent and Patterns of Recurrence Data Inform the Development of Radiation Therapy Treatment Volumes in Solid Malignancies

The ability to deliver highly conformal radiation therapy using intensity-modulated radiation therapy and particle therapy provides for new opportunities to improve patient outcomes by reducing treatment-related morbidities following radiation therapy. By reducing the volume of normal tissue exposed to radiation therapy (RT), while also allowing for the opportunity to escalate the dose of RT delivered to the tumor, use of conformal RT delivery should also provide the possibility of expanding the therapeutic index of radiotherapy. However, the ability to safely and confidently deliver conformal RT is largely dependent on our ability to clearly define the clinical target volume for radiation therapy, which requires an in-depth knowledge of histopathologic extent of different tumor types, as well as patterns of recurrence data. In this article, we provide a comprehensive review of the histopathologic and radiographic data that provide the basis for evidence-based guidelines for clinical tumor volume delineation.

Local control and overall survival for adjuvant stereotactic radiosurgery in patients with residual or recurrent disease

Prior studies of post-operative stereotactic radiosurgery (SRS) have not distinguished between Adjuvant SRS (ARS) versus Adjuvant SRS to residual/recurrent disease (ARD). In this study, we defined ARS and ARD and investigated local control (LC), overall survival (OS), distant development of brain metastases (DBF), and leptomeningeal disease (LMD). We retrospectively identified BM patients who received surgical resection and SRS for BM from an IRB approved database between Jan 2009-Aug 2015. Patients were stratified into two groups: ARS and ARD. LC was determined by follow-up MRI studies and OS was measured from the date of surgery. LC and OS were assessed using the Kaplan-Meier method. 70 cavities underwent surgical resection of BM and received SRS to the post-operative bed. 41 cavities were classified as ARS and 29 as ARD. There was no significant difference in 12-month LC between the ARS and ARD group (71.4 vs. 80.8%, respectively; p = 0.135) from the time point of SRS. The overall 1-year survival for ARS and ARD was 79.9 and 86.1%, respectively (p = 0.339). Mean time to progression was 6.45 and 8.0 months and median follow-up was 10 and 15 months for ARS and ARD, respectively. 11.8% of ARS patients and 15.4% of ARD patients developed LMD, p = 0.72. 29.4% of ARS and 48.0% of ARD patients developed DBF, p = 0.145. Our findings suggest that observation after surgical resection, with subsequent treatment with SRS after the development of local failure, may not compromise treatment efficacy. If validated, this would spare patients who do not recur post-surgically from additional treatment.

The role of radiotherapy in the management of patients with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

QUESTIONS

(1) What is the optimal role of external beam radiotherapy in the management of adult patients with newly diagnosed low-grade glioma (LGG) in terms of improving outcome (i.e., survival, complications, seizure control or other reported outcomes of interest)? (2) Which radiation strategies (dose, timing, fractionation, stereotactic radiation, brachytherapy, chemotherapy) improve outcomes compared to standard external beam radiation therapy in the initial management of low grade gliomas in adults? (3) Do specific factors (e.g., age, volume, extent of resection, genetic subtype) identify subgroups with better outcomes following radiation therapy than the general population of adults with newly diagnosed low-grade gliomas?

TARGET POPULATION

These recommendations apply to adults with newly diagnosed diffuse LGG.

RECOMMENDATIONS

OUTCOMES IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level I Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong progression free survival, irrespective of extent of resection. Level II Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults as an equivalent alternative to observation in preserving cognitive function, irrespective of extent of resection. Level III Radiotherapy is recommended in the management of newly diagnosed low grade glioma in adults to improve seizure control in patients with epilepsy and subtotal resection. Level III Radiotherapy is recommended in the management of newly diagnosed low-grade glioma in adults to prolong overall survival in patients with subtotal resection. Level III Consideration of the risk of radiation induced morbidity, including cognitive decline, imaging abnormalities, metabolic dysfunction and malignant transformation, is recommended when the delivery of radiotherapy is selected in the management of newly diagnosed low-grade glioma in adults. STRATEGIES OF RADIOTHERAPY IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA: Level I Lower dose radiotherapy is recommended as an equivalent alternative to higher dose immediate postoperative radiotherapy (45-50.4 vs. 59.4-64.8 Gy) in the management of newly diagnosed low-grade glioma in adults with reduced toxicity. Level III Delaying radiotherapy until recurrence or progression is recommended as an equivalent alternative to immediate postoperative radiotherapy in the management of newly diagnosed low-grade glioma in adults but may result in shorter time to progression. Level III The addition of chemotherapy to radiotherapy is not recommended over whole brain radiotherapy alone in the management of low-grade glioma, as it provides no additional survival benefit. Level III Limited-field radiotherapy is recommended over whole brain radiotherapy in the management of low-grade glioma. Level III Either stereotactic radiosurgery or brachytherapy are recommended as acceptable alternatives to external radiotherapy in selected patients. PROGNOSTIC FACTORS IN ADULT PATIENTS WITH NEWLY DIAGNOSED LOW GRADE GLIOMA TREATED WITH RADIOTHERAPY: Level II It is recommended that age greater than 40 years, astrocytic pathology, diameter greater than 6 cm, tumor crossing the midline and preoperative neurological deficit be considered as negative prognostic indicators when predicting overall survival in adult low grade glioma patients treated with radiotherapy. Level II It is recommended that smaller tumor size, extent of surgical resection and higher mini-mental status exam be considered as positive prognostic indicators when predicting overall survival and progression free survival in patients in adult low grade glioma patients treated with radiotherapy. Level III It is recommended that seizures at presentation, presence of oligodendroglial histological component and 1p19q deletion (along with additional relevant factors-see Table 1) be considered as positive prognostic indicators when predicting response to radiotherapy in adults with low grade gliomas. Level III It is recommended that increasing age, decreasing performance status, decreasing cognition, presence of astrocytic histological component (along with additional relevant factors (see Tables 1, 2) be considered as negative prognostic indicators when predicting response to radiotherapy.

Emerging operative strategies in neurosurgical oncology

PURPOSE OF REVIEW

In recent years, the safety and efficacy of neurosurgical intervention has rapidly improved for brain tumor patients. Technological advances, combined with refined intraoperative techniques, now enable well tolerated surgical access to any region of the human brain. For patients with gliomas, these improvements have redefined the clinical possibilities, and here we review several emerging operative strategies that are essential for next-generation neurosurgical oncologists and major brain tumor centers.

RECENT FINDINGS

The value of glioma extent of resection remains controversial, but review of the modern literature reveals important opportunities for early neurosurgical intervention. Although microsurgical resection must be balanced by the risk of neurological compromise, improvements in intraoperative stimulation techniques now enable resection of highly eloquent tumors with minimal morbidity. Additionally, the emergence of fluorescence-guided surgery as a new operative paradigm provides a unique opportunity to resect tumors to the margins of microscopic infiltration.

SUMMARY

Neurosurgical intervention remains the first step in effective glioma management. With intraoperative mapping techniques, aggressive microsurgical resection can be safely pursued even when tumors occupy essential functional pathways. With the development of tumor-specific fluorophores, such as 5-aminolevulinic acid, real-time microscopic visualization of tumor infiltration can be surgically targeted prior to adjuvant therapy.

Intraoperative confocal microscopy in the visualization of 5-aminolevulinic acid fluorescence in low-grade gliomas

OBJECT

Greater extent of resection (EOR) for patients with low-grade glioma (LGG) corresponds with improved clinical outcome, yet remains a central challenge to the neurosurgical oncologist. Although 5-aminolevulinic acid (5-ALA)-induced tumor fluorescence is a strategy that can improve EOR in gliomas, only glioblastomas routinely fluoresce following 5-ALA administration. Intraoperative confocal microscopy adapts conventional confocal technology to a handheld probe that provides real-time fluorescent imaging at up to 1000× magnification. The authors report a combined approach in which intraoperative confocal microscopy is used to visualize 5-ALA tumor fluorescence in LGGs during the course of microsurgical resection.

METHODS

Following 5-ALA administration, patients with newly diagnosed LGG underwent microsurgical resection. Intraoperative confocal microscopy was conducted at the following points: 1) initial encounter with the tumor; 2) the midpoint of tumor resection; and 3) the presumed brain-tumor interface. Histopathological analysis of these sites correlated tumor infiltration with intraoperative cellular tumor fluorescence.

RESULTS

Ten consecutive patients with WHO Grades I and II gliomas underwent microsurgical resection with 5-ALA and intraoperative confocal microscopy. Macroscopic tumor fluorescence was not evident in any patient. However, in each case, intraoperative confocal microscopy identified tumor fluorescence at a cellular level, a finding that corresponded to tumor infiltration on matched histological analyses.

CONCLUSIONS

Intraoperative confocal microscopy can visualize cellular 5-ALA-induced tumor fluorescence within LGGs and at the brain-tumor interface. To assess the clinical value of 5-ALA for high-grade gliomas in conjunction with neuronavigation, and for LGGs in combination with intraoperative confocal microscopy and neuronavigation, a Phase IIIa randomized placebo-controlled trial (BALANCE) is underway at the authors' institution.

Image fusion analysis of volumetric changes after interstitial low-dose-rate iodine-125 irradiation of supratentorial low-grade gliomas

The aim of this study was to compare the volumes of tumor necrosis, reactive zone and edema with the three-dimensional dose distributions after brachytherapy treatments of gliomas. The investigation was performed an average of 14.2 months after low-dose-rate (125)I interstitial irradiation of 25 inoperable low-grade gliomas. The prescribed dose was 50-60 Gy to the tumor surface. Dose planning and image fusion were performed with the BrainLab-Target 1.19 software. In the CT/ MRI images, the "triple ring" (tumor necrosis, reactive ring and edema) developing after the interstitial irradiation of the brain tumors was examined. The images with the triple ring were fused with the planning images, and the isodose curves were superimposed on them. The volumes of the three regions were measured. The average dose at the necrosis border was determined from the isodose distribution. For quantitative assessment of the dose distributions, the dose nonuniformity ratio (DNR), homogeneity index (HI), coverage index (CI) and conformal index (COIN) were calculated. The relative volumes of the different parts of the triple ring after the interstitial irradiation compared to the reference dose volume were the following: necrosis, 40.9%, reactive zone, 47.1%, and edema, 367%. The tumor necrosis developed at 79.1 Gy on average. The average DNR, HI, CI and COIN were 0.45, 0.24, 0.94 and 0.57, respectively. The image fusion analysis of the volume of tumor necrosis, reactive ring and edema caused by interstitial irradiation and their correlation with the dose distribution provide valuable information for patient follow-up, treatment options, and effects and side effects of radio therapy.

Place de la chimiothérapie et de la radiothérapie dans le traitement des oligodendrogliomes

Twenty years ago, the discovery of the chemosensitivity of anaplastic oligodendrogliomas considerably boosted interest for these tumors. In spite of difficulties for histological diagnosis, numerous studies on radiotherapy and chemotherapy for oligodendrogliomas appeared these last years. They allowed to detail the appropriate role for these therapeutics. For low grade oligodendrogliomas, radiotherapy delays the anaplastic transformation, but does not modify the overall survival; its indication has to be discussed particularly in the absence of clinical symptoms. Chemotherapy seems to be effective for low grade oligodendrogliomas as well as anaplastic tumors. However, phase III studies are necessary to clarify the contribution of chemotherapy for the treatment of low grade oligodendrogliomas, mainly in relation to radiotherapy. In anaplastic oligodendrogliomas, in spite of the lack of phase III studies, radiotherapy seems to be effective. Chemotherapy is clearly effective, but the most appropriate timing (neoadjuvant, adjuvant, at recurrence) is unknown. Results of current prospective studies are awaited. Recently, molecular genetic analysis, particularly the loss of 1p and 19q chromosomes appears to demonstrate a genetic influence on both prognosis and response to treatment.

[Supratentorial low grade glioma in adults: an experience with 23 surgical cases]

Low-grade supratentorial astrocytomas and oligodendrogliomas in adults are uncommon tumors of the central nervous system. We analyzed retrospectively 23 patients with this type of neoplasia, who were operated on between 1986 and 2002. There were no post-operative deaths. The survival rate at 5 and 10 years post-surgery for the entire sample was 67 and 30% respectively, similar to other outcomes. With 14 patients we achieved a complete removal of the lesion (60.8%) and with 9 (39.2%) partial removal of the tumor. In the sub-group which underwent total resection of the tumor, 89% survived 5 years and 45% attained 10 years of survival, in contrast with the sub-group that underwent partial removal in which only 35% attained 5 years of survival and none 10 years. Due to the deleterious effects of radiation therapy, we preferred to prescribe it only in cases of tumor recurrence.

Hyperfractionated radiation therapy for incompletely resected supratentorial low-grade glioma: a 10-year update of a phase II study

PURPOSE

To provide a 10-year update of hyperfractionated radiation therapy (Hfx RT) in adults with incompletely resected supratentorial low-grade glioma.

METHODS AND MATERIALS

A total of 37 patients were treated with 55 Gy in 50 fractions in 25 treatment days in 5 weeks to tumor plus 2 cm, and additional 17.6 Gy given in 16 fractions in 8 treatment days in 1.5 weeks to tumor plus 1 cm, (1.1 Gy twice daily). Total dose was 72.6 Gy in 66 fractions in 33 treatment days in 6.5 weeks.

RESULTS

After a median follow-up time of 121 months for all patients, the median survival time (MST) for all 37 patients was 145 months, whereas 10-year survival rate was 67%. Median time to tumor progression (MTP) has not yet been attained, but 10-year progression-free survival (PFS) rate was 62%. There was no difference in survival or PFS regarding gender, age, location, site, size, CT enhancement, and histology; whereas lower KPS, higher neurologic status, and lesser extent of surgery had an adverse influence. Infield progression occurred in 15 (88%), whereas in only 2 (12%) patients, tumor progression was described as marginal. Brain necrosis has not been observed so far. Autopsy findings confirmed recurrent glioma and excluded post-RT necrosis in 14 (38%) patients. Of those, 7 (50%) patients had either Grade 3 (n = 4) or Grade 4 (n = 3) glioma.

CONCLUSION

High-dose HFX RT is effective with mild to moderate toxicity. Further studies are warranted with more patients before testing it against standard fractionation RT in this patient population.

Conformal irradiation for pure and mixed oligodendroglioma: the experience of Centre Leon Berard Lyon

PURPOSE

To assess whether conformal radiotherapy (CRT) after incomplete surgery or biopsy for pure oligodendrogliomas and mixed gliomas results in decreased long-term sequelae without impairing local control and while reducing irradiated volume.

MATERIALS AND METHODS

Twenty-six consecutive patients who presented with pure (21) or mixed (5) oligodendrogliomas and who were given incomplete resections were treated according 3 different strategies: CRT alone (12), chemotherapy followed by CRT (4), and chemotherapy and delayed CRT at the time of tumor progression (10). CRT consisted of multiple noncoplanar fields. Median dose was 60 Gy. Quality of CRT was assessed using tumor and normal tissue conformal indexes. The location of recurrences was assessed with MRI and dosimetric data. Late sequelae were assessed by a questionnaire exploring professional outcome, and also by a Mini Mental State Examination test.

RESULTS

The mean overall survival was 5.2 years. Fifteen patients experienced a local relapse. All but 1 occurred in the 95% isodose. Among 11 nonevolutive patients, 6 have a full-time or part-time job.

CONCLUSIONS

Despite CRT, infield recurrence was a common feature in patients with oligodendrogliomas and mixed tumors. Further research, including molecular biology typing of tumors and type of treatment, is warranted to improve survival and quality of life.

Metabolic imaging of low-grade gliomas with three-dimensional magnetic resonance spectroscopy

PURPOSE

The role of radiotherapy (RT) seems established for patients with low-grade gliomas with poor prognostic factors. Three-dimensional (3D) magnetic resonance spectroscopy imaging (MRSI) has been reported to be of value in defining the extent of glioma infiltration. We performed a study examining the impact MRSI would have on the routine addition of 2-3-cm margins around MRI T2-weighted hyperintensity to generate the treatment planning clinical target volume (CTV) for low-grade gliomas.

METHODS AND MATERIALS

Twenty patients with supratentorial gliomas WHO Grade II (7 astrocytomas, 6 oligoastrocytomas, 7 oligodendrogliomas) underwent MRI and MRSI before surgery. The MRI was contoured manually; the regions of interest included T2 hyperintensity and, if present, regions of contrast enhancement on T1-weighted images. The 3D-MRSI peak parameters for choline and N-acetyl-aspartate, acquired voxel-by-voxel, were categorized using a choline/N-acetyl-aspartate index (CNI), a tool for quantitative assessment of tissue metabolite levels, with CNI 2 being the lowest value corresponding to tumor. CNI data were aligned to MRI and displayed as 3D contours. The relationship between the anatomic and metabolic information on tumor extent was assessed by comparing the CNI contours and other MRSI-derived metabolites to the MRI T2 volume.

RESULTS

The limitations in the size of the region "excited" meant that MRSI could be used to evaluate only a median 68% of the T2 volume (range 38-100%), leaving the volume T2c. The CNI 2 volume (median 29 cm(3), range 10-73) was contained totally within the T2c in 55% of patients. In the remaining patients, the volume of CNI 2 extending beyond the T2c was quite small (median 2.3 cm(3), range 1.4-5.2), but was not distributed uniformly about the T2c, extending up to 22 mm beyond it. Two patients demonstrated small regions of contrast enhancement corresponding to the regions of highest CNI. Other metabolites, such as creatine and lactate, seem useful for determining less and more radioresistant areas, respectively.

CONCLUSION

Metabolically active tumor, as detected by MRSI, is restricted mainly to the T2 hyperintensity in low-grade gliomas, but can extend outside it in a limited and nonuniform fashion up to 2 cm. Therefore, a CTV including T2 and areas of CNI extension beyond the T2 hyperintensity would result in a reduction in the size and a change in the shape of the standard clinical target volumes generated by adding uniform margins of 2-3 cm to the T2 hyperintensity.

Preliminary results from a Phase II trail of conformal radiation therapy for pediatric patients with localised low-grade astrocytoma and ependymoma

PURPOSE

To estimate the local control and patterns of failure for pediatric patients with low-grade astroglial tumors (LGA) and ependymoma (EP) treated with three-dimensional conformal radiation therapy (CRT) using an anatomically defined clinical target volume (CTV).

METHODS AND MATERIALS

From an ongoing, prospective Phase II trial initiated in July 1997, 102 pediatric patients with LGA (n = 38) and EP (n = 64) have been treated with CRT using an anatomically defined CTV extending 1.0 cm beyond the gross tumor volume and a 0.5-cm margin (planning target volume) extending outside of the CTV. The prescribed dose was 54 Gy (LGA) and 59.4 Gy (EP).

RESULTS

Patients with EP have been followed for a median of 17 months (range 3--43 months), and six failures have occurred. Patients with LGA have been followed for a median of 17 months (3--44 months), and four failures have occurred. Three-dimensional magnetic resonance (MR) studies performed to document treatment failure were registered with the MR and computed tomography (CT) data used in the treatment planning process. Failure occurred within the CTV for 5 patients with EP, including 3 with concurrent subarachnoid dissemination. One patient with EP developed metastatic disease with no evidence of local failure. Three patients with LGA failed within the CTV and one failed immediately outside of the CTV.

CONCLUSIONS

Treatment of an anatomically defined CTV, encompassing 1.0 cm of non-involved brain beyond the margin of resection or neuroimaging-defined tumor, appears to be safe for pediatric patients with LGA and EP based on these preliminary data. Normal tissue sparing through the use of advanced radiation therapy treatment planning and delivery techniques should be beneficial to pediatric patients if the rate and patterns of failure are similar to conventional techniques and toxicity reduction can be objectively documented.

Diagnosis and management of astrocytomas, oligodendrogliomas and mixed gliomas: a review

Low-grade gliomas are a diverse group of neoplasms which, as the name implies, are thought to arise from glial cells. Common among this group are astrocytomas (low-grade astrocytoma; LGA), oligodendrogliomas and mixed gliomas. Among these, LGA is the commonest low-grade glioma and, occasionally, although incorrectly, the terms are used interchangeably. Advances in imaging technology have improved the accuracy of preoperative diagnosis. The management of low-grade gliomas is controversial. Recent evidence suggests that previously considered standard therapy (i.e. surgery plus radiotherapy) may not be in the patient's best interests. A review of the available published research concerning low-grade gliomas is therefore timely.

Three-dimensional conformal radiation treatment planning and delivery for low- and intermediate-grade gliomas

Three-Dimensional conformal radiation treatment (3D-CRT) planning and delivery is an external beam radiation therapy modality that has the general goal of conforming the shape of a prescribed dose volume to the shape of a 3-dimensional target volume, simultaneously limiting dose to critical normal structures. 3-Dimensional conformal therapy should include at least one volumetric imaging study of the patient. This image should be obtained in the treatment position for visualizing the target and normal anatomic structures that are potentially within the irradiated volume. Most often, computed tomography (CT) and/or magnetic resonance imaging (MRI) are used; however, recently, other imaging modalities such as functional MRI, MR spectroscopy, and positron emission tomography (PET) scans have been used to visualize the clinically relevant volumes. This article will address the clinically relevant issues with regard to low- and intermediate-grade gliomas and the role of 3D-CRT planning. Specific issues that will be addressed will include normal tissue tolerance, target definition, treatment field design in regard to isodose curves and dose-volume histograms, and immobilization.

Postoperative radiotherapy of astrocytomas

Astrocytomas account for the majority of primary brain tumors. Low-grade tumors are slowly growing tumors with relatively long overall survival. However, a high percentage of these tumors transform to more malignant, high-grade tumors. High-grade gliomas (anaplastic astrocytomas and glioblastoma multiforme) have a poor prognosis. Treatment options are capable of prolonging the natural history of the disease, but the long-term survival is poor. This review discusses the different postoperative treatment options and the prognostic factors in low- and high-grade astrocytomas.