Central neurocytoma with unusually intense FDG uptake: case report

The role of single fraction Gamma Knife radiosurgery for intraventricular central neurocytomas and the utility of F-18 fluroethyltyrosine: two case reports

BACKGROUND

Primary treatment of central neurocytomas is surgical resection. Gamma Knife surgery is considered a valuable therapeutic option in case of residual (after subtotal resection) or recurrent central neurocytomas. Here, we focused on the role of F-18 fluroethyltyrosine as a marker to document tumor progression after initial resection, in the context of an atypical central neurocytoma. We also describe MIB-1's role in evaluating therapeutic decision-making.

CASE PRESENTATION

Two patients with central neurocytomas were treated by Gamma Knife surgery in our center. The first case (31-year-old Caucasian male) had atypical central neurocytoma. Four and a half years after surgical resection, magnetic resonance imaging and F-18 fluroethyltyrosine documented clear progression of residual central neurocytoma, further treated by Gamma Knife surgery (18 Gy at 50%, target volume 1.4 cc, and prescription isodose volume 1.8 cc). The initial post-Gamma Knife surgery clinical course was uneventful, with progressive volumetric reduction of residual tumor up to 4.5 years, when out-of-field recurrence was suspected and confirmed by local F-18 fluroethyltyrosine hyperactivity. Second single-fraction Gamma Knife surgery was performed (18 Gy at 50%, target volume 0.49 cc, prescription isodose volume 0.72 cc). The second (32-year-old Caucasian female) had previous subtotal resection and typical central neurocytoma. Seven years later, she had residual tumor progression. Single-fraction Gamma Knife surgery was performed (16 Gy at 50% isodose line, target volume 1.7 cc, and prescription isodose volume 2.5 cc). Last follow-up showed tumor volume reduction. Follow-up magnetic resonance imaging showed important volumetric reduction of both treated lesions.

CONCLUSIONS

In atypical central neurocytomas, F-18 fluroethyltyrosine could be used as postoperative examination to detect small tumor remnants, follow-up evaluation following the Gamma Knife surgery or, in select cases, following surgical resection. The role of MIB-1 is important in therapeutic decision-making, as tumors with MIB-1 exceeding 2% are characterized by more aggressive clinical course. Single-fraction Gamma Knife surgery remains a valuable therapeutic option for postoperative residual atypical central neurocytomas and central neurocytoma recurrences.

Cerebellar Neurocytoma with Excellent Response to Radiotherapy

BACKGROUND

Extraventricular neurocytoma (EVN) is a rare neurocytoma occurring in the brain parenchyma outside the ventricular system that shares similar biological behaviors and histopathologic characteristics with central neurocytoma. Reports of EVN localized in the brainstem and cerebellum are relatively uncommon. In addition, few cases with radiotherapy as the only treatment have been reported and their outcomes were unclear.

CASE DESCRIPTION

We report a case of pathologically confirmed EVN of the brainstem and cerebellum in a 43-year-old male who presented with unprovoked nausea and dizziness. The patient received radiotherapy only and showed a favorable outcome during the 2-year follow-up period.

CONCLUSIONS

These results suggest that patients with EVN who are treated with radiotherapy without surgery may have a favorable prognosis.

Somatostatin Receptor Ligand Therapy-A Potential Therapy for Neurocytoma

CONTEXT

Neurocytoma (NC) is a rare, low-grade tumor of the central nervous system, with a 10-year survival rate of 90% and local control rate of 74%. However, 25% of NCs will be atypical, with an elevated Ki-67 labeling index >2%, and will exhibit a more aggressive course, with a high propensity for local recurrence and/or craniospinal dissemination. Although no standard treatment regimen exists for these atypical cases, adjuvant stereotactic or conventional radiotherapy and/or chemotherapy have been typically offered but have yielded inconsistent results.

CASE DESCRIPTION

We have described the case of a patient with a vasopressin-secreting atypical NC of the sellar and cavernous sinus region. After subtotal resection via endoscopic transsphenoidal surgery, the residual tumor showed increased fluorodeoxyglucose uptake and high somatostatin receptor (SSTR) expression on a 68Ga-DOTA-TATE positron emission tomography/CT scan. Somatostatin receptor ligand (SRL) therapy with lanreotide (120 mg every 28 days) was initiated. Four years later, the residual tumor was stable with decreased fluorodeoxyglucose tumor uptake. Immunocytochemical SSTR2 and SSTR5 expression >80% was further confirmed in a series of NC tissues.

CONCLUSIONS

To the best of our knowledge, we have described the first use of SRL therapy for an atypical NC. Our results support consideration of adjuvant SRL therapy for NC refractory to surgical removal. Our findings further raise the possibility of SSTR-directed peptide receptor radionuclide therapy as NC therapy.

Estimation of proliferative potentiality of central neurocytoma: correlational analysis of minimum ADC and maximum SUV with MIB-1 labeling index

BACKGROUND

Central neurocytoma was initially believed to be benign tumor type, although atypical cases with more aggressive behavior have been reported. Preoperative estimation for proliferating activity of central neurocytoma is one of the most important considerations for determining tumor management.

PURPOSE

To investigate predictive values of image characteristics and quantitative measurements of minimum apparent diffusion coefficient (ADCmin) and maximum standardized uptake value (SUVmax) for proliferative activity of central neurocytoma measured by MIB-1 labeling index (LI).

MATERIAL AND METHODS

Twelve cases of central neurocytoma including one recurrence from January 2001 to December 2011 were included. Preoperative scans were conducted in 11, nine, and five patients for computed tomography (CT), diffusion-weighted imaging (DWI), and fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET), respectively, and ADCmin and SUVmax of the tumors were measured. Image characteristics were investigated using CT, T2-weighted (T2W) imaging and contrast-enhanced T1-weighted (T1W) imaging, and their differences were examined using the Fisher's exact test between cases with MIB-1 LI below and above 2%, which is recognized as typical and atypical central neurocytoma, respectively. Correlational analysis was conducted for ADCmin and SUVmax with MIB-1 LI. A P value <0.05 was considered significant.

RESULTS

Morphological appearances had large variety, and there was no significant correlation with MIB-1 LI except a tendency that strong enhancement was observed in central neurocytomas with higher MIB-1 LI (P = 0.061). High linearity with MIB-1 LI was observed in ADCmin and SUVmax (r = -0.91 and 0.74, respectively), but only ADCmin was statistically significant (P = 0.0006).

CONCLUSION

Central neurocytoma had a wide variety of image appearance, and assessment of proliferative potential was considered difficult only by morphological aspects. ADCmin was recognized as a potential marker for differentiation of atypical central neurocytomas from the typical ones.

FDG PET differentiation of tumor recurrence from post-stereotactic radiosurgical scar in a central neurocytoma

Central neurocytoma is a rare benign tumor of neuronal origin. The tumor is often located in the ventricular system and can proliferate within the ventricle. Five months after stereotactic radiosurgery for recurrent neurocytoma, a 33-year-old woman had a 2.0-cm lesion in the right third ventricle on the MRI. FDG PET demonstrated intense uptake of the lesion. The subsequent MRI follow-up showed growth of the lesion and confirmed recurrence.

3-T Proton Magnetic Resonance Spectroscopy of Central Neurocytoma

Central neurocytoma (CNC), first described by Hassoun et al in 1982, is a rare neuronal tumor of the central nervous system, accounting for 0.25% to 0.5% of all central nervous system tumors. To our knowledge, there are only 5 published articles reporting the magnetic resonance spectroscopy (MRS) findings of neurocytomas. The 3-T proton MRS findings of 3 cases with CNC confirmed by immunohistochemical stains are reported here. Increased choline (Cho)/creatine (Cr) ratios with decreased N-acetylaspartate (NAA)/Cr ratios were observed in all 3 cases, but only 1 case had an increased peak at 3.55 ppm known as glycine (Gly). The other case with an increased alanine peak at 1.5 ppm had a poor prognosis. Therefore, we conclude that the presence of a Gly peak may suggest the diagnosis of CNC but that the absence of Gly does not exclude the diagnosis of CNC.

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.

Treatment of atypical neurocytomas

BACKGROUND

The majority of central neurocytomas are benign. Approximately 25% of these rare central nervous system tumors are more aggressive, with an MIB-1 labeling index > 2% or atypical histologic features, and are classified as atypical neurocytomas. The objective of this analysis was to define the optimal treatment for patients with these atypical tumors.

METHODS

The first atypical neurocytoma was described in 1989. The patients reported since then were reviewed for age, gender, extent of resection, MIB-1 index, histology, irradiation, local control, and survival. In addition to the data available in the literature, more relevant data were obtained from the authors of that literature. Treatment approaches included complete resection alone (CR), complete resection followed by radiotherapy (CR-RT), incomplete resection alone (IR), and incomplete resection followed by radiotherapy (IR-RT). These four therapies were compared for local control and survival using Kaplan-Meier analysis and the log-rank test.

RESULTS

Complete data were available on 85 patients (15 patients who underwent CR, 13 patients who underwent CR-RT, 17 patients who underwent IR, and 40 patients who received IR-RT). Local control rates at 3 years and 5 years were 73% and 57% after CR, 81% and 53% after CR-RT, 21% and 7% after IR, and 85% and 70% after IR-RT, respectively (P < 0.0001). Survival rates at 3 years and 5 years and were 93% and 93% after CR, 90% and 90% after CR-RT, 65% and 43% after IR, and 87% and 78% after IR-RT, respectively (P = 0.0076).

CONCLUSIONS

Patients who underwent CR achieved better local control and survival rates compared with patients who underwent IR. After IR, patients appeared to benefit from RT. A beneficial effect of RT after CR was not observed.

Defining the optimal dose of radiation after incomplete resection of central neurocytomas

PURPOSE

Central neurocytomas are uncommon benign central nervous system tumors. There is uncertainty regarding the most appropriate radiation dose after incomplete resection. This analysis was performed to determine the optimal dose.

METHODS AND MATERIALS

All cases reported since 1982 were reviewed for age, gender, resection status, total dose, dose per fraction, local control, and overall survival. Additional data were obtained from the authors. The inclusion criteria were incomplete resection, postoperative irradiation, complete data, and 12 months' minimal follow-up. Two groups were formed according to the equivalent dose in 2-Gy fractions (EQD2): group A (40.0-53.6 Gy) and group B (54.0-62.2 Gy). Local control and survival were compared using Kaplan-Meier analysis and the log-rank test.

RESULTS

Eighty-nine patients (group A 42, group B 47) met the inclusion criteria. At 5 years, the local control rate was 98% for group B vs. 69% for group A. At 10 years, it was 89% vs. 65% (p = 0.0066). The 5- and 10-year survival rate was 98% for group B vs. 88% for group A (p = 0.1).

CONCLUSIONS

Our data suggest that a EQD2 > or =54 Gy significantly improves local control in patients with subtotally resected neurocytomas. Although the difference in survival was not significant, a trend toward better survival was noted after a EQD2 of > or =54 Gy.