Prognostic importance of temozolomide-induced neutropenia in glioblastoma, IDH-wildtype patients

Standard treatment for patients with primary glioblastoma (GBM) includes surgery, radiotherapy, and concomitant and adjuvant temozolomide (TMZ). Recent reports have demonstrated that TMZ-induced myelosuppression correlates with survival in patients with GBM. However, those results were evaluated before the 2016 revision of the World Health Organization classification. This study examined whether myelosuppression during concomitant TMZ phase correlates with prognosis in GBM, IDH-wildtype patients. We examined circulating blood cell counts in 50 patients with GBM, IDH-wildtype who received the standard treatment protocol between August 2005 and November 2015. We assessed relationships between rates of decrease in blood cells (white blood cells (WBC), neutrophils, lymphocytes, red blood cells, and platelets) during the concomitant TMZ phase and overall survival (OS) using univariate and multivariate analyses including other clinicopathological factors (age, sex, Karnofsky Performance Status (KPS), extent of resection, O⁶-methylguanine-DNA methyltransferase (MGMT) status). Log-rank testing revealed that age, KPS, extent of resection, MGMT status, and decrease rates of WBC, neutrophils, and platelets correlated significantly with OS. On multivariate analysis, age, MGMT status, and decrease rate of neutrophils correlated significantly with OS. Patients with a ≥ 40% decrease in neutrophils showed significantly longer OS than those with < 40% (hazard ratio = 2.815; 95% confidence interval = 1.177-7.038; P = 0.0196). A decrease of ≥ 40% in neutrophils represents a predictor of good prognosis for GBM, IDH-wildtype. Blood cell counts during the concomitant TMZ phase can help predict OS in patients with GBM, IDH-wildtype receiving the standard treatment protocol.

Development of cystic malacia after high-dose cranial irradiation of pediatric CNS tumors in long-term follow-up

PURPOSE

The purpose of this study is to investigate the incidence of cystic malacia in long-term survivors of pediatric brain tumors treated with high-dose cranial irradiation.

MATERIALS AND METHODS

Between 1997 and 2015, we treated 41 pediatric patients (26 males, 15 females; age ranging from 3.3 to 15.7 years, median 9-year-old) of pediatric brain tumors [17 medulloblastomas, 7 primitive neuroectodermal tumors (PNET), 3 pineoblastomas, 6 non-germinomatous germ cell tumors (NGGCT), 8 gliomas (including 4 ependymomas, 1 anaplastic astrocytoma, 1 oligodendroglioma, 1 pilocytic astrocytoma, 1 astroblastoma)] with high-dose craniospinal irradiation. Follow-up ranged from 14.0 to 189.2 months (median 86.0 months, mean 81.5 months), the irradiation dose to the whole neural axis ranged from 18 to 41.4 Gy, and the total local dose from 43.2 to 60.4 Gy. All patients underwent follow-up magnetic resonance imaging (MRI) studies at least once a year. Diagnosis of cystic malacia was based solely on MRI findings. Of the 41 patients, 31 were censored during their follow-up due to recurrence of the primary disease (n = 5), detection of secondary leukemia after development of cystic malacia (n = 1), or the absence of cystic malacia on the last follow-up MRI study (n = 25). We also evaluated the development of post-irradiation cavernous angioma and white matter changes.

RESULTS

Following irradiation treatment, 11 patients developed 19 cystic malacia during a median course of 30.8 months (range 14.9 to 59.3 months). The site of predilection for cystic malacia was white matter around trigone of lateral ventricles with an incidence of 47.4% (9 of 19 lesions, 7 in 11 patients). Patients with supratentorial tumors developed cystic malacia statistically earlier than the patients with infratentorial tumors (P = 0.0178, log-rank test). Among the same patient group, incidence of post-irradiation cavernous angioma increased progressively, while the incidence of post-irradiation cystic malacia did not increase after 5 years. White matter degeneration developed earlier than cystic malacia or cavernous angioma, and these three clinical entities developed mutually exclusive of each other.

CONCLUSION

We attribute the higher incidence of post-irradiation cystic malacia, in our long-term follow-up study, to the cranial irradiation for pediatric brain tumors, particularly supratentorial brain tumors, and recommend a regular, long-term follow-up of brain tumor patients treated with cranial irradiation.

Prognostic implications of the subcellular localization of survivin in glioblastomas treated with radiotherapy plus concomitant and adjuvant temozolomide

OBJECTIVE Currently, the standard treatment protocol for patients with newly diagnosed glioblastoma (GBM) includes surgery, radiotherapy, and concomitant and adjuvant temozolomide (TMZ). Various prognostic biomarkers for GBM have been described, including survivin expression. The aim of this study was to determine whether the subcellular localization of survivin correlates with GBM prognosis in patients who received the standard treatment protocol. METHODS The authors retrospectively examined the subcellular localization of survivin (nuclear, cytoplasmic, or both) using immunohistochemistry in 50 patients with GBM who had received the standard treatment. The relationship between survivin localization and overall survival (OS) was assessed with uni- and multivariate analyses including other clinicopathological factors (age, sex, Karnofsky Performance Scale [KPS] score, extent of resection, the use of second-line bevacizumab, O⁶-methylguanine-DNA methyltransferase [MGMT] status, and MIB-1 labeling index). RESULTS Log-rank tests revealed that patient age, KPS score, extent of resection, MGMT status, and survivin localization (p < 0.0001) significantly correlated with OS. Multivariate analysis indicated that patient age, MGMT status, and survivin localization significantly correlated with OS. Patients with nuclear localization of survivin had a significantly shorter OS than those in whom survivin expression was exclusively cytoplasmic (median OS 19.5 vs 31.7 months, respectively, HR 5.690, 95% CI 2.068-17.612, p = 0.0006). There was no significant difference in OS between patents whose survivin expression was exclusively nuclear or nuclear/cytoplasmic. CONCLUSIONS Nuclear expression of survivin is a factor for a poor prognosis in GBM patients. Subcellular localization of survivin can help to predict OS in GBM patients treated with the standard protocol.

Nonenhancing peritumoral hyperintense lesion on diffusion-weighted imaging in glioblastoma: a novel diagnostic and specific prognostic indicator

OBJECTIVE Glioblastoma differentials include intracranial tumors, like malignant lymphomas and metastatic brain tumors with indiscernible radiological characteristics. The purpose of this study was to identify a distinct radiological feature for the preoperative differentiation of glioblastoma from its differentials, which include malignant lymphomas and metastatic brain tumors. METHODS Preoperative MR images, including diffusion-weighted imaging (DWI) studies (b = 1000 and 4000 sec/mm²), obtained in patients with newly diagnosed malignant tumor, were analyzed retrospectively after receiving approval from the institutional review board. Sixty-four patients with histologically confirmed glioblastoma, 32 patients with malignant lymphoma, and 46 patients with brain metastases were included. The presence of a nonenhancing peritumoral DWI high lesion (NePDHL, i.e., hyperintense lesion in a nonenhancing peritumoral area on DWI) was confirmed in both DWI sequences. Gray matter lesions were excluded. Lesions were termed "definite" if present within 3 cm of the hyperintense tumor border with a signal intensity ratio ≥ 30% when compared with the contralateral normal white matter in both sequences. Discriminant analysis between the histological diagnosis and the presence of Definite-NePDHL was performed, as well as Kaplan-Meier survival analysis incorporating the existence of Definite-NePDHL. RESULTS In 25% of glioblastoma patients, Definite-NePDHL was present, while it was conspicuously absent in patients with malignant lymphoma and metastatic brain tumors. The specificity and positive predictive value were 100%. In the glioblastoma subset, a higher preoperative Karnofsky Performance Scale score (p = 0.0028), high recursive partitioning analysis class (p = 0.0006), and total surgical removal (p = 0.0012) were associated with better median overall survival. Patients with Definite-NePDHL had significantly early local (p = 0.0467) and distant/dissemination recurrence (p < 0.0001) and poor prognosis (p = 0.0007). CONCLUSIONS The presence of Definite-NePDHL is very specific for glioblastoma and indicates poor prognosis. Definite-NePDHL is a significant indicator of early local and distant/dissemination recurrence in patients with glioblastoma. Studying peritumoral DWI and high-b-value DWI is useful for tumor differentiation.

Advantage of High b Value Diffusion-Weighted Imaging for Differentiation of Hemangioblastoma from Brain Metastases in Posterior Fossa

OBJECTIVE

It is sometimes difficult to make a differential diagnosis between brain metastases and hemangioblastomas in the posterior fossa. We assessed whether high b value diffusion-weighted image (DWI) at b = 4000 could differentiate these tumors.

METHODS

We acquired DWI at 3-T magnetic resonance imaging with b = 1000 and b = 4000 seconds/mm² in histologically confirmed 12 patients of hemangioblastoma without von Hippel-Lindau disease and 16 patients with brain metastases originating at the posterior fossa. Apparent diffusion coefficient (ADC) values were measured by manually placing regions of interest on ADC maps at the site of enhanced tumor confirmed on contrast-enhanced T1- weighed image. ADC was expressed as the minimum (ADC_MIN), mean (ADC_MEAN), and maximum (ADC_MAX) values.

RESULTS

All the ADC values of hemangioblastomas were statistically higher than those of metastatic tumor in both b = 1000 and b = 4000 (P < 0.0001 in ADC_MIN, ADC_MEAN, and ADC_MAX; Mann-Whitney U test). With the cutoff value at 0.6 × 10^-3 mm²/second, the positive predictive value of ADC_MIN at b = 4000 was higher than that of ADC_MIN at b = 1000 (100% vs. 89.3%, logistic analysis) to differentiate hemangioblastomas from brain metastases. Moreover, we studied the pathologic subtype of hemangioblastoma and confirmed that ADCs (b = 4000_MIN) of cellular subtype were statistically lower than those of reticular subtype (P = 0.03; Mann-Whitney U test).

CONCLUSIONS

High b value DWI reflects diffusion more accurately than does regular b value. Our results showed that ADC calculation by high b value (b = 4000) DWI at 3-T magnetic resonance imaging is clinically useful for differentiating hemangioblastomas from brain metastases.

Permeability Surface Area Product Using Perfusion Computed Tomography Is a Valuable Prognostic Factor in Glioblastomas Treated with Radiotherapy Plus Concomitant and Adjuvant Temozolomide

OBJECTIVE

The current standard treatment protocol for patients with newly diagnosed glioblastoma (GBM) includes surgery, radiotherapy, and concomitant and adjuvant temozolomide (TMZ). We hypothesized that the permeability surface area product (PS) from a perfusion computed tomography (PCT) study is associated with sensitivity to TMZ. The aim of this study was to determine whether PS values were correlated with prognosis of GBM patients who received the standard treatment protocol.

METHODS

This study included 36 patients with GBM that were newly diagnosed between October 2005 and September 2014 and who underwent preoperative PCT study and the standard treatment protocol. We measured the maximum value of relative cerebral blood volume (rCBVmax) and the maximum PS value (PSmax). We statistically examined the relationship between PSmax and prognosis using survival analysis, including other clinicopathologic factors (age, Karnofsky performance status [KPS], extent of resection, O6-methylguanine-DNA methyltransferase [MGMT] status, second-line use of bevacizumab, and rCBVmax).

RESULTS

Log-rank tests revealed that age, KPS, MGMT status, and PSmax were significantly correlated with overall survival. Multivariate analysis using the Cox regression model showed that PSmax was the most significant prognostic factor. Receiver operating characteristic curve analysis showed that PSmax had the highest accuracy in differentiating longtime survivors (LTSs) (surviving more than 2 years) from non-LTSs. At a cutoff point of 8.26 mL/100 g/min, sensitivity and specificity were 90% and 70%, respectively.

CONCLUSIONS

PSmax from PCT study can help predict survival time in patients with GBM receiving the standard treatment protocol. Survival may be related to sensitivity to TMZ.

Multicentric Glioma Develops via a Mutant IDH1-Independent Pathway: Immunohistochemical Study of Multicentric Glioma

Multicentric gliomas are very rare. Due to differences in their tumor types they remain enigmatic. We focused on the pathogenesis of multicentric gliomas and compared their immunoprofile with that of solitary gliomas. This retrospective study included 6 males and 8 females with multicentric glioma (8 glioblastomas, 2 anaplastic astrocytomas, 4 diffuse astrocytomas). Their age ranged from 27 to 75 years and all were treated between 2004 and June 2015. The expression of mutant isocitrate dehydrogenase 1 (IDH1), α-thalassemia X-linked intellectual disability (ATRX), p53, phosphatase and tensin homolog (PTEN), and epidermal growth factor receptor (EGFR) was examined immunohistochemically; for 1p19q analysis we used fluorescence in situ hybridization (FISH). In all patients, immunohistochemical staining was negative for mutant IDH1 and cytoplasmic PTEN; only 1 patient (7.1%) manifested nuclear PTEN positivity. FISH for 1p19q codeletion was negative in all 9 examined samples; 5 of 14 specimens (35.7%) were p53-positive, 9 (64.3%) were EGFR-positive, and 4 (28.6%) were ATRX-negative. The MIB-1 labeling index was 0.9-15.6% for grades II and III, and ranged between 17.3 and 52.4% for glioblastoma. Our results suggest that the pathogenesis of multicentric gliomas is different from the mutant IDH1-R132H pathogenesis of lower-grade glioma and secondary glioblastomas. More studies are needed to confirm the molecular mechanisms underlying the pathogenesis of multicentric glioma.

Post-traumatic Unilateral Avulsion of the Abducens Nerve with Damage to Cranial Nerves VII and VIII: Case Report

Traumatic injuries of the abducens nerve as a consequence of facial and/or head trauma occur with or without associated cervical or skull base fracture. This is the first report on unilateral avulsion of the abducens nerve in a 29-year-old man with severe right facial trauma. In addition, he exhibited mild left facial palsy, and moderate left hearing disturbance. Magnetic resonance imaging (MRI) using fast imaging employing steady-state acquisition (FIESTA) revealed avulsion of left sixth cranial nerve. We recommend thin-slice MR examination in patients with abducens palsy after severe facial and/or head trauma.

Cavernous angioma after chemotherapy for desmoplastic/nodular medulloblastoma associated with anhidrotic ectodermal dysplasia

PURPOSE

While cavernous angioma (CVA) after cranial irradiation has been documented, its development after high-dose chemotherapy with autologous peripheral blood stem cell transplantation (PBSCT) has not. We present a patient with desmoplastic/nodular medulloblastoma (DNMB) associated with anhidrotic ectodermal dysplasia (AED) who developed CVA 2 years after high-dose chemotherapy and PBSCT.

METHODS

A 1-year-old boy with ingravescent vomiting was admitted to our institute. He presented with a large head, a depressed nasal bridge, low-set ears, thick lips with peg-shaped teeth, hypohidrosis, sparse hair, thin atrophic skin, scaly dermatitis with frontal bossing, and a bulging anterior fontanel. Neuroradiological examination revealed multiple cerebellar masses with heterogeneous enhancement and speckled calcifications and severe obstructive hydrocephalus. The histological diagnosis of surgical specimens was DNMB, and he underwent postoperative multiple-drug chemotherapy with autologous PBSCT. The outcome was favorable and he did not undergo radiotherapy.

RESULTS

After 2 years, intracranial hemorrhage was detected at his regular radiological check-up and he again underwent surgery. The histological diagnosis was CVA.

CONCLUSIONS

To our knowledge, this is the first report of AED-associated DNMB and CVA.

Magnetic resonance spectroscopy detection of high lipid levels in intraaxial tumors without central necrosis: a characteristic of malignant lymphoma

OBJECT

The differentiation of malignant lymphomas from gliomas or malignant gliomas by conventional MRI can be difficult. The authors studied Gd-enhanced MR images to obtain a differential diagnosis between malignant lymphomas and gliomas without central necrosis or cystic changes and investigated the diagnostic value of single-voxel proton MR spectroscopy ((1)H-MRS) using different parameters, including lipid levels.

METHODS

This was a retrospective study of patients with primary malignant CNS lymphoma (n = 17) and glioma (n = 122 [Grades I, II, III, and IV in 10, 30, 33, and 49 patients, respectively]) who were treated between 2007 and 2013. The authors focused on 15 patients with homogeneously enhanced primary malignant CNS lymphomas and 7 homogeneously enhanced gliomas. Images of all the included tumors were acquired with (1)H-MRS at 3 T, and the diagnoses were histologically confirmed.

RESULTS

Using a short echo time (1)H-MRS, large lipid peaks were observed in all 17 patients with a malignant lymphoma, in 39 patients (79.6%) with a Grade IV glioma, and in 10 patients (30.3%) with a Grade III glioma. A focus on homogeneously enhanced tumors revealed large lipid peaks in 15 malignant lymphomas that were free of central necrosis on Gd-enhanced T1-weighted images. Conversely, in the 7 homogeneously enhanced gliomas (glioblastoma and anaplastic astrocytoma, n = 2 each; anaplastic oligodendroglioma, diffuse astrocytoma, and pilomyxoid astrocytoma, n = 1 each), lipid peaks were small or absent.

CONCLUSIONS

Large lipid peaks on (1)H-MRS images of tumors without central necrosis were characteristic of malignant lymphomas. Conversely, small or absent lipid peaks in intraaxial tumors without central necrosis were strongly suggestive of glioma.

p16 Gene Transfer Induces Centrosome Amplification and Abnormal Nucleation Associated with Survivin Downregulation in Glioma Cells

OBJECTIVE

In human glioma cells, p16 gene transfer induced G1/S arrest, increased radiosensitivity and abnormal nucleation (especially bi- and multinucleation). Survivin suppression caused G2/M arrest, radiosensitization and an increase in aneuploidy accompanied by centrosome amplification. Abnormal nucleation and aneuploidy represent chromosome instability (CIN), and it is well known that centrosome amplification leads to CIN. However, little has been reported that suggests that transferring p16 causes centrosome overduplication during the G1/S phase.

METHODS

The p16 gene was transferred into p16-null human glioma cell lines (U251MG and D54MG) using adenovirus with or without irradiation. Centrosome amplification was evaluated by immunofluorescence. We also investigated the DNA replication licensing factor CDT1, its inhibitor geminin and survivin expression as regulators of chromosomal segregation.

RESULTS

p16 gene transfer with radiation initiated the greatest degree of centrosome overduplication. CDT1 showed low levels, geminin was unchanged and survivin decreased in Ax-hp16-infected cells with radiation. Those changes of factors affecting DNA licensing or chromosomal segregation might contribute to CIN.

CONCLUSION

p16 transfer caused centrosome amplification even in G1/S phase-arrested cells. This suggests that p16 is involved in abnormal nucleation and radiosensitization in human glioma cells. © 2015 S. Karger AG, Basel.

[Anti-emetic effect of granisetron in patients undergoing cranial and craniospinal radiotherapy]

PURPOSE

Approximately 30-59% of patients undergoing cranial or craniospinal radiotherapy experience nausea and/or vomiting. Here, we evaluated the effectiveness of granisetron for controlling emesis in patients treated with cranial or craniospinal radiotherapy.

PATIENTS AND METHODS

Between December 2011 and January 2013, 34 patients(19 males, 15 females;age range, 3-80 years)received cranial or craniospinal radiotherapy at our department. All but one male patient, who developed meningitis during the irradiation period were enrolled in this retrospective study. Patients who experienced irradiation-induced vomiting(grade 1)or nausea(grade 2)were treated with granisetron as a rescue anti-emetic. Episodes were graded as(1)no vomiting, no nausea, no anti-emetic;(2)no vomiting, nausea, no anti-emetic;(3)no vomiting, nausea with anti-emetic;and(4)vomiting.

RESULTS

Of the 9 patients who underwent whole-brain or whole neural-axis irradiation, 5(55.6%)experienced grade 2 nausea or vomiting. Two of 6 patients(33.3%)treated with whole ventricle irradiation experienced grade 2 nausea or vomiting. Three of 18 patients(16.7%)who underwent local-field irradiation experienced grade 2 nausea or vomiting. Patients who underwent wide-field irradiation experienced nausea, vomiting, and anorexia(p<0.05). Complete response(no vomiting, no additional rescue anti-emetic, and no nausea)was observed in 5 of 9 patients treated with granisetron. Four of 9 patients(44.4%)treated with granisetron experienced constipation(grade 1 or 2);its administration had no major adverse effects in our study population.

CONCLUSION

Rescue therapy with granisetron is safe and effective to treat nausea and vomiting in patients subjected to cranial or craniospinal irradiation.

Postoperative fever specific to neuroendoscopic procedures

The most common complication of neuroendoscopic surgery is postoperative fever without infection, although the details have not been discussed. The objective of this study was to clarify the clinical features and predicting factors of the postoperative fever following neuroendoscopic procedures. Between March 1998 and March 2013, 83 patients (46 males, 37 females; median age, 14.0 years) who had undergone surgery via the transventricular approach under a neuroendoscopic view were included in this study. A total of 86 neuroendoscopic procedures were performed in 83 patients. The incidence and duration of postoperative fever (≥38.0 and ≥39.0 °C) over the 7 days after surgery were examined. Moreover, the following variables predictive of fever were investigated: age, sex, neuroendoscopic procedure, operative time, and intraoperative irrigation fluid. The incidence of postoperative fever was 65.1 % (≥38.0 °C) and 15.1 % (≥39.0 °C). The median level of the highest fever was 38.6 °C. The fevers developed immediately after surgery and spontaneously disappeared within four postoperative days. Only age was related to postoperative fever (p = 0.032). The postoperative body temperature was negatively correlated with age in all 86 surgeries (p < 0.001, Spearman r = -0.396). In particular, patients under 10 years of age tended to have postoperative fever (p = 0.005). The result of this study demonstrated a peculiar pattern of fever following neuroendoscopic procedures. This type of fever did not cause serious problems; however, special attention should be paid to the high incidence of postoperative fever in patients under 10 years of age.

Preoperative histological grading of meningiomas using apparent diffusion coefficient at 3T MRI

PURPOSE

We assessed whether a high b-value DWI at b=4000s/mm(2) would discriminate the histopathological differentiation of the tumor grade of meningiomas, and also focused on the relationship between radiologic features and the tumor grade.

MATERIALS AND METHODS

We acquired DWI at 3T with b=1000 and b=4000s/mm(2) in 77 patients (42, 31 and 4 patients were WHO grades I (G1), II (G2), and III (G3), respectively). The apparent diffusion coefficient (ADC) was measured by placing multiple regions of interest (ROIs) on ADC maps. The ADC values of each tumor were determined preoperatively from several ROIs, and expressed as the minimum (ADCMIN), mean (ADCMEAN), and maximum absolute values (ADCMAX). We evaluated the relationship between ADCs and histological findings, and assessed the radiologic features such as tumor location, tumor size, presence/absence of peritumoral edema, shape of the tumor, presence/absence of bone destruction or hyperplasia, status of contrast enhancement, presence/absence of calcification and cyst.

RESULTS

ADCs of the meningiomas were inversely correlated with the histological grade of meningiomas. According to results of the discriminant analysis, the apparent log likelihood value was greatest for ADCMIN at b=4000. Furthermore, only the ADCMIN value at b=4000 was significantly correlated with the histological grade of meningiomas when we performed a multiple logistic regression analysis to identify the significant independent factors such as shape of tumor, presence/absence of bone destruction, status of contrast enhancement, presence/absence of cyst and ADCMIN at b=4000.

CONCLUSION

A meningioma with a low ADCMIN at a high b-value might imply a high-grade meningioma.

Magnetic resonance spectroscopic detection of lactate is predictive of a poor prognosis in patients with diffuse intrinsic pontine glioma

Diffuse brainstem glioma has a poor prognosis, and there are few long-term survivors. We looked for clinical, conventional magnetic resonance (MR), and MR spectroscopic (MRS) findings predictive of the prognosis of patients with brainstem glioma. Our institutional review board approved this retrospective study of 23 patients with diffuse intrinsic pontine or diffuse medullary brainstem glioma treated during the period 2000-2009. To evaluate prognostic values, we performed a Kaplan-Meier survival analysis (log-rank test) that incorporated the patients' age and sex, symptom duration, the presence or absence of cranial nerve palsy, long tract sign, ataxia, and cysts, the chemotherapeutic regimen, Gd enhancement, longitudinal and cerebellar extension, basilar artery encasement, and MRS parameters. Of the 23 diffuse brainstem gliomas, 19 were located at the pons (ratio of male to female patients, 1.1:1). The mean age of the 23 patients was 15.9 years (range, 4-50 years); 16 were aged <20 years. The duration of overall survival was 19.7 months; in patients with diffuse intrinsic pontine glioma, it was 16.6 months, and in patients aged <20 years, it was 11.8 months. Clinical and conventional MR findings at presentation were not predictive of the prognosis in children with diffuse intrinsic pontine glioma. In addition, a patient age <20 years and the detection of lactate by MRS were poor prognostic factors. The MRS detection of lactate is a prognostic factor in patients with diffuse intrinsic pontine glioma. Additional studies of larger patient populations using other imaging modalities are needed.