Dual-isotope single-photon emission computerized tomography scanning in patients with glioblastoma multiforme: association with patient survival and histopathological characteristics of tumor after high-dose radiotherapy

Recognition and Management of the Long-term Effects of Cranial Radiation

OPINION STATEMENT

Cranial radiation is ubiquitous in the treatment of primary malignant and benign brain tumors as well as brain metastases. Improvement in radiotherapy targeting and delivery has led to prolongation of survival outcomes. As long-term survivorship improves, we also focus on prevention of permanent side effects of radiation and mitigating the impact when they do occur. Such chronic treatment-related morbidity is a major concern with significant negative impact on patient's and caregiver's respective quality of life. The actual mechanisms responsible for radiation-induced brain injury remain incompletely understood. Multiple interventions have been introduced to potentially prevent, minimize, or reverse the cognitive deterioration. Hippocampal-sparing intensity modulated radiotherapy and memantine represent effective interventions to avoid damage to regions of adult neurogenesis. Radiation necrosis frequently develops in the high radiation dose region encompassing the tumor and surrounding normal tissue. The radiographic findings in addition to the clinical course of the patients' symptoms are taken into consideration to differentiate between tissue necrosis and tumor recurrence. Radiation-induced neuroendocrine dysfunction becomes more pronounced when the hypothalamo-pituitary (HP) axis is included in the radiation treatment field. Baseline and post-treatment evaluation of hormonal profile is warranted. Radiation-induced injury of the cataract and optic system can develop when these structures receive an amount of radiation that exceeds their tolerance. Special attention should always be paid to avoid irradiation of these sensitive structures, if possible, or minimize their dose to the lowest limit.

Clinical Outcomes of Stereotactic Radiosurgery-Related Radiation Necrosis in Patients with Intracranial Metastasis from Melanoma

Background:

Radiation necrosis (RN) is a clinically relevant complication of stereotactic radiosurgery (SRS) for intracranial metastasis (ICM) treatments. Radiation necrosis development is variable following SRS. It remains unclear if risk factors for and clinical outcomes following RN may be different for melanoma patients. We reviewed patients with ICM from metastatic melanoma to understand the potential impact of RN in this patient population.

Methods:

Patients who received SRS for ICM from melanoma at Mayo Clinic Arizona between 2013 and 2018 were retrospectively reviewed. Data collected included demographics, tumor characteristics, radiation parameters, prior surgical and systemic treatments, and patient outcomes. Radiation necrosis was diagnosed by clinical evaluation including brain magnetic resonance imaging (MRI) and, in some cases, tissue evaluation.

Results:

Radiation necrosis was diagnosed in 7 (27%) of 26 patients at 1.6 to 38 months following initial SRS. Almost 92% of all patients received systemic therapy and 35% had surgical resection prior to SRS. Patients with RN trended toward having larger ICM and a prior history of surgical resection, although statistical significance was not reached. Among patients with resection, those who developed RN had a longer period between surgery and SRS start (mean 44 vs 33 days). Clinical improvement following treatment for RN was noted in 2 (29%) patients.

Conclusions:

Radiation necrosis is relatively common following SRS for treatment of ICM from metastatic melanoma and clinical outcomes are poor. Further studies aimed at mitigating RN development and identifying novel approaches for treatment are warranted.

Recurrent Brain Metastasis Versus Radiation-Induced Necrosis: A Case Report and Literature Review

Radiotherapy is the cornerstone of brain metastasis management. With the advancement of therapies, patients are living longer, exposing them to the long-term effects of radiotherapy. Using concurrent or sequential chemotherapy, targeted agents, and immune checkpoint inhibitors may increase the incidence and severity of radiation-induced toxicity. Recurrent metastasis and radiation necrosis (RN) appear indistinguishable on neuroimaging, making it a diagnostic dilemma for clinicians. Here, we present a case of RN in a 65-year-old male patient who previously had brain metastasis (BM) from primary lung cancer, misdiagnosed initially as recurrent BM.

Usefulness of dual isotope 123I-IMP and 201Tl SPECT for the diagnosis of primary central nervous system lymphoma and glioblastoma

BACKGROUND

Preoperative differential diagnosis between primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM) is important because these tumors require different surgical strategies. This study investigated the usefulness of dual isotope, iodine-123-labeled N-isopropyl-p-iodo-amphetamine (¹²³I-IMP) and thallium-201 chloride single-photon emission computed tomography (²⁰¹Tl SPECT) for the differential diagnosis.

METHODS

Twenty-five PCNSL patients and 27 GBM patients who underwent dual isotope imaging, ¹²³I-IMP and ²⁰¹Tl SPECT, are included. Tumor-to-normal (T/N) ratio was calculated from the ratio of maximum tracer counts in the lesion to the mean counts in the contralateral cerebral cortex. The mean and minimum apparent diffusion coefficient values (ADC_mean and ADC_min, respectively) on magnetic resonance imaging were also analyzed.

RESULTS

Delayed phase ¹²³I-IMP SPECT was the most useful imaging examination for the differentiation between PCNSL and GBM compared with early phase ¹²³I-IMP SPECT, early and delayed phase ²⁰¹Tl SPECT, ADC_mean, and ADC_min. However, the median T/N ratios of PCNSL and GBM were 1.32 and 0.83, respectively, in the delayed phase ¹²³I-IMP SPECT. On the other hand, the median T/N ratios of PCNSL and GBM were 3.10 and 2.34, respectively, in the delayed phase ²⁰¹Tl SPECT, with excellent tumor detection.

CONCLUSION

Delayed phase ¹²³I-IMP SPECT could differentiate between PCNSL and GBM with high accuracy, but T/N ratio was low and tumor detection was poor. ²⁰¹Tl SPECT was useful for estimation of the malignancy and localization of the tumors with high T/N ratio. Dual isotope ¹²³I-IMP and ²⁰¹Tl SPECT was useful for the preoperative diagnosis of PCNSL and GBM.

Brain SPECT and perfusion MRI: do they provide complementary information about the tumour lesion and its grading?

AIM

To evaluate the relative and combined utility of ^99mTc-tetrofosmin (^99mTc-TF) brain single-photon-emission computed tomography (SPECT) and dynamic susceptibility contrast (DSC) perfusion magnetic resonance imaging (MRI) in grading brain gliomas.

MATERIALS AND METHODS

Thirty-six patients with clinically suspected brain tumours were assessed by ^99mTc-TF SPECT and DSC-MRI. Brain tumour malignancy was confirmed in all patients at histopathology. On both techniques brain lesions were evaluated via visual and semi-quantitative analysis methods (deriving tetrofosmin index [T-index] and relative cerebral blood volume [rCBV] ratios, respectively).

RESULTS

^99mTc-TF SPECT showed abnormally elevated tracer uptake in 31/36 patients whereas MRI detected the brain tumour in all patients. Optimal cut-off values of each index for discriminating between low- and high-grade gliomas were obtained through receiver operating characteristic (ROC) analyses. A T-index cut-off of 6.35 ensured 82% sensitivity and 71% specificity for discriminating between high- and low-grade gliomas, whereas a relative rCBV ratio cut-off of 1.80 achieved 91% sensitivity and 100% specificity. Requiring a positive result on either technique to characterise a high-grade glioma was associated with similar specificity and slightly increased sensitivity.

CONCLUSION

Both imaging techniques, ^99mTF SPECT and DSC MRI, may provide complementary indices of tumour grade and have an independent diagnostic value for high-risk tumours.

Postradiation imaging changes in the CNS: how can we differentiate between treatment effect and disease progression?

A familiar challenge for neuroradiologists and neuro-oncologists is differentiating between radiation treatment effect and disease progression in the CNS. Both entities are characterized by an increase in contrast enhancement on MRI and present with similar clinical signs and symptoms that may occur either in close temporal proximity to the treatment or later in the disease course. When radiation-related imaging changes or clinical deterioration are mistaken for disease progression, patients may be subject to unnecessary surgery and/or a change from otherwise effective therapy. Similarly, when disease progression is mistaken for treatment effect, a potentially ineffective therapy may be continued in the face of progressive disease. Here we describe the three types of radiation injury to the brain based on the time to development of signs and symptoms--acute, subacute and late--and then review specific imaging changes after intensity-modulated radiation therapy, stereotactic radiosurgery and brachytherapy. We provide an overview of these phenomena in the treatment of a wide range of malignant and benign CNS illnesses. Finally, we review the published data regarding imaging techniques under investigation to address this well-known problem.

The role of imaging in the management of progressive glioblastoma : a systematic review and evidence-based clinical practice guideline

QUESTION

Which imaging techniques most accurately differentiate true tumor progression from pseudo-progression or treatment related changes in patients with previously diagnosed glioblastoma?

TARGET POPULATION

These recommendations apply to adults with previously diagnosed glioblastoma who are suspected of experiencing progression of the neoplastic process.

RECOMMENDATIONS LEVEL II

Magnetic resonance imaging with and without gadolinium enhancement is recommended as the imaging surveillance method to detect the progression of previously diagnosed glioblastoma.

LEVEL II

Magnetic resonance spectroscopy is recommended as a diagnostic method to differentiate true tumor progression from treatment-related imaging changes or pseudo-progression in patients with suspected progressive glioblastoma.

LEVEL III

The routine use of positron emission tomography to identify progression of glioblastoma is not recommended.

LEVEL III

Single-photon emission computed tomography imaging is recommended as a diagnostic method to differentiate true tumor progression from treatment-related imaging changes or pseudo-progression in patients with suspected progressive glioblastoma.

Malignant gliomas: current perspectives in diagnosis, treatment, and early response assessment using advanced quantitative imaging methods

Malignant gliomas consist of glioblastomas, anaplastic astrocytomas, anaplastic oligodendrogliomas and anaplastic oligoastrocytomas, and some less common tumors such as anaplastic ependymomas and anaplastic gangliogliomas. Malignant gliomas have high morbidity and mortality. Even with optimal treatment, median survival is only 12–15 months for glioblastomas and 2–5 years for anaplastic gliomas. However, recent advances in imaging and quantitative analysis of image data have led to earlier diagnosis of tumors and tumor response to therapy, providing oncologists with a greater time window for therapy management. In addition, improved understanding of tumor biology, genetics, and resistance mechanisms has enhanced surgical techniques, chemotherapy methods, and radiotherapy administration. After proper diagnosis and institution of appropriate therapy, there is now a vital need for quantitative methods that can sensitively detect malignant glioma response to therapy at early follow-up times, when changes in management of nonresponders can have its greatest effect. Currently, response is largely evaluated by measuring magnetic resonance contrast and size change, but this approach does not take into account the key biologic steps that precede tumor size reduction. Molecular imaging is ideally suited to measuring early response by quantifying cellular metabolism, proliferation, and apoptosis, activities altered early in treatment. We expect that successful integration of quantitative imaging biomarker assessment into the early phase of clinical trials could provide a novel approach for testing new therapies, and importantly, for facilitating patient management, sparing patients from weeks or months of toxicity and ineffective treatment. This review will present an overview of epidemiology, molecular pathogenesis and current advances in diagnoses, and management of malignant gliomas.

Perioperative single photon emission computed tomography in predicting survival of malignant glioma patients

Single photon emission computed tomography (SPECT) is widely used in the evaluation of glioma patients and has been demonstrated to correlate with glioma malignancy and proliferation indexes. The aim of this study was to evaluate the association between perioperative technetium-99m-methoxyisobutylisonitrile ((99m)Tc-MIBI) uptake on SPECT scans and survival of malignant glioma patients. A total of 17 patients (11 males and 6 women; mean age, 62.2±8.4 years) with histologically confirmed malignant gliomas (16 glioblastoma multiforme and 1 gliosarcoma) underwent (99m)Tc-MIBI SPECT scans 2.8±1.9 days before surgery and 9.8±1.5 days after surgery. The total intensity index (TII) that corresponds to the area and intensity of tracer uptake was calculated before and after surgery. In addition, the change of TII before versus after surgery (Δ TII) was calculated. The overall survival (OS) was defined as the period between the date of surgery and the date of death. The median overall survival time was 12.4 months, ranging from 1.4 to 88 months; there were nine (45%) 12-month survivors. In univariate analyses using a log-rank test, worse OS was significantly associated with higher preoperative TII (≥12), higher postoperative TII (≥6), lower Δ TII (<50%) and higher number of neurological symptoms prior to surgery (≥4). In multivariate analyses, higher postoperative TII, a greater number of neurological symptoms and female gender were found to be factors with independent prognostic value of OS. Patients who survived more than 12 months following surgery had a significantly lower postoperative TII, higher Δ TII and greater rate of gross total resection compared to patients who survived less than 12 months following surgery. Higher peri-operative tracer uptake and lower decrease of tracer uptake following surgery (suggesting less radical resection) were associated with worse OS of malignant glioma patients. Our results suggest that SPECT may be used to predict survival of malignant glioma patients; however, further studies using larger samples are required.

Observed magnetic resonance imaging changes in pediatric patients treated with stereotactic radiosurgery for intracranial tumors

PURPOSE

This study seeks to characterize magnetic resonance imaging (MRI) changes following stereotactic radiosurgery (SRS) of pediatric brain malignancies.

METHODS

Serial MRI evaluations were performed on 21 lesions treated with SRS for either medulloblastoma (n=12), juvenile pilocytic astrocytoma (n=4), ependymoma (n=2), atypical rhabdoid teratoid tumor (n=2), or pineocytoma (n=1). Prescription doses ranged from 14 to 30 Gy in one to five fractions. Tumor response was qualified as complete (CR), partial (PR), stable disease (SD), or progressive disease (PD) according to the RECIST v1.1. Median radiographic follow-up after SRS was 17 months.

RESULTS

A total of 80 follow-up MRI scans were reviewed with a median of eight per patient. During serial MRI evaluation, eight lesions met criteria for PD at a median of 6 months. However, of these, three (37%) represented transient tumor edema with two lesions later developing a CR at a median of 15 months and one persisting as SD at 12 months. The remaining five lesions were true local failures. Of the 13 lesions that did not show evidence of PD, a CR was obtained in 11 lesions at a median of 3 months (range, 2-6), and SD was seen in the remaining two tumors at last follow-up.

CONCLUSION

Lesion enlargement following SRS for pediatric intracranial tumors is common, and a proportion of patients meeting requirements for PD at early radiographic follow-up may later develop complete resolution of their lesions. Physicians should be aware of these radiographic changes to avoid unwarranted medical and surgical interventions.

Investigation of blood perfusion and metabolic activity of brain tumours in adults by using 99mTc-methoxyisobutylisonitrile

OBJECTIVES

(i) To examine blood perfusion and metabolic activity of various brain tumours using radionuclide cerebral angiography (RCA) and single-photon emission tomography (SPET) after a single dose of Tc-methoxyisobutylisonitrile (MIBI). (ii) To examine if the inclusion of RCA can improve insight into the relative contribution of tumour perfusion to the uptake of MIBI shown by SPET, and to improve evaluation of tumour biology. (iii) To determine the value and the roles of MIBI in the management of brain tumour patients.

METHODS

Fifty adult patients (38 male, 12 female) with a total of 56 intracranial space-occupying lesions have been included prospectively, 37 of which were newly diagnosed and the remaining with signs of recurrence/rest of earlier resected and irradiated brain tumours. The control group consisted of nine volunteers with no evidence of organic cerebral disease. Scintigraphic examination consisted of a dynamic first-pass study lasting 60 s (3 s/frame) and two SPET studies (60 projections each, 25 s/projection), starting 15 min and 2 h after intravenous injection of MIBI. Regions of interest of the tumour and normal brain tissue were drawn on RCA and both early and delayed SPET slices. The following tumour/brain activity ratios have been calculated: (i) tumour perfusion index (P); (ii) early uptake index (E); (iii) delayed uptake index (D); and(iv) retention index (R). Analogous indices have been calculated from the same examinations performed in controls, reflecting maximal physiologic regional variations of perfusion and uptake in brain tissue.

RESULTS

Mean P of various brain tumours (low-grade gliomas 0.98, anaplastic gliomas 1.14, glioblastoma multiforme 1.20, metastases 1.09, lymphomas 1.08) differ little from each other and do not exceed maximal physiologic regional variations of cerebral perfusion (1.33), with the exception of meningioma (1.87, F=2.83, P=0.015). The receiver operating characteristics curve analysis of P showed that for the cut-off value of 1.45 the sensitivity for distinguishing meningioma from other tumours is 75%, specificity 87%, positive predictive value 33% and negative predictive value 97%. Mean E of malignant brain tumours (8.3, n=31, 23 primary, eight secondary), except anaplastic gliomas (3.5, n=5), differed significantly (P=0.02) from those of benign gliomas (3, n=9) but not from that of meningioma (11.9, n=4). The cut-off value for distinguishing malignant from benign lesions on the basis of E set at 4.8 resulted in sensitivity 67%, specificity 75%, accuracy 70%, positive predictive value 80% and negative predictive value 60%. D and R showed tendency of wash-out of MIBI from meningiomas, but otherwise did not improve the results substantially.

CONCLUSION

Integrated results of RCA and SPET with Tc-MIBI indicate that blood perfusion, blood-tumour barrier permeability and metabolic activity of the tumour are all very important for the resultant uptake shown by SPET. If the perfusion index is less than 1.45, then meningioma can be ruled out. Early SPET is recommendable for distinguishing glioblastoma from low-grade gliomas, as a complement to standard magnetic resonance imaging and/or computed tomography.

MR spectroscopy in radiation injury

Detecting a new area of contrast enhancement in or in the vicinity of a previously treated brain tumor always causes concern for both the patient and the physician. The question that immediately arises is whether this new lesion is recurrent tumor or a treatment effect. The differentiation of recurrent tumor or progressive tumor from radiation injury after radiation therapy is often a radiologic dilemma regardless the technique used, CT or MR imaging. The purpose of this article was to review the utility of one of the newer MR imaging techniques, MR spectroscopy, to distinguish recurrent tumor from radiation necrosis or radiation injury.

Imaging of the cerebrum

The history of the development of cerebral imaging is a complex combination of the forces of innovation at both the individual and industrial levels. Principal paradigms of neuroimaging shifted as a result of technological breakthroughs, beginning with the discovery of x-rays and continuing with the development of computerized imaging to the latest imaging paradigm, nuclear magnetic resonance imaging. We discuss these landmarks in neuroimaging in historical context, with emphasis on the particularly rapid development of imaging technology during the past 30 to 40 years, including the most recent emerging technologies.

Systematic review of the diagnostic accuracy of 201Tl single photon emission computed tomography in the detection of recurrent glioma

OBJECTIVE

To determine the diagnostic accuracy of 201Tl SPECT in the detection of tumour recurrence in patients with previous radiotherapy for supratentorial glioma.

METHODS

The databases of PubMed and Embase were searched for relevant studies. Two reviewers independently selected and extracted data on study characteristics, quality and accuracy of studies. Studies were included if they comprised at least six eligible patients who underwent 201Tl SPECT (index test) and in whom (histo)pathological confirmation (reference test) of the suspected brain lesion was obtained. Because of the methodological and statistical heterogeneity of the included studies, a quantitative meta-analysis was not performed. Instead, for every individual study, the sensitivity, specificity and diagnostic odds ratio of 201Tl SPECT was calculated.

RESULTS

Eight studies met the inclusion criteria. Only one was considered of high methodological quality. Methodological limitations referred most notably to blinding and patient selection. The diagnostic odds ratio was greater than 1 in all studies included, with a broad range (2-351), and relatively wide 95% confidence intervals. The sensitivity of 201Tl SPECT ranged from 0.43 to 1.00, and the specificity from 0.25 to 1.00.

CONCLUSION

201Tl SPECT seems a valuable method in the detection of tumour recurrence in patients treated with radiotherapy for supratentorial glioma. However, the evidence is not very robust because of the low quality and high heterogeneity of the studies included. Future studies are warranted to further explore the diagnostic potential of 201Tl SPECT, and to determine optimum thresholds for the detection of glioma recurrence.

Correlation of preoperative thallium SPECT with histological grading and overall survival in adult gliomas

BACKGROUND

The management and prognosis of a glioma depend on the tumour's histological grade. Thus, preoperative prediction of the grade is routinely needed to indicate whether surgery or biopsies are required. It has been proposed that thallium single photon emission computed tomography (SPECT), in a relative short series, will aid this prediction.

AIM

To confirm the correlation between the results of preoperative thallium SPECT and grade of tumour as well as patient survival, and to define the cut-off value of the optimal thallium index for the detection of high grade gliomas in a large series of patients.

METHODS

One hundred and eighteen patients treated for glioma were retrospectively included in this study. All patients underwent preoperative 201Tl SPECT upon initial presentation and were referred for neurosurgery. Initial scintigraphic findings were correlated with the histological grade of the tumour and overall patient survival.

RESULTS

Thallium uptake was highly correlated with histological grade; the mean thallium indices for low grade and high grade gliomas were 1.8 and 4.9, respectively. On the basis of receiver operating characteristic analysis, the optimal cut-off value of the thallium index for the detection of high grade glioma was determined. By using 2.2 as the value for the threshold thallium index, the sensitivity and specificity were 93% and 72%, respectively. Kaplan-Meier estimates of the overall survival curves, as a function of the thallium index, indicated that it was correlated with the overall survival (P<0.001).

CONCLUSION

Thallium SPECT provides useful information about the histological grade of the tumour and overall patient survival. Additionally, in spite of its relatively weak resolution, it appears to be a powerful routine clinical tool for the management of gliomas.

Techniques to assess the proliferative potential of brain tumors

Assessment of brain tumor proliferative potential provides important prognostic information that supplements standard histopathologic grading. Many laboratories rely on mitotic figures to quantify the proliferative potential of brain tumors, but this conventional cellular proliferative index is subject to inter-observer variability and not consistently predictive for low-and high-grade tumors. Recent advancements in technology have made it possible to use proliferative indices as a standard supplement in pathology laboratories. Non-invasive tumor tissue measurements of cell proliferation can be performed using- bromodeoxyuridine labeling index (BrdU LI), flow cytometry (FCM), MIB-1 antibody to the Ki-67 antigen (MIB-1), proliferating cell nuclear antigen (PCNA), and argyrophilic nucleolar organizing regions (AgNOR). Each of these assays has been described in the literature with respect to its ability to predict tumor grade or outcome. At the present time MIB-1 and AgNOR are the simplest and most reliable of these techniques. In addition, advances in our understanding of the genetic alterations associated with proliferation promise to provide more specific markers of proliferative potential. Beyond the pathology laboratory, radiographic studies such as positron emission tomography (PET), single photon emission computed tomography (SPECT), and most recently magnetic resonance spectroscopy (MRS) have been used as follow-up measures, assessing response to treatment and tumor recurrence, rather than as predictors of response to treatment. These radiographic tools, however, have the potential to provide an assessment of tumor proliferation without the need for invasive measures. In this article, we present a review of the current techniques utilized to understand the proliferative potential of brain tumors.

Thallium-201 SPECT: the optimal prediction of response in glioma therapy

PURPOSE

The aim of this study was to estimate 201Tl SPECT and CT-MRI cut-off values that lead to a validated prognostic classification for the end-point overall survival, in order to discriminate glioma patients with good and poor prognosis at an early stage during chemotherapeutic treatment.

METHODS

We studied patients who underwent 201Tl SPECT and CT-MRI before and after two courses of chemotherapy. Cut-off values were retrieved from the Cox model. Patients were classified according to the computed cut-off values, creating subgroups of patients with different prognosis in terms of survival [tumour regression (TR); stable disease (SD); tumour progression (TP)]. The differences between the subgroups were assessed by Kaplan-Meier analyses. The predictive performance of the classification procedure was evaluated by a leave-one-out cross-validation method.

RESULTS

201Tl SPECT classified 41% of the patients as SD, 25% as TR and 34% as TP. CT-MRI classified 82% of the patients as SD, and only 4% and 14% as TR and TP, respectively. Of those patients with a relatively long overall survival (i.e. > or =16 months), cross-validation estimates of 201Tl SPECT classification rates were 50% TR and 50% SD, and cross-validation estimates of CT-MRI classification rates were 7% TR, 72% SD, and 21% TP.

CONCLUSION

We constructed a 201Tl SPECT model that makes it possible to identify glioma patients with a good or a poor prognosis at an early stage during chemotherapeutic treatment. With this model, accurate predictions can be made with regard to the expected duration of survival.

Postoperative residual tumour imaged by contrast-enhanced computed tomography and 201Tl single photon emission tomography: can they predict progression-free survival in high-grade gliomas?

AIMS

To evaluate if postoperative residual tumour imaged by either computed tomography or 201Tl single photon emission tomography (SPECT) carried out postoperatively could predict progression-free survival (PFS) in high-grade malignant gliomas.

MATERIALS AND METHODS

Thirty-three patients with high-grade malignant gliomas underwent both contrast-enhanced CT scan and 201Tl-SPECT postoperatively before receiving radiotherapy. The PFS was evaluated against the individual reports of the above two imaging studies by univariate analysis.

RESULTS

CT and 201Tl-SPECT were carried out within a median interval of 17 days after surgery. Of the 33 patients, CT and 201Tl-SPECT were reported as positive for residual tumours in 23 (69.7%) and 30 (91%) patients, respectively. Sensitivity, specificity and overall accuracy were 71.4%, 40% and 66.6% for CT, and 96.4%, 40% and 87.8% for 201Tl-SPECT, respectively, and were based on their last follow-up status (P = 0.627 for CT; P = 0.053 for 201Tl-SPECT). The median PFS for patients reported to be positive or negative on CT scan was 4 and 5 months, respectively (P = 0.202). With 201Tl-SPECT, although the median PFS for patients with a positive 201Tl uptake was also 4 months, it had not even reached for those reported having a negative 201Tl uptake (cumulative survival 66.7% at last follow-up) (P = 0.198). However, Karnofsky performance status (KPS) was the only significant predictor on univariate analysis (KPS: < 80 vs. > or = 80; P < 0.001) for PFS.

CONCLUSIONS

Although both the imaging modalities have a poor specificity, postoperative 201Tl-SPECT had a significantly better accuracy to predict the status at last follow-up than contrast-enhanced CT. Nevertheless, KPS remained the most significant outcome predictor for PFS in high-grade malignant gliomas.

Modifying normal tissue damage postirradiation. Report of a workshop sponsored by the Radiation Research Program, National Cancer Institute, Bethesda, Maryland, September 6-8, 2000

Late effects that develop in normal tissues adjacent to the tumor site in the months to years after radiotherapy can reduce the quality of life of cancer survivors. They can be dose-limiting and debilitating or life-threatening. There is now evidence that some late effects may be preventable or partially reversible. A workshop, "Modifying Normal Tissue Damage Postirradiation", was sponsored by the Radiation Research Program of the National Cancer Institute to identify the current status of and research needs and opportunities in this area. Mechanistic, genetic and physiological studies of the development of late effects are needed and will provide a rational basis for development of treatments. Interdisciplinary teams will be needed to carry out this research, including pathologists, physiologists, geneticists, molecular biologists, experts in functional imaging, wound healing, burn injury, molecular biology, and medical oncology, in addition to radiation biologists, physicists and oncologists. The participants emphasized the need for developing and choosing appropriate models, and for radiation dose-response studies to determine whether interventions remain effective at the radiation doses used clinically. Both preclinical and clinical studies require long-term follow-up, and easier-to-use, more objective clinical scoring systems must be developed and standardized. New developments in biomedical imaging should provide useful tools in all these endeavors. The ultimate goals are to improve the quality of life and efficacy of treatment for cancer patients treated with radiotherapy.

Imaging changes after stereotactic radiosurgery of primary and secondary malignant brain tumors

After radiosurgery of malignant tumors, it can be difficult to discriminate between transient treatment effects, radiation necrosis, and tumor progression on post-treatment imaging. Misinterpretation of an enlarging lesion may lead to inappropriate treatment and contribute to disagreements about treatment efficacy. In an effort to clarify this problem, we reviewed our experience with interpreting post-radiosurgical imaging in patients with malignant primary and secondary brain tumors. We reviewed results of radiosurgery of 30 malignant gliomas and 35 metastatic brain tumors with minimum follow up of 1 year or until death. Of 30 gliomas, 73% were larger a mean of 13 weeks after radiosurgery. Of 35 metatstatic tumors, 22% were larger a mean of 10 weeks after radiosurgery. Eleven had 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) of enlarging lesions. Eight showed increased activity with respect to brain; three decreased activity. Of the eight, six predicted incorrectly based upon the patients' subsequent courses (all alive, mean follow up of 27 months), and two correctly, with the patients dying from the imaged lesions 8 and 13 months later. Of the three with FDG uptake less than brain, one patient was alive with 32 weeks of follow up, and two patients died from the imaged lesion 13 and 21 months later. Radiographic enlargement after radiosurgery is common, especially for gliomas. Physicians caring for these patients should be aware of this phenomenon and be cautious in interpreting post-treatment images. MRI appearance may be useful for metastases. FDG-PET seems unreliable. Further evaluation of Tl-201 and HMPAO SPECT or MRS is warranted.

TI-201 SPECT compared with histopathologic grade in the prognostic assessment of cerebral gliomas

PURPOSE

Although TI-201 SPECT has been used to evaluate the malignant grade of cerebral gliomas, the gold standard continues to be histopathologic examination. The authors assessed and compared the prognostic abilities of the two studies using survival analysis.

MATERIALS AND METHODS

Twenty-nine patients underwent 34 sessions of TI-201 SPECT plus surgery for primary or recurrent cerebral gliomas 12 to 78 months before this analysis. Using conventional survival analyses, such as the log-rank test, Cox regression, and the Akaike cross-tab method, the authors evaluated the prognostic significance of 10 variables: histopathologic grade, TI-201 SPECT, Tc-99m HMPAO SPECT, tumor cell viability, radionecrosis, neurologic defects, clinical improvement, surgery, chemotherapy, and external beam radiotherapy.

RESULTS

TI-201 SPECT was most strongly related to prognosis, followed by histopathologic grade. The other variables had little prognostic value. The Cox stepwise selection procedure indicated that TI-201 SPECT was the only independent predictor of outcome, whereas histopathologic analysis was eliminated from the prognostic model. However, the Kaplan-Meier survival curve and the Akaike method indicated that histopathologically low-grade tumors were more closely associated with longer-term survival than were TI-201 low uptake tumors.

CONCLUSIONS

TI-201 SPECT is not only closely correlated with the histopathologic grade of tumor but is a significantly better predictor of outcome than histopathologic grade. However, histopathologic examination may provide additional information on longer-term survival. TI-201 SPECT is a valuable procedure, especially in patients in whom a histologic diagnosis of possible glioma cannot be made.

A new semiquantitative method for comparing brain tumor uptake of Tc-99m sestamibi and TI-201

PURPOSE

We describe a new method for measuring brain tumor uptake of TI-201 and Tc-99m sestamibi (MIBI) that permits the semiquantitative comparison of tracer uptake to yield comparable "tumor bulk" ratios. We tested this method in patients treated recently and remotely with chemotherapy to determine if this method could identify differences between these two patient groups.

METHODS

Eleven patients with high-grade astrocytoma underwent TI-201 and Tc-99m MIBI SPECT. Each patient received 5 mCi TI-201 intravenously followed by SPECT using a dual-head gamma camera. This was immediately followed by an intravenous injection of 20 mCi Tc-99m MIBI and repeated SPECT. Four patients had recent therapy (from 1 day to 6 weeks before SPECT) and seven had remote treatment (>1 year before SPECT). Regions of interest were outlined in the tumor area using a computer-automated program to include all counts above background activity. Tumor activity counts were obtained from this region of interest. The tumor region of interest was mirrored to the contralateral uninvolved cerebral hemisphere to obtain background control count activity. A hypothetical volume of the number of pixels with background count activity necessary to constitute the tumor count activity (tumor bulk) was calculated using the ratio of total tumor counts (Ct), subtracting background (Cb), and dividing by the average counts per pixel in the control region (Cab). This was multiplied by the number of pixels (P), the pixel volume (Vp), and summed over all sections (i) involved with tumor. This method yields the equation tumor bulk =

RESULTS

The mean Tc-99m MIBI to TI-201 tumor bulk ratio was 1.03 (range, 0.81 to 1.12) in four patients who had recently received chemotherapy. The mean Tc-99m MIBI to TI-201 tumor bulk ratio was 1.55 (range, 1.46 to 1.64) in seven patients who had remote therapy. The difference in the Tc-99m MIBI to TI-201 tumor bulk ratio between the two groups was significant (P = 0.0001). Patients who received recent chemotherapy had relatively lower Tc-99m MIBI uptake compared with TI-201. In remotely treated patients, uptake of the Tc-99m MIBI was greater compared with TI-201.

CONCLUSION

This method allows semiquantitative comparison of different tracer uptake values independent of tracer dose and reduces the variability in drawing a region of interest when measuring tumor uptake. Among the patients studied, those who had recent chemotherapy showed a low Tc-99m MIBI to TI-201 ratio. This method of measuring "tumor bulk" can provide a useful index of viable tumor size in evaluating early tumor response and during ongoing chemotherapy.