Total Tumor Volume on 18F-PSMA-1007 PET as Additional Imaging Biomarker in mCRPC Patients Undergoing PSMA-Targeted Alpha Therapy with 225Ac-PSMA-I&T

Background: PSMA-based alpha therapy using 225Ac-PSMA-I&T provides treatment for metastatic castration-resistant prostate cancer (mCRPC), even after the failure of 177Lu-PSMA radioligand therapy (RLT). In clinical routine, the total tumor volume (TTV) on PSMA PET impacts therapy outcomes and plays an increasing role in mCRPC patients. Hence, we aimed to assess TTV and its changes during 225Ac-PSMA-I&T RLT. Methods: mCRPC patients undergoing RLT with 225Ac-PSMA-I&T with available 18F-PSMA-1007 PET/CT prior to therapy initiation were included. TTV was assessed in all patients using established cut-off values. Image derived, clinical and biochemistry parameters (PSA, LDH, AP, pain score) were analyzed prior to and after two cycles of 225Ac-PSMA. Changes in TTV and further parameters were directly compared and then correlated with established response criteria, such as RECIST 1.1 or mPERCIST. Results: 13 mCRPC patients were included. The median overall survival (OS) was 10 months. Prior to 225Ac-PSMA RLT, there was no significant correlation between TTV with other clinical parameters (p > 0.05 each). Between short-term survivors (STS, <10 months OS) and long-term survivors (LTS, ≥10 months OS), TTV and PSA were comparable (p = 0.592 & p = 0.286, respectively), whereas AP was significantly lower in the LTS (p = 0.029). A total of 7/13 patients completed two cycles and underwent a follow-up 18F-PSMA-1007 PET/CT. Among these patients, there was a significant decrease in TTV (median 835 vs. 201 mL, p = 0.028) and PSA (median 687 ng/dL vs. 178 ng/dL, p = 0.018) after two cycles of 225Ac-PSMA RLT. Here, percentage changes of TTV after two cycles showed no direct correlation to all other clinical parameters (p > 0.05 each). In two patients, new PET-avid lesions were detected on 18F-PSMA-1007 PET/CT. However, TTV and PSA were decreasing or stable. Conclusion: PET-derived assessment of TTV is an easily applicable imaging biomarker independent of other established parameters prior to 225Ac-PSMA RLT in these preliminary follow-up data. Even after the failure of 177Lu-PSMA, patients with extensive TTV seem to profit from RLT. All but one patient who was eligible for ≥2 cycles of 225Ac-PSMA-RLT demonstrated drastic TTV decreases without direct correlation to other biomarkers, such as serum PSA changes. Changes in TTV might hence improve the response assessment compared to standard classifiers by reflecting the current tumor load independent of the occurrence of new lesions.

Dosimetry and optimal scan time of [18F]SiTATE-PET/CT in patients with neuroendocrine tumours

PURPOSE

Radiolabelled somatostatin analogues targeting somatostatin receptors (SSR) are well established for combined positron emission tomography/computer tomography (PET/CT) imaging of neuroendocrine tumours (NET). [18F]SiTATE has recently been introduced showing high image quality, promising clinical performance and improved logistics compared to the clinical reference standard 68Ga-DOTA-TOC. Here we present the first dosimetry and optimal scan time analysis.

METHODS

Eight NET patients received a [18F]SiTATE-PET/CT (250 ± 66 MBq) with repeated emission scans (10, 30, 60, 120, 180 min after injection). Biodistribution in normal organs and SSR-positive tumour uptake were assessed. Dosimetry estimates for risk organs were determined using a combined linear-monoexponential model, and by applying 18F S-values and reference target masses for the ICRP89 adult male or female (OLINDA 2.0). Tumour-to-background ratios were compared quantitatively and visually between different scan times.

RESULTS

After 1 h, normal organs showed similar tracer uptake with only negligible changes until 3 h post-injection. In contrast, tracer uptake by tumours increased progressively for almost all types of metastases, thus increasing tumour-to-background ratios over time. Dosimetry resulted in a total effective dose of 0.015 ± 0.004 mSv/MBq. Visual evaluation revealed no clinically relevant discrepancies between later scan times, but image quality was rated highest in 60 and 120 min images.

CONCLUSION

[18F]SiTATE-PET/CT in NET shows overall high tumour-to-background ratios from 60 to 180 min after injection and an effective dose comparable to 68Ga-labelled alternatives. For clinical use of [18F]SiTATE, the best compromise between image quality and tumour-to-background contrast is reached at 120 min, followed by 60 min after injection.

PET Imaging of Meningioma Using the Novel SSTR-Targeting Peptide 18F-SiTATE

ABSTRACT

PET using 68Ga-labeled somatostatin receptor (SSTR) ligands adds significant information in meningioma patients. 18F-SiTATE is a novel, 18F-labeled SSTR-targeting peptide with remarkable imaging properties. Here, we present a 72-year-old woman with falx meningioma and transosseous extension. 18F-SiTATE PET/CT was performed 12 months after the previous 68Ga-DOTATOC PET/CT with comparable quantitative uptake and very good spatial resolution. So far, the widespread use of SSTR ligands for NET and meningioma imaging is hampered by cost-intensive 68Ge/68Ga generators, low activity amounts, lower spatial resolution, and short half-life. 18F-SiTATE might foster widespread use of SSTR ligands, overcoming the shortcomings of 68Ga-labeled ligands.

Salvage PRRT with 177Lu-DOTA-octreotate in extensively pretreated patients with metastatic neuroendocrine tumor (NET): dosimetry, toxicity, efficacy, and survival

Background

NETTER-1 trial demonstrated high efficacy and low toxicity of four cycles of Peptide Receptor Radionuclide Therapy (PRRT) in patients with metastasized NET. The present study evaluates the outcome of further PRRT cycles in the so called salvage setting in patients after initial response to four therapy cycles and later progression.

Methods

Thirty five patients (pat.) (25 male, 10 female, 63 ± 9 years) with progressive, metastasized NET (23 small intestinal, 5 lung, 4 CUP, 1 rectal, 1 gastric and 1 paraganglioma) were included. All patients previously received 4 PRRT cycles with ¹⁷⁷Lu-DOTATATE and showed initial response. SPECT based dosimetry was applied to determine kidney and tumor doses. Therapy response was evaluated using ⁶⁸Ga-DOTATATE PET/CT (with high dose CT), CT alone or MRI (RECIST 1.1), toxicity was defined using CTCAE 5.0 criteria. ^99mTc99-MAG3 scintigraphy was used to assess potential renal tubular damage. Progression free survival (PFS) and Overall survival (OS) analysis was performed with the Kaplan-Meier-method.

Results

The median PFS after initial PRRT was 33 months (95% CI: 30–36). The mean cumulative dose for including salvage PRRT was 44 GBq (range 33.5–47). One pat. (2.9%) showed grade 3 hematotoxicity. Kidney dosimetry revealed a mean cumulative kidney dose after a median of 6 PRRT cycles of 23.8 Gy. No grade 3 / 4 nephrotoxicity or relevant decrease in renal function was observed. Follow-up imaging was available in 32 patients after salvage therapy. Best response according to RECIST 1.1. was PR in one patient (3.1%), SD in 26 patients (81.3%) and PD in 5 patients (15.6%). PFS after salvage therapy was 6 months (95% CI: 0–16; 8 patients censored). Mean OS after initial PRRT was 105 months (95% CI: 92–119) and 51 months (95% CI: 41–61) after start of salvage therapy. Median OS was not reached within a follow-up of 71 months after initial PRRT and 25 months after start of salvage PRRT, respectively.

Conclusions

Salvage therapy with ¹⁷⁷Lu-DOTATATE is safe and effective even in patients with extensive previous multimodal therapies during disease progression and represents a feasible and valuable therapy option for progressive NET.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-6000-y) contains supplementary material, which is available to authorized users.

Preliminary experience with dosimetry, response and patient reported outcome after 177Lu-PSMA-617 therapy for metastatic castration-resistant prostate cancer

Prostate cancer can be targeted by ligands to the prostate-specific membrane antigen (PSMA). We aimed to evaluate dosimetry, safety and efficacy of 177Lu-PSMA-617 radioligand therapy (RLT) in patients with metastatic castration-resistant prostate cancer (mCRPC).Fifteen patients each received two cycles of 3.7 GBq (n = 5) or 6.0 GBq (n = 10) 177Lu-PSMA-617 at an eight to ten weeks interval. For safety monitoring, each treatment was followed by dosimetry with serial quantitative SPECT as well as inpatient and outpatient recording of adverse events. Response to RLT was primarily determined by baseline to follow-up change in 68Ga-PSMA PET/CT (RECIST1.1), as well as change in prostate-specific antigen (PSA), quality of life (QoL, FACT-P scale), and pain (Brief Pain Inventory) as secondary endpoints.Radiation dose delivered to the tumor (6.1 Gy/GBq) was six to twelve-fold higher than to critical organs (kidney left/right 0.5/0.6 Gy/GBq each, salivary glands 1.0 Gy/GBq). Total radiation dose per kidney did not exceed 23 Gy in any patient. Three patients had sub-acute and latent grade 3 events, i.e. anemia, leukocytopenia, and nausea. No acute events, grade ≥4 events or high grade events for salivary gland or kidney function were observed. After two RLT cycles, 4 (27%) patients had partial response, 6 (40%) had stable disease, and 5 (33%) had progressive disease according to RECIST. Any PSA decline was observed in 12/15 (80%) patients during RLT. Significant pain relief was documented in 7/10 (70%) symptomatic patients and QoL improved in 9/15 (60%) patients.177Lu-PSMA-617 therapy proved safe and indicated promising response rates for both objective and patient-reported outcomes in our small group of mCRPC patients.

Monitoring of Tumor Growth with [(18)F]-FET PET in a Mouse Model of Glioblastoma: SUV Measurements and Volumetric Approaches

Noninvasive tumor growth monitoring is of particular interest for the evaluation of experimental glioma therapies. This study investigates the potential of positron emission tomography (PET) using O-(2-¹⁸F-fluoroethyl)-L-tyrosine ([¹⁸F]-FET) to determine tumor growth in a murine glioblastoma (GBM) model—including estimation of the biological tumor volume (BTV), which has hitherto not been investigated in the pre-clinical context. Fifteen GBM-bearing mice (GL261) and six control mice (shams) were investigated during 5 weeks by PET followed by autoradiographic and histological assessments. [¹⁸F]-FET PET was quantitated by calculation of maximum and mean standardized uptake values within a universal volume-of-interest (VOI) corrected for healthy background (SUVmax/BG, SUVmean/BG). A partial volume effect correction (PVEC) was applied in comparison to ex vivo autoradiography. BTVs obtained by predefined thresholds for VOI definition (SUV/BG: ≥1.4; ≥1.6; ≥1.8; ≥2.0) were compared to the histologically assessed tumor volume (n = 8). Finally, individual “optimal” thresholds for BTV definition best reflecting the histology were determined. In GBM mice SUVmax/BG and SUVmean/BG clearly increased with time, however at high inter-animal variability. No relevant [¹⁸F]-FET uptake was observed in shams. PVEC recovered signal loss of SUVmean/BG assessment in relation to autoradiography. BTV as estimated by predefined thresholds strongly differed from the histology volume. Strikingly, the individual “optimal” thresholds for BTV assessment correlated highly with SUVmax/BG (ρ = 0.97, p < 0.001), allowing SUVmax/BG-based calculation of individual thresholds. The method was verified by a subsequent validation study (n = 15, ρ = 0.88, p < 0.01) leading to extensively higher agreement of BTV estimations when compared to histology in contrast to predefined thresholds. [¹⁸F]-FET PET with standard SUV measurements is feasible for glioma imaging in the GBM mouse model. PVEC is beneficial to improve accuracy of [¹⁸F]-FET PET SUV quantification. Although SUVmax/BG and SUVmean/BG increase during the disease course, these parameters do not correlate with the respective tumor size. For the first time, we propose a histology-verified method allowing appropriate individual BTV estimation for volumetric in vivo monitoring of tumor growth with [¹⁸F]-FET PET and show that standardized thresholds from routine clinical practice seem to be inappropriate for BTV estimation in the GBM mouse model.

68Ga-PSMA PET/CT Detects the Location and Extent of Primary Prostate Cancer

We evaluated the accuracy of PET/CT with ⁶⁸Ga-PSMA-HBED-CC-a ⁶⁸Ga-conjugated ligand of human prostate-specific membrane antigen (PSMA)-to localize cancer in the prostate and surrounding tissue at initial diagnosis.

METHODS

Twenty-one patients with biopsy-proven prostate cancer underwent ⁶⁸Ga-PSMA-HBED-CC (⁶⁸Ga-PSMA) PET/CT at a median of 4 d (range, 0-47 d) before radical prostatectomy. Based on a 6-segment model, the Gleason score and proportion of tumor tissue within each segment (segmental tumor burden, or STB) as determined by histopathology (STB_HP) were correlated with SUV_max and STB as determined by different SUV cutoffs for ⁶⁸Ga-PSMA PET (STB_PET1-6). Furthermore, the involvement of seminal vesicles and other extracapsular extension were assessed by histopathology and PET/CT.

RESULTS

Histopathology-positive segments (n = 100 of 126; 79%) demonstrated a significantly higher mean ± SD SUV_max (11.8 ± 7.6) than histopathology-negative segments (4.9 ± 2.9; P < 0.001). Receiver-operating-characteristic analysis revealed an optimal SUV_max cutoff of 6.5 for discrimination of histopathology-positive segments from histopathology-negative segments (area under the curve, 0.84; P < 0.001), which gave 67% sensitivity, 92% specificity, a 97% positive predictive value, a 42% negative predictive value, and 72% accuracy. STB_PET3 as determined by (2 × blood SUV) + (2 × SD) correlated best with STB_HP (Pearson ρ = 0.68; P < 0.001; mean difference ± SD, 19% ± 15%). PET/CT correctly detected invasion of seminal vesicles (n = 11 of 21 patients; 52%) with 86% accuracy and tumor spread through the capsule (n = 12; 57%) with 71% accuracy.

CONCLUSION

⁶⁸Ga-PSMA PET/CT accurately detected the location and extent of primary prostate cancer. Our preliminary findings warrant further investigation of ⁶⁸Ga-PSMA PET/CT in conjunction with needle biopsy.

FET PET for the evaluation of untreated gliomas: correlation of FET uptake and uptake kinetics with tumour grading

PURPOSE

Treatment and prognosis of gliomas depend on their histological tumour grade. The aim of the study was to evaluate the potential of [(18)F]fluoroethyltyrosine (FET) PET for non-invasive tumour grading in untreated patients.

METHODS

Dynamic FET PET studies were performed in 54 patients who, based on MRI, were estimated to have low grade (LG; n = 20), intermediate (WHO II-III; n = 4) or high grade (HG; n = 30) tumours. For standard evaluation, tumour SUV(max) and the ratio to background (SUV(max)/BG) were calculated (sum image: 20-40 min). For dynamic evaluation, mean SUV values within a 90% isocontour ROI (SUV90) and the SUV90/BG ratios were determined for each time frame to evaluate the course of FET uptake. Results were correlated with histopathological findings from PET-guided stereotactic biopsies.

RESULTS

Histology revealed gliomas in all patients. Using the standard method a statistically significant difference (p = 0.001) was found between LG (n = 20; SUV(max)/BG: 2.16 +/- 0.98) and HG (n = 34; SUV(max)/BG: 3.29 +/- 1.06) gliomas (opt. threshold 2.58: SN71%/SP85%/area under ROC curve [AUC]:0.798), however, with a marked overlap between WHO II to IV tumours. Time activity curves showed slight increase in LG, whereas HG tumours presented with an early peak (10-20 min) followed by a decrease. Dynamic evaluation successfully separated LG from HG gliomas with higher diagnostic accuracy (SN94%/SP100%/AUC:0.967).

CONCLUSIONS

Based on the ratio-based method, a statistically significant difference was found between LG and HG gliomas. Due to the interindividual variability, however, no reliable individual grading was possible. In contrast, dynamic evaluation allowed LG and HG gliomas to be differentiated with high diagnostic power and, thus, should supplement the conventional method.

The effect of the beta-emitting yttrium-90 citrate on the dose-response of dicentric chromosomes in human lymphocytes: a basis for biological dosimetry after radiosynoviorthesis

The production of dicentric chromosomes in human lymphocytes by beta-particles of yttrium-90 (Y-90) was studied in vitro to provide a basis of biological dosimetry after radiosynoviorthesis (RSO) of persistent synovitis by intra-articular administration of yttrium-90 citrate colloid. Since the injected colloid may leak into the lymphatic drainage exposing other parts of the body to radiation, the measurement of biological damage induced by beta-particles of Y-90 is important for the assessment of radiation risk to the patients. A linear dose-response relationship (alpha = 0.0229 +/- 0.0028 dicentric chromosomes per cell per gray) was found over the dose range of 0.2176-2.176 Gy. The absorbed doses were calculated for exposure of blood samples to Y-90 activities from 40 to 400 kBq using both Monte Carlo simulation and an analytical model. The maximum low-dose RBE, the RBE(M) which is equivalent to the ratio of the alpha coefficients of the dose-response curves, is well in line with published results obtained earlier for irradiation of blood of the same donor with heavily filtered 220 kV X-rays (3.35 mm copper), but half of the RBE(M) relative to weakly filtered 220 kV X-rays. Therefore, it can be concluded that for estimating an absorbed dose during RSO by the technique of biological dosimetry, in vitro and in vivo data for the same radiation quality are necessary.

Serial O-(2-[(18)F]fluoroethyl)-L: -tyrosine PET for monitoring the effects of intracavitary radioimmunotherapy in patients with malignant glioma

Purpose

Intracavitary radioimmunotherapy (RIT) offers an effective adjuvant therapeutic approach in patients with malignant gliomas. Since differentiation between recurrence and reactive changes following RIT has a critical impact on patient management, the aim of this study was to analyse the value of serial O-(2-[¹⁸F]fluoroethyl)-l-tyrosine (FET) PET scans in monitoring the effects of this locoregional treatment.

Methods

Following conventional therapy, 24 glioma patients (5 WHO III, 19 WHO IV) underwent one to five RIT cycles with either ¹³¹I-labelled (n=19) or ¹⁸⁸Re-labelled (n=5) anti-tenascin antibodies. Patients were monitored with serial FET PET scans (2–12 scans). For semiquantitative evaluation, maximal tumoural uptake (TU_max) was evaluated and the ratio to background (BG) was calculated. Results of PET were correlated with histopathological findings (n=9) and long-term clinical follow-up for up to 87 months.

Results

In seven tumour-free patients, PET revealed slightly increasing but homogeneous FET uptake surrounding the resection cavity with a peak up to 18 months following RIT (TU_max/BG 2.07±0.25) but stable or decreasing values during further follow-up (last follow-up: TU_max/BG 1.63±0.22). Seventeen patients developed regrowth of residual tumour/tumour recurrence showing additional nodular FET uptake (TU_max/BG 2.79±0.53). A threshold value of 2.4 (TU_max/BG) allowed best differentiation between recurrence and reactive changes (sensitivity 82%, specificity 100%).

Conclusion

FET PET is a sensitive tool for monitoring the effects of locoregional RIT. Homogeneous, slightly increasing FET uptake around the tumour cavity with a peak up to 18 months after RIT, followed by stable or decreasing uptake, points to benign, therapy-related changes. In contrast, nodular uptake is a reliable indicator of recurrence.

Analysis of 18F-FET PET for grading of recurrent gliomas: is evaluation of uptake kinetics superior to standard methods?

The aim of the present study was to evaluate whether extended analyses of O-(2-18F-fluoroethyl)-L-tyrosine (FET) uptake kinetics provide results superior to those of standard tumor-to-background ratios in predicting tumor grade in patients with pretreated gliomas.

METHODS

Dynamic 18F-FET PET studies (0-40 min after injection of 180 MBq of 18F-FET) were performed on 45 glioma patients with suspected tumor recurrence after multimodal treatment. For the standard method, tumoral maximal standardized uptake value (SUVmax) and the ratio to the background were derived from a summed image 20-40 min after injection. Dynamic data evaluation comprised several approaches: first, SUV within a 90% isocontour threshold (SUV90) and the respective ratio to the background calculated for each time frame between 5 and 40 min after injection; second, the time to peak analysis; and third, various parameters accounting for the individual time course of 18F-FET uptake. Results were correlated with the histopathologic findings of MRI/PET-guided stereotactic biopsies and were evaluated with respect to their discriminatory power to separate low- from high-grade tumors using receiver-operating characteristic (ROC) analyses.

RESULTS

The parameters taking into account the individual time course of 18F-FET uptake were able to differentiate low-grade from high-grade recurrent astrocytomas with high diagnostic accuracy, reaching the best differentiation with a sensitivity and specificity of 92% and an area under the ROC curve (AUC) of 0.94. For the other parameters, the respective values were considerably lower (time to peak: 85% sensitivity and 88% specificity; SUV90-to-background ratio for single-frame evaluation of the early-uptake phase: 100% sensitivity, 62% specificity, and 0.81 AUC). The lowest performance was provided by the standard method (SUVmax: 73% sensitivity, 54% specificity, and 0.60 AUC; SUVmax-to-background ratio: 62% sensitivity, 62% specificity, and 0.59 AUC). Time-activity curves (5-40 min after injection) slightly and steadily increased in tumor-free patients and in low-grade tumors, whereas high-grade tumors showed an early peak around 10-15 min after injection followed by a decrease.

CONCLUSION

This study has shown differences in the dynamics of 18F-FET uptake between recurrent low- and high-grade gliomas. Therefore, parameters addressing the different kinetic behaviors allow discrimination with high diagnostic power between these 2 prognostically different groups. Thus, the techniques introduced here are clearly superior to the yet most widely used standard method.

Long-term assessment of striatal dopamine transporters in parkinsonian patients with intrastriatal embryonic mesencephalic grafts

PURPOSE

Single-photon emission computed tomography (SPECT) of striatal dopamine transporters (DAT) has been used to demonstrate presynaptic dopaminergic dysfunction and to monitor the progression of Parkinson's disease. In parkinsonian patients who were implanted with embryonic mesencephalic tissue in the striatum, positron emission tomography (PET) has shown an increase in striatal [(18)F]dopa uptake as an indicator of graft survival and striatal reinnervation. The aim of this study was to investigate two patients who had undergone bilateral intrastriatal transplantation of human embryonic mesencephalic tissue using SPECT and the (123)I-labelled DAT ligand N-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl) tropane (IPT).

METHODS

Two patients were subjected to [(123)I]IPT SPECT according to a standardised protocol prospectively and repeatedly up to 8 years after transplantation.

RESULTS

From baseline to year 3 after transplantation, mean striatal DAT availability increased by a mean of 61% (93% and 29% in patients 1 and 2, respectively). It then remained relatively stable up to 8 years in patient 2, but increased further by another 77% of baseline values in patient 1. Clinically, both patients experienced a moderate improvement in motor performance but developed moderate (patient 2) to severe (patient 1) off-medication dyskinesias.

CONCLUSION

Our data indicate that DAT imaging using IPT and SPECT can be used to demonstrate graft survival following dopaminergic tissue implantation. Because SPECT with DAT ligands is widely available in the routine clinical setting, this methodology may be a useful alternative to [(18)F]dopa PET for repeated scanning of grafted parkinsonian patients. The relevance of the long-term increase in DAT binding for the development of off-medication dyskinesias remains to be elucidated further.

[Lymph kinetics with technetium-99m labeled radiopharmaceuticals. Animal studies]

Aim of this study was to characterize suitable technetium-99m labeled tracers for lymphoscintigraphy by comparative animal tests.

ANIMALS, METHODS

To evaluate the influence of the particle size and the organ tracer-uptake on lymphtransport animal experiments were performed on six different agents (including one control group). Activity distributions were examined in Sprague-Dawley-rats by lymphoscintigraphy; the maximum uptake (count-rate) of the whole body and in lymph nodes were analyzed by regions-of-interest-technique, respectively. Additionally, for characterization of lymphatic and extralymphatic traceruptake an intra-individual relative count-rate ratio of the liver, lung, kidneys, and spleen has been calculated following organ extraction.

RESULTS

Organ specific differences of distribution were clearly demonstrated. Our results indicate that the kinetics of lymphoscintigraphic (99m)Tc-bound agents substantially depends on particle size. Reliable transport from the interstitium to initial lymph vessels and lymph node uptake suggested for tracers suited for lymphoscintigraphy a median size of about <100 nm.

CONCLUSION

Our data could improve standardization of diagnostic methods and lead to an objective consideration of therapeutic procedures.

O-(2-[18F]fluoroethyl)-L-tyrosine PET for monitoring the effects of convection-enhanced delivery of paclitaxel in patients with recurrent glioblastoma

PURPOSE

Convection-enhanced delivery (CED) of paclitaxel is a new locoregional approach for patients with recurrent glioblastoma. The aim of this study was to evaluate O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) in monitoring the effects of this type of direct drug delivery.

METHODS

Eight patients with recurrent glioblastoma underwent CED of paclitaxel, which was infused over stereotactically placed catheters into the tumour. FET PET and MRI were performed before and 4 weeks after therapy and then at 3-month intervals to document follow-up. For quantitative evaluation, SUV(max)(tumour)/SUV(mean)(background) ratios were calculated.

RESULTS

At baseline all tumours showed gadolinium enhancement and high FET uptake (SUV(max)/BG 3.2+/-0.8). Four weeks after CED, a statistically significant decrease in FET uptake was seen (SUV(max)/BG-17%; p<0.01). During follow-up, no recurrence was observed within the CED area. Two out of eight patients with extended tumours died 4 and 5 months after treatment, most probably from local complications. Temporarily stable disease with stable FET uptake was observed in six of eight patients; this was followed by progression and increasing FET uptake ratios (+46%) distant from the CED area in five of the six patients 3-13 months after CED. One patient still presents stable FET uptake 10 months after CED. MRI showed unchanged/increasing contrast enhancement and oedema without ability to reliably assess disease progression.

CONCLUSION

FET PET is a valuable tool in monitoring the effects of CED of paclitaxel. In long-term follow-up, stable or decreasing FET uptake, even in contrast-enhancing lesions, is suggestive of reactive changes, whereas increasing ratios appear always to be indicative of recurrence. Therefore, FET PET is more reliable than MRI in differentiating stable disease from tumour regrowth.

Alteration of the striatal dopaminergic system in human narcolepsy

Striatal D2/D3 dopaminergic receptors have been proposed to play a role in cataplexy. The authors studied the striatal presynaptic dopamine transporter and postsynaptic D2-receptors in seven patients with narcolepsy and seven control subjects using [123I](N)-(3-iodopropene-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl)tropane and [123I](S)-2-hydroxy-3-iodo-6-methoxy-([1-ethyl-2-pyrrolidinyl]methyl)benzamide SPECT. D2-receptor binding was elevated in narcolepsy (p = 0.017) and correlated with the frequency of cataplectic and sleep attacks (R > or = 0.844, p < or = 0.017). The human striatal dopaminergic system is altered in vivo in narcolepsy/cataplexy.

Locoregional radioimmunotherapy in selected patients with malignant glioma: experiences, side effects and survival times

Prognosis of malignant glioma is very unfavourable mainly due to minimal tumour remnants in the peritumoural tissue. Intralesionally applied radioimmunotherapy is a possible therapeutical option with the potential to improve survival of patients with malignant glioma. We investigated side effects and survival after surgery, conventional radiotherapy and additional radioimmunotherapy with labelled tenascin-antibodies in patients with malignant glioma.

METHODS

Since 1995, 37 patients were treated with radioimmunotherapy after resection and radiotherapy of a malignant glioma. Patients received antibodies labelled with yttrium-90 and iodine-131 in different doses into the tumour cavity via a previously implanted ommaya-reservoir. Treatment was applied in up to 8 cycles (mean 2.96 cycles) in time intervals of 6-8 weeks. Mean age was 46 years, histology was anaplastic astrocytoma in 13 patients and glioblastoma in 24 patients.

RESULTS

For the whole group median survival time has not yet been reached. For glioblastoma the median survival time is 17 months, 5-year survival probability for anaplastic astrocytoma is 85% approximately. Quality of life was acceptable. Acute side effects following treatment were headache, seizures and worsening of pre-existing neurological symptoms. Late side effects were skin necrosis and, in 1 case, a delayed aphasia probably due to a vascular lesion.

CONCLUSION

Radioimmunotherapy prolonged survival time in a selected group of patients with malignant gliomas as compared to a historical control group. Patients with anaplastic astrocytomas seem to have more benefit from this therapy than patients with glioblastomas.

Intralesional radioimmunotherapy in the treatment of malignant glioma: clinical and experimental findings

In the last two decades radioimmunotherapy has been used as an additional treatment option for malignant glioma in several centers. More than 400 patients have been reported, who were treated in the framework of different studies. Most of them received labelled antibodies to tenascin, an extracellular matrix-glycoprotein, which is expressed in high amounts in malignant gliomas. We report side effects and survival time of 46 patients, treated after surgical resection and conventional radiotherapy with intralesionally injected labelled (131-Iodine) antibodies to tenascin. Despite the fact, that many treatments have been performed, little is known about the distribution properties of labelled antibodies after injection in the tumour cavity. For an optimal effect labelled antibodies should be able to reach tumour cells, which have migrated into the surrounding tissue. We investigated the propagation velocity and area of distribution of labelled antibodies and their considerably smaller fragments after the injection in C6-gliomas of Wistar rats. Propagation increased with time and was significantly greater after injection of labelled fragments than after injection of labelled antibodies. According to our results labelled fragments might be better able to reach distant tumour cells in the peritumoural tissue of malignant gliomas than labelled antibodies.

[Initial experiences with adjuvant locoregional radioimmunotherapy using 131I-labeled monoclonal antibodies against tenascin (BC-4) for treatment of glioma (WHO III and IV)]

AIM

None of the established treatments (surgery, radiotherapy, chemotherapy) for malignant glioma has improved its very poor prognosis. Adjuvant locoregional radio-immunotherapy (RIT) represents a new therapeutic approach. We present our initial experience with this therapeutic tool with respect to adverse effects, biokinetics and clinical follow-up.

METHODS

Following surgery and radiotherapy, 12 patients with glioma (4, WHO stage III; 8, WHO stage IV) underwent 1-5 RIT-cycles (average dose 1100 MBq 131labelled monoclonal BC-4 antibodies) at six week intervals. Follow-up included serial FDG-PET and MRI investigations. Evaluation of biokinetics included whole body scans, together with analysis of blood, urine and fluid from the tumor cavity.

RESULTS

Following RIT, four patients experienced temporary seizures, which, in one case, were associated with temporary aphasia. Eight patients developed HAMA (human anti-mouse antibodies) during follow-up. Mean biologic half-life of the radiopharmaceutical in the resection cavity was 3.9 d (range: 1.0-10.2 d) and remained stable intraindividually during further RIT-cycles. The antibody/radionuclide conjugate remained stable in the tumor cavity for at least 5 d. Median survival presently stands at 18.5 months compared to 9.7 months in a historical patient group (n = 89) undergoing conventional therapeutic strategies. Five patients show no signs of recurrence. In three patients with post-surgical evidence of residual tumor, one patient showed partial remission, one stable disease, and one progressive disease during RIT. Four patients without evidence of residual tumor mass at the beginning of RIT developed recurrence during therapy.

CONCLUSIONS

Initial experience demonstrates that locoregional RIT is a well tolerated treatment modality that may represent a promising new approach in the management of patients with malignant glioma. Advantages of local application include passage of the blood-brain barrier, high concentration of activity within the resection cavity and low systemic toxicity.

Normal IPT and IBZM SPECT in drug-naive and levodopa-treated idiopathic restless legs syndrome

Fourteen drug-naive and 11 levodopa-treated patients with idiopathic restless legs syndrome (RLS), and 10 controls age-matched to each RLS group separately were examined with polysomnography (PSG), [(123)I]-(N)-(3-iodopropen-2-yl)-2beta-carbomethoxy-3beta-(4-chlorophenyl) tropane ((123)I-IPT) SPECT, and [(123)I]-(S)-2-hydroxy-3-iodo-6-methoxy-[(1-ethyl-2-pyrrolidinyl)methyl] benzamide ((123)I-IBZM) SPECT. Drug-naive and levodopa-treated patients with RLS and controls showed similar striatal dopamine transporter and dopamine D(2)-receptor binding, the latter declining with age. The authors conclude that striatal dopamine transporter and receptor density is normal in drug-naive and levodopa-treated patients with RLS.

Comparison of in vivo dopamine D2 receptor binding of [(123)I]AIBZM and [(123)I]IBZM in rat brain

[(123)I]AIBZM, (S)-5-[(123)I]-Iodo-N-[(1-ethyl-2-pyrrolidinyl)]methyl-4-amine-2-methoxybenzamide is a derivative with high affinity for the D2 receptor. Labeling was achieved by the Iodogen method. The in vivo affinity for the D2 receptor and the biological characteristics were performed in rats. The brain uptake of [(123)I]AIBZM was significantly lower, however the striatum/cerebellum ratio (2h p.i.) was higher than that of [(123)I]IBZM. Because of the high affinity and its possibly lower unspecific binding compared to [(123)I]IBZM, [(123)I]AIBZM may be a potential imaging agent for the D2 dopamine receptor.

Reduced striatal dopamine transporters in idiopathic rapid eye movement sleep behaviour disorder. Comparison with Parkinson's disease and controls

Rapid eye movement (REM) sleep behaviour disorder (RBD) is characterized by complex behaviour during REM sleep. The aetiology of this disorder is still unknown, but a recent study showed an association between RBD and Parkinson's disease. We therefore studied striatal postsynaptic dopamine D2 receptor density with [123I](S)-2-hydroxy-3-iodo-6-methoxy-(1-ethyl-2-pyrrolidinylmethyl ) benzamide ([123I]IBZM) and the striatal presynaptic dopamine transporter with (N)-(3-iodopropene-2-yl)-2beta-carbomethoxy-3beta-(4-chlorop henyl) tropane ([123I]IPT) using single-photon emission computed tomography (SPECT) in patients with idiopathic RBD. We compared the [123I]IPT-SPECT results of five patients with polysomnographically confirmed idiopathic RBD with the [123I]IPT-SPECTs of seven age- and sex-matched controls without a history of sleep disorders, and of 14 patients with Parkinson's disease (Hoehn and Yahr stage I). All RBD patients had significantly reduced striatal [123I]IPT binding compared with the controls (RBD: right, 2.94 +/- 0.32, left, 3.03 +/- 0.41; controls: right, 4.41 +/- 0.17, left, 4.34 +/- 0.21; P = 0.003), but significantly higher striatal [123I]IPT binding compared with the striatum contralateral to the symptomatic body side of the Parkinson's disease patients (Parkinson's disease: ipsilateral, 3.17 +/- 0.36, P = 0.298; contralateral, 2.51 +/- 0.31, P = 0.019). Uptake of [123I]IBZM was not significantly different in the RBD group compared with the controls. This study demonstrates that [123I]IPT-SPECT is a useful diagnostic tool in RBD and that reduced striatal dopamine transporters may be a pathophysiological mechanism of idiopathic RBD. (Results are given as mean +/- standard deviation.)

Simultaneous evaluation of fatty acid metabolism and myocardial flow in an explanted heart

The biodistribution of the fatty acid analog [131I]PHIPA 3-10, was compared to the flow tracer 99mTc-sestamibi by quantitative analysis in a dual-isotope study performed during a heart transplantation.

METHODS

Iodine-131-PHIPA 3-10 and 99mTc-sestamibi were injected simultaneously approximately 20 min prior to the start of surgical procedure. Scintigraphic images of the sliced explanted heart were compared to the preoperative in vivo scans using [123I]PHIPA 3-10, 201TI and 99mTc-sestamibi. In 14 tissue samples of the explanted heart, the radioactive contents from [131I]PHIPA 3-10 and 99mTc-sestamibi were calculated as %ID/g-values and correlated with the corresponding histology.

RESULTS

In the preoperative scans, a mismatch of fatty acid uptake and perfusion ([123I]PHIPA 3-10 > flow) was observed which indicated residual viable myocardium, while a matched defect was associated with scar. In viable myocardium, there was a significantly higher accumulation of [131I]PHIPA 3-10 compared to 99mTc-sestamibi (mean 5.9 x 10(-3) versus 2.7 x 10(-3)%ID/g),whereas in scars the uptake of both tracers was comparable (1.2 x 10(-3) versus 1.4 x 10(-3)%ID/g).

CONCLUSION

Myocardial viability can be defined more accurately with radioiodinated PHIPA 3-10 than with 99mTc-sestamibi. The differences of biodistribution in viable myocardium and scars indicate that not only perfusion but also the metabolic state of the myocardium can be evaluated with radioiodinated PHIPA 3-10.

Uptake of iodine-123-alpha-methyl tyrosine by gliomas and non-neoplastic brain lesions

Using single-photon emission tomography (SPET), the radiopharmaceutical l-3-iodine-123-alpha-methyl tyrosine (IMT) has been applied to the imaging of amino acid transport into brain tumours. It was the aim of this study to investigate whether IMT SPET is capable of differentiating between high-grade gliomas, low-grade gliomas and non-neoplastic brain lesions. To this end, IMT uptake was determined in 53 patients using the triple-headed SPET camera MULTISPECT 3. Twenty-eight of these subjects suffered from high-grade gliomas (WHO grade III or IV), 12 from low-grade gliomas (WHO grade II), and 13 from non-neoplastic brain lesions, including lesions after effective therapy of a glioma (five cases), infarctions (four cases), inflammatory lesions (three cases) and traumatic haematoma (one case). IMT uptake was significantly higher in high-grade gliomas than in low-grade gliomas and non-neoplastic lesions. IMT uptake by low-grade gliomas was not significantly different from that by non-neoplastic lesions. Diagnostic sensitivity and specificity were 71% and 83% for differentiating high-grade from low-grade gliomas, 82% and 100% for distinguishing high-grade gliomas from non-neoplastic lesions, and 50% and 100% for discriminating low-grade gliomas from non-neoplastic lesions. Analogously to positron emission tomography with radioactively labelled amino acids and fluorine-18 deoxyglucose, IMT SPET may aid in differentiating high-grade gliomas from histologically benign brain tumours and non-neoplastic brain lesions; it is of only limited value in differentiating between non-neoplastic lesions and histologically benign brain tumours.