Jörg Steinbach

Exploratory prospective trial of hypoxia-specific PET imaging during radiochemotherapy in patients with locally advanced head-and-neck cancer

PURPOSE To explore in a prospective trial the prognostic value of hypoxia imaging before and during radiochemotherapy in patients with locally advanced head and neck cancer. PATIENTS AND METHODS Twenty-five patients with stage III/IV head and neck cancer were investigated with [(18)F]-fluoromisonidazole (FMISO) PET/CT at four time points during radiochemotherapy (baseline, 8-10 Gy, 18-20 Gy,50-60 Gy). FMISO PET/CT image parameters were extracted including maximum-tumour-to-background (TBR(max)) and thresholded volume at different TBR ratios. CT volume and baseline FDG-PET/CT image parameters were also included. Parameters at all time points were investigated for their prognostic value with the local-progression-free-survival endpoint (LPFS). Significance was evaluated with multivariate Cox (including clinical parameters) and Log-rank tests. RESULTS FMISO-image parameters were found to have a strong association with the LPFS endpoint, and were strongest at the week 1 and 2 time points (p = 0.023-0.048 and 0.042-0.061 respectively on multivariate Cox). Parameters measured at baseline were only significant on univariate analysis. None of the clinical parameters, and also FDG- or CT-delineated volumes, were significantly associated with LPFS. CONCLUSION This prospective, exploratory study demonstrated that FMISO-PET/CT imaging during the initial phase of treatment carries strong prognostic value. FMISO-PET/CT imaging at 1 or 2 weeks during treatment could be promising way to select patients that would benefit from hypoxia modification or dose-escalated treatment. A validation study is on-going.

Additional PET/CT in week 5-6 of radiotherapy for patients with stage III non-small cell lung cancer as a means of dose escalation planning?

BACKGROUND AND PURPOSE Loco-regional failure after radiotherapy with total doses of 60-70 Gy for non-small cell lung cancer (NSCLC) remains a major clinical problem. Escalation of radiation dose is often limited because of exceeding normal tissue constraints. The present study was designed to test the hypothesis that a reduction in disease volume during radiotherapy detected by FDG PET/CT would facilitate radiation dose escalation, whilst remaining within normal tissue constraints. MATERIALS AND METHODS Ten patients with localised inoperable NSCLC were prospectively enrolled. Each received standard 3D-conformally planned radiotherapy to a dose of 66 Gy in 33 fractions over 6.5 weeks. FDG PET/CT imaging in the treatment position was performed prior to treatment and repeated following 50 or 60 Gy. CT and PET-delineated gross tumour volumes were generated and a composite created. A margin of 15mm was added in all planes to form the planning target volume (PTV). Treatment planning was performed to compare two dose escalation strategies: 78 Gy delivered to the initial PTV with treatment in two phases (shrinking field), i.e., 66 Gy to the initial PTV with a 12 Gy-boost to the PTV after 50/60 Gy. As an alternative planning approach the maximal dose without exceeding normal tissue constraints was evaluated for each patient (individualized dose prescription). RESULTS There was a median PTV reduction after 50/60 Gy of 20%. Delivering 78 Gy to the initial PTV could have been achieved in 4/10 patients. Of the remaining 6, delivering 78 Gy to the initial PTV would have exceeded normal tissue constraints and no benefit was seen when delivered in two phases. The results from the individualized dose prescription indicated a higher median maximal dose when treatment would be given in two phases compared to one phase resulting in a modest increase of calculated tumour control probability. CONCLUSIONS Our data suggest that despite tumour shrinkage determined by subsequent FDG PET/CT during treatment the tested adaptive targeting strategy would result only in a modest improvement in the context of dose escalation. Further studies on the optimal use of FDG PET/CT and other approaches for dose escalation in loco-regionally advanced NSCLC are warranted.

Basic hydrolysis of 2-[18F]fluoro-1,3,4,6-tetra-O-acetyl--glucose in the preparation of 2-[18F]fluoro-2-deoxy-d-glucose

Abstract In contrast to the commonly used acid hydrolysis of 2-[ 18 F ] fluoro -1,3,4,6- tetra -O- acetyl- d -glucose to [18F]FDG, basic hydrolysis is a short, high-yield procedure at room temperature. In case of nucleophilic [18F]FDG synthesis the yield of removing the protective groups is quantitative. Using the electrophilic procedure the yield is about 20% higher than in acid hydrolysis. Under optimal conditions (0.3 M NaOH) the reaction is already completed within 1 min. In alkaline solutions the formed [18F]FDG is stable for more than 20 min. Additionally, the formation of 2-deoxy-2-chloro- d -glucose is avoided.

Module-assisted preparation of 64Cu with high specific activity.

In this work the production of (64)Cu via the (64)Ni(p,n)(64)Cu reaction with optimized conditions for low current irradiation is presented. Different target setups and cleaning steps for lowering metal contaminations in the product were applied. (64)Cu with high specific activities up to 1685 GBq/μmol was produced despite low overall activity (≈ 4.2 GBq per run). The module processing leads to a highly reproducible, reliable product quality (<1 μg Cu and <7 μg Ni). Besides its diagnostic value (64)Cu may be of interest even for therapeutic purposes due to its decay characteristics.

Radiolabeled Cetuximab Conjugates for EGFR Targeted Cancer Diagnostics and Therapy.

The epidermal growth factor receptor (EGFR) has evolved over years into a main molecular target for the treatment of different cancer entities. In this regard, the anti-EGFR antibody cetuximab has been approved alone or in combination with: (a) chemotherapy for treatment of colorectal and head and neck squamous cell carcinoma and (b) with external radiotherapy for treatment of head and neck squamous cell carcinoma. The conjugation of radionuclides to cetuximab in combination with the specific targeting properties of this antibody might increase its therapeutic efficiency. This review article gives an overview of the preclinical studies that have been performed with radiolabeled cetuximab for imaging and/or treatment of different tumor models. A particularly promising approach seems to be the treatment with therapeutic radionuclide-labeled cetuximab in combination with external radiotherapy. Present data support an important impact of the tumor micromilieu on treatment response that needs to be further validated in patients. Another important challenge is the reduction of nonspecific uptake of the radioactive substance in metabolic organs like liver and radiosensitive organs like bone marrow and kidneys. Overall, the integration of diagnosis, treatment and monitoring as a theranostic approach appears to be a promising strategy for improvement of individualized cancer treatment.

Automatische Volumenabgrenzung in der onkologischen PET – Bewertung eines entsprechenden Software-Werkzeugs und Vergleich mit manueller Abgrenzung anhand klinischer Datensätze

AIM Evaluation of a dedicated software tool for automatic delineation of 3D regions of interest in oncological PET. PATIENTS, METHODS The applied procedure encompasses segmentation of user-specified subvolumes within the tomographic data set into separate 3D ROIs, automatic background determination, and local adaptive thresholding of the background corrected data. Background correction and adaptive thresholding are combined in an iterative algorithm. Nine experienced observers used this algorithm for automatic delineation of a total of 37 ROIs in 14 patients. Additionally, the observers delineated the same ROIs also manually (using a freely chosen threshold for each ROI) and the results of automatic and manual ROI delineation were compared. RESULTS For the investigated 37 ROIs the manual delineation shows a strong interobserver variability of (26.8±6.3)% (range: 15% to 45%) while the corresponding value for automatic delineation is (1.1±1.0)% (range: <0.1% to 3.6%). The fractional deviation of the automatic volumes from the observer-averaged manual ones is (3.7±12.7)%. CONCLUSION The evaluated software provides results in very good agreement with observer-averaged manual evaluations, facilitates and accelerates the volumetric evaluation, eliminates the problem of interobserver variability and appears to be a useful tool for volumetric evaluation of oncological PET in clinical routine.

Spatial distribution of FMISO in head and neck squamous cell carcinomas during radio-chemotherapy and its correlation to pattern of failure

ABSTRACT Background. Tumour hypoxia can be measured by FMISO-PET and negatively impacts local tumour control in patients with head and neck squamous cell carcinoma (HNSCC) undergoing radiotherapy. The aim of this post hoc analysis of a prospective clinical trial was to investigate the spatial variability of FMISO hypoxic subvolumes during radio-chemotherapy and the co-localisation of these volumes with later recurrences as a basis for individualised dose prescription trials with dose escalation defined by FMISO-PET. Methods. Sequential FMISO scans of 12 (of 25) patients presenting residual hypoxia taken before (FMISOpre) and during (FMISOw1–FMISOw5) radio-chemotherapy were analysed regarding the stability of the FMISO subvolumes and, in case of local failure, their correlation to local relapse. Results. Consecutive FMISO-PET positive volumes could be classified as moderately stable with Dice conformity indices of 62% and 58% up to the second week of treatment. Substantial volumetric variation during treatment was observed, with more than 20% geographic miss in all patients and more than 40% in half of the patients. The localisation of the maximum standardised uptake value (SUVmax) differed with a mean distance of 7.0 mm and 13.5 mm between the pre-therapeutic and first or second FMISO-PET during treatment. A stable hypoxic consensual volume (i.e. overlap of pre-therapeutic FMISO and intra-treatment FMISO subvolumes up to week two, generated by different contouring methods) was determined for six patients with imaging information of local recurrence. Three of these six local recurrences were located within this consensual volume. Conclusions. Our data suggest that selective dose painting to hypoxic tumour subvolumes requires adaptation during treatment and sufficient margins. An alternative strategy is to escalate the dose to the gross tumour volume, accepting lesser escalation of dose outside hypoxic areas if indicated by constraints for organs at risk.

Synthesis of S-([18F]fluoromethyl)-(+)-McN5652 as a potential PET radioligand for the serotonin transporter.

The present study describes the synthesis of the [18F]fluoromethyl analogue of (+)-McN5652 ([18F]FMe-McN) as a new potential tracer for the serotonin transporter. In vitro binding studies have shown that FMe-McN displays only slightly lower affinity for the serotonin transporter (K(i) = 2.3 +/- 0.1 nM) than (+)-McN5652 (K(i) = 0.72 +/- 0.2 nM). The radiofluorinated tracer [18F]FMe-McN was prepared by reaction of normethyl (+)-McN5652 with the fluoromethylation agent [18F]bromofluoromethane in an overall radiochemical yield of 5 +/- 1% (decay-corrected, related to [18F]fluoride) and with high specific radioactivity (200-2,000 GBq/micromol at the end of synthesis).

A method for model-free partial volume correction in oncological PET

BackgroundAs is well known, limited spatial resolution leads to partial volume effects (PVE) and consequently to limited signal recovery. Determination of the mean activity concentration of a target structure is thus compromised even at target sizes much larger than the reconstructed spatial resolution. This leads to serious size-dependent underestimates of true signal intensity in hot spot imaging. For quantitative PET in general and in the context of therapy assessment in particular it is, therefore, mandatory to perform an adequate partial volume correction (PVC). The goal of our work was to develop and to validate a model-free PVC algorithm for hot spot imaging.MethodsThe algorithm proceeds in two automated steps. Step 1: estimation of the actual object boundary with a threshold based method and determination of the total activity A measured within the enclosed volume V. Step 2: determination of the activity fraction B, which is measured outside the object due to the partial volume effect (spill-out). The PVE corrected mean value is then given by Cmean = (A+B)/V. For validation simulated tumours were used which were derived from real patient data (liver metastases of a colorectal carcinoma and head and neck cancer, respectively). The simulated tumours have characteristics (regarding tumour shape, contrast, noise, etc.) which are very similar to those of the underlying patient data, but the boundaries and tracer accumulation are exactly known. The PVE corrected mean values of 37 simulated tumours were determined and compared with the true mean values.ResultsFor the investigated simulated data the proposed approach yields PVE corrected mean values which agree very well with the true values (mean deviation (± s.d.): (−0.8±2.5)%).ConclusionsThe described method enables accurate quantitative partial volume correction in oncological hot spot imaging.

Studies on the synthesis of 16α-[18F]fluoroestradiol

Abstract For preparing 16α-[18F]fluoroestradiol, a new one-pot procedure reported in the literature was elaborated in detail. The experimental conditions for synthesizing the required precursor and for converting it into 16α-fluoroestradiol or 16α-[18F]fluoroestradiol are given. The synthesis consists of the fluoridation reaction and hydrolysis reactions. For rapid hydrolysis of the fluorosteroid formed in the fluoridation reaction two methods are presented. The synthesis time does not exceed 1 h. Pure 16α-[18F]fluoroestradiol can be obtained in a 70% overall radiochemical yield.