A Retrospective Comparative Study of Sodium Fluoride Na18F-PET/CT and 68Ga-PSMA-11 PET/CT in the Bone Metastases of Prostate Cancer Using a Volumetric 3-D Radiomic Analysis.

Bone is the most common metastatic site in prostate cancer (PCa). 68Ga-PSMA-11 (or gozetotide) and sodium fluoride-18 (Na18F) are rather new radiopharmaceuticals for assessing PCa-associated bone metastases. Gozetotide uptake reflects cell membrane enzyme activity and the sodium fluoride uptake measures bone mineralization in advanced PCa. Here, we aim to characterize this difference and possibly provide a new method for patient selection in targeted therapies. Methods: The study consisted of 14 patients with advanced PCa (M group > 5 lesions), who had had routine PET/CT both with PSMA and NaF over consecutive days, and 12 PCa patients with no skeletal metastases (N). The bone regions in CT were used to coregister the two PET/CT scans. The whole skeleton volume(s) of interest (VOIs) were defined using the CT component of PET (HU > 150); similarly, the sclerotic/dense bone was defined as HU > 600. Additional VOIs were defined for PET, with pathological threshold values for PSMA (SUV > 3.0) and NaF (SUV > 10). Besides the pathological bone volumes measured with each technique (CT, NaF, and PSMA-PET) and their contemporaneous combinations, overlapping VOIs with the CT-based skeletal and sclerotic volumes were also recorded. Additionally, thresholds of 4.0, 6.0, and 10.0 were tested for SUVPSMA. Results: In group M, the skeletal VOI volumes were 8.77 ± 1.80 L, and the sclerotic bone volumes were 1.32 ± 0.50 L; in contrast, in group N, they were 8.73 ± 1.43 L (skeletal) and 1.23 ± 0.28 L (sclerosis). The total enzyme activity for PSMA was 2.21 ± 5.15 in the M group and 0.078 ± 0.053 in the N group (p < 0.0002). The total bone demineralization activity for NaF varied from 4.31 ± 6.17 in the M group and 0.24 ± 0.56 in group N (p < 0.0002). The pathological PSMA volume represented 0.44−132% of the sclerotic bone volume in group M and 0.55−2.3% in group N. The pathological NaF volume in those patients with multiple metastases represented 0.27−68% of the sclerotic bone volume, and in the control group, only 0.00−6.5% of the sclerotic bone volume (p < 0.0003). Conclusions: These results confirm our earlier findings that CT alone does not suit the evaluation of the extent of active skeletal metastases in PCa. PSMA and NaF images give complementary information about the extent of the active skeletal disease, which has a clinical impact and may change its management. The PSMA and NaF absolute volumes could be used for planning targeted therapies. A cut-off value 3.0 for SUVPSMA given here is the best correlation in the presentation of active metastatic skeletal disease.

Single Center Experience with a 4-Week 177Lu-PSMA-617 Treatment Interval in Patients with Metastatic Castration-Resistant Prostate Cancer.

Background: 177Lu-PSMA-617 is a promising theragnostic treatment for metastatic castration-resistant prostate cancer (mCRPC). However, both the optimal treatment dose and interval in mCRPC and the rate of identification of responders from non-responders among possible treatment candidates are unknown. Methods: 62 men with mCRPC who were treated with 177Lu-PSMA-617 during 1/2017−2/2019 were included in the study. Treatment responses, overall survival (OS) and progression free survival (PFS) were determined. The median follow-up time was 1.4 years (IQR 0.5−2.2). Tumor volume of metastases (MTV), SUVmax and tumor lesion activity (TLA) were quantitated from pre-treatment PSMA PET/CT images together with pre-treatment PSA. Results: An average of three treatment cycles (2−5) were given within a four-week interval. PFS was 4.9 months (2.4−9.6) and OS was 17.2 months (6−26.4). There were no major adverse events reported. A significant PSA response of >50% was found in 58.7% of patients, which was significantly associated with longer OS, p < 0.004. PSA response was not associated with staging PSMA-derived parameters. Conclusions: 177Lu-PSMA-617 treatment in four-week intervals was safe and effective. Almost 60% of patients had a significant PSA response, which was associated with better OS. Pre-treatment PSA kinetics or staging PSMA PET/CT-derived parameters were not helpful in identifying treatment responders from non-responders; better biomarkers are needed to aid in patient selection.

Eye Symptoms in a Patient With Prostate Cancer.

A 66-year-old man with castration-resistant prostate cancer was evaluated with F-prostate-specific membrane antigen (PSMA) 1007 PET/CT, which revealed extensive PSMA-positive skeletal metastases in the skull, thorax, spine, pelvis, and extremities. He was then treated Lu-PSMA-617 therapy. Twenty-four-hour SPECT/CT revealed additional activity not seen with F-PSMA adjacent to his left eye. The lesion was biopsied after the first cycle due to pain. This activity was not visible on SPECT/CT after the second treatment cycle, and his eye pain has resolved.

Comparison of I-131 Biokinetics after Recombinant Human TSH Stimulation and Thyroid Hormone Withdrawal Measured by External Detector in Patients with Differentiated Thyroid Cancer.

The aim of this study was to compare radioactive iodine (I-131) biokinetics after recombinant human TSH stimulation (rhTSH) and thyroid hormone withdrawal (THW) in patients with differentiated thyroid cancer (DTC). External effective dose rates were measured using external detectors and imaged quantitatively at the time of discharge from the isolation wards. We retrospectively analyzed 32 patients who had been diagnosed with DTC, papillary or follicular, and underwent remnant ablation after either rhTSH stimulation (n=22) or THW (n=10). The uptake of I-131 by remnant thyroid tissue was measured from 20.0 cm, 100.0 cm and 200.0 cm distances using a handheld external detector. The remnant thyroid tissue measured by the whole body images two to five days from administration was 10.7+26.0% (range 0.5 to 60.0%). The values measured at 20 cm were best correlated to the thyroid residual uptake measured by SPECT/CT. The half-lives of I-131washout (T1/2) in rhTSH group measured by external detector were shorter than those of THW group. T1/2 becomes longer when it was measured over longer distances. They were 10.9, 12.3 and 13.1 hours at distances of 20, 100, and 200 cm in rhTSH group, respectively. The TWH group showed 12.8, 14.9 and 17.7 hours, respectively. We conclude that I-131 biokinetics can be measured by external detector after high dose I-131 therapy for DTC. It showed that washout of I-131 was faster after rhTSH stimulation than THW, and slower in patients with distant metastasis than those without metastasis.

Multimodal Primary Treatment of Metastatic Prostate Cancer with Androgen Deprivation and Radiation.

AIM: We combined anti-androgen therapy with radiotherapy in a first-line setting for metastatic prostate cancer aiming to cause maximal cancer-cell death to delay the emergence of castration-resistant disease. MATERIALS AND METHODS: In this non-randomized retrospective series of 46 patients, the initial median prostate-specific antigen (PSA) was 98.5 µg/l (range=6.7-15,500), median Gleason score 9 and most men had at least T3N1M1 disease. All patients received luteinizing hormone releasing hormone analog or degarelix with bicalutamide. If PSA remained above 1 µg/l, docetaxel was initiated. At PSA nadir, all patients received radical radiotherapy of the prostate. RESULTS: The median follow-up time was 4.38 years (range=0.36-11.24). Most radiotherapy-related adverse events were grade 1 and transient. There were no grade 4 events. Overall survival (OS) at 5 years was 81.3%. CONCLUSION: The feasibility and safety of aggressive multimodality treatment were good resulting in an excellent median OS of 8.35 years.

Imaging of Accidental Contamination by Fluorine-18 Solution: A Quick Troubleshooting Procedure.

To the best of our knowledge, imaging of accidental exposure to radioactive fluorine-18 (F-18) due to liquid spill has not been described earlier in the scientific literature. The short half-life of F-18 (t½=110 min), current radiation safety requirements, and Good Manufacturing Practice (GMP) regulations on radiopharmaceuticals have restrained the occurrence of these incidents. The possibility of investigating this type of incidents by gamma and positron imaging is also quite limited. Additionally, a quick and precise analysis of radiochemical contamination is cumbersome and sometimes challenging if the spills of radioactive materials are low in activity. Herein, we report a case of accidental F-18 contamination in a service person during a routine cyclotron maintenance procedure. During target replacement, liquid F-18 was spilled on the person responsible for the maintenance. The activities of spills were immediately measured using contamination detectors, and the photon spectrum of contaminated clothes was assessed through gamma spectroscopy. Despite protective clothing, some skin areas were contaminated, which were then thoroughly washed. Later on, these areas were imaged, using positron emission tomography (PET), and a gamma camera (including spectroscopy). Two contaminated skin areas were located on the hand (9.7 and 14.7 cm2, respectively), which showed very low activities (19.0 and 22.8 kBq respectively at the time of incident). Based on the photon spectra, F-18 was confirmed as the main present radionuclide. PET imaging demonstrated the shape of these contaminated hot spots. However, the measured activities were very low due to the use of protective clothing. With prompt action and use of proper equipments at the time of incident, minimal radionuclide activities and their locations could be thoroughly analyzed. The cumulative skin doses of the contaminated regions were calculated at 1.52 and 2.00 mSv, respectively. In the follow-up, no skin changes were observed in the contaminated areas.

Radiotherapy Boost for the Dominant Intraprostatic Cancer Lesion-A Systematic Review and Meta-Analysis.

External beam radiotherapy (EBRT) for prostate cancer can be performed with a high dose of 86 Gy; however, one-tenth or more of the patients will develop recurrence. Prostate cancer is mainly multifocal, but a dominant intraprostatic lesion (DIL) is often the site of local recurrence after EBRT. We undertook a systematic review and meta-analysis to clarify whether functional imaging might identify the DIL and whether a RT boost to the DIL might be increased to an ultrahigh dose level of ≥ 90 Gy without increased toxicity. Of 62 selected studies, 13 reported the size of the DIL. The mean of the median DIL volumes was 2.4 cm(3) (95% confidence interval, 0.9-4.4 cm(3)). Eighteen diagnostic studies with 1205 patients evaluated the diagnostic accuracy using multiparametric magnetic resonance imaging for intraprostatic cancer lesions. Evaluating 14,654 prostate segments, the diagnostic accuracy was 77%. Eleven therapeutic studies with 988 patients reported a RT boost for the DIL. The summary boost dose for the DIL was a mean of 89 Gy in 5 studies using intensity modulated RT (calculated as the equivalent dose in 2-Gy fractions) and a mean of 141 Gy in 4 studies using a combination of EBRT and brachytherapy (P = .018, t test). In 1 therapeutic study, 239 patients had a 98% 10-year disease-free survival rate. Many of our therapeutic studies used a boost dose to the DIL of > 90 Gy. The reported boost for DIL is effective and safe.

PET/CT Dose Planning for Volumetric Modulated Arc Radiation Therapy (VMAT) -Comparison with Conventional Approach in Advanced Prostate Cancer Patients.

Molecular imaging is the only way of defining biological target volume (BTV) for externalbeam radiation therapy (EBRT) and may be used for advanced targeting in dose planning and dose painting. There are, however, no reports about the EBRT response when dose planning is based on BTV target definition in advanced prostate cancer. Clinical and biochemical results of two clinically equal group of patients with advanced prostate cancer patients were compared. Both groups were treated with volumetric modulated arc therapy (VMAT) based on target definition by PET/CT (1(st) group) or conventional imaging (2(nd) group). Biochemical relapse occurred in 16.6% (in 1 out of 6) of the patients in the first group and 50% (3 out of 6) patients in the second group during the follow up period. Clinical manifestation of disease occurred in 33% (2 out of 6) patients of the first group and in 5 out of 6 (83,3%) patients in the second one. 4 patients in the first group had no biochemical relapse and no clinical manifestation during the follow up period. The difference in the duration of progression free period was statistically significant between the groups (p<0.010) being in the first group 16.5±5.4 (10-24) months and 4.6±2.9 (2-10) months in the second one. Because patients with PET/CT based VMAT had lower incidence of biochemical relapse, less clinical manifestations and longer, statistically significant duration of progression free period as compared to patients treated with VMAT based on conventional imaging, our preliminary results suggest introducing BTV definition based on PET imaging for VMAT in the EBRT of prostate cancer.

VMAT technique enables concomitant radiotherapy of prostate cancer and pelvic bone metastases.

BACKGROUND: Prostate cancer (PCa) patients with metastatic disease often suffer from skeletal pain and urinary retention impairing their quality of life. Prophylactic radiotherapy to bone metastases planned concomitantly with primary PCa radiotherapy could enable more precise control of combined dose in healthy tissues when compared to sequential palliative treatment. MATERIALS AND METHODS: Volumetric modulated arc therapy (VMAT) was planned for 14 PCa patients with primary bone metastases. The bone planning target volume (PTVbone) was contoured together with the PTVs of prostate (pr), pelvic lymph nodes (ln) and seminal vesicles (sv). Another virtual plan was calculated excluding PTVbone for dose volume histogram (DVH) comparison. DVHs were additionally compared to a set of actual VMAT treatment plans of a control cohort of 13 high risk PCa patients treated with PTVpr, PTVsv and PTVln. The prescribed doses varied between 42 and 76 Gy for PTVbone. RESULTS: Recommended healthy tissue tolerances (Quantec) were not exceeded except for one patient's rectum V50Gy value. Rectum doses did not increase significantly due to the inclusion of PTVbone. For bladder, there was a slight increase for V65Gy and V50Gy (2.7% and 7.4%). The DVHs of metastatic and non-metastatic patients were comparable. There were no differences in the PTVpr DVH parameters, while mean PTVln dose increased by 3.7 Gy-4.4 Gy due to the increased treatment volume related to PTVbone. All side effects were

Evaluation of Alpha-Therapy with Radium-223-Dichloride in Castration Resistant Metastatic Prostate Cancer-the Role of Gamma Scintigraphy in Dosimetry and Pharmacokinetics.

Radium-223-dichloride ((223)RaCl2) is a new bone-seeking calcium analogue alpha-emitter, which has obtained marketing authorization for the treatment skeletal metastases of hormone-refractory prostate cancer. The current treatment regimen is based on six consecutive doses of (223)RaCl2 at 4 week intervals and the administered activity dose, 50 kBq/kg per cycle is based on patient weight. We analyzed two patients using quantitative serial gamma imaging to estimate dosimetry in tumors and see possible pharmacokinetic differences in the treatment cycles. The lesions were rather well visualized in gamma scintigraphy in spite of low gamma activity (<1.1% gamma radiation) at 0, 7 and 28 days using 30-60 min acquisition times. Both our patients analyzed in serial gamma imagings, had two lesions in the gamma imaging field, the mean counts of the relative intensity varied from 27.8 to 36.5 (patient 1), and from 37.4 to 82.2 (patient 2). The half-lives varied from 1.8 days to 4.5 days during the six cycles (patient 1), and from 1.5 days to 3.6 days (patient 2), respectively. In the lesion half-lives calculated from the imaging the maximum difference between the treatment cycles in the same lesion was 2.0-fold (1.8 vs. 3.6). Of these patients, patient 1 demonstrated a serum PSA response, whereas there was no PSA response in patient 2. From our data, there were maximally up to 4.0-fold differences (62.1 vs. 246.6 ) between the relative absorbed radiation doses between patients as calculated from the quantitative standardized imaging to be delivered in only two lesions, and in the same lesion the maximum difference in the cycles was up to 2.3-fold (107.4 vs. 246.6). Our recommendation based on statistical simulation analysis, is serial measurement at days 0-8 at least 3 times, this improve the accuracy significantly to study the lesion activities, half-lives or calculated relative absorbed radiation doses as calculated from the imaging. Both our patients had originally two metastatic sites in the imaging field; the former patient demonstrated a serum PSA response and the latter demonstrated no PSA response. In these two patients there was no significant difference in the lesion activities, half-lives or calculated relative absorbed radiation doses as calculated from the quantitative imaging. Our results, although preliminary, suggest that dose monitoring can be included as a part of this treatment modality. On the other hand, from the absorbed radiation doses, the response cannot be predicted because with very similar doses, only the former patient responded.

Volumetric-modulated arc therapy for a pelvic lymph node metastasis from prostate cancer: a case report.

A 50-year-old patient had an early biochemical recurrence after radical prostatectomy and androgen deprivation therapy and castration. An anti-1-amino-3-[¹8F] fluorocyclobutane-1-carboxylic acid positron emission tomography/computed tomography scan showed a single pelvic lymph node metastasis. The patient was given volume-modulated arc therapy with a cumulative dose of 50 Gy for the volume with pelvic lymph nodes and 78 Gy to the boost volume for the lymph node metastasis. He experienced only a transitory mild toxicity from the rectum and the urinary bladder and had a partial remission for 16 months.

4D SPECT/CT acquisition for 3D dose calculation and dose planning in (177)Lu-peptide receptor radionuclide therapy: applications for clinical routine.

Molecular radiotherapy combines the potential of a specific tracer (vector) targeting tumor cells with local radiotoxicity. Designing a specific tumor-targeting/killing combination is a tailoring process. Radionuclides with imaging capacity serve best in the selection of the targeting molecule. The potential of targeted therapy with radiolabeled peptides has been reported in many conditions; peptide receptor radionuclide therapy (PRRT) is already part of Scandinavian guidelines for treating neuroendocrine tumors. Lu-177- and Y-90-labeled somatostatin analogs, including DOTATOC, DOTANOC, and DOTATATE, are most the commonly used and have turned out to be effective. For routine use, an efficient, rapid, and reliable dose calculation tool is needed. In this chapter we describe how serial pre- and posttherapeutic scans can be used for dose calculation and for predicting therapy doses. Our software for radionuclide dose calculation is a three-dimensional, voxel-based system. The 3D dose calculation requires coregistered SPECT image sets from several time points after infusion to reconstruct time-activity curves for each voxel. Image registration is done directly by SPECT image registration using the first time point as a target. From the time-activity curves, initial activity and total half-life maps are calculated to produce a cumulated activity map. The cumulated activity map is then convoluted with a voxel-dose kernel to obtain a 3D dose map. We performed dose calculations similarly for both therapeutic and preplanning images. Preplanning dose was extrapolated to predict therapy dose using the ratio of administered activities. Our 3D dose calculation results are also compared with those of OLINDA. Our preliminary results indicate that dose planning using pretherapeutic scanning can predict critical organ and tumor doses. In some cases, the dose planning prediction resulted in slight, and slightly dose-dependent, overestimation of final therapy dose. Real tumor dose was similar in both pretherapeutic and posttherapeutic scans using our software. The OLINDA software and our program gave similar normal organ doses, whereas tumor doses could be calculated in a more detailed manner using the 3D program.

Comparison of in vitro breast cancer visibility in analyser-based computed tomography with histopathology, mammography, computed tomography and magnetic resonance imaging.

High-resolution analyser-based X-ray imaging computed tomography (HR ABI-CT) findings on in vitro human breast cancer are compared with histopathology, mammography, computed tomography (CT) and magnetic resonance imaging. The HR ABI-CT images provided significantly better low-contrast visibility compared with the standard radiological images. Fine cancer structures indistinguishable and superimposed in mammograms were seen, and could be matched with the histopathological results. The mean glandular dose was less than 1 mGy in mammography and 12-13 mGy in CT and ABI-CT. The excellent visibility of in vitro breast cancer suggests that HR ABI-CT may have a valuable role in the future as an adjunct or even alternative to current breast diagnostics, when radiation dose is further decreased, and compact synchrotron radiation sources become available.

[Modern radiation therapy]. / Moderni sädehoito.

For decades, radiation therapy has constituted one of the main forms of therapy for cancer, and has undergone rapid technical development. New techniques in radiotherapy make it possible to treat a tumor with larger doses than before, while at the same time reducing damage to healthy tissues. The development in imaging techniques has allowed a more precise delimitation of tumors and monitoring of the efficacy of therapy. Three-dimensional tumor delimitation and dose calculation have long been the standard in radiation therapy. Four-dimensional and functional imaging in defining the target area for radiation therapy is becoming part of routine radiotherapy.

Scintigraphy in prediction of the salivary gland function after gland-sparing intensity modulated radiation therapy for head and neck cancer.

BACKGROUND AND PURPOSE: To evaluate salivary gland scintigraphy in prediction of salivary flow following radiation therapy. PATIENTS AND METHODS: Twenty patients diagnosed with head and neck cancer were treated with intensity modulated radiation therapy with an intention to spare the salivary gland function. The total quantitative saliva secretion was measured prior to and 6 and 12 months after therapy, and the function of the major salivary glands was monitored using Tc-99m-pertechnetate scintigraphy. Two models were designed for prediction of the post-treatment salivary flow: an average model, based on the average proportions of saliva produced by each of the four major glands in healthy subjects, and an individual model, based on saliva produced by each gland as measured by scintigraphy prior to therapy. These models were compared with volume-based (Lyman) normal tissue complication probability models using two published sets of model parameters. RESULTS: The D(50) for the parotid and the submandibular gland function assessed at 6 and 12 months after radiotherapy was approximately 39Gy. The scintigraphy-based individual model predicted well the measured post-treatment saliva flow rates. The correlation coefficient between the predicted stimulated and the measured saliva flow rate was 0.77 (p<0.0001) at 6 months and 0.55 (p=0.034) at 12 months after completion of radiotherapy. The relative changes in unstimulated and stimulated salivary flow rates showed similar dependency on the cumulative radiation dose. CONCLUSIONS: Salivary gland function assessed by scintigraphy prior to radiotherapy is useful in prediction of the residual salivary flow after radiotherapy.

Brain function during multi-trial learning in mild cognitive impairment: a PET activation study.

We explored functional brain changes with positron emission tomography (PET) in mild cognitive impairment (MCI) patients and elderly normal controls by employing an episodic memory task that included two successive encoding trials of semantically related word-pairs and final retrieval. Both groups demonstrated significant learning across the two trials. The control group showed predominantly left frontal activity during encoding, and right frontal plus left temporal activity during retrieval. However, the MCI patients recruited partly different brain regions. They failed to activate right frontal and left temporal areas during retrieval, and failed to show any different activation for encoding on the first and second trials, whereas the controls activated a region of posterior cingulate. There was indication of compensatory increases in rCBF of the occipital cortex during incremental learning and the left frontal lobe during retrieval in the patients. These results suggest different episodic memory processing in the MCI group, and a possible over-reliance on semantic processing. Subtle functional changes occur in the pre-Alzheimer brain before there are marked structural or behavioural abnormalities.

Sparing of the submandibular glands by intensity modulated radiotherapy in the treatment of head and neck cancer.

BACKGROUND AND PURPOSE: The submandibular glands produce most of the unstimulated saliva output and are the key in prevention of radiation-related xerostomia. We investigated whether sparing of the submandibular function is feasible with intensity modulated radiotherapy (IMRT). PATIENTS AND METHODS: Thirty-six patients diagnosed with head and neck cancer were treated with IMRT and had at least one parotid gland excluded from the planning target volume. In a subset, of these patients (n=18) where the risk of cancer recurrence in the contralateral submandibular region was judged low, the contralateral submandibular gland was spared from full-dose irradiation. The total unstimulated and stimulated salivary flow rates and adverse effects were monitored. RESULTS: Twelve months following IMRT mean unstimulated saliva flow was 60% of the baseline value among patients who had one submandibular gland spared and 25% among those who did not (P=0.006). Patients whose contralateral submandibular was spared reported less grade two or three xerostomia (4 vs. 11; P=0.018), and used less saliva substitutes. No cancer recurrences were detected at the vicinity of the spared glands during a median follow-up time of 31 months. CONCLUSIONS: Submandibular gland sparing with IMRT is safe in selected patients treated for head and neck cancer. It is effective in prevention of radiation-associated xerostomia.