Patient-specific dosimetry for intracavitary 32P-chromic phosphate colloid therapy of cystic brain tumours

Brachytherapy in craniopharyngiomas: a systematic review and meta-analysis of long-term follow-up

OBJECTIVE

Brachytherapy has been indicated as an alternative option for treating cystic craniopharyngiomas (CPs). The potential benefits of brachytherapy for CPs have not yet been clarified. The purpose of this work was to conduct a meta-analysis to analyze the long-term efficacy and adverse reactions profile of brachytherapy for CPs.

MATERIALS AND METHODS

The relevant databases were searched to collect the clinical trials on brachytherapy in patients with CPs. Included studies were limited to publications in full manuscript form with at least 5-year median follow-up, and adequate reporting of treatment outcomes and adverse reactions data. Stata 12.0 was used for data analysis.

RESULTS

According to the inclusion and exclusion criteria, a total of 6 clinical trials involving 266 patients with CPs were included in this meta-analysis. The minimum average follow-up was 5 years. The results of the meta-analysis showed that 1-year, 2-3 years and 5 years progression free survival rates (PFS) are 75% (95%CI: 66-84%), 62% (95%CI: 52-72%) and 57% (95%CI: 22-92%), respectively. At the last follow-up, less than 16% of patients with visual outcomes worser than baseline in all included studies. While, for endocrine outcomes, less than 32% of patients worser than baseline level.

CONCLUSION

In general, based on the above results, brachytherapy should be considered as a good choice for the treatment of CP.

Response assessment in pediatric craniopharyngioma: recommendations from the Response Assessment in Pediatric Neuro-Oncology (RAPNO) Working Group

BACKGROUND

Craniopharyngioma is a histologically benign tumor of the suprasellar region for which survival is excellent but quality of life is often poor secondary to functional deficits from tumor and treatment. Standard therapy consists of maximal safe resection with or without radiation therapy. Few prospective trials have been performed, and response assessment has not been standardized.

METHODS

The Response Assessment in Pediatric Neuro-Oncology (RAPNO) committee devised consensus guidelines to assess craniopharyngioma response prospectively.

RESULTS

Magnetic resonance imaging is the recommended radiologic modality for baseline and follow-up assessments. Radiologic response is defined by 2-dimensional measurements of both solid and cystic tumor components. In certain clinical contexts, response to solid and cystic disease may be differentially considered based on their unique natural histories and responses to treatment. Importantly, the committee incorporated functional endpoints related to neuro-endocrine and visual assessments into craniopharyngioma response definitions. In most circumstances, the cystic disease should be considered progressive only if growth is associated with acute, new-onset or progressive functional impairment.

CONCLUSIONS

Craniopharyngioma is a common pediatric central nervous system tumor for which standardized response parameters have not been defined. A RAPNO committee devised guidelines for craniopharyngioma assessment to uniformly define response in future prospective trials.

Brachytherapy in paediatric craniopharyngiomas: a systematic review and meta-analysis of recent literature

PURPOSES

Brachytherapy has been indicated as an alternative option for treating cystic craniopharyngiomas. Despite the difficulties regarding the complex nuclear infrastructure and consequent small number of brachytherapy studies, recent discoveries relating tumour characteristics to sensitivity to brachytherapy have stimulated this extensive systematic review and meta-analysis of the recent results aiming to summarise its efficacy and complications.

METHODS

The systematic review was structured using PRISMA statements. The MEDLINE database was systematically reviewed from March 2010 to February 2021 to identify qualified trials dealing with radioisotope brachytherapy in cystic craniopharyngiomas in the paediatric population, emphasising tumour control rates and complications.

RESULTS

A total of 228 individuals were analysed, of which 66 were children. The minimum average follow-up was 5 years. Considering the paediatric trials, partial and complete responses were achieved in 89% of patients with exclusively cystic lesions, compared to 58% in non-exclusively cystic lesions. The former observed progression in 3% of patients, while in the latter, 35% was reported. Visual and endocrine improvement reached 64% and 20%, respectively, in the first group, in contrast to 48% and 7% in the second group, respectively. There were similar results considering the non-exclusive paediatric series, but with less expressive numbers.

CONCLUSION

These results reinforce the positive impact of radioisotope brachytherapy in the treatment of predominant monocystic or multicystic craniopharyngiomas, especially in the paediatric population, grounded by impressive tumour control rates, lower morbidities and single application in the majority of the cases. In the future, specific morphological tumour characteristics might be considered for a more assertive patient selection.

Phase II study of peginterferon alpha-2b for patients with unresectable or recurrent craniopharyngiomas: a Pediatric Brain Tumor Consortium report

BACKGROUND

Craniopharyngiomas account for approximately 1.2-4% of all CNS tumors. They are typically treated with a combination of surgical resection and focal radiotherapy. Unfortunately, treatment can lead to permanent deleterious effects on behavior, learning, and endocrine function.

METHODS

The Pediatric Brain Tumor Consortium performed a multicenter phase 2 study in children and young adults with unresectable or recurrent craniopharyngioma (PBTC-039). Between December 2013 and November 2017, nineteen patients (median age at enrollment, 13.1 y; range, 2-25 y) were enrolled in one of 2 strata: patients previously treated with surgery alone (stratum 1) or who received radiation (stratum 2).

RESULTS

Eighteen eligible patients (8 male, 10 female) were treated with weekly subcutaneous pegylated interferon alpha-2b for up to 18 courses (108 wk). Therapy was well tolerated with no grade 4 or 5 toxicities. 2 of the 7 eligible patients (28.6%) in stratum 1 had a partial response, but only one response was sustained for more than 3 months. None of the 11 stratum 2 patients had an objective radiographic response, although median progression-free survival was 19.5 months.

CONCLUSIONS

Pegylated interferon alpha-2b treatment, in lieu of or following radiotherapy, was well tolerated in children and young adults with recurrent craniopharyngiomas. Although objective responses were limited, progression-free survival results are encouraging, warranting further studies.

Rhein-PEG-nHA conjugate as a bone targeted drug delivery vehicle for enhanced cancer chemoradiotherapy

Bone-targeted therapies have been the choice of treatments for cancer metastases in bone to minimize skeletal morbidity and preserve patients' quality of life. Rhein is of particular interest due to its high bone affinity. Here we reported a novel Rhein- polyethylene glycol (PEG)-nano hydroxyapatite (nHA) conjugate to deliver doxorubicin (DOX) and Phosphorus-32 (³²P) simultaneously for enhanced cancer chemo-radiotherapy. The synthetic Rhein-PEG-nHA conjugates were sphere in shape with an average diameter of ~120 nm. Their morphology, drug release and bone affinity were confirmed in vitro. The release profiles of DOX depend on pH condition, but ³²P exhibited good stability. Rhein-PEG-nHA also showed high bone affinity in vivo, and the tumor volume decreased after the DOX@Rhein-PEG-nHA and ³²P@Rhein-PEG-nHA treatments. Most importantly, the DOX/³²P@Rhein-PEG-nHA showed the strongest inhibition on the growth of bone metastases of breast cancer. We revealed the potential of Rhein-PEG-nHA in combined chemo-radiation treatment for bone metastases of breast cancer.

Evaluation of Bremsstrahlung radiation dose in stereotactically radiocolloid therapy of cystic craniopharyngioma tumors with 32P radio-colloid

Over 90% of craniopharyngeal brain tumors are cystic, which enables the injection of beta emitters such as phosphorus-32 (³²P) radio-colloid into cysts for their treatment. The aim of this study was to evaluate the clinical and theoretical modelling of Bremsstrahlung radiation dose resulting from stereotactic radio-colloid therapy of cystic craniopharyngioma tumors with ³²P. ³²P radio-colloid with appropriate activity concentration was injected to a head phantom, and then the Bremsstrahlung radiation spectrum and planar images were obtained using a gamma camera. Both phantom and gamma camera were simulated using MCNPX code, and the results were compared with practical results. Bremsstrahlung radiation spectrum was measured using a handheld gamma spectrometer for two patients treated with stereotactic radio-colloid therapy with ³²P in different positions and compared to Monte Carlo simulation. Results of counting and determining sensitivity coefficients in the air and the attenuating environment were obtained. Also, comparing the counting sensitivity from practical and simulation methods indicated the agreement of the data between the two methods. Comparison of the spectra from different positions around patient's head indicated the ability to use this detector to quantify the activity in the operating room. Selection of the spectrum is important in Bremsstrahlung radiation imaging. We can take advantage of spectrometry measurement using gamma camera, handheld gamma spectrometer for patient, and theoretical modeling with Monte Carlo code to evaluate radiopharmaceutical distribution, leakage, as well as estimate activity and predict therapeutic effects in other adjacent structures and ultimately optimize radio-colloid therapy in cystic craniopharyngeal patients.

Investigation of Newly Prepared Biodegradable 32P-chromic Phosphate-polylactide-co-glycolide Seeds and Their Therapeutic Response Evaluation for Glioma Brachytherapy

³²P high-dose rate brachytherapy allows high-dose radiation delivery to target lesions with less damage to adjacent tissues. The early evaluation of its therapeutic effect on tumours is vital for the optimization of treatment regimes. The most commonly used ³²P-CP colloid tends to leak with blind therapeutic area after intratumour injection. We prepared ³²P-chromic phosphate-polylactide-co-glycolide (³²P-CP-PLGA) seeds with biodegradable PLGA as a framework and investigated their characteristics in vitro and in vivo. We also evaluated the therapeutic effect of ³²P-CP-PLGA brachytherapy for glioma with the integrin αvβ3-targeted radiotracer ⁶⁸Ga-3PRGD₂. ³²P-CP-PLGA seeds (seed group, SG, 185 MBq) and ³²P-CP colloid (colloid group, CG, 18.5 MBq) were implanted or injected into human glioma xenografts in nude mice. Scanning electron microscopy (SEM) of the seeds, micro-SPECT imaging, and biodistribution studies were performed at different time points. The tumour volume was measured using a caliper, and ⁶⁸Ga-3PRGD₂ micro-PET-CT imaging was performed to evaluate the therapeutic effect after ³²P intratumour administration. The delayed release of ³²P-CP was observed with biodegradation of vehicle PLGA. Intratumoural effective half-life of ³²P-CP in the SG (13.3 ± 0.3) d was longer than that in the CG (10.4 ± 0.3) d (P < 0.05), with liver appearance in the CG on SPECT. A radioactivity gradient developed inside the tumour in the SG, as confirmed by micro-SPECT and SEM. Tumour uptake of ⁶⁸Ga-3PRGD₂ displayed a significant increase on day 0.5 in the SG and decreased earlier (on day 2) than the volume reduction (on day 8). Thus, ³²P-CP-PLGA seeds, controlling the release of entrapped ³²P-CP particles, are promising for glioma brachytherapy, and ⁶⁸Ga-3PRGD₂ imaging shows potential for early response evaluation of ³²P-CP-PLGA seeds brachytherapy.

Drug distribution and clinical safety in treating cystic craniopharyngiomas using intracavitary radiotherapy with phosphorus-32 colloid

The present study evaluated drug distribution and clinical safety in treating patients with cystic craniopharyngioma (CP) with intracavitary radiotherapy using phosphorus-32 (³²P) colloid. In total, 40 patients who were recently diagnosed with primary or recurrent cystic CP were enrolled into the study. Patients underwent stereotactic intracavitary therapy and were administered ³²P colloid and iopamidol-300 (1:1 dilution). Head computed tomography (CT) scans were performed 2 h after surgery in order to assess drug distribution and leakage. Results obtained from the ophthalmic examination (visual acuity, visual field and fundus), enhanced head magnetic resonance imaging and/or CT scans, blood analysis, coagulation tests, electrolyte tests, pituitary hormone level analysis, and hepatic and renal function tests were compared between the 0.5, 1, 1.5 and 2 mCi groups. The ³²P colloid per minute radioactive count was quantitatively measured in urine and blood samples using a CAPRAC well-type NaI γ counter at 1, 3 and 7 days post-surgery. In total, 6, 2 and 1 case(s) from the 2, 1.5 and 1 mCi groups, respectively, demonstrated heterogeneous drug distribution and intracavitary cerebrospinal fluid leakage. Furthermore, out of 24 patients, no significant differences were identified in blood analysis, blood biochemical measurements and pituitary hormone levels prior to and 7 days after surgery. Blood ³²P deposition returned to normal levels within 3 days after surgery, whereas urine deposition returned to normal within 7 days after surgery. Methods utilized in the present study were advantageous in terms of convenience, speed and low cost, therefore, these techniques are suitable for continuous monitoring of patient ³²P colloid deposition.

Phase I/II trials of 186Re-HEDP in metastatic castration-resistant prostate cancer: post-hoc analysis of the impact of administered activity and dosimetry on survival

PURPOSE

To investigate the role of patient-specific dosimetry as a predictive marker of survival and as a potential tool for individualised molecular radiotherapy treatment planning of bone metastases from castration-resistant prostate cancer, and to assess whether higher administered levels of activity are associated with a survival benefit.

METHODS

Clinical data from 57 patients who received 2.5-5.1 GBq of 186Re-HEDP as part of NIH-funded phase I/II clinical trials were analysed. Whole-body and SPECT-based absorbed doses to the whole body and bone lesions were calculated for 22 patients receiving 5 GBq. The patient mean absorbed dose was defined as the mean of all bone lesion-absorbed doses in any given patient. Kaplan-Meier curves, log-rank tests, Cox's proportional hazards model and Pearson's correlation coefficients were used for overall survival (OS) and correlation analyses.

RESULTS

A statistically significantly longer OS was associated with administered activities above 3.5 GBq in the 57 patients (20.1 vs 7.1 months, hazard ratio: 0.39, 95 % CI: 0.10-0.58, P = 0.002). A total of 379 bone lesions were identified in 22 patients. The mean of the patient mean absorbed dose was 19 (±6) Gy and the mean of the whole-body absorbed dose was 0.33 (±0.11) Gy for the 22 patients. The patient mean absorbed dose (r = 0.65, P = 0.001) and the whole-body absorbed dose (r = 0.63, P = 0.002) showed a positive correlation with disease volume. Significant differences in OS were observed for the univariate group analyses according to disease volume as measured from SPECT imaging of 186Re-HEDP (P = 0.03) and patient mean absorbed dose (P = 0.01), whilst only the disease volume remained significant in a multivariable analysis (P = 0.004).

CONCLUSION

This study demonstrated that higher administered activities led to prolonged survival and that for a fixed administered activity, the whole-body and patient mean absorbed doses correlated with the extent of disease, which, in turn, correlated with survival. This study shows the importance of patient stratification to establish absorbed dose-response correlations and indicates the potential to individualise treatment of bone metastases with radiopharmaceuticals according to patient-specific imaging and dosimetry.

Pre-clinical quantitative imaging and mouse-specific dosimetry for 111In-labelled radiotracers

BACKGROUND

Accurate quantification in molecular imaging is essential to improve the assessment of novel drugs and compare the radiobiological effects of therapeutic agents prior to in-human studies. The aim of this study was to investigate the challenges and feasibility of pre-clinical quantitative imaging and mouse-specific dosimetry of 111In-labelled radiotracers. Attenuation, scatter and partial volume effects were studied using phantom experiments, and an activity calibration curve was obtained for varying sphere sizes. Six SK-OV-3-tumour bearing mice were injected with 111In-labelled HER2-targeting monoclonal antibodies (mAbs) (range 5.58-8.52 MBq). Sequential SPECT imaging up to 197 h post-injection was performed using the Albira SPECT/PET/CT pre-clinical scanner. Mice were culled for quantitative analysis of biodistribution studies. The tumour activity, mass and percentage of injected activity per gram of tissue (%IA/g) were calculated at the final scan time point and compared to the values determined from the biodistribution data. Delivered 111In-labelled mAbs tumour absorbed doses were calculated using mouse-specific convolution dosimetry, and absorbed doses for 90Y-labelled mAbs were extrapolated under the assumptions of equivalent injected activities, biological half-lives and uptake distributions as for 111In.

RESULTS

For the sphere sizes investigated (volume 0.03-1.17 ml), the calibration factor varied by a factor of 3.7, whilst for the range of tumour masses in the mice (41-232 mg), the calibration factor changed by a factor of 2.5. Comparisons between the mice imaging and the biodistribution results showed a statistically significant correlation for the tumour activity (r = 0.999, P < 0.0001) and the tumour mass calculations (r = 0.977, P = 0.0008), whilst no correlation was found for the %IA/g (r = 0.521, P = 0.29). Median tumour-absorbed doses per injected activity of 52 cGy/MBq (range 36-69 cGy/MBq) and 649 cGy/MBq (range 441-950 cGy/MBq) were delivered by 111In-labelled mAbs and extrapolated for 90Y-labelled mAbs, respectively.

CONCLUSIONS

This study demonstrates the need for multidisciplinary efforts to standardise imaging and dosimetry protocols in pre-clinical imaging. Accurate image quantification can improve the calculation of the activity, %IA/g and absorbed dose. Diagnostic imaging could be used to estimate the injected activities required for therapeutic studies, potentially reducing the number of animals used.