Radiation, Volume 4, Issue 2 (June 2024) – 4 articles

The physiological process of iodine uptake in the thyroid is used for ¹³¹I treatment of thyroid diseases. Children are more sensitive to radiation compared to adults and may react differently to ¹³¹I exposure. The aims of this study were to evaluate the effects on thyroid protein expression in young and adult rats one year after ¹³¹I injection and identify potential biomarkers related to ¹³¹I exposure, absorbed dose, and age. Twelve Sprague Dawley rats (young and adults) were i.v. injected with 50 kBq or 500 kBq ¹³¹I and killed twelve months later. Twelve untreated rats were used as age-matched controls. Quantitative proteomics, statistical analysis, and evaluation of biological effects were performed. The effects of irradiation were most prominent in young rats. Protein biomarker candidates were proposed related to age, absorbed dose, thyroid function, and cancer, and a panel was proposed for ¹³¹I exposure. In conclusion, the proteome of rat thyroid was differentially regulated twelve months after low-intermediate dose exposure to ¹³¹I in both young and adult rats. Several biomarker candidates are proposed for ¹³¹I exposure, age, and many of them are known to be related to thyroid function or thyroid cancer. Further research on human samples is needed for validation. Data are avaiable via ProteomeXchange with identifier PXD024786. Full article

PET/CT scans are being used to assess patients who have experienced biochemical failure following surgery or radiation therapy for localized prostate cancer. We aimed to evaluate the language used in report impressions and to determine the level of confidence that radiologists have when reporting on lesions in various anatomic sites. Between 2015 and 2021, 295 F18-fluciclovine PET/CT scan reports were identified. Thirteen phrases commonly used by radiologists in the report impression section to describe a lesion of interest were identified and categorized into three confidence categories: definitive (positive and negative), likely (consistent with, most likely, favors, probable), and unsure (suspicious for, concerning for, non-specific, conspicuous, compatible with, borderline, unknown). The use of definitive language varied depending on the anatomic site, with the highest use in bone (87.1%) and the lowest use in the intact prostate (34.6%). In patients with a PSA < 0.5, there was the highest degree of definitive certainty (89.2%), whereas in patients with a PSA > 1, there was the least definitive certainty (66.2%). The language used in these reports has not been standardized, with definitive, likely, and unsure findings reported in 68.6%, 9.7%, and 21.7% of scans, respectively. Full article

For patients with recurrent brain metastases, there is an urgent need for a more effective and less toxic treatment approach. Accumulating evidence has shown that spatially fractionated radiation therapy (SFRT) is able to provide a significantly higher therapeutic ratio with lower toxicity compared to conventional radiation using a uniform dose. The purpose of this study was to explore the potential low toxicity benefit of mini-beam radiotherapy (MBRT), a form of SFRT, for whole-brain re-irradiation in a healthy mouse model. Animals first received an initial 25 Gy of uniform whole-brain irradiation. Five weeks later, they were randomized into three groups to receive three different re-irradiation treatments as follows: (1) uniform irradiation at 25 Gy; (2) MBRT at a 25 Gy volume-averaged dose (106.1/8.8 Gy for peak/valley dose, 25 Gy-MBRT); and (3) MBRT at a 43 Gy volume-averaged dose (182.5/15.1 Gy for peak/valley dose, 43 Gy-MBRT). Animal survival and changes in body weight were monitored for signs of toxicity. Brains were harvested at 5 weeks after re-irradiation for histologic evaluation and immunostaining. The study showed that 25 Gy-MBRT resulted in significantly less body weight loss than 25 Gy uniform irradiation in whole-brain re-irradiation. Mice in the 25 Gy-MBRT group had a higher level of CD11b-stained microglia but also maintained more Ki67-stained proliferative progenitor cells in the brain compared to mice in the uniform irradiation group. However, the high-dose 43 Gy-MBRT group showed severe radiation toxicity compared to the low-dose 25 Gy-MBRT and uniform irradiation groups, indicating dose-dependent toxicity. Our study demonstrates that MBRT at an appropriate dose level has the potential to provide less toxic whole-brain re-irradiation. Future studies investigating the use of MBRT for brain metastases are warranted. Full article

Background: Stereotactic body radiotherapy (SBRT) targeted at metastatic sites of disease progression is emerging as a potential therapeutic approach for managing oligoprogressive prostate cancer. However, a definitive benefit has yet to be demonstrated. Herein, we present our institution’s experience with this treatment approach. Methods: From April 2018 to March 2023, 11 patients affected by oligoprogressive prostate cancer were treated with SBRT targeting the nodal or bone sites of progression while maintaining the ongoing systemic therapy. Three patients were undergoing single-agent ADT (Androgen Deprivation Therapy), while the remaining eight were receiving a subsequent line of systemic therapy. All patients were evaluated with a pre-treatment 68Ga-PSMA-11 or 18F-fluorocholine PET/CT, which demonstrated between one and five localizations of disease. All the active sites were treated with SBRT in one (15–24 Gy) or three (21–27 Gy) fractions, except for one patient, who was treated in five fractions (35 Gy). PSA serum levels were tested at baseline, one month after RT and at least every three months; all patients underwent a post-treatment 68Ga-PSMA-11 or 18F-fluorocholine PET/CT. The evaluated endpoints were PSA response, defined as a post-treatment decrease >50% from baseline measured within 6 months, time to next-line systemic treatment (NEST), local control (LC), biochemical progression-free survival (bPFS), radiological progression-free survival (rPFS) and freedom from polymetastatic progression (FPP). Results: Nineteen lesions were treated (seven nodal and twelve bone). At a median follow-up of 19 months (7–63), 9 of the 11 patients had a PSA response; all patients had local control of the treated metastases. A total of six patients switched to a next-line systemic treatment, with a median NEST of 13 months. Six patients had polymetastatic progression with an FPP median time of 19 months. No patients died during the follow-up period. The SBRT-related toxicity was negligible. Conclusions: Our data support the use of SBRT targeting the sites of oligoprogressive disease before moving to a subsequent line of systemic treatment in patients with metastatic prostate cancer. Prospective studies to evaluate the potential impact of this approach on overall survival are warranted. Full article