Tolerance of normal tissue to therapeutic irradiation

Combination of radiotherapy and ICIs in advanced hepatocellular carcinoma: A systematic review of current evidence and future prospects (Review)

Hepatocellular carcinoma (HCC) is a global health concern because of its rising prevalence and high fatality rates. Conventional treatments for advanced HCC (aHCC) have limited success, emphasizing the need for novel treatment options. Radiotherapy (RT) treatments, such as stereotactic body radiation and proton therapy, improve local tumor management via precision targeting. Moreover, immune checkpoint inhibitors (ICIs) that target the programmed cell death protein 1(PD-1)/PD ligand 1 (PD-L1) and cytotoxic T lymphocyte associated protein 4 (CTLA-4) pathways have promise for systemic antitumor effectiveness. The combination of RT and ICIs takes advantage of their complementary mechanisms: RT kills immunogenic cells and controls the tumor microenvironment to increase antigen presentation, whereas ICIs enhance and maintain antitumor immune responses. This combination enhances tumor regression and immune response in aHCC, improving response rate and progression-free survival with manageable safety. The present review aimed to summarize the rationale for combining RT + ICIs in patients with aHCC and clinical outcomes, as well as ways to enhance this combination technique. The combination of these models is a promising technique for improving outcomes for patients with aHCC and warrants further investigation.

Maximizing therapeutic potential and safety: Exploring multi/dual-payload antibody conjugates as cancer theranostics

Tumor heterogeneity greatly contributes to the failure of traditional cancer treatments. This leads to tumor relapse, recurrence, and ultimately metastasis, presenting serious clinical challenges. In recent decades, advances in antibody-based immunotherapy have emerged as promising new pillars to combat cancers. Although single payload antibody drug conjugates (ADCs) have resulted in drastic improvements in patient outcomes compared with unconjugated antibodies, multiple de novo and acquired resistance mechanisms inherent with cancer cells have left patients with less than desired outcomes. Newer studies are exploring the use of dual and multiple payload ADCs to enhance effectiveness. These payloads include chemotherapeutic and/or radiotherapeutic agents. The approaches leverage the synergistic effects of the different payloads alongside the immunotherapeutic properties of the antibody carriers. This review presents a comprehensive overview of dual-payload monoclonal antibody conjugates for cancer therapy and diagnosis (theranostics). Additionally, it explores the use of various imageable radiometals that are conjugated to the ADCs for imaging/diagnosis. It discusses the role of radioisotope decay schemes (such as alpha emission, beta emission, or Auger electron emission) along with factors such as linker type and chelator, as well as drug-to-antibody ratio (DAR), which are aimed at enhancing the synergistic effects between the therapeutic payloads while ensuring safety. Because none of these dual-payload ADCs have reached the clinic, this review employs a predictive method to estimate human equivalent dose (HED), maximum tolerable dose (MTD), and radiotoxicity in humans based on preclinical data. Additionally, it discusses the combinatorial behavior of two cytotoxic payloads linked to a monoclonal antibody.

Does Time to Retreatment Matter? A Normal Tissue Complication Probability Model to Predict Radionecrosis After Repeat Stereotactic Radiosurgery for Recurrent Brain Metastases Incorporating Time-dependent Discounted Dose

PURPOSE

To develop and compare normal tissue complication probability (NTCP) models for recurrent brain metastases (BMs) treated with repeat single-fraction stereotactic radiosurgery (SRS), considering time-dependent discounted prior dose.

METHODS AND MATERIALS

We developed three NTCP models (M0, M1-retreat, and M1-combo models) of BMs treated with GammaKnife-based SRS. The maximum dose is 0.2 cc (D0.2cc) of the lesion-specific brain, and the 1-year radionecrosis risk is modeled using a logistic response with doses converted into equivalent dose in 2-Gy fractions (EQD2) based on a linear quadratic linear model. The M0 and M1-retreat models, respectively, predicted radionecrosis risk after SRS to 1029 nonrecurrent lesions (patients, 262) and second SRS to 149 recurrent lesions (patients, 87). The M1-combo model accounted for the second SRS and time-dependent discounted first SRS dose for recurrent lesions estimated using a modified Gompertzian function.

RESULTS

All 3 models fitted the data well (χ2, 0.039-0.089, and P = 0.999-1.000). The fitted EQD250 was ∼ 103 Gy for the M0 model, ∼ 88 Gy for the M1-retreat model, and ∼ 165 Gy for the M1-combo model. The fitted γ50 exhibited a progressively flatter dose-response curve across the three models, with values of 1.2 per gray for the M0 model, 0.6 per gray for the M1-retreat model, and 0.4 per gray for the M1-combo model. For the brain D0.2cc of 29 and 19 Gy, the steepest to shallowest dose-response or largest change in NTCP values, ie, NTCP29Gy - NTCP19Gy, was observed in the M1-retreat (0.16), M0 (0.14), and M1-combo (0.06) models.

CONCLUSIONS

The model-fitted parameters predicted that recurrent BMs would have a lower threshold dose tolerance and a more gradual dose response to the second SRS than nonrecurrent BMs. This gradual dose-response becomes even more apparent when considering the time-dependent discounted first SRS as a cumulative second SRS. Tailoring SRS retreatment protocols based on NTCP modeling can potentially enhance therapeutic efficacy.

Rethinking Dosimetry: A European Perspective

Radiopharmaceutical therapy (RPT) is entering a new era of personalization, driven by advances in molecular imaging, radiopharmaceutical development, and a growing body of clinical evidence linking absorbed dose to treatment outcomes. Although external-beam radiotherapy has long integrated dosimetry into standard practice, RPT historically relied on fixed radiopharmaceutical activities and absorbed dose-effect relationships adapted from external-beam radiotherapy, often without accounting for the unique pharmacokinetics, absorbed dose rate dynamics, and biologic responses of systemically administered radiopharmaceuticals. As RPT expands into earlier disease stages, at which patients have longer life expectancies and better performance status, the role of dosimetry in optimizing treatment is becoming increasingly evident. However, despite growing recognition of its benefits, the implementation of dosimetry in clinical practice remains limited, partly because of a self-reinforcing cycle in which the lack of routine dosimetry limits clinical evidence, which in turn hinders its broader adoption. Breaking this cycle is essential to advancing RPT and ensuring that evaluation of dosimetry is based on clinical merit rather than logistic constraints. This article examines the current landscape of RPT dosimetry, highlighting key challenges and opportunities from a European perspective and aiming to foster a more factual and constructive discussion on the topic. We discuss the fundamental differences between dosimetry-driven treatment planning and posttherapy absorbed dose verification, emphasizing the latter as a practical entry point for clinical adoption. We underscore the need for harmonized standards, improved imaging resolution, and tailored absorbed dose-effect relationships that reflect the heterogeneity of RPT delivery and the complexity of tumor and organ responses. The paper also addresses regulatory, infrastructural, and resource barriers to RPT dosimetry implementation and highlights ongoing European initiatives to strengthen frameworks, enhance stakeholder collaboration, and integrate absorbed dose biomarkers into authorization processes and clinical decision-making. By rethinking dosimetry and promoting standardized, evidence-based approaches, the field can advance beyond fixed-activity protocols toward truly individualized RPT. However, achieving clinically feasible integration of dosimetry into routine practice requires structured efforts to generate high-quality clinical evidence and improve accessibility. Ultimately, reliable, patient-centered dosimetry has the potential to enhance therapeutic efficacy, manage toxicity more effectively, and support the long-term evolution of RPT as a cornerstone of precision oncology.

Radioembolization of hepatocellular carcinoma with 90Y glass microspheres: an earlier administration day unexpectedly improves tumour control probability

PURPOSE

90Y glass microspheres have a shelf life of 12 days from the calibration date, allowing flexible administration after a variable decay interval. For a fixed intended activity, a longer interval results in a higher number of administered microspheres per GBq and in a lower activity per sphere as. This study aimed to demonstrate that, for a fixed Tumour Absorbed Dose (TAD), Tumour Control Probability (TCP) is higher when the decay interval is shorter (4 days vs. 8 days). In the second part of the study, we focused on fully perfused lesions, i.e. those showing matching perfused and radiological volumes, where calculating mean microsphere spatial density (ρ) is meaningful. We investigated which variable was associated with radiological response.

METHODS

We retrospectively analysed lesion-by-lesion response at the best response time using the mRECIST criterion. Two chronologically sequential cohorts of patients were compared. Both cohorts were planned and treated with lobar administration, with exactly the same methodology, except for the post-calibration decay interval (Administration day: day 4 vs day 8). Infiltrative lesions and those with additional treatments post-radioembolization were excluded. To compare efficacy at the same TAD, we plotted TCP curves as a function of TAD and stratified TCP by lesion mass (M), using an arbitrary 50 g cut-off (equivalent to a 4.6 cm diameter). On fully perfused lesions, TCP was analyzed also as function of ρ and mass. We then conducted univariate ROC and multivariate analysed to assess response impact based on TAD, ρ, as, and M, grouping CR + PR (Objective Response, OR) versus SD + PD, as well as CR versus PR + SD + PD.

RESULTS

A total of 94 patients with 150 lesions were analyzed. TCP (for TAD up to 600 Gy) was significantly higher for the 59 lesions treated on Day 4 compared to the 91 lesions treated on Day 8, though the difference diminished at higher TAD values. In fully perfused lesions, TCP plateaued at 344 Gy and 160 Gy for lesions treated on Day 8 and Day 4 respectively. ROC analysis for fully perfused lesions showed poor AUC values for CR + PR versus SD + PD: 0.62, p = 0.01 for as, 0.63, p = 0.01 for TAD, and 0.60 p = 0.01 for M, with AUC for ρ being non-significant. When comparing CR versus PR + SD + PD classes, only M was significant, with a fair AUC value of 0.71, p = 0.01. Multivariate analysis showed that CR + PR was significantly associated only to as, with 79% higher response probability for administration on Day 4. When considering CR alone, significance was confirmed only for M, with an odd ratio of 0.19.

DISCUSSION

Our findings on TCP confirmed our preliminary unpublished studies from a different lesion cohort assessed by two independent radiologists. Additionally, our results align with recent experimental histological studies on complete pathological necrosis (CPN) in explanted liver samples after neoadjuvant segmentectomy prior to liver transplantation. However, our data and the CPN findings contrast with previously published simulations based purely on physical parameters (dose-volume histograms at microscopic scale). No explanation is currently available for this discrepancy.

CONCLUSION

When considering OR probability, administration of 90Y glass microsphere on Day 8 is not recommended, favouring Day 4 instead. For tumours < 50 g treated on Day 4, increasing TAD beyond 160 Gy does not improve response probability but may increase toxicity risk in lobar administrations. Conversely, larger lesions benefit from a maximal tolerable activity approach. TRIAL REGISTRATION : NumberDose in TARE, INT 154/19. Registered on 8 August 2019.

Machine Learning-Based Dose Prediction in [177Lu]Lu-PSMA-617 Therapy by Integrating Biomarkers and Radiomic Features from [68Ga]Ga-PSMA-11 PET/CT

PURPOSE

The study aimed to develop machine learning (ML) models for pretherapy prediction of absorbed doses (ADs) in kidneys and tumoral lesions for metastatic castration-resistant prostate cancer (mCRPC) patients undergoing [177Lu]Lu-PSMA-617 (Lu-PSMA) radioligand therapy (RLT). By leveraging radiomic features (RFs) from [68Ga]Ga-PSMA-11 (Ga-PSMA) PET/CT scans and clinical biomarkers (CBs), the approach has the potential to improve patient selection and tailor dosimetry-guided therapy.

METHODS

Twenty patients with mCRPC underwent Ga-PSMA PET/CT scans prior to the administration of an initial 6.8±0.4 GBq dose of the first Lu-PSMA RLT cycle. Post-therapy dosimetry involved sequential scintigraphy imaging at approximately 4, 48, and 72 h, along with a SPECT/CT image at around 48 h, to calculate time-integrated activity (TIA) coefficients. Monte Carlo (MC) simulations, leveraging the Geant4 application for tomographic emission (GATE) toolkit, were employed to derive ADs. The ML models were trained using pretherapy RFs from Ga-PSMA PET/CT and CBs as input, while the ADs in kidneys and lesions (n=130), determined using MC simulations from scintigraphy and SPECT imaging, served as the ground truth. Model performance was assessed through leave-one-out cross-validation (LOOCV), with evaluation metrics including R² and root mean squared error (RMSE).

RESULTS

The mean delivered ADs were 0.88 ± 0.34 Gy/GBq for kidneys and 2.36 ± 2.10 Gy/GBq for lesions. Combining CBs with the best RFs produced optimal results: the extra trees regressor (ETR) was the best ML model for predicting kidney ADs, achieving an RMSE of 0.11 Gy/GBq and an R² of 0.87. For lesion ADs, the gradient boosting regressor (GBR) performed best, with an RMSE of 1.04 Gy/GBq and an R² of 0.77.

CONCLUSION

Integrating pretherapy Ga-PSMA PET/CT RFs with CBs shows potential in predicting ADs in RLT. To personalize treatment planning and enhance patient stratification, it is crucial to validate these preliminary findings with a larger sample size and an independent cohort.

Deep Learning-Based Synthetic CT for Personalized Treatment Modality Selection Between Proton and Photon Therapy in Thoracic Cancer

Objectives: Identifying patients' advantageous radiotherapy modalities prior to CT simulation is challenging. This study aimed to develop a workflow using deep learning (DL)-predicted synthetic CT (sCT) for treatment modality comparison based solely on a diagnostic CT (dCT). Methods: A DL network, U-Net, was trained utilizing 46 thoracic cases from a public database to generate sCT images predicting planning CT (pCT) scans based on the latest dCT, and tested on 15 institutional patients. The sCT accuracy was evaluated against the corresponding pCT and a commercial algorithm deformed CT (MdCT) based on Mean Absolute Error (MAE) and Universal Quality Index (UQI). To determine advantageous treatment modality, clinical dose-volume histogram (DVH) metrics and Normal Tissue Complication Probability (NTCP) differences between proton and photon treatment plans were analyzed on the sCTs via concordance correlation coefficient (CCC). Results: The AI-generated sCTs closely resembled those of the commercial deformation algorithm in the tested cases. The differences in MAE and UQI values between the sCT-vs-pCT and MdCT-vs-pCT were 19.38 HU and 0.06, respectively. The mean absolute NTCP deviation between sCT and pCT was 1.54%, 0.21%, and 2.36% for esophagus perforation, lung pneumonitis, and heart pericarditis, respectively. The CCC between sCT and pCT was 0.90 for DVH metrics and 0.97 for NTCP, indicating moderate agreement for DVH metrics and substantial agreement. Conclusions: Radiation oncologists can potentially utilize this personalized sCT based approach as a clinical support tool to rapidly compare the treatment modality benefit during patient consultation and facilitate in-depth discussion on potential toxicities at a patient-specific level.

Efficacy of palliative hemostatic radiotherapy for tumor bleeding and pain relief in locally advanced pelvic gynecological malignancies

PURPOSE

The appearance of symptomatic tumor-related vaginal bleeding and pain in advanced incurable cancer patients with pelvic gynecological malignancies remains a therapeutic challenge in oncological treatment. The aim of our analysis was to evaluate the efficacy and safety of palliative hemostatic radiotherapy.

METHODS

We retrospectively identified patients who had received palliative hemostatic radiotherapy (RT) at our institution between 2011 and 2023 and evaluated acute toxicity, local control, cessation of bleeding, and pain relief.

RESULTS

In total, 40 patients with a median planning target volume of 804 cm3 were treated with a median total dose of 39 Gy in 13 fractions, resulting in 6‑month and 1‑year local control rates of 66.9 and 60.8%, respectively. No higher-grade (>grade III) acute RT-induced toxicity appeared. Complete cessation of bleeding was achieved in 80.0% of all patients after a median of 16 days and pain relief was documented in 60.9% at first follow-up. 37.5% of the women required a blood transfusion and 25% an additional tamponade with local hemostatic agents. Successful stopping of bleeding was significantly less frequent in patients receiving anticoagulation concurrently with radiation and in the case of infield re-irradiation. Patients with a higher total RT dose had cessation of bleeding significantly more often, with a cut-off value of at least EQD2 (α/β = 10) = 36 Gy. The applied RT technique and planning target volume had no significant influence on the occurrence of bleeding cessation.

CONCLUSION

Palliative hemostatic radiotherapy for locally advanced pelvic gynecological malignancies is safe and effective in achieving high control rates of hemostasis in tumor bleeding and pain relief.

The fractionation effect on proton RBE in a late normal tissue damage model in vivo

BACKGROUND AND PURPOSE

A constant relative biological effectiveness (RBE) of 1.1 is used in clinical proton therapy (PT) to convert prescribed photon doses into isoeffective proton doses. However, the RBE is not constant; it is a dynamic parameter highly influenced by factors such as linear energy transfer, tissue type, biological endpoint, and dose/fraction. Preclinical in vivo proton RBE studies using fractionated doses and late damage endpoints are almost nonexistent. The aim is to test the hypotheses that the RBE varies between single and fractionated doses and that the late damage development differs between proton and photon irradiation using a 6 MV linac as a reference modality in a murine leg model.

MATERIALS AND METHODS

The right hindlimb of unanesthetized mice was irradiated with single or four fractions of protons or 6 MV photons. Over one year after treatment, the mice were analyzed every fourteenth day using a joint contracture assay to investigate severe radiation-induced late damage.

RESULTS

The results indicated a higher RBE for severe late damage endpoint of 1.25 ± 0.06 (1.13-1.36) for fractionated doses than single doses, exhibiting an RBE of 1.16 ± 0.08 (1.00-1.31). The onset of late damage is earlier for protons than photons for doses higher than 47 Gy and fractionated doses above 50 Gy (12.5 Gy per fraction).

CONCLUSION

The findings demonstrate that fractionated doses enhance the RBE for a late damage endpoint and lead to an earlier onset of severe late effects than its photon counterpart in vivo.

The Effects of Extracorporeal Shock Wave Therapy on Cutaneous Radiation Injury in a Mouse Model

BACKGROUND

Although radiation-induced skin injuries are a concern in patients receiving radiation therapy, there are few effective treatments. The aim of this study was to evaluate the protective effects of extracorporeal shock wave therapy (ESWT) on irradiated fibroblasts and mouse skin.

METHODS

In this in vitro study of human dermal fibroblasts, the experimental group was subjected to ESWT after irradiation (20 Gy). The control groups were only irradiated or only subjected to ESWT. At 24 or 48 hours after ESWT, cell viability, cell migration, and mRNA and protein expression were measured. In the in vivo study, the experimental group (7 mice) was treated with ESWT after irradiation (45 Gy). The control group (7 mice) was only irradiated. At 8 weeks after irradiation, dorsal skin was harvested for histopathologic examination and protein isolation.

RESULTS

In dermal fibroblasts, treatment with ESWT increased viability of irradiated cells compared with irradiated-only and untreated cells ( P = 0.005). ESWT increased cell migration 24 hours after irradiation ( P = 0.002) and decreased transforming growth factor-β (TGF-β) protein expression 48 hours after irradiation ( P = 0.024). In mice, ESWT decreased the level of radiation-related skin injury ( P = 0.006). Treatment of irradiated skin with ESWT decreased TGF-β1 ( P = 0.009) and phospho-Smad3 ( P = 0.009) protein expression, decreased myofibroblasts ( P = 0.047), and increased vessel density ( P < 0.001).

CONCLUSION

This study demonstrated that ESWT alleviated radiation-induced fibrosis by downregulating TGF-β1 expression, suggesting the potential of ESWT for the treatment of radiation-induced fibrosis.

Historical view of the effects of radiation on cancer cells

Introduction

Since Röntgen's discovery of X-rays in 1895, advancements in radiobiology have significantly shaped radiotherapy practices. This historical review traces the evolution of radiobiological theories and their impacts on current therapeutic strategies.

Materials and Methods

Databases such as PubMed were utilized to trace the evolution of concepts in radiobiology.

Results/Discussion

One of the first theories concerning the effect of radiation was Dessauer's target theory, introduced in the 1920s. He found that damage to critical molecular cellular targets leads to cell death. In the early 20th century, Muller contributed to the understanding of DNA structure and radiation-induced mutations, highlighting theories on the impact of radiation on genetic material and cellular damage. In 1972, Kellerer and Rossi introduced the theory of dual radiation action, which explains that ionizing radiation induces sequential damage to DNA, starting with single-strand breaks and progressing to irreparable double-strand breaks. Recent advances have enhanced the understanding of the effects of radiation on the microenvironment and immune responses, thereby improving therapeutic outcomes. The significance of the sigmoid dose-response curve and the initial shoulder effect were recognized early, leading to theoretical models such as the multitarget single-hit, linear-quadratic and repair-misrepair models. The history of fractionation and the 4R/5R principles have informed today's ultrahigh fractionation techniques, including single doses of approximately 20 Gy.

Conclusion

Although significant advances have been made toward understanding the effects of radiation on cancerous and healthy tissues, many clinical observations, such as the effects of very high doses or FLASH therapy, remain poorly understood.

Application of 3D-printed compensators for proton pencil beam scanning of shallowly localized pediatric tumors

BACKGROUND

In modern proton radiotherapy facilities with pencil beam scanning technology, the lowest energy of a proton beam typically ranges between 60 and 100 MeV, corresponding to a proton range in water of 3.1-7.5 cm. The irradiation of superficial lesions usually requires the application of a range shifter (RS) to further reduce the proton range. A certain distance from the patient to the RS increases the spot size, causing worse plan conformity. As an alternative solution, a patient-specific 3D-printed proton beam compensator (BC) can be applied to reduce the air gap and beam scattering.

MATERIALS AND METHODS

This study is based on treatment planning system simulations using retrospectively selected data from six pediatric patients with diagnosed sarcomas located in the head and neck area. For three of these patients, 3D-printed compensators were utilized during the treatment phase, prior to the retrospective analysis. Treatment plans for children with shallow lesions treated using RSs and BCs were compared. Planning target volume constraints (D98% >95%, D2%< 107%) and organs-at-risk (brainstem, spinal cord, visual organs, chiasm, cochlea) constraints (D2%, Dmax and DMean) were applied. The entire process of using a BCs in the treatment of pediatric superficial tumors is presented, including 3D printing procedure (via fused filament fabrication method), dosimetric verification of the material (Water Equivalent Ratio measurements) and assessment of its homogeneity, print quality and Hounsfield Unit specification. Beam parameters analysis including spot sizes and penumbras, were performed. Treatment plans were compared in terms of plan conformity and sparing of critical organs.

RESULTS

The application of BCs reduced the low-dose irradiation areas, improved conformity and reduced critical organs exposure. BCs decreased the lateral spot size by approximately 57% and the penumbras by 41-47% at different depths in the cube target. The variation in BC homogeneity was less than 3.5%, meeting the criteria for plan robustness evaluation.

CONCLUSIONS

Compared with RS placement at the nozzle, the placement of 3D-printed BCs in the near vicinity of the patient for the treatment of superficial tumors led to a more conformal dose distribution.

Impacts of Radiation on Metabolism and Vascular Cell Senescence

Significance: This review investigates how radiation therapy (RT) increases the risk of delayed cardiovascular disease (CVD) in cancer survivors. Understanding the mechanisms underlying radiation-induced CVD is essential for developing targeted therapies to mitigate these effects and improve long-term outcomes for patients with cancer. Recent Advances: Recent studies have primarily focused on metabolic alterations induced by irradiation in various cancer cell types. However, there remains a significant knowledge gap regarding the role of chronic metabolic alterations in normal cells, particularly vascular cells, in the progression of CVD after RT. Critical Issues: This review centers on RT-induced metabolic alterations in vascular cells and their contribution to senescence accumulation and chronic inflammation across the vasculature post-RT. We discuss key metabolic pathways, including glycolysis, the tricarboxylic acid cycle, lipid metabolism, glutamine metabolism, and redox metabolism (nicotinamide adenine dinucleotide/Nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADP+)/NADPH). We further explore the roles of regulatory proteins such as p53, adenosine monophosphate-activated protein kinase, and mammalian target of rapamycin in driving these metabolic dysregulations. The review emphasizes the impact of immune-vascular crosstalk mediated by the senescence-associated secretory phenotype, which perpetuates metabolic dysfunction, enhances chronic inflammation, drives senescence accumulation, and causes vascular damage, ultimately contributing to cardiovascular pathogenesis. Future Directions: Future research should prioritize identifying therapeutic targets within these metabolic pathways or the immune-vascular interactions influenced by RT. Correcting metabolic dysfunction and reducing chronic inflammation through targeted therapies could significantly improve cardiovascular outcomes in cancer survivors. Antioxid. Redox Signal. 00, 000-000.

Temporal dynamics of lymphocytes in prostate cancer patients treated with proton therapy

Radiotherapy can be both immunosuppressive and immunostimulatory. Radiation-induced lymphopenia (RIL) is an ongoing challenge in cancer treatment. We investigated weekly changes in the absolute lymphocyte count (ALC) during proton radiotherapy, evaluating the effects of different dosage, fractionation schedules, and pelvic node irradiation (PNI). Prostate cancer patients were prospectively chosen for this study, due to their relatively homogenous treatment plans. Treatment protocols were categorized into three groups: Group A (n=52) received 36.25 Gy/5-fractions, Group B (n=60) underwent 63 Gy/21-fractions and group C (n=69) received 63 Gy/21-fractions plus PNI. To account for individual characteristic differences, a new categorization method was made, according to the change in ALC relative to the baseline. Lymphopenia (ALC < 1000 K/μL) developed in 8%, 17% and 84% of patients in groups A, B, and C, respectively. An initial increase in ALC occurred in 44%, 47% and 28% of groups A, B and C, respectively, and declined with proceeding fractions. Patients with PNI had the most pronounced reduction in their ALC relative to the baseline. Increased dosage and fractionation led to a higher incidence of lymphopenia. Understanding which factors influence ALC in particle therapy is vital for leveraging the immune-enhancing effects of radiotherapy, while minimising its immunosuppressive impacts.

Radiation-Induced Nephrotoxicity: Role of Sphingomyelin Phosphodiesterase Acid-like 3b

PURPOSE

Radiation nephropathy (RN) can be a significant late complication after radiation therapy (RT) for abdominal and paraspinal tumors. The mechanisms for the development of RN are thought to involve disruption of podocyte function, leading to podocyte cell death and, finally, impaired renal function. This study investigated the mechanistic role of sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) in regulating podocyte injury and renal function after irradiation. The aim of the study was to investigate the potential linkage between (1) RT-induced renal dysfunction and podocyte SMPDL3b expression and (2) RT-induced podocyte injury and expansion of the glomerular basement membrane (GBM).

METHODS AND MATERIALS

SMPDL3b wild-type, siSMPDL3b, and SMPDL3b-overexpressing podocytes were irradiated in cell culture, and cell death was assessed. SMPDL3b wild-type and podocyte-specific SMPDL3b knockout mice were treated with focal bilateral kidney X-irradiation (14 Gy, or 6 × 5 Gy), and podocyte apoptosis, renal function parameters, glomerular filtration rate, glomerular histology, and GBM ultrastructural changes via transmission electron microscopy were assessed.

RESULTS

Following RT treatment, a notable decrease in SMPDL3b expression was observed, accompanied by heightened levels of DNA damage, cytoskeletal alterations, and apoptotic events in cultured podocytes. SMPDL3b overexpression notably prevented DNA damage and apoptosis in cultured podocytes. Additionally, in vivo, RT exposure led to a significant decline in SMPDL3b expression, podocyte count, and renal function while concomitantly elevating GBM thickness, mesangial expansion, and renal fibrosis at the 20-week post-RT. Furthermore, in vivo, rituximab pretreatment before RT prevented SMPDL3b downregulation, podocyte loss, mesangial expansion, GBM expansion, and renal fibrosis and ultimately enhanced renal function post-RT.

CONCLUSIONS

Our findings collectively suggest a novel function for SMPDL3b in orchestrating the DNA damage response triggered by radiation. This study proposes that SMPDL3b exerts a regulatory influence on the repair of double-strand breaks within podocytes, consequently averting podocyte loss, GBM expansion, and the onset of RN.

Pathological Clavicular Fracture Following Brachial Plexopathy Occurring Over 50 Years After Radiation Therapy: A Case Report

Radiotherapy is a common cancer treatment that may cause long-term complications such as bone and neurological disorders. This study presents a pathological clavicular fracture that occurred 50 years after radiotherapy for a sarcoma. A 67-year-old female with a history of radiation therapy following surgery at the age of 10 years developed a clavicular fracture without trauma. Prior to the fracture, the patient experienced progressive brachial plexopathy over the past 15 years. Biopsy revealed no malignancy, which led to the diagnosis of a pathological fracture. This study illustrates the delayed onset of radiation-induced complications, with neurological damage appearing earlier than the fracture. Moreover, it underscores the importance of considering radiation-induced bone fragility in patients with unexplained fractures, particularly individuals with prior radiation exposure. Early detection of neurological damage, such as brachial plexopathy, may offer an opportunity for preventive care. Furthermore, it highlights the necessity of patient education regarding the long-term effects of radiation therapy, including bone fragility and the risk of pathological fractures.

Exon Sequence Analysis of the ATG5, ATG12, ATG9B Genes in Colorectal Cancer Patients During Radiotherapy

Radiotherapy (RT) which is a treatment regime for cancer patients may cause genetic instability and side effects. Etiological associations exist amongst autophagy-related gene (ATG) mutation and cancer. RT increases the rate of autophagy previously proven in vitro. The aforementioned background diverted us to conduct exon mutation analysis for ATG5, ATG12, and ATG9B genes of colorectal cancer patients who were receiving neoadjuvant RT. Peripheral blood DNA from different time points (before/middle/after RT) of the same patients was isolated and most tandem repeat-containing exons of ATG5, ATG12, and ATG9B were polymerase chain reaction-amplified and examined for mutations by Sanger sequencing. CA19-9/CEA (Tumor marker of colorectal cancer/Carcinoembryonic Antigen) serum levels were retrieved from the clinic. No exon variations detected for ATG5 and ATG12 genes. However, 4 patients (17.4%) showed frameshift mutation for ATG9B gene. Exon variation analysis of 2 (8.7%) patients resulted in GGG deletion at 8G mononucleotide tandem repeat region of ATG9B. Assigning patients as before RT and after RT, CA19-9 levels in ATG9B (Mutation) patients were higher compared to ATG9B (Wild Type) patients. ATG9B is highly likely to mutate during RT and ATG9B mutation correlates to higher CEA and CA19-9 levels and patients show poor prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12291-023-01177-6.

Novel 177Lu-Labeled [Thz14]Bombesin(6-14) Derivatives with Low Pancreas Accumulation for Targeting Gastrin-Releasing Peptide Receptor-Expressing Cancer

Background/Objectives: Gastrin-releasing peptide receptor is a promising target for cancer diagnosis and therapy. However, the high pancreas uptake of reported GRPR-targeted radioligands limits their clinical applications. Our group previously reported one 68Ga-labeled GRPR antagonist, [68Ga]Ga-TacsBOMB5 (68Ga-DOTA-Pip-[D-Phe6,NMe-Gly11,Leu13ψThz14]Bombesin(6-14)), and two agonists, [68Ga]Ga-LW01110 (68Ga-DOTA-Pip-[D-Phe6,Tle10,NMe-His12,Thz14]Bombesin(6-14)) and [68Ga]Ga-LW01142 (68Ga-DOTA-Pip-[D-Phe6,His7,Tle10,NMe-His12,Thz14]Bombesin(6-14)) showing minimal pancreas uptake. Thus, in this study, we prepared their 177Lu-labeled analogs, evaluated their therapeutic potentials, and compared them with the clinically evaluated [177Lu]Lu-AMBA. Methods: GRPR binding affinities were determined by in vitro competition binding assay using PC-3 prostate cancer cells. Longitudinal SPECT/CT imaging and ex vivo biodistribution studies were conducted in PC-3 tumor-bearing mice. Dosimetry data were calculated from the biodistribution results. Results: The Ki(GRPR) values of Lu-TacsBOMB5, Lu-LW01110, Lu-LW01142, and Lu-AMBA were 12.6 ± 1.02, 3.07 ± 0.15, 2.37 ± 0.28, and 0.33 ± 0.16 nM, respectively. SPECT/CT images and biodistribution results demonstrated good tumor accumulation of [177Lu]Lu-TacsBOMB5, [177Lu]Lu-LW01110, and [177Lu]Lu-LW01142 at early time points with rapid clearance over time. The pancreas uptake of all three [Thz14]Bombesin(6-14)-derived ligands was significantly lower than that of [177Lu]Lu-AMBA at all time points. The calculated absorbed doses of [177Lu]Lu-TacsBOMB5, [177Lu]Lu-LW01110, and [177Lu]Lu-LW01142 in PC-3 tumor xenografts were 87.1, 312, and 312 mGy/MBq, respectively, higher than that of [177Lu]Lu-AMBA (79.1 mGy/MBq), but lower than that of the previously reported [177Lu]Lu-RM2 (429 mGy/MBq). Conclusions: Our data suggest that [177Lu]Lu-TacsBOMB5 and [177Lu]Lu-LW01142 reduce radiation exposure to the pancreas. However, further optimizations are needed for both radioligands to prolong their tumor retention and enhance treatment efficacy.

Dosimetric and radiobiological evaluation of stereotactic radiosurgery using volumetric modulated arc therapy and dynamic conformal arc therapy for multiple brain metastases

This paper presents a clinical comparison of the target dose, normal tissue complication probability (NTCP), and plan quality between volumetric modulated conformal arc therapy (VMAT) against dynamic conformal arc therapy (DCAT) techniques to facilitate clinical decision-making in multiple brain metastases (MBM) treatment. A total of 11 cases having 33 lesions were recruited at the Union Oncology Centre, Union Hospital, Hong Kong SAR. With CT images available, all plans were optimized using both HyperArc (HA) and Brainlab Elements Multiple Brain Metastases (Elements MBM). Target coverage, normal tissue sparing, and dose distribution were compared pairwise between VMAT and DCAT. Results showed that the plans generated using both techniques achieved adequate target coverage to meet up with the oncologist's prescription. With similar levels of NTCP, the normal brain received low doses of radiation using both techniques and the risk of brain necrosis was kept equally low. This indicated that VMAT and DCAT produced similar high-quality treatment plans with low risks of brain necrosis. Meanwhile, VMAT showed better homogeneity which could potentially be more useful for large targets, while DCAT showed better target conformity especially for targets smaller than 1 cc. In general, both HA and Elements MBM demonstrated ability to generate high-quality clinical plans.

Biological effects of high-LET irradiation on the circulatory system

PURPOSE

High-linear energy transfer (LET) radiation is generally thought to be more biologically effective in various tissues than low-LET radiation, but whether this also applies to the circulatory system remains unclear. We therefore reviewed biological studies about the effects of high-LET radiation on the circulatory system.

CONCLUSIONS

We identified 76 relevant papers (24 in vitro, 2 ex vivo, 51 in vivo, one overlapping). In vitro studies used human, bovine, porcine or chick vascular endothelial cells or cardiomyocytes, while ex vivo studies used porcine hearts. In vivo studies used mice, rats, rabbits, dogs or pigs. The types of high-LET radiation used were neutrons, α particles, heavy ions and negative pions. Most studies used a single dose, although some investigated fractionation effects. Twenty-one studies estimated the relative biological effectiveness (RBE) that ranged from 0.1 to 130, depending on radiation quality and endpoint. A meta-analysis of 6 in vitro and 8 in vivo studies (selected based on the feasibility of estimating the RBE and its uncertainty) suggested an RBE of 6.69 (95% confidence intervals (CI): 2.51, 10.88) for in vitro studies and 1.14 (95% CI: 0.91, 1.37) for in vivo studies. The meta-analysis of these 14 studies yielded an RBE of 2.88 (95% CI: 1.52, 4.25). This suggests that high-LET radiation is only slightly more effective than low-LET radiation, although substantial inter-study heterogeneity complicates interpretation. Therapeutic effects have also been reported in disease models. Further research is needed to better understand the effects on the cardiovascular system and to improve radiation protection.

Dummy run study for outlining and plan quality of intensity-modulated radiotherapy in elderly patients with newly diagnosed glioblastoma: The Japan clinical oncology group study JCOG1910 (AgedGlio-PIII)

BACKGROUND

A dummy run was conducted to ensure the quality of intensity-modulated radiotherapy (IMRT) before registration in a randomized phase III study of elderly patients with newly diagnosed glioblastoma by the Japan Clinical Oncology Group 1910 (JCOG1910).

METHODS

All 41 institutions enrolled in this study were required to report outlining that included gross tumor volume (GTV), clinical target volume (CTV), planning target volume (PTV), and treatment planning for one benchmark case. First, deviations in outlining were evaluated using the Dice similarity coefficient (DSC) and mean distance agreement (MDA), compared to reference targets delineated by the research secretariat. Second, the participating institutions were required to create treatment plans for arms A (40.05 Gy in 15 fractions) and B (25 Gy in 5 fractions) using IMRT techniques. The quality of the outlining and dose-volume criteria for each target and organs at risk were evaluated.

RESULTS

Six institutions failed to adhere to the protocol and required revision due to insufficient GTV outlining, not considering anatomical barriers for CTV, and modifying PTV against protocols. Compared to the reference outlining, the means and standard deviations of DSC and MDA were 0.37 ± 0.19 and 9.41 ± 3.99 mm for GTV; 0.80 ± 0.08 and 4.31 ± 1.85 mm for CTV; and 0.83 ± 0.05 and 4.23 ± 1.45 mm for PTV, respectively. Regarding dose-volume criteria, 40 of the 41 institutions met the per-protocol limits; only one was within the acceptable limits.

CONCLUSIONS

Several institutions demonstrated deviations in outlining that necessitated revisions. Thus, appropriate feedback and periodic sharing of information with participating institutions is necessary in the upcoming prospective JCOG1910 study.

Responses of the carotid artery to acute, fractionated or chronic ionizing irradiation, and differences from the aorta

The circulatory system receives ionizing radiation at various dose rates. Given mounting epidemiological evidence of elevated radiation risks for diseases of the circulatory system (DCS), the International Commission on Radiological Protection recently recommended the first ever dose threshold for DCS. However, very little knowledge exists about whether radiation effects differ with dose rates and among tissues of the circulatory system. Here, we investigated the impact of dose rates in the carotid artery (CA) and compared it with the aorta. CA was obtained from mice irradiated with the same total dose that was delivered either acutely, 25 fractions, 100 fractions or chronically. CA underwent immunofluorescence and histochemistry staining. Irradiation led to vascular damage, inflammation and fibrosis in CA. The integrative analysis for 14 prelesional endpoints revealed that the magnitude of carotid changes was greater in 25 fractions, smaller in 100 fractions, and much smaller in chronic irradiation, compared with acute irradiation. Radiation responses of the aorta were qualitatively similar to, but quantitatively greater than those of CA. Irradiation causes sparing and enhancing dose protraction effects in a manner that is not a simple function of dose rate, and that radiosensitivity varies within the circulatory system.

Cardiotoxicity following thoracic radiotherapy for lung cancer

Radiotherapy is the standard of care treatment for unresectable NSCLC, combined with concurrent chemotherapy and adjuvant immunotherapy. Despite technological advances in radiotherapy planning and delivery, the risk of damage to surrounding thoracic tissues remains high. Cardiac problems, including arrhythmia, heart failure and ischaemic events, occur in 20% of patients with lung cancer who undergo radiotherapy. As survival rates improve incrementally for this cohort, minimising the cardiovascular morbidity of RT is increasingly important. Problematically, the reporting of cardiac endpoints has been poor in thoracic radiotherapy clinical trials, and retrospective studies have been limited by the lack of standardisation of nomenclature and endpoints. How baseline cardiovascular profile and cardiac substructure radiation dose distribution impact the risk of cardiotoxicity is incompletely understood. As Thoracic Oncology departments seek to expand the indications for radiotherapy, and as the patient cohort becomes older and more comorbid, there is a pressing need for cardiotoxicity to be comprehensively characterised with sophisticated oncology, physics and cardio-oncology evaluations. This review synthesises the evidence base for cardiotoxicity in conventional radiotherapy, focusing on lung cancer, including current data, unmet clinical needs, and future scientific directions.

Sex-Based Bias in Artificial Intelligence-Based Segmentation Models in Clinical Oncology

Artificial intelligence (AI) advancements have accelerated applications of imaging in clinical oncology, especially in revolutionizing the safe and accurate delivery of state-of-the-art imaging-guided radiotherapy techniques. However, concerns are growing over the potential for sex-related bias and the omission of female-specific data in multi-organ segmentation algorithm development pipelines. Opportunities exist for addressing sex-specific data as a source of bias, and improving sex inclusion to adequately inform the development of AI-based technologies to ensure their fairness, generalizability and equitable distribution. The goal of this review is to discuss the importance of biological sex for AI-based multi-organ image segmentation in routine clinical and radiation oncology; sources of sex-based bias in data generation, model building and implementation and recommendations to ensure AI equity in this rapidly evolving domain.

Quality assessment of automatically planned o-ring linac SBRT plans for pelvic lymph node and lung metastases, evaluating the optimal minimum target size

The purpose of this study is to assess the influence of Planning Target Volume (PTV) on the quality of automatic planned O-Ring Halcyon linac stereotactic body radiation therapy (SBRT) plans of pelvic lymph nodes (LN) and lung metastases and to evaluate an absolute PTV volume threshold as a plan quality prediction criterion. A total of 21 pelvic LN and 18 lung clinical treatment plans were replanned for Halcyon with unattended autoplanning. The prescription dose range was 26-40 Gy for LN and between 39-54 Gy for the lung in the mean 3 fractions. The mean/median PTV was 4.0/ 3.6 cm3 for LN and 4.9/ 4.3 cm3 for the lung. The criteria for the plan quality evaluation consisted of using dose metrics for conformity, spillage, and coverage and dose limits on healthy tissue assessment. A statistical study was performed based on systematic Mann-Whitney U test and cluster analysis to evaluate a PTV volume predictor threshold of plan quality. 95% (n = 20) LN and 100% (n = 18) lung plans met all tolerance criteria. For both cohorts of plans, a PTV threshold was determined, indicating a reduction of particular dose indices when below this threshold. Low risk of toxicity in healthy tissues was predicted. A PTV threshold of 4.0 cm3 was estimated as quality criteria in both cohorts of plans. The results of our study demonstrated the promising performance of Halcyon for pelvic and lung SBRT for small tumors, although plan-specific QA is required to verify machine performance during plan delivery.

On the automated radiosynthesis of pharmaceutical grade [68Ga]Ga-Pentixafor, its pre-clinical evaluation, clinical application and radiation dosimetry aspects

The current study outlines a consistent and reproducible protocol for the routine clinical dose preparation of [68Ga]Ga-Pentixafor using the Eckert and Ziegler 'Modular-Lab Standard' non-cassette based automated module, that can be effectively used in the hospital radiopharmacy unit of a high volume nuclear medicine centre. The pre-clinical studies (including in-vitro cell line studies, in-vivo PET/CT imaging and pre-clinical dosimetry) were conducted to show the promising potential of the product for clinical use in targeting CXCR4 tumor overexpression. PET/CT image of SCID mouse bearing lymphoma xenograft tumor, at 2 h post-injection, clearly delineated the tumor. The pre-clinical dosimetry results show the suitability of the product for clinical use in patients. [68Ga]Ga-Pentixafor when administered to patients with primary aldosteronism exhibited distinct uptake in the adrenal nodules. The clinical PET/CT scan of the patients demonstrated the potential use of CXCR4 targeted imaging as a promising surgical decision-making tool for patients with primary aldosteronism.

Dose Recommendations for Prostrate-specific Membrane Antigen Positron Emission Tomography (PSMA PET) Guided Boost Irradiation to Lymphatic Tissue in Prostate Adenocarcinoma

AIMS

Prostrate-specific membrane antigen positron emission tomography (PSMA-PET) imaging has led to an increase in identifiable small volume metastatic disease in prostate adenocarcinoma. There is clinical equipoise in how to treat these using radiotherapy regimens. The aim of this study is to determine an adequate dosing regimen for small volume lymphatic metastases in prostate adenocarcinoma.

MATERIALS AND METHODS

The authors first estimated the cell count of small volume metastases in prostate adenocarcinoma and then used a Poisson distribution-based estimation of the tumour control probability distribution, the required doses for 95% and 99% probabilities of tumour sterilisation were calculated using the linear quadratic formula.

RESULTS

Lymph node metastases of 3, 5, and 10 mm diameter were estimated to harbour 1.4, 6.5, and 52.3 million clonogens, respectively. When attempting for a 95% tumour control probability, estimated BEDs of 116.5, 127.0, and 141.1Gy were required. This translated to doses of 26.0, 27.3, and 29.0Gy in 5 fraction regimens. When attempting for a 99% tumour control probability, estimated biological effective doses (BEDs) of 127.6, 138.1, and 152.2 Gy were required. This translated to doses of 27.4, 28.6, and 30.2 Gy in 5 fraction regimens.

CONCLUSION

In prostate cancers with small-volume metastatic disease, doses can be adjusted according to tumour size without likely to compromise tumour control. This would have positive implications on radiotherapy planning and possibly lead to decreased risks of toxicity in scenarios where planning difficulty is encountered. Clinical evaluation of efficacy and safety for these dose regimens is warranted.

Automated CT Measurement of Total Kidney Volume for Predicting Renal Function Decline after 177Lu Prostate-specific Membrane Antigen-I&T Radioligand Therapy

Background Lutetium 177 (177Lu) prostate-specific membrane antigen (PSMA) radioligand therapy is a novel treatment option for metastatic castration-resistant prostate cancer. Evidence suggests nephrotoxicity is a delayed adverse effect in a considerable proportion of patients. Purpose To identify predictive markers for clinically significant deterioration of renal function in patients undergoing 177Lu-PSMA-I&T radioligand therapy. Materials and Methods This retrospective study analyzed patients who underwent at least four cycles of 177Lu-PSMA-I&T therapy between December 2015 and May 2022. Total kidney volume (TKV) at 3 and 6 months after treatment was extracted from CT images using TotalSegmentator, a deep learning segmentation model based on the nnU-Net framework. A decline in estimated glomerular filtration rate (eGFR) of 30% or greater was defined as clinically significant, indicating a higher risk of end-stage renal disease. Two-sided t tests and Mann-Whitney U tests were used to compare baseline nephrotoxic risk factors, changes in eGFR and TKV, prior treatments, and the number of 177Lu-PSMA-I&T cycles between patients with and without clinically significant eGFR decline at 12 months. Threshold values to differentiate between these two patient groups were identified using receiver operating characteristic curve analysis and the Youden index. Results A total of 121 patients (mean age, 76 years ± 7 [SD]) who underwent four or more cycles of 177Lu-PSMA-I&T therapy with 12 months of follow-up were included. A 10% or greater decrease in TKV at 6 months predicted 30% or greater eGFR decline at 12 months (area under the receiver operating characteristic curve, 0.90 [95% CI: 0.85, 0.96]; P < .001), surpassing other parameters. Baseline risk factors (ρ = 0.01; P = .88), prior treatments (ρ = -0.06; P = .50), and number of 177Lu-PSMA-I&T cycles (ρ = 0.08; P = .36) did not correlate with relative eGFR percentage decrease at 12 months. Conclusion Automated TKV assessment on standard-of-care CT images predicted deterioration of renal function 12 months after 177Lu-PSMA-I&T therapy initiation in metastatic castration-resistant prostate cancer. Its better performance than early relative eGFR change highlights its potential as a noninvasive marker when treatment decisions are pending. © RSNA, 2025 Supplemental material is available for this article.

Radiotherapy toxicities: mechanisms, management, and future directions

For over a century, radiotherapy has revolutionised cancer treatment. Technological advancements aim to deliver high doses to tumours with increased precision while minimising off-target effects to organs at risk. Despite advancements such as image-guided, high-precision radiotherapy delivery, long-term toxic effects on healthy tissues remain a great clinical challenge. In this Review, we summarise common mechanisms driving acute and long-term side-effects and discuss monitoring strategies for radiotherapy survivors. We explore ways to mitigate toxic effects through novel technologies and proper patient selection and counselling. Additionally, we address policies and management strategies to minimise the severity and impact of toxicity during and after treatment. Finally, we examine the potential advantages of emerging technologies and innovative approaches to improve conformity, accuracy, and minimise off-target effects.

Initial clinical experience with [177Lu]Lu-PNT2002 radioligand therapy in metastatic castration-resistant prostate cancer: dosimetry, safety, and efficacy from the lead-in cohort of the SPLASH trial

Introduction

SPLASH (NCT04647526) is a multicenter phase III trial evaluating the efficacy and safety of [177Lu]Lu-PNT2002 radioligand therapy in metastatic castration-resistant prostate cancer (mCRPC). This study leveraged a lead-in phase to assess tissue dosimetry and evaluate preliminary safety and efficacy, prior to expansion into a randomized phase. Here we report those results.

Methods

Enrolled participants had mCRPC that progressed on one prior androgen receptor pathway inhibitor (ARPI), were prostate-specific membrane antigen (PSMA) PET-positive as determined by a central reader, were chemotherapy-naïve for mCRPC, and had adequate bone marrow and end-organ reserve. Participants received up to 4 cycles of [177Lu]Lu-PNT2002 at 6.8 GBq (± 10%) intravenously per cycle every 8 weeks. Dosimetry (planar + SPECT/CT [n=7]; planar only [n=20]), safety, prostate-specific antigen (PSA) response, objective response rate (ORR), and radiographic progression-free survival (rPFS) per blinded independent central review were assessed.

Results

Of 34 individuals screened, 32 underwent PSMA-PET/CT; 27 met all eligibility criteria. Median (range) age was 72 (57-86) years; all participants were enrolled in North America; 40.7% initiated prior ARPI treatment without distant metastases (M0) and 25.9% while hormone sensitive. Nineteen of 27 (70.4%) participants completed all 4 planned cycles. Organs receiving the largest mean (median, range) specific absorbed doses were lacrimal glands at 1.2 (0.9, 0.4-6.7) Gy/GBq (planar only [n=27]), followed by kidneys at 0.73 (0.63, 0.22-1.8) Gy/GBq (planar + SPECT/CT [n=7]; planar only [n=20]). Mean (median, range) tumor specific absorbed dose was 4.3 (2.1, 0.3-33.4) Gy/GBq (approximately 29 Gy/cycle) based on planar + SPECT/CT of 21 lesions in seven participants. [177Lu]Lu-PNT2002 was associated with no treatment-related deaths, few treatment-related grade ≥3 treatment-emergent adverse events (TEAEs), and no discontinuations for unacceptable toxicity. Treatment-related TEAEs occurring in ≥10% of participants included dry mouth (22.2%; all grade 1), fatigue (18.5%; grades 1-2), nausea (18.5%; grades 1-2), and anemia (14.8%; grades 1-3). Median (95% CI) rPFS was 11.5 (9.2-19.1) months, a PSA decline of ≥50% occurred in 42.3% (11/26) of participants, and confirmed ORR for evaluable disease was 50% (5/10).

Conclusion

[177Lu]Lu-PNT2002, administered at 6.8 GBq/cycle for 4 cycles, demonstrated a favorable dosimetry and safety profile, as well as promising preliminary efficacy.

Clinical trial registration

https://clinicaltrials.gov/, identifier NCT04647526.

Preclinical Comparison of [111In]In- and [225Ac]Ac-DOTA-Trastuzumab IgG, F(ab')2 and Fab for Theranostic SPECT/CT Imaging and α-Particle Radioimmunotherapy of HER2-Positive Human Breast Cancer

Radioimmunotherapy (RIT) with α-particle-emitting, 225Ac complexed to trastuzumab may offer an alternative treatment for patients who progress on HER2-targeted therapies. Moreover, RIT with [225Ac]Ac-DOTA-trastuzumab could be combined with SPECT/CT imaging with [111In]In-DOTA-trastuzumab in a theranostic approach. In this study, we compared DOTA-conjugated trastuzumab IgG, F(ab')2 or Fab complexed to 111In or 225Ac for SPECT/CT imaging and α-particle RIT of subcutaneous (s.c.) HER2-positive 164/8-1B/H2N.luc+ human BC tumors in NRG mice. SPECT/CT imaging and tumor and normal tissue uptake were compared in NRG or NOD-SCID mice coinjected i.v. with [111In]In-DOTA-trastuzumab IgG, F(ab')2 or Fab and [225Ac]Ac-DOTA-trastuzumab IgG, F(ab')2 or Fab. Radiation absorbed doses in the tumor and normal organs for [225Ac]Ac-DOTA-trastuzumab IgG, F(ab')2 or Fab were estimated based on the biodistribution of the [111In]In-DOTA-trastuzumab IgG, F(ab')2 or Fab. Normal tissue toxicity was assessed by hematology and blood biochemistry analyses and monitoring body weight in NRG mice injected i.v. with 2 and 4 kBq of [225Ac]Ac-DOTA-trastuzumab IgG, F(ab')2 or Fab separated by 8 d. RIT studies were performed in NRG mice with s.c. 164/8-1B/H2N.luc+ tumors injected i.v. with 2 kBq and 4 kBq of [225Ac]Ac-DOTA-trastuzumab IgG, F(ab')2 or Fab separated by 8 d or irrelevant [225Ac]Ac-DOTA-IgG1, two doses of unlabeled trastuzumab IgG or 0.9% NaCl. A tumor growth index (TGI) was plotted vs time (d) and Kaplan-Meier median survival estimated. [111In]In-DOTA-trastuzumab IgG or F(ab')2 exhibited 4.1-fold and 3.3-fold significantly greater tumor uptake at 2 d postinjection (p.i.) than Fab at 24 h p.i. However, spleen uptake at 2 d p.i. for [111In]In-DOTA-trastuzumab IgG was 3.3-fold significantly higher than F(ab')2 and 13.2-fold higher than Fab at 24 h p.i. [111In]In-DOTA-trastuzumab F(ab')2 and Fab exhibited higher kidney uptake than IgG. Tumors were imaged by SPECT/CT with [111In]In-DOTA-trastuzumab IgG and F(ab')2 but were not well-visualized with [111In]In-DOTA-trastuzumab Fab. The absorbed dose in the tumor was 2.2-fold greater for [225Ac]Ac-DOTA-trastuzumab F(ab')2 than IgG and 3.4-fold greater than Fab. Hematological toxicity was observed for [225Ac]Ac-DOTA-trastuzumab IgG but not for [225Ac]Ac-DOTA-trastuzumab F(ab')2 or Fab. No kidney or liver toxicity or decreased body weight was observed for any RIT agent. Tumor growth was significantly inhibited by [225Ac]Ac-DOTA-trastuzumab IgG, F(ab')2 or Fab but [225Ac]Ac-DOTA-trastuzumab F(ab')2 was most effective for increasing median survival (46 d vs 22 d for IgG and 29 d for Fab). We conclude that [111In]In- and [225Ac]Ac-DOTA-trastuzumab F(ab')2 exhibited superior properties for theranostic imaging and α-particle RIT of HER2-positive human BC xenografts in NRG mice.

Dose constraints in breast cancer radiotherapy. A critical review

Radiotherapy plays an essential role in the treatment of breast cancer (BC). Recent advances in treatment technology and radiobiological knowledge have a major impact in BC patients with locoregional disease as the majority are now long-term survivors. Over the last three decades, intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and deep inspiration breath-hold (DIBH) techniques, together with the increasing adoption of moderately hypofractionated and ultra-hypofractionated treatment schedules as well as the possibility to offer partial breast radiotherapy to a well-defined patient subset have significantly changed radiotherapy for BC patients. As dose-volume constraints (DVCs) have to be adapted to these new treatment paradigms we have reviewed available evidence-based data concerning dose-constraints for the main organs at risk (OARs) that apply to the treatment of whole breast/chest wall radiotherapy, whole breast/chest wall radiotherapy including regional nodal irradiation (RNI) and partial breast irradiation (PBI), for the most relevant fractionation schedules that have been introduced recently. This narrative review provides a comprehensive summary that may help to harmonize treatment planning strategies.

A novel mouse model of image-guided radiation-induced acute kidney injury using SARRP

Radiation therapy is crucial for cancer treatment, but it often causes tissue damage. The kidney, which is sensitive to radiation, is under-researched in this context. This study aimed to develop a mouse model for radiation-induced acute kidney injury (AKI) using a small animal radiation research platform (SARRP) to mimic clinical radiation conditions. To establish the optimal AKI model, six-week-old male BALB/c mice were irradiated at doses of 5, 10, 20, and 30 Gy. Based on serum creatinine and blood urea nitrogen (BUN) levels, as well as immunohistochemical staining for neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), a 30 Gy dose was selected. This dose was applied in three ways: (1) single arc after a CT scan (K1, one kidney), (2) two arcs and two static beams after a CT scan (K2, both kidneys), and (3) abdominal irradiation after a single X-ray image (AI, including the kidneys). AKI was assessed 5 days post-irradiation. All irradiated groups exhibited more weight loss compared to the sham group, with the K2 group showing the most significant loss (p < 0.001 vs. K1, p < 0.05 vs. AI). The K2 group also demonstrated a significant reduction in kidney weight (p < 0.05 vs. K1) and higher serum BUN levels (p < 0.05 vs. sham, p < 0.01 vs. K1). Histopathological analysis revealed severe damage in the K2 group, including granular casts and tubular necrosis. The K2 group had elevated NGAL, KIM-1, γ-H2AX, malondialdehyde, and caspase-3 levels, indicating increased AKI severity and DNA damage. The SARRP-created AKI model effectively targeted renal tissue while sparing extrarenal tissues, offering a more clinically relevant model compared to traditional methods. This model bridges the gap between clinical and preclinical studies, enhancing the accuracy and relevance of research on radiation-induced kidney injury.

Papillary Tumor of the Pineal Region Treated With Surgery and Postoperative Radiotherapy: A Case Report

Papillary tumors of the pineal region (PTPR) are extremely rare malignancies that make up less than 0.1% of primary brain tumors. They are usually treated with surgery and adjuvant tumor bed radiotherapy (RT). We review the case of a man in his late 60s who presented with two weeks of confusion and ataxia. Imaging the head with computed tomography (CT) and magnetic resonance imaging (MRI) showed hydrocephalus and a 2 cm pineal region mass. We review the presenting symptoms, investigations, and differential diagnosis for patients with pineal region masses. The pathological features, initial hydrocephalus management, and curative treatment of his tumor with surgery and RT are discussed. We also review the PTPR literature, including prognostic features and the evidence for treatment modalities, and report adjuvant radiotherapy treatment planning volumes. The patient is symptom-free and without evidence of recurrent disease on follow-up MRI 18 months after treatment. PTPR has very high recurrence rates following treatment; less than 20% of patients have local control at 10 years, and further research is needed to find more effective interventions and improve patient outcomes.

Bladder Tumor-Focused Adaptive Radiation Therapy: Clinical Outcomes of a Phase I Dose Escalation Study

PURPOSE

We determine the maximum tolerated tumor-focused dose (MTD) for the radical treatment of muscle invasive bladder cancer enabled by image guided adaptive radiation therapy and long-term clinical outcomes.

METHODS AND MATERIALS

Fifty-nine patients with T2 to T4aN0M0 unifocal urothelial muscle invasive bladder cancer suitable for daily radical radiation therapy were recruited prospectively to an ethics-approved protocol (NCT01124682). The uninvolved bladder (PTVbladder) was planned to 52 Gy in 32 fractions. The bladder tumor (PTVtumor) was planned to an assigned dose level of 68, 70, 72, or 74 Gy. If organ at risk dose constraints were violated, then PTVtumor was planned to 64 Gy. Dose level allocation was determined by concurrent toxicity assessment of all previous patients recruited. Acute toxicity was evaluated using Common Terminology Criteria for Adverse Events v3.0; late toxicity was evaluated using Radiation Therapy Oncology Group criteria. The MTD was predefined as the highest dose level with an estimated probability of ≤ 15% ≥ G3 late toxicity and an observed rate of <50% acute G3 and <10% acute G4 toxicity.

RESULTS

Twenty-six patients were assigned to 68 Gy, of whom 6 were planned to 64 Gy; 29 patients were assigned to 70 Gy of whom 1 was planned to 68 Gy, 2 patients were assigned and planned to 72 Gy; no patients were assigned to 74 Gy. Three patients did not complete the treatment as planned, of whom only 1 patient stopped treatment because dose-limiting toxicity occurred. The MTD was 70 Gy. Acute genito-urinary and gastro-intestinal G3 acute toxicity was seen in 19% and 7% of patients, respectively. No acute G4 genito-urinary or gastro-intestinal toxicity was seen. Late toxicity (any) G3 and G4 was seen in 14% and 2% of patients, respectively. The 5-year overall survival was 58% (95% CI, 44%-71%). The bladder preservation rate was 89% (95% CI, 88%-96%) with 6 patients not retaining native bladder function.

CONCLUSIONS

Bladder tumor-focused dose escalation to 70 Gy using image guided adaptive radiation therapy is feasible with acceptable toxicity. This dose level has been evaluated in a phase II randomized control trial (RAIDER NCT02447549).

Dosimetric and Radiobiological Impact of Patient Setup Errors in Intensity-modulated Radiotherapy for Esophageal Cancer

PURPOSE

To evaluate the impact of patient setup errors on the dosimetry and radiobiological models of intensity-modulated radiotherapy (IMRT) for esophageal cancer.

METHODS AND MATERIALS

This retrospective study with 56 patients in thermoplastic mask (TM) and vacuum bag (VB) groups utilized real setup-error (RSE) data from cone-beam CT scans to generate simulated setup-error (SSE) data following a normal distribution. The SSE data were applied to simulate all treatment fractions per patient by shifting the plan isocenter and recalculating the dose. A simulated plan sum (SPS) was created by accumulating all simulated fraction plans. Comparisons of target dose, improved homogeneity index (iHI), conformity index (CI), tumor control probability (TCP) and normal tissue complication probability (NTCP) were conducted between SPSs and original treatment plans (OTPs). Correlations between RSE and TCP/NTCP were analyzed.

RESULTS

Compared to OTPs in the TM group, the planning target volume (PTV) of SPSs showed reductions in D95%, D98%, iHI, CI and TCP by 1.2%, 2.2%, 2.3%, 7.3% and 1.2%, while D2% increased by 0.3%; D2% of clinical target volume (CTV) increased by 0.2% (P < .05). In the VB group, D95%, D98%, iHI, CI and TCP of PTV decreased by 2.5%, 4.5%, 4.2%, 15.6% and 2.0%, with D2% increasing by 0.5%; D2% of CTV increased by 0.5% while D98% decreased by 0.2% (P < .05). The dose of organs at risk (OARs) changed slightly in both groups. The mean and standard deviation of absolute RSE negatively correlated with the TCP of PTV, while the mean RSE positively correlated with the NTCP of lung and spinal cord.

CONCLUSIONS

Setup errors may reduce dose homogeneity and conformity, potentially reducing TCP of PTV and increasing NTCP, especially when mean RSE shifts the isocenter towards OARs. VB immobilization may result in relatively larger impacts of setup errors, but this needs future validation.

Management of liver metastases (oligometastatic) by high-dose-rate interstitial brachytherapy: A case series

PURPOSE

To evaluate the feasibility, efficacy, and safety of interstitial brachytherapy in cases of oligo-metastatic liver disease.

MATERIALS AND METHOD

Four cases of liver metastases were managed over a period of 1 year in our center with close follow-up. All patients had progressive disease with histopathologially proven liver metastases and were ineligible for surgery. The procedure involved placement of brachytherapy catheters under computed tomography (CT) guidance post placement of a single 6F angiography sheath. The median size of metastasis was 2.9 cm (range 2.2-3.4 cms) in diameter, and a single fraction of radiation dose (10 to 13 Gy) was delivered. The angiography sheath and brachytherapy catheters were removed under fluoroscopic guidance post completion of the procedure with the help of an interventional radiologist. The fluoro guidance for removal of catheters was to observe any bleed. Response to treatment in terms of control of the metastases along with complications, safety, and efficacy of the procedure was observed.

RESULTS

All patients underwent re-evaluation with WB-PET-CT after 1 and 6 months. In three cases, complete response with no metabolic activity was noted on WB-PET-CT scan, and in one case, there was a partial response with a decrease in the size and metabolic activity of the metastasis. No fatal complications were noted; however, acute complications like grade 1 nausea, grade 1 vomiting, pain, and local hemorrhage were noted within 1 week of the procedure.

CONCLUSION

Liver interstitial brachytherapy is a feasible option in patients with maybe oligo metastatic solid tumors requiring a multi-disciplinary team effort. It is also an option for patients who are unfit for surgical excision. This is the first reported case series in India using high-dose-rate (HDR) brachytherapy techniques with an angiography sheath and flexible brachytherapy catheters.

NRG Oncology White Paper on the Relative Biological Effectiveness in Proton Therapy

This position paper, led by the NRG Oncology Particle Therapy Work Group, focuses on the concept of relative biologic effect (RBE) in clinical proton therapy (PT), with the goal of providing recommendations for the next-generation clinical trials with PT on the best practice of investigating and using RBE, which could deviate from the current standard proton RBE value of 1.1 relative to photons. In part 1, current clinical utilization and practice are reviewed, giving the context and history of RBE. Evidence for variation in RBE is presented along with the concept of linear energy transfer (LET). The intertwined nature of tumor radiobiology, normal tissue constraints, and treatment planning with LET and RBE considerations is then reviewed. Part 2 summarizes current and past clinical data and then suggests the next steps to explore and employ tools for improved dynamic models for RBE. In part 3, approaches and methods for the next generation of prospective clinical trials are explored, with the goal of optimizing RBE to be both more reflective of clinical reality and also deployable in trials to allow clinical validation and interpatient comparisons. These concepts provide the foundation for personalized biologic treatments reviewed in part 4. Finally, we conclude with a summary including short- and long-term scientific focus points for clinical PT. The practicalities and capacity to use RBE in treatment planning are reviewed and considered with more biological data in hand. The intermediate step of LET optimization is summarized and proposed as a potential bridge to the ultimate goal of case-specific RBE planning that can be achieved as a hypothesis-generating tool in near-term proton trials.

Lumbosacral plexopathy after short-course neoadjuvant radiotherapy for rectal cancer: A case report

ABSTRACT

Radiation-induced lumbosacral plexopathy (RILSP) is a rare complication associated with pelvic radiotherapy. Literature is scant about the incidence of RILSP after a neoadjuvant short-course radiotherapy (RT) in rectal cancer. In this report, we detail the symptoms, signs, and management of RILSP. Volumetric modulated arc therapy was used for delivering preoperative short-course RT in our rectal cancer patient. Six months after the completion of RT, the patient presented with symptoms of lower extremity motor and sensory impairment. An electrodiagnostic study revealed a pattern of bilateral sciatic nerve injury or a lower lumbosacral plexus abnormality. Magnetic resonance imaging showed radiation-related edema in the region of the lumbosacral plexus. Further blood and serum investigations ruled out other inflammatory and infectious differential diagnoses, thus a diagnosis of RILSP was made. He was initiated on analgesics and was also referred to physiotherapy and rehabilitation. After 2 months, his symptoms stabilized.

Survival impact of [225Ac]Ac-DOTATOC alpha-therapy in a preclinical model of pancreatic neuroendocrine tumor liver micrometastases

Although peptide radionuclide therapy (PRRT) using a somatostatin analog (SSA) radiolabeled with a beta- emitter: [177Lu]Lu-DOTATATE has shown a good clinical efficacy in neuroendocrine tumors (NETs), most of the patients only achieved tumoral stabilization and rare but severe long-term hematological toxicities have been reported. One of the promising options to improve PRRT is targeted alpha therapy. It is therefore essential to propose animal models that can mimic systemic spread disease, especially microscopic disease such as early stage of NET liver metastases to explore targeted alpha therapy. Herein, we report the evaluation of efficacy and toxicity of [225Ac]Ac-DOTATOC in an original preclinical murine model simulating the development of well-characterized liver metastases of pancreatic NETs with SSTR overexpression.

METHODS

A mouse model of liver metastases of pancreatic NETs was developed by intraportal injection of AR42J cells and explored using [68 Ga]Ga-DOTATOC and [18F]F-FDG PET/MRI. Biodistribution study and radiation dosimetry of [225Ac]Ac-DOTATOC were determined in subcutaneous tumor-bearing NMRI-nude mice. Efficacy and toxicity were determined by intravenous injection of increasing activities of [225Ac]Ac-DOTATOC 10 days after intraportal graft.

RESULTS

Liver tumors showed a high uptake of [68 Ga]Ga-DOTATOC and no uptake of [18F]F-FDG confirming the well-differentiated phenotype. All groups treated with [225Ac]Ac-DOTATOC showed a significant increase in overall survival compared with DOTATOC-treated mice, especially those treated with the highest activities: 53 days with 240 kBq (p = 0.0001), and 58 days with 2 × 120 kBq (p < 0.0001) vs 28 days with non-radiolabeled DOTATOC. On blood tests, a transient and moderate decreased in white blood cells count after treatment and no severe hepatic or renal toxicity were observed after treatment which was consistent with pathological and radiation dosimetry findings.

CONCLUSION

[225Ac]Ac-DOTATOC exhibit a favorable efficacy and toxicity profile in a mouse model of liver micrometastatic pancreatic NET.

Nanotechnology for the Diagnosis and Treatment of Liver Cancer

Liver cancer has become a major global health challenge due to its high incidence, high rate of late diagnosis and limited treatment options. Although there are many clinical treatments available for liver cancer, the cure rate is still very low, and now researchers have begun to explore new aspects of liver cancer treatment, and nanotechnology has shown great potential for improving diagnostic accuracy and therapeutic efficacy and is therefore a promising treatment option. In diagnosis, nanomaterials such as gold nanoparticles, magnetic nanoparticles, and silver nanoparticles can realize highly sensitive and specific detection of liver cancer biomarkers, supporting diagnosis and real-time monitoring of the disease process. In terms of treatment, nanocarriers can realize precise targeted delivery of drugs, improve the bioavailability of liver cancer therapeutic drugs and reduce systemic toxic side effects. In addition, advanced technologies such as nanoparticle-based photothermal therapy and photodynamic therapy provide innovative solutions to overcome drug resistance and local tumor ablation. Therefore, in this paper, we will introduce nanotechnology for hepatocellular carcinoma in terms of tumor marker detection, targeted drug delivery, and synergistic PDT/CDT therapy.

Minimizing Long-Term Toxicities for Patients with Primary Mediastinal B-Cell Lymphoma Undergoing Modern Radiotherapy: Results from a Monocentric Biophysical Risk Evaluation

Introduction: Primary mediastinal B-cell lymphoma (PMBCL) is a rare form of aggressive B-cell lymphoma with a predominant onset in young patients. The minimization of potential (late) side effects is of cardinal interest for these patients. An anticipation of the individual risk profile is desirable to counsel the patient on the putative impact of radiotherapy (RT). Methods: RT plans for a cohort of 25 patients with PMBCL were prospectively designed. One plan with two parallel- opposing fields (APPA) and another with volume-modulated arc therapy (VMAT) technique with 40 Gy in 2 Gy fractions each. Normal The normal tissue complication probability (NTCP) was calculated using the Lyman--Kutcher--Burman model for heart, lung and oesophageal toxicity. Results: APPA planning resulted in lower median doses (Dmedian) for the heart and lungs, whereas all other dose metrics for heart, lungs and esophagus were lower in VMAT planning. A significant difference in the mean NTCPs when comparing the APPA to VMAT plans was seen for increased cardiac mortality, pneumonitis and esophagitis. PTV size correlated with increased cardiac mortality and esophagitis in both plan variations and with pneumonitis for VMAT plans. Dmean, Dmedian, and V20Gy correlated with the risk for pneumonitis, and Dmean, Dmedian, and V1% with the risk for esophagitis in both variants. Conclusions: We showed decreased risk of different NTCPs for VMAT and APPA planning for thoracic toxicities. The use of an IMRT technique like VMAT showed advantages for several DVH metrics in organs at risk and should therefore be recommended for radiation treatment of PMBCL.

Phase I study of neoadjuvant chemoradiotherapy with S-1 for clinically resectable type 4 or large type 3 gastric cancer in elderly patients aged 75 years and older (OGSG1303)

Purpose The prognosis for type 4 and large type 3 gastric cancer (GC) is extremely poor, especially in elderly patients (≥ 75 years). To improve the prognosis of these types of GC, we performed a phase I study to determine the recommended dose (RD) of S-1 combined with neoadjuvant radiotherapy. Methods Patients with clinically resectable type 4 and large type 3 GC were enrolled to successive cohorts in a conventional 3 + 3 design. Three dose levels were designed, as follows: level 0: S-1 60 mg/m2/day on Days 1-14; level 1: S-1 80 mg/m2/day on Days 1 -14; level 2: S-1 80 mg/m2/day on Days 1-14 and Days 22-35. The starting dose was level 1. Radiotherapy was delivered at a total dose of 40 Gy in fractions for 4 weeks. Results Ten patients were enrolled from July 2014 to August 2018. Six patients were registered at level 1, and one patient developed a dose limiting toxicity as gastric stenosis (grade 3). Two of four patients enrolled at level 2 developed dose limiting toxicity (inability to receive S-1 for hematological reasons). Therefore, the RD was determined as level 1. All patients underwent the protocol surgery; one patient underwent R1 resection because of positive peritoneal washing cytology. There were no treatment-related deaths, and the pathological response rate was 80%. The 5-year overall- and progression-free survival rates were both 60.0%. Conclusion The RD was determined as level 1. A phase II trial using the RD should be initiated.

Ultra-hypofractionated 5-fraction radiation therapy for early breast cancer into whole breast and regional nodes: experience in a tertiary hospital

INTRODUCTION

Post-surgery radiotherapy to the breast and regional lymph nodes decreases locoregional tumour recurrence and related mortality. The FAST-Forward approach, with 5 daily fractions, shows non-inferiority to the conventional 15-fraction scheme with similar safety. Authors suggest Simultaneous Integrated Boost (SIB) for the tumour bed and regional nodal irradiation (RNI) for comparable toxicity.

OBJECTIVES AND PURPOSES

To describe acute and delayed toxicity in adjuvant radiotherapy patients using FAST-Forward scheme with SIB and analyze associations with patient characteristics.

MATERIALS AND METHODS

An observational, descriptive, retrospective study on 120 early breast cancer patients (pT1-3, pN0-1, M0), treated with surgery and adjuvant radiotherapy using the FAST-Forward scheme with SIB at our center. Some also received RNI. Study conducted from June 2021 to October 2023.

RESULTS

Median age: 55 years (range 30-86). Main histological type: infiltrating ductal carcinoma (80%), with Luminal A as predominant molecular subtype (58.5%). Stage IA tumours (61%), pT1c (40%), G2 (50%). Treatment included: neoadjuvant chemotherapy (18.3%), adjuvant chemotherapy (23.5%), hormonal treatment (82.5%), surgery (99%). Radiotherapy with SIB in 90% of conservative surgeries with a median dose 30 Gy (range: 29-33.6). There was no significant association between acute/chronic toxicity and SIB found. However, there was increased risk of acute induration with neoadjuvant chemotherapy. Adjuvant chemotherapy was linked to significant rates of acute and delayed hyperpigmentation. The acute toxicity in first 6 months post-radiotherapy was only G1. The most frequent late toxicities were G1 indurations, edema, hyperpigmentation.

CONCLUSIONS

The FAST-Forward scheme with SIB and RNI in 5 daily fractions seems well-tolerated without severe acute or delayed toxicity.

DNA double-strand break repair capacity and normal tissue toxicity induced by radiotherapy

Radiation therapy is used in the treatment of various cancers, and advancements in irradiation techniques have further expanded its applicability. For radiation oncologists, predicting adverse events remains a critical challenge, even with these technological advancements. Although numerous studies have been conducted to predict individual radiosensitivity, no biomarkers have been clinically applied thus far. This review focuses on γ-H2AX foci and chromosomal aberrations, providing an overview of their association with normal tissue toxicities.

Radiation induced liver injury (RILI) evaluation using longitudinal computed tomography (CT) in image-guided precision murine radiotherapy

Purpose

We aim to perform image-guided, dose-escalated, well-controlled liver-irradiated animal studies and subsequently evaluate radiation induced liver injury (RILI) using longitudinal CT.

Methods

Eighteen 6-8 weeks mice were divided into three groups: control, 15Gy and 30Gy irradiated groups. The animal protocol was approved by the animal care ethics committee of our institution. Precision radiotherapy started with CT simulation, followed by treatment planning using volumetric modulated arc therapy (VMAT), image guidance with cone beam CT (CBCT) and radiation delivery on a medical linear accelerator. Weekly CT was conducted on the same CT simulator using same scanning parameters. At the end of fifth week, all mice were sacrificed, and histological staining was performed. Body weight, liver volume, HU values and histogram distributions were analyzed.

Results

Body weight of irradiation groups was significantly reduced compared to that of the control group (p<0.05). Liver volume in irradiated groups was reduced too. The average liver HU was significantly reduced in irradiated groups (HU mean = 62±3, 48±6, and 36±8 for the control, 15Gy and 30Gy respectively; p control vs. 15Gy < 0.05, p control vs. 30Gy < 0.05). A linear relationship between liver HU and radiation dose was found. Furthermore, HU histogram changes with time and dose showed not only density but also structure might be affected by radiation. HE and Masson Trichrome staining confirmed histological change and increased collagen deposition in irradiated liver.

Conclusion

Longitudinal unenhanced CT is a useful imaging tool to evaluate the severity and progression of radiation induced liver injury.

Efficacy and safety of rechallenge with [177Lu]Lu-PSMA-I&T radioligand therapy in metastatic castration resistant prostate cancer

BACKGROUND

The purpose of this study was to evaluate the safety and outcome of rechallenge [177Lu]Lu-PSMA-I&T in newly progressed mCRPC patients after response to initial [177Lu]Lu-PSMA radioligand therapy (PRLT).

METHODS

We retrospectively included 18 patients who underwent rechallenge with [177Lu]Lu-PSMA-I&T. All patients presented with (i) newly progressed disease after response to initial PRLT; (ii) a [68Ga]Ga-PSMA-11 PET/CT confirming the presence of PSMA-positive metastases; iii) ECOG performance status 0-1. Adverse events were graded according to CTCAE v5.0. Response was assessed by PSA and classified according to PCWG3 recommendations. For patients who underwent restaging with [68Ga]Ga-PSMA-11 PET/CT, imaging response was categorised according to adapted PERCIST v1.0. In patients with discordant [68Ga]Ga-PSMA-11 PET/CT and PSA, other available imaging modalities were evaluated to confirm disease status. Overall survival (OS) was calculated from the first cycle of initial PRLT and rechallenge PRLT, respectively, until last patient contact or death.

RESULTS

Patients were initially treated with a median of 5 cycles (range 4-7) and were rechallenged after a median of 9 months (range 3-13). Each patient received a median of 4 (range 2-7) rechallenge cycles (median cumulative activity 26.1 GBq). None of the patients experienced life-threatening G4 adverse events during either treatment period. Grade 3 adverse events included one case of anaemia, one case of thrombocytopenia, and one case of renal failure. In 8/18 patients long-term toxicities were evaluated. Serious toxicities (≥ Grade 3) occurred in 3/8 patients (n = 1 G4 thrombocytopenia, n = 1 G4 renal failure and n = 1 pancytopenia and G4 renal failure). Best PSA50%-response was observed in 44% of patients and PSA-disease control was confirmed in 56% of patients at the last cycle. Of the 12/18 patients restaged by imaging, 6/12 (50%) patients had disease control (partial response/stable disease), 1/12 had a mixed response, and 5/12 had progression. After a median follow-up time of 25 months (range 14-44), 10 patients had died, 7 were still alive, and one patient was lost at follow-up. The median OS was 29 months (95%CI, 14.3-43.7 months) for the initial treatment and 11 months (95%CI, 8.1-13.8 months) for the first rechallenge course.

CONCLUSION

More than half of patients benefit from rechallenge PRLT. Our analysis suggests that rechallenge may prolong survival in selected patients, with an acceptable safety profile.

Automatic Treatment Planning for Radiation Therapy: A Cross-Modality and Protocol Study

Purpose

This study investigated the applicability of 3-dimensional dose predictions from a model trained on one modality to a cross-modality automated planning workflow. Additionally, we explore the impact of integrating a multicriteria optimizer (MCO) on adapting predictions to different clinical preferences.

Methods and Materials

Using a previously created 3-stage U-Net in-house model trained on the 2020 American Association of Physicists in Medicine OpenKBP challenge data set (340 head and neck plans, all planned using 9-field static intensity modulated radiation therapy [IMRT]), we retrospectively generated dose predictions for 20 patients. These dose predictions were, in turn, used to generate deliverable IMRT, VMAT, and tomotherapy plans using the fallback plan functionality in Raystation. The deliverable plans were evaluated against the dose predictions based on primary clinical goals. A new set of plans was also generated using MCO-based optimization with predicted dose values as constraints. Delivery QA was performed on a subset of the plans to assure clinical deliverability.

Results

The mimicking approach accurately replicated the predicted dose distributions across different modalities, with slight deviations in the spinal cord and external contour maximum doses. MCO optimization significantly reduced doses to organs at risk, which were prioritized by our institution while maintaining target coverage. All tested plans met clinical deliverability standards, evidenced by a gamma analysis passing rate >98%.

Conclusions

Our findings show that a model trained only on IMRT plans can effectively contribute to planning across various modalities. Additionally, integrating predictions as constraints in an MCO-based workflow, rather than direct dose mimicking, enables a flexible, warm-start approach for treatment planning, although the benefit is reduced when the training set differs significantly from an institution's preference. Together, these approaches have the potential to significantly decrease plan turnaround time and quality variance, both at high-resource medical centers that can train in-house models and smaller centers that can adapt a model from another institution with minimal effort.

Biodistribution and Radiation Dosimetry for 68 Ga-DOTA-CCK-66, a Novel CCK 2 R-Targeting Compound for Imaging of Medullary Thyroid Cancer

ABSTRACT

Cholecystokinin 2 receptor (CCK 2 R) is a promising target for imaging and treatment of medullary thyroid cancer due to its overexpression in over 90% of tumor cells. 68 Ga-DOTA-CCK-66 is a recently introduced PET tracer selective for CCK 2 R, which has shown favorable pharmacokinetics in vivo in preclinical experiments. In order to further investigate safety and suitability of this tracer in the human setting, whole-body distribution and radiation dosimetry were evaluated.

PATIENTS AND METHODS

Six patients with a history of medullary thyroid cancer were injected intravenously with 169 ± 19 MBq of 68 Ga-DOTA-CCK-66. Whole-body PET/CT scans were acquired at 10 minutes, 1 hour, 2 hours, and 4 hours after tracer injection. Time-activity curves per organ were determined, and mean organ-absorbed doses and effective doses were calculated using OLINDA/EXM.

RESULTS

Injection of a standard activity of 150 MBq of 68 Ga-DOTA-CCK-66 results in an effective dose of 4.5 ± 0.9 mSv. The highest absorbed organ doses were observed in the urinary bladder wall (40 mGy) and the stomach (15 mGy), followed by the kidneys (6 mGy), as well as the liver and the spleen (3 mGy each). CCK 2 R-expressing tumor manifestations could be detected in 2 of the 6 patients, including lymph node, bone, and liver metastases.

CONCLUSIONS

68 Ga-DOTA-CCK-66 exhibits a favorable dosimetry. Beyond physiologic receptor expression of the stomach, no other relevant tracer accumulation could be observed, rendering this organ at risk in case of subsequent radioligand therapy using 177 Lu-DOTA-CCK-66.

Replacing 2 Gy Per Fraction Equivalent Dose with Fractionation-Specific Biological Equivalent Dose for Normal Tissues

The 2 Gy per fraction equivalent dose (EQD2) is an important quantity used in determining equivalent prescription doses for different fractionation regimens and evaluating different fractionation regimens, but it does not match its definition when it is used for normal tissues. We propose to use the fractionation-specific biological equivalent dose to determine normal tissue dose constraints for different fractionation regimens. The concept of the biological equivalent dose is defined based on the linear-quadratic equation. The EQD2 is derived based on the biological effective dose (BED), mimicking the prescription dose of a standard fractionation regimen with a fractional dose of 2 Gy and a fixed number of fractions. The FEQD(n) is also defined based on the BED as a function of the number of fractions, n, which is determined by the dose prescription. The FEQD(n) mimics any fractionation regimens with any fractional doses and numbers of fractionations. A given dose constraint can have different BED values and EQD2 values for different fractionation regimens. The number of fractions for a given 2 Gy per fraction regimen derived from the EQD2 for the target dose is different from that for the normal tissues. The value of the EQD2 derived for the target represents the total dose for the target for the 2 Gy fractional dose regimen, but the EQD2 value derived for the normal tissues does not represent the total dose for the normal tissue for the same fractionation regimen. The fractionation-specific biological equivalent dose (FEQD(n)) for both target and normal tissues has the same number of fractions for any fractionation regimen, and represents the total dose for either the target or the normal tissue. Based on the clinical outcomes, the FEQD(n) curves for the brainstem, spinal cord, rectum, and lung were derived and can be directly used as dose constraints for various fractionation regimens in clinical practice. The EQD2 does not match its definition and is not realistic when describing the biological equivalent dose for normal tissues. It is also not practical when used in determining tolerance doses or dose constraints. Instead, the FEQD(n) can be used to determine or convert the normal tissue dose constraints for any fractionation regimens in a realistic and practical manner. Using the FEQD(n), the dose constraints as a function of the number of fractions for the brainstem, spinal cord, rectum, and lung, which correspond to the given toxicity rates, were derived and can be directly used in clinical practice.