International Journal of Particle Therapy最新文献

Purpose: Monte Carlo (MC) simulations provide gold-standard accuracy for carbon ion therapy dose calculations but are computationally intensive, limiting their use in adaptive workflows. Analytical pencil beam algorithms offer speed but reduced accuracy in heterogeneous tissues. This study develops the first AI-based dose engine capable of predicting relative biological effectiveness-weighted doses. Absorbed dose, α, and β parameters for optimization are calculated at MC-level accuracy with a drastically reduced computational time.

Materials and methods: We extended the transformer-based DoTA architecture to predict absorbed dose (C-DoTA-d), α (C-DoTA-α), and β (C-DoTA-β), introducing a cross-attention mechanism for α and β to combine dose and energy inputs. The training dataset consisted of approximately 70 000 pencil beams from 187 head-and-neck patients, with ground-truth values obtained using the GPU-accelerated MC toolkit FRED. Performance was evaluated on an independent test set using gamma pass rate (1%/1 mm), depth-dose, and isodose contour Dice coefficients. MC dropout-based uncertainty analysis was performed.

Results: Median gamma pass rates exceeded 98% for all predictions (99.76% for dose, 99.14% for α, 98.74% for β), with minima above 85% in the most heterogeneous anatomies. The Dice coefficient was 0.95 for 1% isodose contours, with slightly reduced agreement in high-gradient regions. Compared to MC FRED, inference was over 400× faster (0.032 vs 14 seconds per pencil beam) while maintaining accuracy. Uncertainty analysis showed high stability, with mean standard deviations below 0.5% for all models.

Conclusions: This AI-based dose engine achieves MC-quality predictions of absorbed dose and relative biological effectiveness model parameters in ∼30 ms per beamlet. Its speed and accuracy support online adaptive planning, paving the way for more effective carbon ion therapy workflows. Future work will expand to additional anatomical sites, beam geometries, and clinical beamlines.

Purpose: Radiotherapy (RT) is often used as a combined modality therapy for patients with Hodgkin (HL) and aggressive Non-Hodgkin Lymphoma (aNHL). RT options include photon intensity-modulated radiotherapy (IMRT) or proton therapy (PT). As PT is a limited and costly resource, it is important to identify cases in which PT may best benefit in order to offer providers and patients the best possible information for decision-making. Accordingly, the purpose of this study was to assess the difference in OAR sparing between photon IMRT and pencil-beam scanning (PBS) based on disease location using the Ann Arbor (AA) staging system.

Materials and methods: A cohort was established including all patients with HL or aNHL (n = 156) treated with RT at a single institution from 2007 to 2020. Two plans (IMRT and PBS) were developed for each patient using consistent planning techniques with a prescribed dose of 30 Gy. Disease anatomic classification was classified using AA, and OAR differences were assessed based on disease location. Mediastinal involvement was divided between upper, middle, and lower (UML). OAR doses were comparatively assessed by the AA site looking at absolute (AS) and relative sparing (RS) using patient plan pairs using the Wilcoxon signed-rank test.

Results: PBS reduced the mean heart dose with the largest AS (6.4 Gy) for patients with UML mediastinal involvement. Greatest AS and RS for lung V20 was seen for patients with bilateral axillary involvement (20.9% AS, 53.5% RS), and for mean breast dose greatest sparing was seen for those with bilateral hilar disease (5.1 Gy AS, 58.6% RS).

Conclusion: The use of PBS resulted in a substantial decrease in the mean dose to OARs, the magnitude of which depended on the location in which disease was present. This work advances that the anatomic location of involvement is an important influence on the relative benefit of PT.

Background: Surface-guided radiotherapy (SGRT) is a real-time, non-ionizing optical imaging technology that monitors patient surfaces during radiation treatment by creating 3D reconstructions from surface coordinate measurements. LAP has recently released a new SGRT solution, and we are the first proton therapy center to adopt this SGRT solution in a full rotating gantry. This work aims to present the commissioning results and quality assurance procedures at our center and to highlight the challenges of installing SGRT on a full rotating gantry.

Methods: Following closely the recommendations in TG-302, 6 different measurements were performed during the commissioning of the SGRT system, which was mounted linearly on the same beam due to space constraints. These measurements included spatial drift measurement, static localization accuracy, dynamic localization accuracy, end-to-end localization accuracy, field-of-view (FOV) characterization of different treatment sites, and stability upon gantry rotation. These measurements subsequently served as baseline values for the different quality assurance procedures recommended in TG-302.

Results: The moving average for spatial drift measurement across 200 minutes was 0.0233 mm, while the average deviation for static and dynamic localization was less than 0.2 mm across. The largest deviation was 0.182 mm in the LR direction at 40 mm for static localization, while dynamic localization has a maximum deviation from the Anzai laser tracking at 0.1 minute point with a value of 0.734 mm. End-to-end localization test reported a difference of 0.08 cm between x-ray imaging and LUNA 3D's isocenter. The FOV was in general mostly visible for all treatment sites except for the lower neck region and lateral prostate surfaces due to the placement of the cameras. Stability during gantry rotation is kept within 0.2 mm with gantry angle 30.4° and 335.8° having the largest magnitude deviations of 0.151 and 0.156 mm, respectively.

Conclusion: The successful commissioning of the LUNA 3D SGRT system at our center can serve as a reference for other particle therapy centers with a full rotating gantry. This work will allow them to include the relevant tests as well as understand the limitations of FOV for different treatment sites when adopting similar camera arrangement like ours in a full rotating gantry.

Background and purpose: The role of proton radiation (PT) for infradiaphragmatic targets in lymphoma patients is unknown. We report on radiation planning details, doses achieved to organs at risk (OARs), and outcomes for this population.

Patient/material and methods: This is a single-institution retrospective study of patients with biopsy-proven lymphoma who received PT to infradiaphragmatic targets between 2011 and 2022. Comparison photon plans were generated for all patients. Toxicity was reported using CTCAE version 5.0. Dosimetric and clinical factors associated with toxicity and oncologic outcomes were assessed via Cox regression, while the paired t-test or Wilcoxon signed rank test was used for dosimetric analyses.

Results: 38 patients comprising 40 PT courses were included. Median follow-up was 48 months. Top diagnoses were DLBCL (58%) and Hodgkin lymphoma (16%). 28% of PT courses had direct overlap with prior radiation and 20% were palliative. Median dose was 30.6 Gy over 17 fractions to locations including the spine/paraspinal region (30%), retroperitoneum (28%), and pelvis (22%). There were no acute G3+ toxicities. Among patients treated with curative intent, 44% experienced progression of disease (POD), mostly distant. 5/38 patients had a second malignancy after PT. Among the photon comparison plans, PT significantly decreased doses to the kidneys (mean and V5), small/large bowel (V5, V15), and numerous other abdominopelvic organ metrics. Large bowel V30 Gy was higher with PT (12.4 vs. 7.6 cc, p = p = .007).

Interpretation: PT is well-tolerated and leads to excellent outcomes. PT can significantly reduce doses to key abdominopelvic OARs compared to photons.

Introduction: Adenoid cystic carcinoma (ACC) of the head and neck is a rare malignancy with a high risk of perineural invasion, local recurrence, and distant metastasis. Recurrent ACC poses unique challenges due to its aggressive nature, resection limited by morbidity, and prior radiation. Proton therapy, with its ability to spare normal tissues via the Bragg peak, may offer a promising and safe re-irradiation approach, especially in patients not amenable to resection requiring high definitive doses. The purpose of this study was to evaluate outcomes of patients with recurrent ACC treated with proton radiation.

Methods: We reviewed the records of all patients with recurrent head and neck ACC treated with proton therapy between November 2012 and December 2023. This cohort included patients with both resected and unresected disease. Standard imaging, including MRI for perineural spread and PET for distant recurrence, was used in all cases. Descriptive statistics were used to analyze patient, tumor, and treatment characteristics, and the Kaplan-Meier method and cumulative incidence curves were utilized to estimate overall survival (OS) and loco-regional recurrence (LRR), respectively.

Results: A total of 19 patients were included, with 6 (32%) receiving adjuvant re-irradiation and 13 (68%) receiving definitive proton re-irradiation. Median dose in the adjuvant group was 63.36 (59.40-70.07), and 59.20 (14.80-70.00) in the primary RT group. The median OS for all patients was 62% at 24 months and 48% at 48 months. Patients receiving adjuvant therapy had an OS of 80% at 24 and 48 months, while those not receiving surgery had an OS of 52% and 31% at 24- and 48-months. LRR at 24 months was 11% for all patients. No grade 5 toxicities were observed.

Conclusion: This study demonstrates the feasibility and potential benefits of proton re-irradiation for recurrent ACC, with promising local-regional control and minimal toxicity.

The symposium "Hadrontherapy for life," held in Caen, on March 10 and 11, 2025, brought together over 100 international experts of heavy ions particle therapy. Clinical aspects of current indications and future strategies were discussed. If protontherapy remains the cornerstone of current strategies dealing with pediatric malignancies, in order to better spare normal tissues from deleterious effects of radiation, heavier ions such as carbon ions could play a role in selected highly radio-resistant processes such as bone and non rhabdomyosrcomas soft tissue sarcomas. A special mention should be made to helium ions tested since 2021 in Europe that mimic protons with further ballistic selectivity. If immediate and early side effects of heavy ions look modest, long-term tolerance still needs to be carefully evaluated, including risks of carcinogenesis.

The symposium "Hadrontherapy for Life," held in Caen, on February 10 and 11, 2025, brought together over 100 international experts of heavy ions particle therapy. Clinical aspects of current indications and future strategies were discussed. Pancreatic cancer that may reach the second cause of cancer mortality in the next decade, was prioritized. Stimulating clinical data accumulated in Japan and more recently in Europe suggest an important role for carbon ion radiotherapy (CIRT) in advanced presentations but also in a preoperative setting, at the price of acceptable toxicity. Biological aspects also plead for combinations of CIRT with bio or immune therapy.

Purpose: The goal of this study is to report the feasibility and outcomes of hypofractionated proton reirradiation in patients with recurrent thoracic tumors.

Materials and methods: Data were retrospectively collected for patients who received hypofractionated proton therapy for recurrent lung cancer at a single facility. Proton reirradiation was delivered using a total of 15 fractions. Patient and tumor characteristics, adverse events, and dose-volume histogram parameters were collected and analyzed descriptively. Tumor control and patient survival were analyzed using Kaplan-Meier statistics. Univariate logistic regression was performed to analyze the relationship between dose-volume histogram parameters and acute and late toxicity.

Results: Thirty-one patients who received thoracic proton reirradiation were included. The median patient age was 71.4. Most patients (77.4%) were treated to a total of 60 Gy (RBE) in 15 fractions and had tumors smaller than 50 cc (64.5%). The median interval between the 2 radiation courses was 21.3 months (2.9-227.1). Twenty-one out of 31 plans (67.7%) successfully reached a target PTV coverage with V95% > 95%. Complete prior plan dosimetric information was available for 19 out of 31 plans. The median value of the equivalent dose in 2 Gy (RBE) fractions (EQD2) from the plan sum for the lung V20 Gy (RBE) was 24.9%, and for the V5 Gy (RBE) was 44.8%. The median follow-up was 9.0 months. One-year local, regional, and distant control were 92.3% (95% CI 78.9-100), 71.1% (95% CI 52.1-97.0), and 80.6% (95% CI 64.6-100), respectively. Only two patients experienced grade 3 or higher acute or late toxicities. Acute esophagitis was associated with the esophagus Dmax (P = .031) and Dmean (P = .041).

Conclusion: This study demonstrates the feasibility and efficacy of a hypofractionated course of proton reirradiation for recurrent thoracic tumors.

Data availability: The data that support the findings of this study are available on request from the corresponding author.

Purpose: Proton therapy, with its high conformality and superior dose distribution, is becoming an increasingly prevalent modality in radiation oncology. Although a generic relative biological effectiveness (RBE) value of 1.1 for treatment planning has been adopted, evidence suggests that RBE varies with dose, linear energy transfer (LET), and biological endpoints. This variation raises concerns about underestimating the RBE-weighted dose, which may significantly impact treatment outcomes. To assess the awareness and management of RBE variability in clinical practice, we conducted a survey among US proton therapy centers.

Materials and methods: The survey consisted of 32 questions grouped into subtopics, such as awareness of RBE variability, practices to account for variability, and future needs. It was distributed among 29 centers through the auspices of the Particle Therapy Co-Operative Group - North America.

Results: The response rate was 80% and revealed significant apprehension about the assumption of a constant RBE. All respondents used a fixed RBE of 1.1, yet expressed varying degrees of concern about its appropriateness. Most centers report unanticipated toxicities and local recurrences potentially linked to an underestimation of RBE, highlighting the need for revisiting current practices. The survey indicated that nearly all centers consider RBE variability during beam arrangement, and some perform LET and variable RBE calculations for patient-specific treatments. There is a strong consensus on the need for multi-institutional databases, studies to accumulate clinical evidence, and education on proton RBE to better understand RBE's clinical implications.

Conclusions: This study is an overview of current clinical practices regarding proton RBE and identifies key priorities for future research. Although deviations from the generic RBE of 1.1 is commonly considered in treatment planning, the absence of standardized approaches leads to inconsistencies. Developing consensus guidelines and integrating advanced RBE and LET-based models into treatment planning could improve the precision and safety of proton therapy.

Purpose: Radiotherapy can lead to radiation-induced optic neuropathy, with vision loss and visual field deficits related to localized damage to the optic pathways. Accurately quantifying visual field deficits and establishing their spatial relationship with anatomical structures and radiation dose distribution remains a significant challenge. We applied archetypal analysis of visual fields as a novel artificial intelligence approach in oncology to identify distinct, interpretable patterns of visual field loss and to model their spatial evolution over time after pencil beam scanning proton therapy.

Methods: Machine learning of standardized automated static visual field perimetry was used to decompose the high-dimensional visual field data into convex combinations of representative visual loss patterns, that is, visual archetypes, at both the eye and patient levels. Associations between archetype proportions and radiation dose metrics were evaluated using linear regression, stratified by baseline visual field to account for pre-existing deficits.

Results: In 236 patients, 7 archetypal patterns of visual field loss were identified, including tunnel vision, temporal hemianopia, and diffuse full-field loss. More severe patterns were more frequently observed in patients with meningiomas and pituitary adenomas. Longitudinal analysis revealed an annual reduction of 1.9% in the normal visual field archetype in patients with no-to-mild baseline deficits and 9.7% in those with moderate deficits. Dose-archetype associations were clinically significant after adjusting for baseline deficits. Each 1 Gy increase in minimum chiasm dose was associated with a 0.2% decrease in the normal vision archetype.

Conclusion: This is the first application of archetypal analysis for predicting radiation-induced optic neuropathy. It enables spatially grounded reconnection between patient perception and radiation damage along optic pathways. This approach offers new mechanistic insights into optic pathway injury towards voxel-level correlation between radiation dose and functional loss and supports data-driven personalization of radiotherapy.