International Journal of Particle Therapy最新文献

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.

Purpose: To systematically compare fully automated planning for 36-field discrete proton arc therapy (36PAT) with: (1) intensity-modulated proton therapy (IMPT) with 4- and 6-field clinical beam-angle class solutions (4CS, 6CS), (2) IMPT with patient-specific, computer-optimized beam-angle configurations with 6, 8 or 10 fields (6BAO, 8BAO, 10BAO), and (3) 36-field equiangular ''Utopia'' IMPT (36Utopia; total focus on dosimetric quality, no delivery time considerations) for oropharyngeal cancer patients.

Materials and methods: All automated plan generations were performed with Erasmus-iCycle. An energy layer (EL) reduction algorithm was developed in Erasmus-iCycle to balance plan quality with delivery time in discrete PAT planning. Patient-tailored beam-angle configurations for BAO plans were obtained with the earlier published iCycle-pBAO. In 36Utopia plans, no EL reductions were applied. While beam configurations varied among approaches, all final plans were automatically generated using the published wish-list driven SISS-MCO optimizer with dosimetry-based sparsity-induced spot selection (SISS), followed by multi-criterial spot weight optimization (MCO) and resulting in Pareto-optimality in spot weights. The same wish-list for all delivery approaches prevented planning bias across approaches.

Results: 36PAT plans achieved organs at risk (OAR) doses and normal tissue complication probability (NTCP) approaching 36Utopia plans. Relative to CS plans, 36PAT plans reduced normal tissue dose, decreasing xerostomia and dysphagia NTCPs. Compared to 4CS, 36PAT reduced summed NTCPs for grade 2 toxicity by 6.1%-point (P = .002) and grade 3 by 2.1%-point (P = .002). For 6CS, reductions were 4.7%-point (P = .002) and 1.2%-point (P = .01), respectively. 36PAT plans also outperformed BAO plans with 6 and 8 fields but were comparable to 10BAO in OAR doses and NTCPs for similar EL numbers and Monitor Units (MU).

Conclusion: PAT demonstrated superior dosimetric quality over clinical class solutions for oropharyngeal cancer and approached Utopia. Ten-field IMPT with personalized beam angles could be an alternative to 36-field PAT with similar expected toxicity, ELs and MUs, but a lower number of fields.

[This corrects the article DOI: 10.1016/j.ijpt.2024.100646.].

Purpose: Although carbon-ion radiation therapy (CIRT) creates a sharp dose distribution, inaccurate irradiation positioning may reduce the tumor dose. In pancreatic CIRT, interfractional tumor motion is a factor causing tumor dose reduction. This motion is typically accounted for in the planning target volume, and it cannot provide sufficient margin because the tumor is surrounded by the gastrointestinal tract. Online adaptive radiation therapy (ART) can solve this problem, but other problems such as equipment design and excessive time consumption remain in CIRT. The purpose of this feasibility study was to evaluate the effectiveness of dose matching (DM), which is more convenient than ART in pancreatic CIRT.

Materials and methods: On the in-room computed tomography images, search isocenters were placed 3 dimensionally around the isocenter determined by target matching (TM) at 0.2 cm intervals. The fractional dose distributions were then calculated at each isocenter. The coordinate with the best clinical target volume coverage (CTV V95%) was determined as the DM isocenter. In actual treatment, the use of couch shifting is assumed for irradiation in accordance with the DM isocenter. To evaluate the effectiveness of DM, variations from the initial plan for CTV V95% (ie, ΔCTV V95%) and organ-at-risk (OAR) dose (ΔD_OAR) in bone matching (BM), TM, and DM were compared.

Results: The median ΔCTV V95% values in BM, TM, and DM were -2.18%, -1.39%, and -0.36%, respectively. DM significantly improved CTV V95%. OAR doses were within their limits. Toxicity in DM was considered equivalent to that in BM because the maximum ΔD_OAR in DM was similar to the BM results.

Conclusion: DM significantly improved CTV V95% in pancreatic CIRT within dose constraints of OARs. However, DM should be properly applied by considering treatment efficacy and efficiency. The appropriate use of TM, DM, and online/offline ART is required for each treatment site to improve the target coverage.

Clear cell adenocarcinoma of the uterine cervix is a rare and aggressive subtype of cervical cancer, typically resistant to conventional radiation therapy and lacking dedicated treatment guidelines. We present the case of a young patient with an ataxia telangiectasia mutation and locally advanced disease, who was unfit for brachytherapy following standard chemoradiotherapy and subsequently received a carbon ion radiation therapy boost. This mixed-beam strategy was well tolerated and led to durable local control along with a nodal response, which is suggestive of a possible abscopal effect. These findings underscore the potential of carbon ion radiation therapy in overcoming radioresistance and suggest a contributory role of genetic background in mediating systemic immune effects.

Purpose: Robustness evaluation is routinely used in clinics to ensure the intended dose delivery for intensity-modulated proton therapy (IMPT). Various methods have been proposed, but there is no consensus on which method should be adopted in clinical practice. This study examined various methods within the widely used worst-case approach to provide insights into IMPT plan evaluation.

Materials and methods: We evaluated the robustness of 20 clinical IMPT plans (10 prostate and 10 head and neck). Five robustness evaluation methods were assessed: error-bar dose distribution (ebDD), root-mean-square error dose (RMSED) distribution, voxel-wise worst-case, physical scenario worst-case, and dose-volume histogram (DVH) band. Correlations between these methods were analyzed. Each method was reviewed for their quantitative and qualitative capabilities to identify potential underdosing or overdosing.

Results: Strong correlations were found between ebDD and RMSED, and between voxel-wise worst-case and physical scenario worst-case. The DVH band method provides a straightforward way to assess whether the worst DVH meets plan criteria and to illustrate dose variations but lacks spatial detail to pinpoint areas of potential underdosing or overdosing. The voxel-wise worst-case captures the worst dose distribution across all evaluation metrics, allowing spatial identification of areas of concern within a single distribution. The physical scenario worst-case also pinpoints specific areas of concern but requires individual assessment for each region of interest and evaluation metric, which can be cumbersome. A 3D visualization with ebDD and RMSED highlights regions of dose variation but does not necessarily indicate clinically meaningful impact.

Conclusion: Different robustness evaluation methods offer different types of information. Our study provides valuable insights to help identify an effective and practical approach for clinical practice. Based on our findings, we propose a potential evaluation strategy: use the DVH band derived from physical uncertainty scenarios to assess whether the worst boundary values meet plan evaluation criteria, and, when concerns arise, apply the voxel-wise worst-case dose distribution to localize areas of potential risk.