Purpose: Multi-field intensity-modulated proton therapy (IMPT) is a novel treatment protocol design method proposed to reduce range uncertainty. This study aimed to investigate whether multi-field IMPT has a dose distribution advantage over photon intensity-modulated radiation therapy (IMRT) and CyberKnife in stereotactic body radiotherapy (SBRT) for stage I non-small cell lung cancer (NSCLC).

Methods: Twenty-nine patients who underwent photon SBRT from February 2021 to September 2022 at Shandong Cancer Hospital were included. Their Computed Tomography (CT) images were used to design CyberKnife and multi-field IMPT plans. For the photon plan (IMRT and CyberKnife), the planning target volume (PTV), which was extended from the internal gross target volume (IGTV), was prescribed at 50 Gy. For the proton plans, the planning beam-specific target volume (PBSTV) based on the IGTV was created to meet the same area as the photon PTV. Multi-field IMPT was simulated by adding additional beam angles to conventional IMPT. Dose distribution assessment factors included D_mean and dose gradient index (GI) for PTV/PBSTV, and D_mean and the hottest 0.1 cm³ dose (D_0.1cc) for organs at risk (OARs).

Results: With each patient receiving 7–11 beams, multi-field IMPT had a better target GI than IMRT. For the lung, heart, spinal cord, chest wall, and ribs doses, the D_mean of the multi-field IMPT was smaller than that of the other two plans for all metrics. CyberKnife was significantly less protective of the OARs than the other two planning modalities, owing to the presence of a high target center dose.

Conclusion: Multi-field IMPT achieves favorable target coverage and OAR protection compared to IMRT and CyberKnife for SBRT of NSCLC.

Background: When validating intracranial multi-lesion CyberKnife M6/S7 plans with SRSmapcheck, setting the array to a fixed 0° measures only one target dose distribution, leaving the other lesions unmeasured. Moreover, the CyberKnife treatment planning system does not support roll verification tools, and testing confirms that X-sight fiducial marker guidance is incompatible with free array roll. A novel method and workflow are required to validate multi-lesion plans with random positions.

Methods: A geometric model was established based on the relationship between SRSmapcheck and the tumor location. For two tumors spaced 77 mm apart (each 20 mm in diameter, or one 40 mm apart and the other infinitesimally small), the corresponding array roll angle interval was approximately 15.05°. The SRSmapcheck and StereoPHAN computed tomography (CT) images were acquired at 15° intervals, starting at 0°, and preprocessed into phantom plans for verification. A total of 101 intracranial multi-lesion plans were verified using the fixed 0° and pre-set roll angle methods to optimize the dose distribution, particularly in high-dose and rapidly varying areas. A two-sample test compared the results of the 0° versus pre-set roll angle verification and assessed the performance under different criteria to determine suitable criteria for pre-set roll angle verification.

Results: The equivalent diameter of the 296 tumors ranged from 5 to 45 mm (average: 21.86 mm). Each plan had an average of 2.97 lesions. Using the pre-set roll angle method, 2.34 targets were assessed on average (89.83% of lesions had diameters ranging from 10 to 40 mm), compared to 1.32 targets on average in 0° plans. Statistically significant differences occurred at 2 mm/1% and 2 mm/2% in the γ analysis, showing that plan pass rates were stable between the fixed 0° and pre-set roll angle methods. Relaxing either the distance to agreement or dose deviation significantly increased the pass rates during pre-set roll angle verification, whereas cross-transforming criteria had minimal impact. For pre-set roll angle methods, it is recommended to use 1 mm/1% (action limit: 86.0% ± 13.3%) and 1 mm/2% (action limits: 91.6% ± 7.9%) for γ analysis.

Conclusion: SRSmapcheck with the pre-set roll angle method can verify intracranial multi-lesion CyberKnife plans by measuring multiple targets in a single validation and comparing the 1 mm/1% and 1 mm/2% γ analysis criteria.

Objective: Radiation recall pneumonitis (RRP) is a localized inflammatory reaction occurring in previously irradiated lung regions, typically triggered by certain anticancer agents. In clinical settings, we have observed that COVID-19 infection may also act as a precipitating factor for RRP. However, its true incidence and possible risk factors remain poorly defined.

Methods: Lung cancer patients who received radiotherapy and were diagnosed with COVID-19 between November 2022 and February 2023 were included. RRP was defined as pulmonary changes limited to the previously irradiated regions, occurring at least 6 months after radiotherapy. Patients medical records and radiation dose distribution data were analyzed to identify potential contributing factors to RRP.

Results: The study included 140 patients who underwent thoracic radiotherapy with a minimum six-month interval before COVID-19 diagnosis. Among these, 62 patients (44.2%) developed RRP, and 45% of these experienced grade ≥ 2 pneumonitis. No radiotherapy dose-related factors were significantly associated with RRP. However, statistical analysis showed that RRP incidence was significantly associated with baseline T-stage (P = 0.034) and the time interval from radiotherapy completion to COVID-19 infection (P < 0.001).

Conclusions: A 44.2% incidence of COVID-19-related RRP was identified, which is notably higher than previously reported. While radiotherapy dosimetry did not correlate with RRP risk, baseline T-stage and timing of COVID-19 infection after radiotherapy were significantly associated with its occurrence.

Purpose: This study aimed to investigate the dose dependency of asymptomatic radiation pneumonitis (aRP) in patients with lung cancer following radiotherapy, focusing on the predictive value of dosimetric parameters.

Methods: This study included 72 patients with primary lung cancer who underwent radiotherapy between January 2019 and June 2022. The patients were divided into an aRP group (n = 30) and a non-RP group (n = 42). The physical dose was converted to an equivalent dose using the Linear-Quadratic (LQ) model, with an α/β value of 3. Three lung structures were defined, and the corresponding dose-volume histogram parameters were collected. The Mann–Whitney U test was used to compare dose parameters between the two groups, and multivariate logistic regression was performed to remove correlations among different parameters. A logistic function and receiver operating characteristic curve were constructed to predict aRP. This study analyzed the impact of different clinical characteristics on the aRP incidence.

Results: The lungs-planning target volume (PTV) V_15(Gy) was ultimately identified as the best predictive parameter. Significant dose–response relationships were observed, with V_15(Gy) achieving an area under the curve of 0.666 ± 0.067 (P = 0.017). The optimal cutoff value for lungs-PTV V_15(Gy) was 21.1%, below which the incidence of aRP decreased significantly. Immunotherapy has been identified as an independent risk factor for aRP.

Conclusion: The occurrence of aRP in patients with lung cancer after radiotherapy has a clear dose dependency, with lungs-PTV, V_15(Gy) being the best dose parameter for prediction, and the optimal cutoff value based on this study was 21.1%.

Purpose: To systematically compare the dosimetric performance of conventional (Ray Tracing, AAA) and advanced (Monte Carlo, Acuros XB) dose calculation algorithms across homogeneous and heterogeneous tissues in stereotactic radiotherapy (SRT) and stereotactic body radiotherapy (SBRT).

Methods: A retrospective analysis of 125 SRT cases (brain: 50, lung: 20, liver: 20, spine: 35) was conducted using CyberKnife and Varian systems. Plans were originally created using Type B (Anisotropic Analytical Algorithm [AAA] and Ray Tracing) algorithms and were subsequently recalculated using Type C (Acuros XB and Monte Carlo) algorithms, while maintaining identical beam geometry and monitor units. Dosimetric parameters (D_95%, D_mean, D_max, CI, HI, GI) were evaluated. Validation included point dose measurements with Cheese Phantom and gamma index analysis using the PTW 1600 SRS Phantom.

Results: In lung cases, Type B algorithms overestimated D_95% by 14% compared to Monte Carlo, which reduced D_mean by 13.7% and CI by 25.8%. In liver, Acuros XB lowered D_mean by 21.4% with a 0.8% CI reduction. For spine, Monte Carlo reduced D_95% by 3.4%, with a 1.1% drop in D_mean and stable CI. Brain cases showed minimal differences, with Monte Carlo increasing CI by 2.5% (1.19 vs. 1.16). Gamma pass rates exceeded 98% for Monte Carlo and Acuros XB, surpassing Ray Tracing and AAA (≤96%).

Conclusion: Advanced algorithms demonstrated superior dose accuracy, homogeneity, and organs at risk (OAR) sparing in heterogeneous anatomical regions. Despite higher computational requirements, their clinical implementation is justified for SRT/SBRT planning. This study supports a site-specific approach, advocating for advanced algorithm use in anatomically complex scenarios.

Purpose: This study evaluated the geometric and dosimetric uncertainties during online adaptive radiotherapy (ART) for prostate cancer.

Methods: Sequential cone beam computed tomography (CBCT) scans from 52 sessions involving 13 patients were analyzed. An ART plan was generated using CBCT1, followed by a verification scan (CBCT2) acquired 13.1 ± 3.0 minutes before treatment delivery. New contours (prostate, seminal vesicles, bladder, rectum, and bowel) were delineated on CBCT2 and transferred to CBCT1 for dose distribution analysis. Three dimensional contour variations were quantified, new planning target volume (PTV) margins were calculated, and their dosimetric benefits were assessed.

Results: No significant differences were observed in the high-dose volumes (V60 Gy and V57 Gy) of the bladder and rectum (P > 0.05). PTV margins were 2.6 mm, 2.4 mm, and 2.6 mm in the lateral, vertical, and longitudinal directions for the prostate, and 3.9 mm, 3.8 mm, and 4.3 mm for the seminal vesicles, respectively. These margin reductions led to a 37% reduction in the dose to the surrounding critical organs, while maintaining consistent target coverage.

Conclusion: This study supports symmetric PTV margins of 3 mm for the prostate and 4.5 mm for the seminal vesicles in online ART, thereby contributing to the development of optimized treatment strategies for prostate cancer.

Proton beam therapy has demonstrated significant clinical efficacy across multiple malignancies, primarily attributed to its distinct physical dose deposition characteristics. However, clinical implementation remains constrained by resource limitations and accumulated experience, particularly regarding radiation tolerance thresholds for organs at risk (OARs). Unlike photon-based radiotherapy where consensus guidelines like QUANTEC have been established, standardized dose constraints for proton therapy require further validation. This systematic review synthesizes decade-long evidence from peer-reviewed literature and clinical guidelines, critically evaluating current understanding of OARs tolerance in proton therapy. The comprehensive analysis aims to inform clinical decision-making and protocol development for emerging proton therapy.

Central nervous system (CNS) involvement in peripheral T-cell lymphoma (PTCL) is rare and is associated with poor prognosis. This report presents two pathologically confirmed PTCL cases. Although cerebrospinal fluid (CSF) flow cytometry did not detect tumor cells, CSF analysis revealed significantly elevated interleukin (IL)-10 levels and an increased IL-10/IL-6 ratio, suggesting CNS involvement. Following effective chemotherapy, which crossed the blood-brain barrier, IL-10 levels and the IL-10/IL-6 ratio decreased significantly, with clinical improvement. These findings suggest that IL-10 is a valuable supplementary diagnostic marker for CNS involvement in PTCL. Whole-brain radiation therapy, as a consolidative treatment, may be effective for residual or refractory lesions and improve prognosis. We review these patients’ clinical and diagnostic features and discuss the role of radiotherapy in the treatment of CNS involvement in PTCL.