International Journal of Radiation Oncology Biology Physics最新文献

Purpose: The incidence and risk factors associated with radiation-induced Moya-Moya Syndrome (RIMMS) in pediatric brain tumor patients treated with proton radiotherapy (PRT) remain poorly understood. The objective of this study was to determine the incidence of RIMMS in the setting of CNS proton radiotherapy (PRT) in a pediatric cohort and assess its relationship with dose to the Circle of Willis (COW) or optic chiasm (OC).

Methods & materials: We performed a retrospective review of pediatric brain tumor patient treated with intracranial PRT (1995-2021). The exposure of interest was mean dose to the optic chiasm due to close proximity to the COW vasculature. Wilcoxon rank-sum test was used to determine the association between OC dose and RIMMS. Univariable logistic regression modeling was used to determine the odds of developing RIMMS based on a cutpoint of 52Gy.

Results: Of 676 patients, 14 developed RIMMS, with a median onset of 1.9 years. The cumulative incidence of RIMMS at 8 years was 2.4%. Patients with RIMMS had higher mean OC dose than those without (51.5 Gy vs 23.7 Gy, p<0.0001). Univariable logistic regression showed patients with an OC dose > 52 Gy had increased RIMMS risk compared to those with dose < 52 Gy (OR = 9.9, p<0.001).

Conclusions: The incidence of RIMMS remains low in our primarily proton-treated pediatric cohort with a cumulative incidence of 2.4% over 8 years and is similar to photon-treated cohorts. Development of RIMMS was associated with higher doses to the COW and OC.

Purpose: To test a first generation clinical PCCT scanner's capabilities to characterize materials in an anthropomorphic head phantom for radiation therapy purposes.

Methods and materials: A CIRS 731-HN head-and-neck phantom (CIRS/SunNuclear, Norfolk, USA) was scanned on a NAEOTOM Alpha photon-counting CT (PCCT) and a SOMATOM Definition AS+ with single-energy and dual-energy CT techniques (SECT and DECT, respectively), both scanners manufactured by Siemens (Siemens Healthineers, Forscheim, Germany). A method was developed to derive relative electron density (RED) and effective atomic number (EAN) from linear attenuation coefficients (LAC) of virtual mono-energetic images and applied for the PCCT and DECT data. For DECT, Siemens' syngo.via 'Rho/Z'-algorithm was also utilized. Proton stopping-power ratios (SPR) were calculated based on RED/EAN with the Bethe equation. For SECT, a stoichiometric calibration to SPR was used. Nine materials in the phantom were segmented, excluding border pixels. Distributions and root-mean-square deviations (RMSD) within the material regions were evaluated for LAC, RED/EAN and SPR, respectively. Two example ray-projections were also examined for LAC, SPR and water-equivalent thickness (WET), for illustrations of a more treatment-like scenario.

Results: There was a tendency towards narrower distributions for PCCT compared to both DECT methods for the investigated quantities, observed across all materials for RED only. Likewise the scored RMSDs showed overall superiority for PCCT with a few exceptions: for water-like materials, EAN and SPR were comparable between the modalities; for titanium the RED and SPR estimates were inferior for PCCT. The PCCT data gave the smallest deviations from theoretic along the more complex example ray profile whereas the more standard projection showed similar results between the modalities.

Conclusions: This study shows promising results for tissue characterization in a human-like geometry for radiotherapy purposes using PCCT. The significance of improvements for clinical practice remains to be demonstrated.

Purpose: Presence of MYC and BCL2 translocations (i.e. double-hit lymphoma, DHL) in large B-cell lymphoma (LBCL) is associated with reduced chemosensitivity, but less is known on its impact on radiotherapy (RT) efficacy.

Methods/materials: Patients with LBCL that received their first course of RT for relapsed/refractory (r/r) disease between 2008-2020 were eligible if there was adequate pathologic evaluation to be categorized as DHL versus non-DHL as per WHO (5^th edition). Separate analyses were conducted by treatment intent. Predictors for response (complete and partial) and local recurrence (LR) were evaluated using Cox regression analysis. LR analysis was restricted to curative-intent patients to ensure adequate follow-up.

Results: 383 patients (102 DHL, 281 non-DHL, 44% curative) were treated to 447 sites. Median time from diagnosis to RT was 11.6 months, with 38.7% patients having primary chemorefractory disease, 37.4% having received >2 lines of systemic therapy, and 24% status post stem cell transplant. Median biological equivalent dose (alpha/beta 10) was 28 Gy (range 3.2-60.0) for palliative and 46.9 Gy (range 6.4-84.0) for curative-intent patients. With a median follow-up of 41.1 and 41.5 months among curative and palliative patients, respectively, response was high (81.1% curative, 60.1% palliative). On univariate analysis, DHL pathology was not associated with RT response in either curative or palliative patients. Among curative patients, 2-year LR rate was 38.8%. On multivariable analysis, DHL pathology was associated with a 2 times higher risk of LR (95% CI 1.05-3.67,p=.03), with a crude LR rate of 42.9% (DHL) versus 28.9% (non-DHL). RT was well tolerated with low rates of grade 3 or higher acute toxicity (1.8% curative, 2.9% palliative).

Conclusions: Relapsed/refractory LBCL remains radioresponsive with 60-80% response rate to RT. While DHL pathology does not appear to influence RT response, its presence is associated with higher rates of local recurrence, suggesting it may be more radioresistant.