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内容記述 |
Purpose: Radiotherapy for localized prostate cancer often treatsthe entire prostate with a uniform dose, even in the presence ofhypoxic high-risk dominant intraprostatic lesions (DILs). Giventhat approximately 60% of these tumors exhibit pO2 < 5 mmHg,which correlates with poor biochemical outcomes, novelhypoxic strategies are necessary. This study investigated thefeasibility of focal dose-averaged linear energy transfer (LETd)boost for prostate carbon-ion radiotherapy to increase LETd toDILs while maintaining dose coverage and sparing organs at risk(OARs).Methods: A retrospective planning study was conducted on 15localized prostate cancer cases, with DILs identified by multiparametricMRI to define the boost target (PTVboost). Twoopposing lateral beams delivered 51.6 Gy RBE-weighted doseover 12 fractions. Two treatment plans were designed for eachcase: 1) conventional plan using single-field uniform dose technique,and 2) boost plan using multifield optimization and LETpainting to achieve high LETd within PTVboost, while limitingvariations of dose coverage (D90% and D50%) to 1% and satisfyingurethra planning risk volume (PRV) constraint (D0.1 cc ≤51.6 Gy). Dose and LETd metrics of the targets and OARs werecompared between the two plans.Results: Compared to conventional plans, boost plans deliveredclinically satisfied dose coverage with significant increases inminimum and mean LETd for PTVboost (63.9±2.8 vs. 44.0±1.3 keV/μm, p < 0.001; and 73.9±1.4 vs. 46.0±1.0 keV/μm, p< 0.001). Similar results were observed for CTV (minimumLETd 46.5±1.9 vs. 43.1±1.2 keV/μm, p < 0.001; mean LETd55.8±2.1 vs. 46.3±1.1 keV/μm, p < 0.001). This improvementwas consistent across all cases, indicating robustness to interindividualanatomical variability in boost volume size, location,and shape.Conclusion: Focal LETd boosting in prostate carbon-ion radiotherapyis a feasible hypoxic strategy, enhancing LETd withoutcompromising dose coverage or OAR constraints. This approachalso demonstrated insensitivity to OAR proximity, supporting itspotential for clinical application and simplified focal boost planning for high-risk lesions. |
