International journal of radiation oncology, biology, physics · 2026
Comparing Strategies for Pencil Beam Scanning Carbon Ion Radiation Therapy in Stage I Peripheral Non-Small Cell Lung Cancer: Toward Optimized Clinical Decision-Making Planning.
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Lu Yan, Chen Jian, Sheng Yinxiangzi, Wang Weiwei, Mao Jingfang
Аннотация
PURPOSE: To identify the optimal planning strategy for pencil beam scanning carbon ion radiation therapy (CIRT) in stage I peripheral non-small cell lung cancer, including ground-glass opacity (GGO) and solid lesions.
METHODS AND MATERIALS: Thirty patients (15 GGO and 15 solid) receiving 8 Gy (relative biological effectiveness [RBE]) × 9 fractions were analyzed. The clinical target volume (CTV) was defined as a 7-mm isotropic expansion of the internal gross tumor volume. Eight plans per patient were generated by combining 3 strategies: margin expansion (ME, CTV+7 mm), density override (DO), and robust optimization (RO). The accumulated deformed dose was calculated from two 4-dimensional quality assurance computed tomographies (pre- and mid-CIRT, weighted 5:4). Target coverage was assessed by the percentage volume of CTV receiving ≥95% prescription dose (CTV V95%); ipsilateral lung (excluding internal gross tumor volume) dose by mean lung dose (MLD) and the percentage of the lung volume receiving ≥x Gy (RBE) (Vx, V5-V70). Range and setup uncertainties were assessed by applying ±3.5% stopping power variations and 3-mm translational shifts in 6 cardinal directions, respectively, with accumulated doses generated using the same workflow.
RESULTS: All single strategies improved CTV V95% but increased lung dose. DO increased CTV V95% by 3.3% to 4.1% with a minimal MLD increase of 0.15 to 0.92 Gy (RBE). RO increased CTV V95% by 4.8% to 5.1% with a moderate MLD increase of 1.77-1.79 Gy (RBE). ME yielded similar CTV gains but the highest MLD increase of 3.78 to 4.86 Gy (RBE). For GGOs, CTV+RO provided adequate coverage with the lowest lung dose. For solid tumors, CTV+RO+DO achieved near-complete coverage with improved consistency (range, 92.8%-100% vs 85.2%-100%) and a minimal additional MLD of ∼0.15 Gy (RBE). With range and setup uncertainties, results remained consistent with nominal conditions when RO was applied. In the absence of RO, the addition of DO to CTV+ME reduced the risk of target underdosage for both GGO and solid tumors at a cost of increased MLD of -0.08 to 0.53 Gy (RBE).
CONCLUSIONS: This study provides quantitative data for evidence-based planning strategy selection in stage I peripheral non-small cell lung cancer receiving CIRT. Without RO, a larger margin (CTV+ME) is recommended; DO is advised for solid tumors and may also benefit GGOs under uncertainty. With RO, a smaller margin (CTV) is sufficient, and DO remains valuable for solid tumors.
METHODS AND MATERIALS: Thirty patients (15 GGO and 15 solid) receiving 8 Gy (relative biological effectiveness [RBE]) × 9 fractions were analyzed. The clinical target volume (CTV) was defined as a 7-mm isotropic expansion of the internal gross tumor volume. Eight plans per patient were generated by combining 3 strategies: margin expansion (ME, CTV+7 mm), density override (DO), and robust optimization (RO). The accumulated deformed dose was calculated from two 4-dimensional quality assurance computed tomographies (pre- and mid-CIRT, weighted 5:4). Target coverage was assessed by the percentage volume of CTV receiving ≥95% prescription dose (CTV V95%); ipsilateral lung (excluding internal gross tumor volume) dose by mean lung dose (MLD) and the percentage of the lung volume receiving ≥x Gy (RBE) (Vx, V5-V70). Range and setup uncertainties were assessed by applying ±3.5% stopping power variations and 3-mm translational shifts in 6 cardinal directions, respectively, with accumulated doses generated using the same workflow.
RESULTS: All single strategies improved CTV V95% but increased lung dose. DO increased CTV V95% by 3.3% to 4.1% with a minimal MLD increase of 0.15 to 0.92 Gy (RBE). RO increased CTV V95% by 4.8% to 5.1% with a moderate MLD increase of 1.77-1.79 Gy (RBE). ME yielded similar CTV gains but the highest MLD increase of 3.78 to 4.86 Gy (RBE). For GGOs, CTV+RO provided adequate coverage with the lowest lung dose. For solid tumors, CTV+RO+DO achieved near-complete coverage with improved consistency (range, 92.8%-100% vs 85.2%-100%) and a minimal additional MLD of ∼0.15 Gy (RBE). With range and setup uncertainties, results remained consistent with nominal conditions when RO was applied. In the absence of RO, the addition of DO to CTV+ME reduced the risk of target underdosage for both GGO and solid tumors at a cost of increased MLD of -0.08 to 0.53 Gy (RBE).
CONCLUSIONS: This study provides quantitative data for evidence-based planning strategy selection in stage I peripheral non-small cell lung cancer receiving CIRT. Without RO, a larger margin (CTV+ME) is recommended; DO is advised for solid tumors and may also benefit GGOs under uncertainty. With RO, a smaller margin (CTV) is sufficient, and DO remains valuable for solid tumors.