“…The finding that the 3-year LCR of stage IB NSCLC was 65% lower than that of stage IA was also supported by previous reports, ranging from 60 to 80% regardless of photon, proton, or carbon [6,13,15,24]. Although we did not observe a dose-response relationship of PBT in the present study, several SABR and hypofractionated PBT studies confirmed the dose-response relationship in early-stage NSCLC, particularly in stage IB tumors [15,24,25]. Larger tumors exhibited a trend toward improved LCR with a higher dose to the target [15].…”
“…The finding that the 3-year LCR of stage IB NSCLC was 65% lower than that of stage IA was also supported by previous reports, ranging from 60 to 80% regardless of photon, proton, or carbon [6,13,15,24]. Although we did not observe a dose-response relationship of PBT in the present study, several SABR and hypofractionated PBT studies confirmed the dose-response relationship in early-stage NSCLC, particularly in stage IB tumors [15,24,25]. Larger tumors exhibited a trend toward improved LCR with a higher dose to the target [15].…”
“…Several authors have reported that age, sex, Eastern Cooperative Oncology Group performance status (PS), tumor size, and T stage are prognostic factors of early-stage NSCLC treated with SBRT (2)(3)(4). We previously identified sex and tumor size as prognostic factors and proposed using recursive partitioning analysis (RPA) classification based on sex and T stage to predict clinical outcomes in those who have undergone SBRT for NSCLC (2).…”
“…In the study by Fakiris et al, grades 3-5 toxicity occurred in 27% of patients with central lesions, compared to 10% of patients with peripheral tumors treated with a dose of 60-66 Gy in three fractions [15]. However, acceptable levels of early pulmonary toxicity have been reported for central lung lesions treated with less aggressive fractionation schemes such as 50-60 Gy in eight to ten fractions [16], 50 Gy in five fractions [17], 48 Gy in four fractions [18] and 60 Gy in eight fractions [19]. In all these studies, lung lesions are categorized as central or peripheral based solely on the nearest distance from the main bronchial tree.…”
Purpose: Stereotactic body radiation therapy is an emerging technique in the treatment of peripheral lung tumors. However, due to early reports of increased toxicity, the treatment of central lung lesions with hypo-fractionated high-dose regimen remains controversial. Thus far, lung lesions have been defined as either central or peripheral depending solely on their nearest distance from the major airways. The goal of this study is to develop a quantitative method to categorize the location of lung lesions mapped in three-dimensional space. Furthermore, a set of parameters are proposed for assessing risk factors based on target locations. Methods and Materials: A MATLAB program was developed to quantify the distance between the tumor and the airways, and to calculate the percentage of the target volume lying within a given distance from the main bronchial tree. The program was tested on 20 patients with centrally located lung lesions treated with CyberKnife. A dosimetric analysis was performed to investigate the relationship between dose delivered to the critical structures and target location. Results: The absolute target volume located within a distance of 20 mm from the airways was used to quantify the tumor proximity to the bronchial tree. A strong correlation was found between this parameter and the dose delivered to the critical organs, showing that a detailed knowledge of target location can be used to assess the risk of toxicity during the planning stage. Conclusions: We have developed a tool to quantify the lesion proximity to the bronchial tree. We expect that riskadapted strategies, accounting for the exact geometric relationship between the tumor and the airways, may improve the management of centrally located lung lesions.
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