Browsing by Subject "Intensity-modulated radiation therapy (IMRT)"

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    Failure patterns of locoregional recurrence after reducing target volumes in patients with nasopharyngeal carcinoma receiving adaptive replanning during intensity-modulated radiotherapy: a single-center experience in China
    (Springer Nature, 2023-11-16) Zhou, Xiate; Zhu, Jian; Zhou, Chao; Wang, Wei; Ding, Weijun; Chen, Meng; Chen, Kuifei; Li, Shuling; Chen, Xiaofeng; Yang, Haihua; Radiation Oncology, School of Medicine
    Background: Previous researches have demonstrated that adaptive replanning during intensity-modulated radiation therapy (IMRT) could enhance the prognosis of patients with nasopharyngeal carcinoma (NPC). However, the delineation of replanning target volumes remains unclear. This study aimed to evaluate the feasibility of reducing target volumes through adaptive replanning during IMRT by analyzing long-term survival outcomes and failure patterns of locoregional recurrence in NPC. Methods: This study enrolled consecutive NPC patients who received IMRT at our hospital between August 2011 and April 2018. Patients with initially diagnosed, histologically verified, non-metastatic nasopharyngeal cancer were eligible for participation in this study. The location and extent of locoregional recurrences were transferred to pretreatment planning computed tomography for dosimetry analysis. Results: Among 274 patients, 100 (36.5%) received IMRT without replanning and 174 (63.5%) received IMRT with replanning. Five-year rates of locoregional recurrence-free survival (LRFS) were 90.1% (95%CI, 84.8% to 95.4%) and 80.8% (95%CI, 72.0% to 89.6%) for patients with and without replanning, P = 0.045. There were 17 locoregional recurrences in 15 patients among patients with replanning, of which 1 (5.9%) was out-field and 16 (94.1%) were in-field. Among patients without replanning, 19 patients developed locoregional recurrences, of which 1 (5.3%) was out-field, 2 (10.5%) were marginal, and 16 (84.2%) were in-field. Conclusions: In-field failure inside the high dose area was the most common locoregional recurrent pattern for non-metastatic NPC. Adapting the target volumes and modifying the radiation dose prescribed to the area of tumor reduction during IMRT was feasible and would not cause additional recurrence in the shrunken area.
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    Impacting Parameter Analysis for Intensity Modulated Radiation Treatment
    (Office of the Vice Chancellor for Research, 2010-04-09) Wu, Huanmei
    Introduction: Intensity-modulated radiation therapy (IMRT) accurately delivers radiation doses with high degree of conformity by modulating the intensity of the radiation beam in multiple small segments. Usually small fields have large variation in dose. For some TPS, there are no restrictions on plan parameters. Guideline for plan optimization is needed that allows the IMRT QA to pass satisfactorily. IMRT plan parameters are analyzed to correlate the success and failure of an IMRT QA plan. Materials and Methods: Based on IMRT QA results, 15 IMRT treatment plans, divided into 3 groups, are studies. Plans in group 1 passed IMRT QA with high gamma index passing rates and plan in group 2 passed with marginal passing rates. Plans in group 3 failed the IMRT QA. Statistical analysis has been performed on plan parameters, including beam number, segment number for each beam, MU in total or for each segment, the width variations of the leaf/jaw positions for each segment, the segment area sizes, and dose delivery for different segments of each beam, to discover the relationships between IMRT quality and these parameters. Results: The statistical results showed there is no correlation between plan quality and MU or beam/segment numbers. However, there are noticeable correlations between the IMRT quality and the segment sizes and widths. For each plan group, the IMRT quality decreased with the decreasing field sizes and segment widths. The histograms of these factors showed that failed IMRT plans have peak distributions with small field sizes (< 30cm2) and narrow widths (<20mm). Conclusion: Initial results showed that the passing rates of IMRT treatment plans have strong correlation with the segment field sizes and the opening widths of the leaf/jaw positions. Large number of segments with small fields produces unacceptable IMRT QA and should be avoided during IMRT planning.
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    Long-term outcomes of replanning during intensity-modulated radiation therapy in patients with nasopharyngeal carcinoma: An updated and expanded retrospective analysis
    (Elsevier, 2022-05) Zhou, Xiate; Wang, Wei; Zhou , Chao; Zhu , Jian; Ding , Weijun; Chen, Meng; Chen, Kuifei; Shi, Yangyang; Chen , Xiaofeng; Kong, Feng-Ming; Yang , Haihua; Radiation Oncology, School of Medicine
    Background and purpose Recent studies show that adaptive replanning for patients with nasopharyngeal carcinoma (NPC) during intensity-modulated radiation therapy (IMRT) improve the short-term local–regional recurrence-free survival (LRFS), and quality of life (QoL). We aimed to assess the long-term survival outcomes and QoL in patients with non-metastatic NPC who received IMRT with replanning compared to those who received IMRT without replanning. Methods and materials We conducted an updated and expanded retrospective analysis from an existing prospective cohort for non-metastatic NPC patients undergoing IMRT in our institution. Non-metastatic NPC patients receiving IMRT from June 2007 to December 2015 were consecutively enrolled based on electronic medical record. Patients who were still alive were eligible for the QoL study. The survival outcomes and QoL were compared between patients with and without replanning. Results Among 290 patients, 147 (50.7%) received IMRT without replanning and 143 (49.3%) received IMRT with replanning. Replanning group had a higher 8-year LRFS rate (87.4% vs. 75.6%, P = 0.025). However, 8-year overall survival rate was not statistically significant. Patients with replanning compared to those who without replanning had significant improvements in social functioning (P = 0.016), insomnia (P = 0.048), dry mouth (P = 0.004), and sticky saliva (P = 0.005). Additionally, the score of the role functioning was marginally higher in patients treated with IMRT replanning (P = 0.063). Conclusion This extended follow-up study demonstrates the long-term security and validity for adaptive radiotherapy in IMRT for non-metastatic NPC patients. We highly recommend that adaptive replanning should be routinely implemented for non-metastatic NPC patients.
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    Radiation-Induced Lymphopenia Risks of Photon Versus Proton Therapy for Esophageal Cancer Patients
    (Elsevier, 2021-04-07) Ebrahimi, Saba; Lim, Gino; Liu, Amy; Lin, Steven H.; Ellsworth, Susannah G.; Grassberger, Clemens; Mohan, Radhe; Cao, Wenhua; Radiation Oncology, School of Medicine
    Purpose: To assess possible differences in radiation-induced lymphocyte depletion for esophageal cancer patients being treated with the following 3 treatment modalities: intensity-modulated radiation therapy (IMRT), passive scattering proton therapy (PSPT), and intensity-modulated proton therapy (IMPT). Methods and materials: We used 2 prediction models to estimate lymphocyte depletion based on dose distributions. Model I used a piecewise linear relationship between lymphocyte survival and voxel-by-voxel dose. Model II assumes that lymphocytes deplete exponentially as a function of total delivered dose. The models can be fitted using the weekly absolute lymphocyte counts measurements collected throughout treatment. We randomly selected 45 esophageal cancer patients treated with IMRT, PSPT, or IMPT at our institution (15 per modality) to demonstrate the fitness of the 2 models. A different group of 10 esophageal cancer patients who had received PSPT were included in this study of in silico simulations of multiple modalities. One IMRT and one IMPT plan were created, using our standards of practice for each modality, as competing plans to the existing PSPT plan for each patient. We fitted the models by PSPT plans used in treatment and predicted absolute lymphocyte counts for IMRT and IMPT plans. Results: Model validation on each modality group of patients showed good agreement between measured and predicted absolute lymphocyte counts nadirs with mean squared errors from 0.003 to 0.023 among the modalities and models. In the simulation study of IMRT and IMPT on the 10 PSPT patients, the average predicted absolute lymphocyte count (ALC) nadirs were 0.27, 0.35, and 0.37 K/μL after IMRT, PSPT, and IMPT treatments using Model I, respectively, and 0.14, 0.22, and 0.33 K/μL using Model II. Conclusions: Proton plans carried a lower predicted risk of lymphopenia after the treatment course than did photon plans. Moreover, IMPT plans outperformed PSPT in terms of predicted lymphocyte preservation.