Sun Yat-Sen University Cancer Center Guang Dong Province, Guangdong
B. Dong1, S. Zheng2, K. Chen3, S. Huang2, X. Zhu4, Q. Li5, and M. Chen6; 1Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Sun Yat-sen University, Guangzhou, Guangdong, China, 2Department of Radiation Oncology, Sun Yat-sen University Cancer Center, Guangzhou, China, 3Department of Population Health Sciences, Duke University School of Medicine, Durham, NC, 4Zhejiang University School of Medicine First Affiliated Hospital, Hangzhou, China, 5Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Sun Yat-sen University, Guangzhou, China, 6Sun Yat-sen University Cancer Center, Guangzhou, Guangdong, China
Purpose/Objective(s): The administrated dose during radiotherapy for lung cancer may deviate from the approved treatment plan due to tumor and anatomical changes. In this phase II study, we tested the feasibility of image-guided online adaptive radiotherapy (oART) in limited-stage small cell lung cancer (LS-SCLC) and hypothesized that ART would lower the risk of toxicities. Materials/
Methods: Anatomical changes in LS-SCLC patients during radiotherapy with 3 Gy×15 fractions were monitored on fan-beam CT (FBCT) scans used for daily soft-tissue matching. If systematic changes above the pre-defined trigger criteria were observed, an oART were performed. Dose-volume histograms (DVHs) were quantitatively compared between the initial and adaptive plans. Logistic regression was applied to analyze the dose-response relationship. Clinical endpoints included time consumption of oART implementation, grade =2 acute radiation pneumonitis (RP) and esophagitis (RE). Results: Twenty-three eligible patients were consecutively included with the planning target volume (PTV) reduced by a median of 36% after 24 to 39 Gy radiotherapy dose accumulation. And all patients completed oART successfully, taking an average of 27 minutes and 37 seconds from the start of four-dimensional FBCT simulation to the completion of beam delivery with limit placement errors and highly tolerance. By adapting to tumor and anatomical changes, average target coverage of PTV improved from 0.95±0.01 to 0.98±0.01 (p-value <0.05), while organs at risk (OAR) dosimetric parameters decreased significantly. The composite plan of the original plan plus the adaptive plan resulted in better DVHs for all the OAR that were evaluated compared to the original plan (p-value <0.05), including V5, V20, and V30 of total lung; V40, and the maximum dose of the esophagus. The mean lung dose decreased from 15.6 Gy to 13.2 Gy on average (p=0.02), and the mean esophagus dose was lower by 5.6 Gy (p-value <0.01). At a median follow-up of 6.0 months, we found grade =2 acute RP in 4 patients (17.4%), and RE in 5 patients (21.7%). Commonly used lung and esophagus dose metrics were significantly associated with RP and RE (p=0.02). Conclusion: We demonstrated that the implementation of oART for LS-SCLC is clinically acceptable, and it may potentially improve target coverage and lower treatment-related toxicity. Further large cohort analyses should be made in providing evidence towards feasibility and clinical benefit of oART for lung cancer. The study was registered with Chictr.org.cn, ChiCTR2300067831.
