Toxic Effects of Volume-modulated Arc Therapy for Esophageal Squamous Cell Cancer: Preliminary Clinical Results.

BACKGROUND/AIM: To evaluate the toxic effects associated with various factors, including the presence or absence of concurrent chemotherapy with volume-modulated arc therapy (VMAT) and dose parameters for esophageal cancer (EC), and to assess the safety and feasibility of the VMAT protocol. PATIENTS AND METHODS: Patients with EC who received definitive VMAT between December 2016 and December 2020 were retrospectively analyzed. VMAT plans were designed to deliver 60 Gy to the primary tumor, 54 Gy to high-risk sites, and 51.3 Gy to regional lymph node sites. Toxic effects were evaluated for esophagitis, neutropenia, esophageal stricture, pericardial effusion, radiation-associated pneumonia. RESULTS: Forty-five patients received concurrent chemoradiotherapy (CCRT), while 29 were treated with radiation therapy (RT) alone. The following grade 3 complications were detected: Neutropenia in four patients (5.4%), esophagitis in two (2.7%), and esophageal stricture in one (1.4%). Grade 4 or more complications were not observed. The median age of the CCRT group (67 years) was significantly lower than that of the RT-alone group (77 years) (p<0.0001). The incidence of esophagitis was significantly higher in the CCRT group (75.5%) than in the RT group (48.3%) (p=0.033). The univariate analysis identified increasing mean dose to the pericardium as a significant risk factor for pericardial effusion, and CCRT and performance status ≥1 as significant for radiation-associated pneumonia. These factors were not significant in the multivariate analysis. Neutropenia and esophageal stricture were not associated with any factor examined. CONCLUSION: VMAT alone and in CCRT performed with our protocol was safe and feasible in patients with esophageal squamous cell cancer.

Dose to contralateral breast from whole breast irradiation by automated tangential IMRT planning: comparison of flattening-filter and flattening-filter-free modes.

Background: The most common secondary cancer is contralateral breast (CLB) cancer after whole breast irradiation (WBI). The aim of this study was to quantify the reduction of CLB dose in tangential intensity modulated radiotherapy (t-IMRT) for WBI using flattening-filter-free (FFF) beams. Materials and methods: We generated automated planning of 20 young breast cancer patients with limited user interaction. Dose-volume histograms of the planning target volume (PTV), ipsilateral lung, heart, and CLB were calculated. The dose of PTV, the most medial CLB point, and the CLB point below the nipple was measured using an ionization chamber inserted in a slab phantom. We compared the two t-IMRT plans generated by FFF beams and flattening-filter (FF) beams. Results: All plans were clinically acceptable. There was no difference in the conformal index, the homogeneity for FFF was significantly worse. For the ipsilateral lung, the maximum dose (Dmax) was significantly higher; however, V20 showed a tendency to be lower in the FFF plan. No differences were found in the Dmax and V30 to the heart of the left breast cancer. FF planning showed significantly lower Dmax and mean dose to the CLB. In contrast to the calculation results, the measured dose of the most medial CLB point and the CLB point below the nipple were significantly lower in FFF mode than in FF mode, with mean reductions of 21.1% and 20%, respectively. Conclusions: T-IMRT planning using FFF reduced the measured out-of-field dose of the most medial CLB point and the CLB point below the nipple.

Impact of Regional Lymph Node Irradiation on Reducing Lymph Node Recurrence in Esophageal Cancer Patients.

Background/Aim: To evaluate the preventive effects of regional lymph node irradiation on lymph node recurrence in esophageal cancer (EC). Patients and Methods: The study included 289 patients who received definitive radiotherapy for EC. The regional lymph node area of group 1 was determined as the area with the highest probability of lymph node metastasis and group 2 was determined as the area with the next highest probability of lymph node metastasis depending on the primary site of EC. Results: The patients in whom group 2 was completely included in the irradiated field had a significantly lower rate of recurrence of regional lymph node metastasis than those in whom group 2 was not or insufficiently included (p=0.0337). There was no significant difference in overall survival (p=0.4627) or disease-specific survival (p=0.6174) between the two groups. Conclusion: Regional lymph node irradiation did not have survival-prolonging effects but significantly reduced regional lymph node recurrence.

Relationship Between Radiation Pneumonitis Following Definitive Radiotherapy for Non-small Cell Lung Cancer and Isodose Line.

BACKGROUND/AIM: It is important to identify radiation pneumonitis above Common Terminology Criteria for Adverse Events Grade 2 (G2) in order to safely continue durvalumab maintenance after chemoradiotherapy for advanced lung cancer. The aim of this study was to discover factors that predict pneumonitis above G2. PATIENTS AND METHODS: A follow-up computed tomography (CT) image was superimposed on the planning CT image using deformable image registration (DIR). The pneumonitis area was contoured on follow-up CT after DIR and the dose-volume histogram parameters of the contoured pneumonitis area were calculated. RESULTS: V5 (Percentage of total volume receiving ≥5 Gy) to V50 of pneumonitis were significantly lower in patients with G2 pneumonitis than in those with G1 pneumonitis. The pneumonitis V15 was the most significant. The group with pneumonitis V15 <87.10% had significantly more G2 pneumonitis than the group with pneumonitis V15 ≥87.10%. CONCLUSION: Pneumonitis V15 <87.10% was a risk factor for G2 pneumonitis.