Integrating 18 F-FDG PET/CT with lung dose-volume for assessing lung inflammatory changes after arc-based radiotherapy for esophageal cancer: A pilot study.

OBJECTIVE: The incidence of radiation pneumonitis (RP) has a highly linear relationship with low-dose lung volume. We previously established a volume-based algorithm (VBA) method to improve low-dose lung volume in radiotherapy (RT). This study assessed lung inflammatory changes by integrating fluorine-18-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG PET/CT) with VBA for esophageal cancer patients undergoing arc-based RT. METHODS: Thirty esophageal cancer patients received 18 F-FDG PET/CT imaging pre-RT and post-RT were included in a retrospective pilot study. We fused lung doses and parameters of PET/CT in RT planning. Based on VBA, we used the 5Gy isodose curve to define high-dose (HD) and low-dose (LD) regions in the lung volume. We divided patients into non-RP (nRP) and RP groups. The maximum, mean standardized uptake value (SUVmax, SUVmean), global lung glycolysis (GLG), mean lung dose (MLD) and V5-30 in lungs were analyzed. Area under the curve values were utilized to identify optimal cut-off values for RP. RESULTS: Eleven patients in the nRP group and 19 patients in the RP group were identified. In 30 RP lungs, post-RT SUVmax, SUVmean and GLG of HD regions showed significant increases compared to values for pre-RT lungs. There were no significant differences in values of 22 nRP lungs. Post-RT SUVmax and SUVmean of HD regions, MLD, and lung V5 and V10 in RP lungs were significantly higher than in nRP lungs. For detecting RP, the optimal cut-off values were post-RT SUVmax > 2.28 and lung V5  > 47.14%. CONCLUSION: This study successfully integrated 18 F-FDG PET/CT with VBA to assess RP in esophageal cancer patients undergoing RT. Post-RT SUVmax > 2.28 and lung V5  > 47.14% might be potential indicators of RP.

Planning evaluation of a novel volume-based algorithm for personalized optimization of lung dose in VMAT for esophageal cancer.

Radiotherapy treatment planning (RTP) is time-consuming and labor-intensive since medical physicists must devise treatment plans carefully to reduce damage to tissues and organs for patients. Previously, we proposed the volume-based algorithm (VBA) method, providing optimal partial arcs (OPA) angle to achieve the low-dose volume of lungs in dynamic arc radiotherapy. This study aimed to implement the VBA for esophageal cancer (EC) patients and compare the lung dose and delivery time between full arcs (FA) without using VBA and OPA angle using VBA in volumetric modulated arc therapy (VMAT) plans. We retrospectively included 30 patients diagnosed with EC. RTP of each patient was replanned to 4 VMAT plans, including FA plans without (FA-C) and with (FA + C) dose constraints of OARs and OPA plans without (OPA-C) and with (OPA + C) dose constraints of OARs. The prescribed dose was 45 Gy. The OARs included the lungs, heart, and spinal cord. The dose distribution, dose-volume histogram, monitor units (MUs), delivery time, and gamma passing rates were analyzed. The results showed that the lung V5 and V10 in OPA + C plans were significantly lower than in FA + C plans (p < 0.05). No significant differences were noted in planning target volume (PTV) coverage, lung V15, lung V20, mean lung dose, heart V30, heart V40, mean heart dose, and maximal spinal cord dose between FA + C and OPA + C plans. The delivery time was significantly longer in FA + C plans than in OPA + C plans (237 vs. 192 s, p < 0.05). There were no significant differences between FA + C and OPA + C plans in gamma passing rates. We successfully applied the OPA angle based on the VBA to clinical EC patients and simplified the arc angle selection in RTP. The VBA could provide a personalized OPA angle for each patient and effectively reduce lung V5, V10, and delivery time in VMAT.

Volume-based algorithm of lung dose optimization in novel dynamic arc radiotherapy for esophageal cancer.

This study aims to develop a volume-based algorithm (VBA) that can rapidly optimize rotating gantry arc angles and predict the lung V5 preceding the treatment planning. This phantom study was performed in the dynamic arc therapy planning systems for an esophageal cancer model. The angle of rotation of the gantry around the isocenter as defined as arc angle (θA), ranging from 360° to 80° with an interval of 20°, resulting in 15 different θA of treatment plans. The corresponding predicted lung V5 was calculated by the VBA, the mean lung dose, lung V5, lung V20, mean heart dose, heart V30, the spinal cord maximum dose and conformity index were assessed from dose-volume histogram in the treatment plan. Correlations between the predicted lung V5 and the dosimetric indices were evaluated using Pearson's correlation coefficient. The results showed that the predicted lung V5 and the lung V5 in the treatment plan were positively correlated (r = 0.996, p < 0.001). As the θA decreased, lung V5, lung V20, and the mean lung dose decreased while the mean heart dose, V30 and the spinal cord maximum dose increased. The V20 and the mean lung dose also showed high correlations with the predicted lung V5 (r = 0.974, 0.999, p < 0.001). This study successfully developed an efficient VBA to rapidly calculate the θA to predict the lung V5 and reduce the lung dose, with potentials to improve the current clinical practice of dynamic arc radiotherapy.

Helical tomotherapy with a complete-directional-complete block technique effectively reduces cardiac and lung dose for left-sided breast cancer.

OBJECTIVES: To evaluate the feasibility and optimal restricted angle of the complete-directional-complete block (CDCB) technique in helical tomotherapy (HT) by including regional nodal irradiation (RNI) with the internal mammary node (IMN) in left-sided breast cancer. METHODS: Ten left-sided breast cancer patients treated with 50 Gy in 25 fractions were compared with five-field intensity-modulated radiation therapy (5F-IMRT) and six types of HT plans. In the HT plans, complete block (CB), organ-based directional block (OBDB) and CDCB with different restricted angles were used. RESULTS: The conformity index (CI) between the CDCB0,10,15,20 and 5F-IMRT groups was similar. Compared to CB, OBDB and 5F-IMRT, CDCB20 resulted in a decreased ipsilateral mean lung dose. The low-dose region (V5) of the ipsilateral lung in OBDB (84.0%) was the highest among all techniques (p < 0.001). The mean dose of the heart in CB was significantly reduced (by 11.5-22.4%) compared with other techniques. The V30 of the heart in CDCB20 (1.9%) was significantly lower than that of CB, OBDB and 5F-IMRT. Compared to the mean dose of the left anterior descending (LAD) artery of 5F-IMRT (27.0 Gy), CDCB0, CDCB10, CDCB15, CDCB20 and OBDB reduced the mean dose effectively by 31.7%, 38.3%, 39.6%, 42.0 and 56.2%, respectively. Considering the parameters of the organs-at-risk (OARs), CDCB10,15,20 had higher expectative values than the other techniques (p = 0.01). CONCLUSIONS: HT with the CDCB technique is feasible for treating left-sided breast cancer patients. The CDCB10-20 techniques not only achieved similar planning target volume coverage, homogeneity and dose conformity but also allowed better sparing of the heart and bilateral lungs. ADVANCES IN KNOWLEDGE: For left-sided breast cancer patients whose RNI field includes the IMN, heart avoidance is an important issue. The CDCB technique achieved good PTV coverage, homogeneity and dose conformity and allowed better sparing of the mean dose of the lung, the LAD artery, and the heart and reduced the V30 of the heart.

Fan-shaped complete block on helical tomotherapy for esophageal cancer: a phantom study.

Radiation pneumonitis (RP) is a common complication for radiotherapy of esophageal cancer and is associated with the low dose irradiated lung volume. This study aims to reduce the mean lung dose (MLD) and the relative lung volume at 20 Gy (V 20) and at low dose region using various designs of the fan-shaped complete block (FSCB) in helical tomotherapy. Hypothetical esophageal tumor was delineated on an anthropomorphic phantom. The FSCB was defined as the fan-shaped radiation restricted area located in both lungs. Seven treatment plans were performed with nonblock design and FSCB with different fan angles, that is, from 90° to 140°, with increment of 10°. The homogeneous index, conformation number, MLD, and the relative lung volume receiving more than 5, 10, 15, and 20 Gy (V 5, V 10, V 15, and V 20) were determined for each treatment scheme. There was a substantial reduction in the MLD, V 5, V 10, V 15, and V 20 when using different types of FSCB as compared to the nonblock design. The reduction of V 20, V 15, V 10, and V 5 was 6.3%-8.6%, 16%-23%, 42%-57%, and 42%-66% for FSCB 90°-140°, respectively. The use of FSCB in helical tomotherapy is a promising method to reduce the MLD, V 20, and relative lung volume in low dose region, especially in V 5 and V 10 for esophageal cancer.