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

Combined modality therapy for patients with esophageal squamous cell carcinoma: Radiation dose and survival analyses

BACKGROUND

We aimed to analyze the radiation dose and compare survival among combined modality therapy using modern radiation techniques for patients with esophageal squamous cell carcinoma (ESCC).

METHODS

This retrospective study included patients with clinically staged T1-4N0-3M0 ESCC from 2014 to 2018. Patients who received combined modality therapies with curative intent were enrolled. The overall survival (OS) rates among combined modality therapy were compared. The clinical variables and impacts of radiation dose on survival were analyzed by the Kaplan-Meier method and Cox regression model.

RESULTS

Of the 259 patients, 141 (54.4%) received definitive concurrent chemoradiotherapy (DCCRT); 67 (25.9%) underwent neoadjuvant chemoradiotherapy followed by surgery (NCRT+S); 51 (19.7%) obtained surgery followed by adjuvant chemoradiotherapy (S+ACRT). Two-year OS rates of the DCCRT, NCRT+S and S+ACRT group were 48.9, 61.5 and 51.2%. In the subgroup analysis of DCCRT group, the 2-year OS of patients receiving radiation dose 55-60 Gy was 57.1%. Multivariate analyses showed that clinical stage (p = 0.004), DCCRT with 55-60 Gy (p = 0.043) and NCRT+S with pathological complete response (pCR) (p = 0.014) were significant prognostic factors for better OS. The radiation dose-survival curve demonstrated a highly positive correlation between higher radiation dose and better survival.

CONCLUSION

Our results suggest that NCRT+S can provide a favorable survival for patients with ESCC, especially in patients who achieved pCR. The optimal radiation dose might be 55-60 Gy for patients receiving DCCRT via modern radiation techniques. Further randomized clinical studies are required to confirm the survival benefits between NCRT+S and DCCRT with escalated dose.

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 V_5-30 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, V_10, and delivery time in VMAT.