Olive Wong

Survival Impact of Cardiac Dose Following Lung Stereotactic Body Radiotherapy

Micro‐Abstract Heart dose has been emerging as a strong predictor of outcomes in radiation therapy treatment for lung cancer. It is necessary to determine the impact of dose to substructures of the heart on overall survival. Heart substructures were contoured retrospectively on 189 patients treated with stereotactic body radiotherapy. Clinical variables and the dose to these structures were correlated with non–cancer‐related deaths. Higher bilateral ventricles max dose is associated with poorer survival. Heart dose parameters should be considered when planning patients for stereotactic body radiotherapy. Introduction: The purpose of this study was to determine the impact of radiation dose to substructures of the heart in lung stereotactic body radiotherapy (SBRT) patients on non–cancer‐related deaths. Methods: Patients treated with lung SBRT at a single institution from 2005 to 2013 were included. The heart and its substructures were contoured, and dose was calculated including mean, max, and max 10 cc dose. Clinical variables including stage, histology, age, gender, Charlson comorbidity index (CCI), preexisting cardiac disease, pulmonary function (forced expiratory volume in 1 second, diffusion capacity), and smoking status were explored for association with non–cancer‐related deaths in univariable (UVA) and multivariable (MVA) analyses. Heart dosimetric parameters were correlated with the risk of radiation pneumonitis (RP) using UVA and MVA. Results: A total of 189 patients were included with median age of 76 years (range, 48‐93 years). Of these patients, 45.5% were female, 27.5% were T2, 16.9% were current smokers, 64% had preexisting cardiac risk factors, and 34.5% had CCI score of ≥ 3. Mean lung dose ± SD was 456 ± 231 cGy. Heart max, mean, and 10 cc doses were 1867 ± 1712 cGy, 265 ± 269 cGy, and 1150 ± 1075 cGy, respectively. There were 14 (7.4%) ≥ Grade 2 RP and 3 (1.6%) were ≥ Grade 3. The median overall survival was 37.3 months (95% confidence interval, 29.8‐45.3 months). On UVA, female gender (P < .01), higher Eastern Cooperative Oncology Group (P = .01), cardiac risk (P < .01), CCI (P < .01), and bilateral ventricles max dose (P = .02) were associated with non–cancer‐related deaths; on MVA, bilateral ventricles max dose was significant (P = .05). No heart parameters were associated with RP. Conclusions: Higher bilateral ventricles max dose is associated with poorer survival. Heart dose parameters should be considered when planning patients for SBRT.

Impact of Pre-Treatment Interstitial Lung Disease on Radiation Pneumonitis and Survival in Patients Treated with Lung Stereotactic Body Radiation Therapy (SBRT)

Micro‐Abstract Interstitial lung disease (ILD) in patients with lung cancer is a management challenge. In this study of 537 patients who underwent lung stereotactic body radiation therapy, we found that patients with ILD (vs. patients without ILD) had greater risk of radiation pneumonitis. On multivariable analysis, ILD and mean lung dose were predictors of radiation pneumonitis. Computed tomography scans should be assessed for ILD before stereotactic body radiation therapy is considered. Introduction: The purpose of this study was to determine the impact of interstitial lung disease (ILD) on radiation pneumonitis (RP) and overall survival (OS) in lung stereotactic body radiation therapy (SBRT). Methods: Patients treated with lung SBRT from 2004 to 2015 were included. Pretreatment computed tomography scans were reviewed and classified for interstitial changes by thoracic radiologists using American Thoracic Society guidelines and Washko and Kazerooni scores. RP was scored prospectively using Common Terminology Criteria for Adverse Events, version 3.0. Pretreatment imaging characteristics, clinical variables, and dosimetry were assessed by univariate (UVA) and multivariate analysis (MVA). OS was assessed by the log‐rank test, and the impact of ILD on OS was assessed by Cox regression. Results: Of the 537 patients assessed, 39 had interstitial changes (13 usual interstitial pneumonia [UIP], 24 possible UIP, and 2 inconsistent with UIP). RP was significantly higher in patients with ILD than in patients without ILD (grade ≥ 2, 20.5% vs. 5.8%; P < .01; grade ≥ 3, 10.3% vs. 1.0%; P < .01). Two of 3 grade 5 RP had imaging features of ILD. On UVA, ILD, Washko score, lung parameters performance status, and dose were significant predictors of grade ≥ 2 RP. On MVA, ILD (odds ratio, 5.81; 95% confidence interval, 2.28‐14.83; P < .01) and mean lung dose (odds ratio, 1.40; 95% confidence interval, 1.14‐1.71; P < .01) were predictors of RP. ILD did not significantly affect OS on UVA or MVA. Median survival was 27.4 months in the ILD cohort and 34.8 in the ILD‐negative cohort (P = .17). Discussion: ILD is a significant risk factor for RP in patients treated with lung SBRT. Computed tomography scans should be reviewed for evidence of ILD prior to SBRT.

Sci-Fri PM: Radiation Therapy, Planning, Imaging, and Special Techniques - 08: Retrospective Dose Accumulation Workflow in Head and Neck Cancer Patients Using RayStation 4.5.2

Purpose: We have developed a semi-automated dose accumulation workflow for Head and Neck Cancer (HNC) patients to evaluate volumetric and dosimetric changes that take place during radiotherapy. This work will be used to assess how dosimetric changes affect both toxicity and disease control, hence inform the feasibility and design of a prospective HNC adaptive trial. Methods: RayStation 4.5.2 features deformable image registration (DIR), where structures already defined on the planning CT image set can be deformably mapped onto cone-beam computed tomography (CBCT) images, accounting for daily treatment set-up shifts and changes in patient anatomy. The daily delivered dose can be calculated on each CBCT and mapped back to the planning CT to allow dose accumulation. The process is partially automated using Python scripts developed in collaboration with RaySearch. Results: To date we have performed dose accumulation on 18 HNC patients treated at our institution during 2013–2015 under REB approval. Our semi-automated process establishes clinical feasibility. Generally, dose accumulation for the entire treatment course of one case takes 60–120 minutes: importing all CBCTs requires 20–30 minutes as each patient has 30 to 40 treated fractions; image registration and dose accumulation require 60–90 minutes. This is in contrast to the process without automated scripts where dose accumulation alone would take 3–5 hours. Conclusions: We have developed a reliable workflow for retrospective dose tracking in HNC using RayStation. The process has been validated for HNC patients treated on both Elekta and Varian linacs with CBCTs acquired on XVI and OBI platforms respectively.

Prognostic value of pretreatment circulating neutrophils, monocytes, and lymphocytes on outcomes in lung stereotactic body radiotherapy

PURPOSE In the present study, we determined the association of pretreatment circulating neutrophils, monocytes, and lymphocytes with clinical outcomes after lung stereotactic body radiotherapy (sbrt). METHODS All patients with primary lung cancer and with a complete blood count within 3 months of lung sbrt from 2005 to 2012 were included. Overall survival (os) was calculated using the Kaplan-Meier method. Factors associated with os were investigated using univariable and multivariable Cox proportional hazards regression. Fine-Gray competing risk regression was performed to test the association of the neutrophil:lymphocyte (nlr) and monocyte:lymphocyte (mlr) ratios with two types of failure: disease-related failure and death, and death unrelated to disease. RESULTS Of the 299 sbrt patients identified, 122 were eligible for analysis. The median and range of the nlr and mlr were 3.0 (0.3-22.0) and 0.4 (0.1-1.9) respectively. On multivariable analysis, sex (p = 0.02), T stage (p = 0.04), and nlr (p < 0.01) were associated with os. On multivariable analysis, T stage (p < 0.01) and mlr (p < 0.01) were associated with disease-related failure; mlr (p = 0.03), nlr (p < 0.01), and sbrt dose of 48 Gy in 4 fractions (p = 0.03) and 54 Gy or 60 Gy in 3 fractions (p = 0.02) were associated with disease-unrelated death. Median survival was 4.3 years in the nlr≤3 group (95% confidence interval: 3.5 to not reached) and 2.5 years in the nlr>3 group (95% confidence interval: 1.7 to 4.8; p < 0.01). CONCLUSIONS In lung sbrt patients, nlr and mlr are independently associated with os and disease-unrelated death. If validated, nlr and mlr could help to identify patients who would benefit most from sbrt.