International Journal of Radiation Oncology Biology Physics
E398 Poster Viewing Abstracts 2991; Table 1 Absolute number and percentage of displacements 5mm in 76 SBRT fractions Post Treatment CBCT values (mm in module) Lateral (X) plane 5mm > 5 mm Total Cranial-caudal (Y) plane 5mm > 5 mm Total Anterior-Posterior (Z) plane 5mm > 5 mm Total X,Y,Z plane (> 5 mm at least one direction) 5mm > 5 mm Total
N (%) 75 (98,7) 1 (1,3) 76 (100) 73 (96,1) 3 (3,9) 76 (100) 73 (96,1) 3 (3,9) 76 (100)
71 (93,4) 5 (6,6) 76 (100)
87% of patients. ITV mean volume was 20 cm3 (15.8). Seventy-six post treatments CBCT were analyzed for X, Y, Z displacements (228 total displacements assessed). Mean displacement (standard deviation) on lateral, cranial-caudal and anterior-posterior planes was 0.14 (0.22), 0.18 (0.18), 0.19 (0.19) centimeters, respectively. Displacements in any direction (X, Y, and Z) were 5mm and 3mm in 93.4% and 77.6%, respectively (Table 1). Displacements > 3 mm were more frequent on cranial-caudal (11.6%; PZ0.0477) and anterior-posterior (14.5% PZ0.0135) axes when compared to the lateral plane (2.6%). BMI (< 27 v 27; PZ0.711), presence of comorbidities (Yes v No; PZ0.188), ECOG (0-1 v 2; PZ0.647) and ITV volume ( 20 v > 20; PZ1.00) were not statistically significantly associated with displacement >3mm. Conclusion: Image-guidance is essential for lung SBRT. Once target match is performed, the intra-fraction positional changes through a course of lung SBRT are small and displacements >5mm are infrequent. The 5 mm margin for PTV from the ITV is adequate and confirmed by our current SBRT approach. Author Disclosure: F.Y. Moraes: None. G.S. Siqueira: None. C.K. Haddad: None. J.F. Silva: None. C.E. Abreu: None.
2992 A Retrospective Analysis in Patients With EGFR-Mutant Lung Adenocarcinoma: Is EGFR Mutation Associated With Higher Incidence of Brain Metastasis? G. Han,1 J. Bi,2 W. Tan,3 X. Wei,2 X. Guo,4 X. Ying,2 X. Zhou,2 X. Wang,1 D. HU,2 and W. Zhen5; 1Hubei Cancer Hospital, Wuhan, China, 2 Department of Radiation Oncology, Hubei Cancer Hospital, Wuhan, China, 3Department of Oncology, Shenzhen People Hospital, Shenzhen, China, 4Department of Radiology, Hubei Cancer Hospital, Wuhan, China, 5 University of Nebraska Medical Center, Omaha, NE Purpose/Objective(s): Lung adenocarcinomas are more commonly associated with metastatic disease to the brain as compared with other histologic types of non-small cell lung carcinoma (NSCLC). Epidermal growth factor receptor (EGFR) mutations have been demonstrated to be both predictive and prognostic for patients with lung adenocarcinoma. However, its impact on brain metastases (BM) remains inconclusive. This study aimed to explore the potential association between EGFR mutation and the risk of BM in patients with pulmonary adenocarcinoma. Furthermore we also intended to identify other risk factors for BM, which may guide the selection of management strategies. Materials/Methods: Clinical data of 234 patients at our institution from March 2007 to November 2014 were retrospectively reviewed. All patients in this cohort had known EGFR mutation status and brain magnetic resonance imaging (MRI). The relationships between EGFR mutation and
BM at the initial presentation and at the last follow-up were analyzed. Multivariate analysis was performed to identify the independent factors associated with BM. Results: A total of 76 out of 234 patients (32.5%) had developed BM during their disease course amongst 39 patients (16.7%) had BM at their initial diagnosis. Within the entire cohort, 108 patients (46.2%) had EGFR mutations. As compared with that of wild type EGFR patients, the frequency of EGFR mutation was statistically higher for patients with BM at the initial diagnosis (64.1% vs. 35.9%, PZ0.014) and at the last follow-up (63.2% vs. 36.8%, PZ0.000). However, there was no significant difference in the incidence of extracranial metastases regardless of EGFR mutation status either at the time of diagnosis or at the last follow-up (40.9% vs. 59.1%, PZ0.313; 43.3% vs. 56.7%, PZ0.494). In Multivariate Logistic regression analysis, EGFR mutation was significantly associated with the risk for BM at the initial diagnosis (ORZ0.393, 95% CIZ0.165-0.943, PZ0.034). Among those 195 patients without BM at initial diagnosis, 1year and 2-year accumulative rates of subsequent BM were significantly different between the patients with EGFR-mutant and EGFR-wild disease (15.0% vs. 4.2%, 37.7% vs. 18.7%; PZ0.001). In Multivariate Cox regression analysis, only EGFR mutation was the independent factor for the risk of BM (HRZ3.446, pZ0.000). Conclusion: In our study, we demonstrated that BM was more common among patients with EGFR-mutant lung adenocarcinoma, which may represent one of the distinct clinical features for EGFR-mutant tumors. EGFR mutation was the only independent predictive and prognostic risk factor for BM. The potential utility of prophylactic cranial irradiation (PCI) for patients with EGFR-mutant lung adenocarcinoma should be further explored. Author Disclosure: G. Han: None. J. Bi: None. W. Tan: None. X. Wei: None. X. Guo: None. X. Ying: None. X. Zhou: None. X. Wang: None. D. HU: None. W. Zhen: None.
2993 Risk Factors of Brain Metastases as Initial Failure for Completely Resected Stage IIIA (N2) Non-Small Cell Lung Cancer Q. Zhang,1 X. Fu,2 W. Feng,1 X.W. Cai,1 and W. Yu2; 1Shanghai Chest Hospital, Shanghai, China, 2Shanghai Chest Hospital, Shanghai Jiaotong University, Shanghai, China Purpose/Objective(s): Brain metastasis (BM) is the main sign of failure of locally advanced non-small cell lung cancer (LA-NSCLC). The lymph node (LN) status is a major determinant of outcome in patients with NSCLC, but whether or not the LN status is a major determinant of BM remains unclear. In the present study, we focused on completely resected staged IIIA (N2) LA-NSCLC to explore the correlation between LN status and BM. We also aimed to identify the risk factors of BM as the initial site of failure, as well as the potential highest-risk candidates who are most likely to benefit from prophylactic cranial irradiation (PCI). Materials/Methods: The medical records of 357 consecutive patients with stage IIIA (N2) NSCLC who underwent complete surgery were reviewed between January 2005 and June 2012. Time to BM as the initial site of failure was measured from the date of surgery to the date of BM in the patients who developed distant metastases or both local and distant recurrence as the initial failure, with BM defined as an event. The cumulative incidence of BM as the initial site of failure and survival were determined using the KaplaneMeier analysis. To assess the risk factors of BM, the log-rank test was used for univariate analysis, and Cox regression was used for multivariate analysis. Results: A total of 73 (20.4%) patients developed BM, and 60 patients had BM as their initial site of failure. The 1-, 3-, and 5-year risks for patients developing BM as the initial site of failure were 9.1%, 27.4%, and 35.4%, respectively. Univariate analysis showed that non-squamous cell cancer (P Z 0.000), positive extra-capsular extension of LN metastasis (PZ0.041), number of metastatic LN > 4 (P Z 0.018), multiple N2 stations (P Z 0.027), and multiple regions of mediastinal LN (MLN)