Neutrophil to lymphocyte ratio associated with prognosis of lung cancer.

PURPOSE: Many studies recently focus on complicated and expensive genomic tests, but the prognostic values of biochemical markers which are easily obtained in clinics are largely overlooked and without further exploration. This study assesses the association of neutrophil-lymphocyte-ratio (NLR) with prognosis of lung cancer patients. METHODS: In 1032 patients with histologically confirmed lung cancer, the association of pretreatment NLR values with overall survival (OS) was evaluated using a Cox proportional hazards model and the temporal relationship of longitudinal NLR was assessed using a mixed effects model. RESULTS: Compared to the patients with a low pretreatment NLR value, those with elevated NLR exhibited a statistically significant worse OS with a hazard ratio (HR) of 1.50 (P < 0.0001) after adjusting for age, gender, race, smoking status, drinking status, tumor stage, tumor grade, histology, and treatments. A significant trend of increasing HRs along with increasing NLR values was observed. The increased risk of death conferred by pretreatment NLR values reached a peak level around 2 years after diagnosis. Moreover, in longitudinal analysis, we observed a trend of dramatically increased NLR values in patients who died during follow-up, but stable NLR values in those who were still alive, with a significant interaction of death-alive status with follow-up time (P < 0.0001). CONCLUSIONS: Elevated NLR is a potential biomarker to identify lung cancer patients with poor prognosis and should be validated in a future clinical trial.

SU-E-J-04: Initial Experience with 4D-CBCT for Lung Cancer: Physician Verification of Computed Shifts Remains Necessary.

PURPOSE: Four-dimensional cone-beam CT (4D-CBCT) is a novel imaging technique used to guide treatment setup for patients with pulmonary lesions by providing additional information about tumor motion at the time of treatment. This study aimed to evaluate the efficacy of the 4D-CBCT capability in ensuring accurate patient setup during SBRT. METHODS: Twelve patients with pulmonary lesions were imaged pre-treatment with Elekta XVI4.5 using the Symmetry protocol resulting in a respiratory correlated 4D-CBCT. Reconstruction produced 10 phased-based and one average 3DCT image set. Patient shifts were derived from contour-based(mask) registration driven by the weighted average of shifts from each phased CT(4D shifts). Physicians reviewed registration and manually adjusted shifts based on visual registration. We exported the average 3DCT to MIM Vista Software 5.1.1 in reference volume coordinates and manually fused to the reference CT. All manual fusions were contour-based registrations performed by a single observer. No rotations were permitted in manual fusion to mimic clinical procedure. Translational 3D shifts from manual fusion were compared to 4D(automatic registration) shifts and final physician-corrected shifts. RESULTS: Mean differences between 4D and 3D shifts in lateral, longitudinal, and vertical directions were 1.07mm, 5.92mm, and 1.43mm, respectively. Mean differences between physician-corrected and 3D shifts were 1.41mm, 4.83mm, and 1.61mm. Differences between 4D shifts and 3D shifts increased with increasing tumor motion. One patient had consistently large longitudinal differences between 4D and 3D shifts (mean=3.0cm). Further review revealed poor 4D registration(via mask and clipbox) on the XVI system which was corrected by physician adjustment prior to treatment. CONCLUSIONS: 4D-CBCT is a valuable imaging tool in patient setup. Physician review of contour-based registration is imperative in preventing a geometrical miss. Caution must be employed in tumors that exhibit a large degree of motion. Further research is necessary in determining functional limits of the 4D-CBCT system.

SU-E-J-12: Initial Clinical Experiences in Using 4D-CBCT as Image Guidance for Lung SBRT.

PURPOSE: The authors started to use Symmetry 4D-CBCT as image guidance for lung SBRT in August 2011. Here the authors present the initial clinical experiences with this novel image guidance technique. METHODS: In total 118 4D-CBCT scans have been acquired for 17 lung patients among which 15 received SBRT and the other 2 received hypofractionated treatments. 4D-CBCT scans are acquired with Elekta XVI 4.5 usingSymmetry, a procedure module in XVI that acquires 4D-CBCT, registers daily images to reference 3D-CT and generates shifts for patient setup. RESULTS: Typical thoracic 4D-CBCT scans with Symmetry take 3 minutes with a 200 degree gantry rotation. Symmetry automatically sorts images into 10 phases based on automatic detection of diaphragm position. Then Symmetry generates two independent intensity-based registrations, one according to a pre-defined large volume of interest including the tumor, surrounding tissues and bony structures, the other only according to an expanded target volume. The registrations are obtained by registering each phase image to the reference image and averaging across all phases in a time-weighted manner. Eventually Symmetry provides users the freedom to pick either one of the two registrations, a compromise, or a manual tuning. Compared to regular 3D-CBCT, 4D-CBCT enables physicians to visually place the moving target in the center of PTV, greatly reducing the probability of missing target due to respiratory motion, thus enables possible reduction in PTV margin. 4D-CBCT also provides the ability to repeatedly evaluate the quality of ITV. It is possible that ITV does not fully cover the tumor motion due to a low quality 4D-CT simulation for a patient with difficulties in regular breathing. CONCLUSIONS: 4D-CBCT is a superior image guidance technique for lung SBRT treatments for its ability to visualize moving target. It provides physicians more confidence in tumor targeting and ability to repeatedly evaluate ITV quality during the treatment course.