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for SBRT, 3DCRT respectively; 57% were women for SBRT while 61% were women for 3DCRT (p = NS). More AfricanAmericans had SBRT (15% v 5%, p\0.01). All patients were medically inoperable. Median percentage predicted DLCOwas 53% and 42% (p\0.01) for 3DCRT and SBRT, respectively. There were no differences in percentage predicted FEV1between groups (62% SBRT v 59% 3DCRT). Although overall T-stages were similar between groups, 3DCRT patients hadlarger tumors with a median size of 2.7cm for SBRT v 3.6 for 3DCRT (p\0.01). The median dose for 3DCRT was 70 Gyin 35 fractions (54-79.2 Gy), and for SBRT was 48 Gy in 4 fractions (40-60 Gy). Follow-up was $2y in both groups.

Results: With a mean follow-up of 1.57 years, SBRT had a significantly lower rate of local recurrence (LR) at 2 years, 8%,compared to 21% with 3DCRT (p = 0.02). No statistically significant differences were identified, however, in the rates ofregional recurrence (RR) 12% SBRT v 9% 3DCRT (p = NS) or distant metastasis (DM) 19% in both groups. Disease-freesurvival was also similar in both groups, 49% in each. Although overall survival (OS) and cause-specific survival (CSS)were somewhat higher in the SBRT group, these differences did not reach statistical significance in this patient dataset. 2yOS was 65% after SBRT v 54% after 3DCRT (p = NS); 2y CSS was 91% after SBRT and 80% after 3DCRT (p = NS).The only statistically significant difference in treatment-related toxicity between the two groups was a higher rate of $ grade2 dermatitis after 3DCRT (11% v 1%, p = 0.02). Otherwise, the rates of $ grade 2 pneumonitis (6% SBRT v 5% 3DCRT),acute esophagitis (0% v 2%), chronic myositis (5% v 2%) and rib fracture (5% v 0%) were statistically similar. For all patients,no statistically significant predictor of LR could be identified other than 3DCRT. Only gender (Male) predicted RR (p\0.01) orDFS (p = 0.02).

Conclusions: In this dataset, online image-guided SBRT was associated with superior local control versus standard fractionation3DCRT for stage I NSCLC, but not a significant improvement in survival. Toxicity profiles were similar between the two groups.These findings support the continued use of hypofractionated SBRT.

Author Disclosure: M. Mislmani, None; I.S. Grills, None; J.M. Robertson, None; H. Ye, None; E. McInerney, None; S. Martin,None; L.L. Kestin, None.

2691 Prediction of Radiation-induced Pulmonary Function Loss in Post-operative Radiotherapy for Non-small

Cell Lung Cancer Using a Fibrosis Volume Model

O. Noh, H. Jang, Y. Oh, K. Park, K. Park, M. Kim, M. Chun

Ajou University Hospital, Suwon 433-721, Republic of Korea

Purpose/Objective(s): To evaluate radiation-induced pulmonary function loss in post-operative radiotherapy (PORT) for non-small cell lung cancer (NSCLC) using the volume of radiation-induced pulmonary fibrosis.

Materials/Methods: Patients with NSCLC who were treated with PORT were enrolled in this investigation. Pulmonary functiontests (PFTs) were determined pre-operatively, pre-PORT, and . 6 months after PORT. Pre-PORT PFTs were also estimated frompreoperative PFTs using a quantitative CT method. The volume of radiation-induced pulmonary fibrosis (Vf) was evaluated onchest CT scan . 6 months after the completion of PORT. The correlations among the dosimetric parameters of the lung, Vf,and radiation-induced pulmonary function loss were analyzed.

Results: Between January 2003 and January 2007, 48 patients were treated with conformal radiotherapy. The mean values ofFEV1 were 2.16 L pre-operatively, 1.65 L pre-PORT; 1.61 L estimated pre-operatively, and 1.59 L during follow-up PFTs.PORT showed no additional decline in FEV1 (estimated pre-PORT FEV1 vs. follow-up FEV1 [1.63 L vs. 1.59 L]; p = 0.48).The radiation-induced pulmonary function loss was well-correlated with the dosimetric parameters (V25; r = -0.734; p \ .01),as well as the Vf (r = -0.695; p \ .01).

Conclusions: The degree of radiation-induced pulmonary function loss can be predicted by the dosimetric parameters of the lung inpatients with NSCLC who underwent surgical resection followed by PORT. Radiation-induced fibrosis volume can be used asa quantitative imaging marker in assessment of radiation-induced pulmonary injury.

Author Disclosure: O. Noh, None; H. Jang, None; Y. Oh, None; K. Park, None; K. Park, None; M. Kim, None; M. Chun, None.

2692 Heterogeneity Corrections Alters the Delivered Dose, Potentially Impacting Complications in Patients

Treated with Stereotactic Body Radiotherapy (SBRT) of the Lung

C. E. Rutter1, S. A. Naqvi1, B. Zhang2, K. Marter2, M. Koshy1, A. Dhople1, S. J. Feigenberg1, W. D. D’Souza1

1University of Maryland, School of Medicine, Baltimore, MD, 2University of Maryland Medical Center, Baltimore, MD

Purpose/Objective(s): SBRT using heterogeneity corrections is not widely used in North America, but may have an impact oncomplications and local control on tumors treated in the lung. This study evaluated the impact of patient and tumor related factorson dose to the tumor and surrounding normal structures with and without heterogeneity correction.

Materials/Methods: Fifty-one consecutive patients treated with SBRT for malignant lung tumors between September2005 and December 2008 were examined. SBRT treatments were delivered using RTOG 0236 guidelines, withoutheterogeneity corrections. Using the same beam arrangement and monitor units used for the actual treatment, thedose distributions were recomputed using heterogeneity correction. Dose-volume histograms were generated for the in-ternal target volume (ITV) with and without heterogeneity corrections. The percent differences in dose to 5% (hot spot),50%, and 95% of the ITV (D5, D50, D95) between homogenous dose calculation and heterogeneity correction werecomputed. Correlation analysis and independent samples t-tests were used to identify significant differences in thesestatistics based on tumor distance from the chest wall, lobe involved, ITV volume, GTV volume and the body massindex (BMI).

Results: On average, the use of heterogeneity correction resulted in increases in D95 (3.8%; range -7.7% to 11.2%), D50 (7.0%;range -3.0% to 15.3%), and D5 (8.7%; range -14.4% to 17.6%). Tumors greater than one centimeter away from the chest wallwere associated with a significantly larger increase in D5 (10.1% vs. 7.4%, p = 0.046). The magnitude of increase in D95 wascorrelated to ITV volume (R = 0.277, p = 0.049). ITV volume greater than the median value (13.9 cm3) resulted in a larger increase

S514 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 3, Supplement, 2010

in D50 (5.8% vs. 8.1%, p = 0.035) and D95 (1.8% vs. 5.8%, p = 0.002). Tumors of the lower lobes were associated with trendstoward significance for increase in D5 (9.8% vs. 7.8%, p = 0.079) and D50 (8.3% vs. 6.3%, p = 0.078). Tumors of the left upperlobe were associated with smaller increases in D50 (5.0% vs. 7.5%, p = 0.043). GTV volume and BMI had no impact on dosimetricvalues.

Conclusions: The use of heterogeneity correction appears to significantly increase dose to the ITV. The magnitude of this effect isincreased by larger ITV, tumor location in the lower lobes where diaphragmatic excursion causes greater tumor motion, andincreased distance from tumor to chest wall.

Author Disclosure: C.E. Rutter, None; S.A. Naqvi, None; B. Zhang, None; K. Marter, None; M. Koshy, None; A. Dhople, None;S.J. Feigenberg, None; W.D. D’Souza, None.

2693 Frameless 4DCT-guided Stereotactic Body Radiotherapy with Daily Image Guidance for Early Stage Lung

Cancer: Clinical Outcomes

A. Sandhu, S. K. Nath, D. Kim, A. Bharne, P. D. Nobiensky, J. D. Lawson, M. Fuster, L. Bazhenova, A. J. Mundt

University of California San Diego, La Jolla, CA

Purpose/Objective(s): Stereotactic Body Radiotherapy (SBRT) can offer exceptionally high local control rates for stage I/II lungcancer. Traditionally, stereotactic body frames have been used during SBRT for patient immobilization and set-up. Newer imagingmodalities now allow for improved set-up and target visualization prior to treatment, potentially obviating the need for bodyframes. We report here on our clinical experience using frameless image-guided SBRT and analyze a subgroup of patients treatedwith the current RTOG 0915 dosing schedule.

Materials/Methods: Forty-eight patients (pts) (52 lesions) with stage I/II non-small cell lung cancer (NSCLC) were treatedbetween 2007 and 2009 with SBRT without a body frame. Median patient age was 78 years (range, 64-88). Average tumorsize was 2.7 cm (range, 1.0-5.7), and 71% of lesions were located in the periphery as defined by the RTOG 0236 protocol.Prescription doses were 48-52 Gy in 4-5 fractions. Patients were planned using a four-dimensional CT (4DCT) acquisitionprotocol, and daily image guidance was performed using orthogonal kV-imaging and/or cone-beam computed tomography(CBCT). Follow-up occurred every 2-3 months and consisted of a clinical exam and imaging. Local control (LC) and over-all survival (OS) were calculated using the Kaplan-Meier method. Toxicity was graded by the Common Toxicity Criteriaversion 3.0.

Results: Median follow-up was 15 months for all pts (range, 4-35 months), and 20 months for surviving pts. Out of 46 ptsevaluable for LC, only a single local failure was detected during our period of surveillance, corresponding to a 12- and24-month actuarial LC rate of 98% (95% confidence interval [CI], 93-100%) at both times. First failure site was regional in5 pts (11%) and distant in 12 pts (26%). The 12- and 24-month actuarial OS rates were 78% (95% CI, 65-90%) and 54%(95% CI, 38-70%). Grade 3 or higher toxicity occurred in 2 pts (4%), and consisted of pericardial effusion and severeesophagitis. Of the 27 pts treated with the dose of 48 Gy in 4 fractions used in the current RTOG 0915, 12- and 24-monthactuarial LC was 96% (95% CI, 89-100%) at both times. The 12- and 24-month actuarial OS for this group was 80%(95% CI, 64-96%) and 69% (95% CI, 50-89%), respectively.

Conclusions: Although longer follow-up is needed, our preliminary results indicate that frameless 4DCT-guided SBRTwith daily image-guidance can produce excellent LC with acceptable survival and toxicity outcomes. These datacompare favorably to traditional frame-based SBRT techniques and support the continued role of this modality inthe management of early stage NSCLC patients. Additionally, clinical outcomes using 48 Gy in 4 fractions wereexcellent.

Author Disclosure: A. Sandhu, None; S.K. Nath, None; D. Kim, None; A. Bharne, None; P.D. Nobiensky, None; J.D. Lawson,None; M. Fuster, None; L. Bazhenova, None; A.J. Mundt, None.

2694 Consolidation Chemotherapy following Concurrent Chemo-radiotherapy has a Trend of Improving

Survival in Patients with Stage III Non-small Cell Lung Cancer

Y. Tang, J. Cao, J. Li, X. Zhang, L. Wang

Cancer Institute and Hospital, Chinese Academy of Medical Science and Peking Union Medical College, Beijing, China

Purpose/Objective(s): Concurrent chemo-radiotherapy (CCRT) has been regarded as the standard treatment for unresectablelocally advanced non-small cell lung cancer (NSCLC). However, the effect of consolidation chemotherapy following CCRTwas still in question. The objective of this retrospective study is to evaluate the value of consolidation chemotherapy followingCCRT in stage III NSCLC patients.

Materials/Methods: From January 2001 to December 2007, 145 patients with stage III NSCLC treated with CCRT in ourinstitute were retrospectively analyzed. Among them, 32 (22.1%) patients were in stage IIIA and 113 (77.9%) in stage IIIB.One-hundred and fourteen (78.6%) patients received radiation with three-dimensional conformal/intensity modulated radiationtechnique while the others with traditional one. The median radiation dose of the whole group was 60 Gy (range: 45-74 Gy).Paclitaxel combined with cisplatin/carboplatin was the most commonly used concurrent chemotherapy regimen (76 patients,52.4%), while etoposide combined with cisplatin/carboplatin was the second common one (44 patients, 30.3%). Sixty-nine(47.6%) patients received consolidation chemotherapy following CCRT (CCRT/CT group), and the other 76 (52.4%) patientsdid not (CCRT group). The baseline characteristics of two groups were compared. Kaplan-Meier method was used to calculatethe overall survival (OS) and progress-free survival (PFS) rates in both groups. The log-rank test was used for the comparisonof the survival curves.

Results: The median follow-up was 17 months for the whole group and 30 months for the survival. The baseline characteristicsof the two groups were similar except that patients in CCRT/CT group were younger (median age: 55.2 years vs. 58.6 years,p = 0.00). The 1-year, 3-year and 5-year OS was 73.9%, 36% and 21.6% respectively in CCRT/CT group, and 61.8%, 19.8%