Proceedings of the 52nd Annual ASTRO Meeting S529

2726 The Relationship between Host Factors such as FEV1.0 and Therapeutic Factors such as Normal Lung V20

in the Occurrence of Severe Radiation Pneumonitis

N. Okano1, K. Karasawa1, N. Kubo1, N. Hanyu1, T. Chang1, G. Kuga1, T. Okano1, T. Kaminuma2

1Tokyo Metropolitan Komagome Hospital, Tokyo, Japan, 2Hidaka Hospital, Gunma, Japan

Purpose/Objective(s): In lung irradiation, the most severe side effect is radiation pneumonitis (RP). Knowing the risk estimationof the patient before treatment, we will be more able to prevent RP and also to arrange the safer and more curative plans. In thisstudy, we investigated the relationship between various factors and RP.

Materials/Methods: We examined 84 patients who were treated with 3D non-coplanar conformal radiation therapy at our insti-tution from Oct. 2005 to Nov. 2008. All cases were followed more than 6 months. Target tumors were, primary lung tumor in 69cases, recurrent tumor in 5 cases, and metastasis in 10 cases. No elective nodal irradiation was performed. Total dose ranged 60-75Gy, and fraction dose ranged 2.4-3Gy. Following factors were selected as variables: respiratory function (VC, %VC, FEV1.0,and FEV1.0%), kidney function (Creatinine, GFR), diabetes mellitus, PTV size, irradiated volume / normal lung volume (V5-V40),and mean lung dose. In addition, we estimated the correlation relationship between these factors and RP (NCI-CTCAE ver.3.0 G0/1vs. G2/3, G0/1/2 vs. G3) using chi-square test. We also tested the combination of these factors.

Results: Respiratory functions were VC: 1.27-4.57L (mean 2.47L), %VC: 52-126% (89.1%), FEV1.0:0.51-3.29L (1.65L),FEV1.0%:33.6-93.6% (68.5%). Irradiated volume / normal lung volume were V5:4.31-46.4% (23.4%), V10:3.3-39.24%(19.50%), V15:2.64-32.46% (15.72%), V20:2.08-21.8% (11.20%), V25:1.75-16.3% (8.81%), V30:1.48-12.78% (7.09%),V35:1.26-9.89% (5.63%), V40:1.07-8.38% (4.53%)). PTV size ranged 33.84-276.27ml (88.59ml). Mean lung dose ranged 1.5-14.8ml (7.71ml). The numbers of Grade 0/1/2/3 are 4/46/28/6. Low dose volume percentage (V5-V15) was related with the oc-currence of RP Grade 2 or higher (p \ 0.005), and high dose volume percentage (V20-) was not related with RP, but tended tobe related with severe RP (Grade3; p [severeRP] \ p [RP]). Patients with low %VC were significantly easier to have severeRP than their counterpart (p \ 0.005). Patients with lower FEV1.0 tended to have severe RP even with lower V20 by scattergram. Patients with low GFR might have RP easier than their counterpart. Other factors had no significant relationship with RP.

Conclusions: Restrictive defect ventilator impairment and severe radiation pneumonitis were strongly correlated. High dose vol-ume percentage (V20-) had also significant relationship with occurrence of severe radiation pneumonitis. With the same level ofV20, Patients with low FEV1.0 were easier to have severe radiation pneumonitis. V20 limitation might be shown by the formula asa function of FEV1.0.

Author Disclosure: N. Okano, None; K. Karasawa, None; N. Kubo, None; N. Hanyu, None; T. Chang, None; G. Kuga, None; T.Okano, None; T. Kaminuma, None.

2727 Implementation of iPlan RT Monte Carlo Dose Algorithm for Stereotactic Lung Cancer Treatment

J. van Santvoort, A. Petoukhova, P. van de Vaart, P. Koper, R. Harmsen-Jongerden

Radiotherapy Centre West, Den Haag, Netherlands

Purpose/Objective(s): To implement the iPlan RT Monte Carlo Dose Algorithm (MC) (BrainLab) for stereotactic lung treatments.This study compares doses calculated and optimized with MC with doses calculated with a Pencil Beam algorithm (PB) usingpatient data.

Materials/Methods: Between 1/2009 and 2/2010 20 patients with stage I non-small cell lung cancer (NSCLC) were treated withstereotactic radiotherapy at our institution. Multiple spiral scans on an AcQSim CT scanner (consisting of one full-range scan andsix co-registered scans limited to the tumor region) were used to define the internal target volumes (ITVs) during free breathing. Foreach patient, a PTV is constructed using the ITV plus 5 mm margin in the left-right and antero-posterior direction and 6 mm marginin the longitudinal direction. Mean PTV volume was 44.8 cm3 (15.9-101.7 cm3). Our lung patients were irradiated in 3 fractions of20 Gy or in 5 fractions of 12 Gy prescribed at the 80% isodose. The treatment plans consisted of 7-10 coplanar 6 MV photon beamsof a Novalis accelerator. For these 20 patients, MC calculations were compared to the original PB calculations and the existing planwas adapted according to the prescriptions of a phase III multi-centre randomized trial (ROSEL) (C.W. Hurkmans et al., RadiationOncology 2009, 4:1). Different parameters from RTOG trial 2036 were calculated. MC calculations were performed with full MLCgeometry simulation, a spatial resolution of 2 mm, a variance of 1% and a dose type ‘‘Dose to medium’’.

Results: Between the PB and MC calculation differences of up to 30% in local dose were observed within the PTV. The dosereceived by 95% of the PTV (D95) was calculated using MC and PB for every patient. The PB calculated D95 was (by definition)60 Gy and the MC calculated D95 was 50.4 ± 4.3 Gy. The mean PTV dose calculated with PB was 72.2 ± 1.1 Gy and calculatedwith MC 59.2 ± 4.1 Gy. After re-optimizing the plan using MC and with a lower fraction dose, according to the ROSEL protocol foradvanced algorithms (3 x 18 Gy or 5 x 11 Gy), the mean PTV dose was 60.6 ± 1.6 and D95 was 54.5 ± 0.5 Gy.

Conclusions: The PB algorithm significantly overestimates the PTV dose. The mean dose to the PTV for the plans re-optimized with MCand adapted according to the ROSEL trial is comparable to the mean dose for the historical patient group, but the dose homogeneity is muchbetter. The doses in the critical structures are comparable. We are going to implement MC calculations for stereotactic lung treatments.

Author Disclosure: J. van Santvoort, None; A. Petoukhova, None; P. van de Vaart, None; P. Koper, None; R. Harmsen-Jongerden,None.

2728 Lung Metastases Treated with Image-Guided Stereotactic Body Radiation Therapy

A. Baschnagel, V. S. Mangona, J. Robertson, H. Ye, L. L. Kestin, I. S. Grills

William Beaumont Hospital, Troy, MI

Purpose/Objective(s): To evaluate outcomes after treatment with image-guided stereotactic body radiation therapy (SBRT) usingdaily online cone beam CT for lung metastases.

S530 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 3, Supplement, 2010

Materials/Methods: Thirty-six lung metastases in 24 patients were treated on a prospective trial with volumetrically-guidedSBRT. Median age was 62 years (21-79). Primaries included colorectal (n = 7), sarcoma (n = 3), NSCLC (n = 3), renal cell(n = 2), thymoma (n = 2), head and neck (n = 2), melanoma (n = 1), thyroid (n = 1), endometrial (n = 1), esophageal (n = 1)and bladder (n = 1). The number of lung metastases treated per patient ranged from 1 - 3 (mean 1.5). Tumor sizes ranged from0.7 - 5.1 cm in maximal diameter (median 1.6 cm). SBRT was prescribed to the edge of the target volume with a median doseof 60 Gy (48 - 65 Gy) and median of 4 fractions (4 - 10). Most lesions were treated with 12 Gy/fraction (89%) to a total of 48or 60 Gy. Median number of days elapsed during RT was 10. Half of patients had lung metastases as their only known distantdisease and received SBRT as first line treatment for metastases. The other half had previously treated metastatic disease priorto SBRT that was stable. Three patients received external beam RT to the lung for prior disease. Thirteen patients (54%) had priorlung surgery, including 13 wedge resections and 3 lobectomies for primary or metastatic disease. Thirteen patients (54%) receivedsystemic therapy. Five patients (21%) had active extra thoracic disease being treated aggressively at time of SBRT.

Results: Median follow-up was 14.6 months (range, 8 - 52). 1- and 2-year local control rates for all treated lesions were 97% and82%, respectively. Out of the two patients with local failure, one had progression of all three treated lesions. Both patients (and all 4lesions) who failed had a colorectal primary. The one year local failure rate for colorectal primary cases was 8% vs. 0% for all othercases (p = 0.05). One year local failure in the low dose group (48 Gy) was 10% vs. 0% in the high dose (60 Gy) (p = 0.05). One andtwo year overall survival from time of SBRT completion was 96% and 90%, respectively. Distant progression occurred in 17 pa-tients (71%) at a median of 6.4 months after SBRT (range, 1.4 - 34.1). Overall progression free survival was 33% and 26% at 1 andtwo years. Median time to disease progression in patients where the lung was the only site of metastasis and treated with SBRT was10.1 months vs. 5.5 months in patients with previous treated metastatic disease (p = 0.68). There was no Grade 4 toxicity. Grade 3toxicity (pneumonitis and dyspnea) occurred in 1 out of 24 patients (4%).

Conclusions: SBRT using daily online CBCT for limited lung metastases achieved excellent local tumor control and low toxicity.In this cohort, patients with colorectal metastases and treated with a lower dose had a higher rate of local failure.

Author Disclosure: A. Baschnagel, None; V.S. Mangona, None; J. Robertson, None; H. Ye, None; L.L. Kestin, None; I.S. Grills,None.

2729 Clinical Outcomes of Stereotactic Body Radiotherapy for Lung Metastases

Y. Kosaka1, M. Kokubo2, H. Nishimura3, N. Ueki1, Y. Tagawa1, Y. Okuno1

1Kobe City Medical Center General Hospital, Kobe, Japan, 2Institution of Biomedical Research and Innovation, Kobe, Japan,3Kobe University Hospital, Kobe, Japan

Purpose/Objective(s): To evaluate the outcomes of patients undergoing stereotactic body radiotherapy (SBRT) for lung metastases.

Materials/Methods: Between 2002 and 2008, 65 lesions in 46 patients with four or fewer lung metastases were treatedby SBRT.Thirtywere male and 16 were female. Their ages ranged between 29 and 85, and the median was 68. The primary involved organs were thecolorectum (n = 21), head and neck (n = 7), ureter and bladder (n = 3), uterus (n = 3), and other sites (n = 12). Four to eight, non-coplanar,static 4-MV photon beams were used. In most lesions, 48-60 Gy in 4-5 fractions within 4-24 (median = 4) days was prescribed for theisocenter of the planning target volume using the Clarkson algorithm with effective path length correction. Retrospectively, we also re-calculated each treatment plan using the superposition algorithm, maintaining the original monitor units and beam orientations.

Results: With a median follow-up of 27.6 months, the 2-year overall survival, progression-free survival, and local control rateswere 85.1%, 22.7%, and 73.1%, respectively. Lesions originating from the colorectum were significantly correlated with worselocal control, and a larger tumor size had a trend toward worse local control. The biologically effective dose was not significantlycorrelated with local control using either the Clarkson algorithm or the superposition algorithm. Grade 2 pneumonitis occurred in10 patients (16%), and 1 patient (2%), who had originally had poor respiratory function, developed Grade 4 pneumonitis. Onepatient (2%) developed Grade 4 dermatitis and Grade 2 soft tissue necrosis of the thorax.

Conclusions: SBRT of 48-60 Gy in 4-5 fractions for lung metastases was effective and safe in this retrospective study. Largerlesions or lesions originating from the colorectum were difficult to control with this dose fractionation, so dose escalation is nec-essary to control these lesions.

Author Disclosure: Y. Kosaka, None; M. Kokubo, None; H. Nishimura, None; N. Ueki, None; Y. Tagawa, None; Y. Okuno, None.

2730 Cryptogenic Organizing Pneumonia after Stereotactic Body Radiotherapy of the Lung

T. Murai1, Y. Shibamoto1, F. Baba2, S. Ayakawa3, A. Miyakawa1, S. Otsuka1, H. Ogino1, T. Yanagi1, H. Iwata1, C. Sugie1

1Department of Radiology, Nagoya City University, Nagoya, Japan, 2Department of Radiology, Nagoya Chukyo hospital,Nagoya, Japan, 3Department of Radiology, Nagoya Daini Red Cross Hospital, Nagoya, Japan

Purpose/Objective(s): To investigate clinical and radiological features of cryptogenic organizing pneumonia (COP) occurringafter stereotactic body radiotherapy (SBRT) of the lung and its incidence.

Materials/Methods: Patients undergoing SBRT of the lung between 2004 and 2008 and followed with periodical chest CT for 1 year orlonger were investigated. SBRT was performed using a linear accelerator with 6-MV photons. Three coplanar and 4 noncoplanar static portswere used. Irradiation to the contralateral lung was avoided as much as possible. The total dose prescribed at isocenter was 44, 48 or 52 Gy,depending on tumor size, in 4 fractions for primary lung cancer and lung metastasis ($ 1.5 cm), and 34 or 36 Gy in 2 fractions for smallerlung metastasis. Patients with previous irradiation to the chest were excluded. Blood test and chest CT were performed at intervals of 1 to 3months after SBRT. The criteria for the diagnosis of COP were: 1) mixture of patchy and ground-glass opacity, 2) general and/or respiratorysymptoms lasting for at least 2 weeks, 3) radiographic lesion in the lung volume receiving\0.5 Gy, and 4) no evidence of a specific cause.

Results: One hundred forty-eight patients (130 with stage I lung cancer and 18 with single lung metastasis) were analyzed (follow-up:1-6.6 years). Seven patients developed COP. The incidence of the post-radiation COP was 3.4%, 4.8%, and 4.8% at 1, 2 and 3 years,respectively. Two patients had received 48 Gy and 5 had received 52 Gy. V20Gy, V5Gy and mean lung dose were 7.5% (range: 5.8-9.7%), 24.6% (15.5-28.2%) and 5.6 Gy (3.6-10.1 Gy), respectively, in these patients. These data were not different from those of pa-tients developing no COP. Seven patients presented with symptomatic radiation pneumonitis (RP) in and around the planning target