S466 I. J. Radiation Oncology d Biology d Physics Volume 72, Number 1, Supplement, 2008

2663 One Segment Inverse Planning Method for the Lung SRT

H. Nagano1, M. Kato2, Y. Tashima1, H. Hashimoto2, T. Shimo1, T. Ichinose1, M. Agawa1, M. Munakata1, Y. Ohta1, T. Ohkawa1

1Tokyo-west Tokushukai Hospital, Akishima, Japan, 2Chigasaki Tokushukai General Hospital, Chigasaki, Japan

Purpose/Objective(s): Stereotactic radiotherapy has been an on going method to treat T1-2N0M0 non-small cell lung carcinoma.Some cases of tumors are located near the chest wall or the mediastinum, so it is hard to deliver enough irradiation doses to thetumor sparing the normal tissues in the same time. One segment per beam inverse planning (one-seg) method may be useful inthese cases.

Materials/Methods: We compared 3D-CRT (using beam weight optimization), one-seg method and IMRT (50 segments) of tencases. The tumors were sited near the chest wall or the mediastinum. We planned the same prescribed doses (minimal PTV 48 Gy/4fxs, maximum 60 Gy/4fxs) under the same constrains (PTV ring; Max dose 48 Gy, Surround ring; Max dose 40 Gy, Lungs; MaxDVH 20 Gy 20%, Normal tissue; Max DVH 40 Gy 5%, Override; Max DVH 50 Gy 50%) using 10 beams in the same directions.These doses were calculated by Pinnacle3 ver. 7.6c. Isodose volume (IsoV), conformity index (CI = IsoV/PTV), coverage ($48 GyPTV/PTV), D95 of PTV, V20 of the lungs, minimal PTV dose (min), maximum PTV dose (max), homogeneity index (HI = max/min), St40 (soft tissue volume irradiated equal or over 40 Gy) were evaluated and the mean values of them were analyzed usingStudent’s t test.

Results: One-seg method was superior to 3D-CRT in coverage (86% vs. 95% p\0.01), D95 (4,598 cGy vs. 4,914 cGy, p = 0.001),min (3,979 cGy vs. 4,343 cGy, p = 0.001), max (5,885 cGy vs. 6,055 cGy, p\0.05), HI (1.5 vs. 1.4, p\0.05) and St40 (7.7 ml vs.5.2 ml, p\0.05). But the mean values of IsoV (22.0 ml vs. 23.5 ml), CI (1.0 vs. 1.1) and V20 (5.5% vs. 5.1%) were not different.Mean values of these parameters of one-seg and IMRT were not different statistically except coverage (95% vs. 96%, p \ 0.05).Dose sufficiency and homogeneity in the tumor volume and the sparing of the normal tissue may be well achieved by one-segmethod to the almost same extent done by IMRT except for the mean value of the coverage. This difference was significant butthe value of the difference was negligible (only 1%).

Conclusions: Considering a respiratory movement, IMRT can not always reproduce planned dose distribution precisely. One-segmethod will enable many doctors to seek fruitful solution compared with 3D-CRT and IMRT in the treatment of lung tumors nearthe chest wall and/or mediastinum.

Author Disclosure: H. Nagano, None; M. Kato, None; Y. Tashima, None; H. Hashimoto, None; T. Shimo, None; T. Ichinose,None; M. Agawa, None; M. Munakata, None; Y. Ohta, None; T. Ohkawa, None.

2664 Fractionated Stereotactic Body Radiation Therapy for Central or Peripheral Stage I Non-small Cell Lung

Cancer on Consecutive Days

S. Song1, W. Choi1, S. Shin1, S. Lee1, S. Ahn1, J. Kim1, C. Park2, J. Lee3, E. Choi1

1Radiation Oncology, Asan Medical Center, College of Medicine, University of Ulsan, Seoul, Republic of Korea, 2RadiationOncology, Seoul National University Hospital, Seoul, Republic of Korea, 3Medical Oncology, Asan Medical Center, College ofMedicine, University of Ulsan, Seoul, Republic of Korea

Purpose/Objective(s): To evaluate the treatment outcome after Stereotactic body radiation therapy (SBRT) on 3-4 consecutivedays for stage I Non-small cell lung cancer (NSCLC) and compare the treatment related pulmonary toxicity between centrally-and peripherally-located tumors.

Materials/Methods: From Jun 1999 to May 2006, 32 patients diagnosed as stage I, T1N0 or T2N0, resectable NSCLC weretreated with body-frame based fractionated SBRT. Pathology was squamous cell carcinoma, adenocarcinoma or not other specified(NOS). The reasons of SBRT were variable. Thirty-one patients had several medical problems conflicting surgical procedure andthe other one patient refused surgery although they could be a surgical candidate. Fractionated SBRT on consecutive 3-4 days andstereotactic body frame was used for improving setup accuracy. Doses of 10-20 Gy per fraction were delivered to the planningtarget volume (PTV) up to a total dose of 40-60 Gy with three to four fractions on consecutive days. Centrally located tumorwas defined as the tumor within 2 cm apart from large bronchial tree, and was subdivided into bronchial (main/lobar bronchus)and peribronchial (segmental or distal).

Results: Median follow-up was 26.5 months. The 6-month major response rate, complete or partial response, was 53.1%. Onepatient showed progressive disease 1 month after SBRT. 1- and 2-year actuarial local tumor control was the same, 85.3%. Overallsurvival was 70.9% at 1 year and 38.5% at 2 year. Survival was not different according to SBRT dose. Pulmonary toxicity wasdifferent by tumor location. Three (33%) patients among 9 patients with centrally-located tumor experienced grade 3-5 pulmonarytoxicities in contrary to peripheral lung tumor, and their locations were all bronchial (main/lobar). Eight patients showed partial orcomplete bronchial stricture and secondary volume loss of normal lung. Median time to bronchial stricture was 13 months and itsrange was 1-39 months. Overall survival was not different by tumor location.

Conclusions: Fractionated SBRT is an effective treatment modality for inoperable stage I NSCLC. SBRT in tumors on main/lobarbronchus must be cautioned owing to pulmonary toxicity derived from bronchial stricture, unlike peripheral tumor or tumor onsegmental/distal bronchus.

Author Disclosure: S. Song, None; W. Choi, None; S. Shin, None; S. Lee, None; S. Ahn, None; J. Kim, None; C. Park, None; J.Lee, None; E. Choi, None.

2665 Novalis Stereotactic Body Radiotherapy for Recurrent and Newly Diagnosed Poor Risk Non-small Cell

Lung Cancer (NSCLC)

Y. Chen, M. Milano, G. G. Roloff, T. Smudzin, P. Okunieff

University of Rochester Medical Center, Rochester, NY

Purpose/Objective(s): Stereotactic body radiotherapy (SBRT) using hypofractionated dose schedule has gained popularity in themanagement of pulmonary nodules due to relatively low toxicity and apparent efficacy. The fraction size of 18 Gy to 20 Gy for