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7143 Background: To evaluate the relationship between 99mTc-HL91 (99mTc labeled 4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime) SPECT (single photon emission computed tomography) hypoxia imaging and the radiotherapy outcome and also to assess changes in tumor oxygenation during the course of treatment. Methods: 32 patients with pathologically proven non-small cell lung cancer received three-dimensional conformal radiotherapy were enrolled into the study. All patients were performed 99mTc-HL91 SPECT scanning at one or two days before radiotherapy. 18 patients were also performed during radiotherapy (30–40 Gy) and one or two days after radiotherapy. Anterior, posterior and lateral planar images were collected at 2 hours, 4 hours and 6 hours respectively after intravenous injection approximately 740MBq 99mTc-HL91. Regions of interest (ROIs) were drawn in the tumor and contralateral normal lung tissue and the radioactivity ratios of tumor to normal tissue (T/N) were calculated. Results: The relationship between T/N ratios at 4h images after injection which was shown as the best of three acquired images before radiotherapy and the response and over survival to radiotherapy were analyzed for all 32 patients. The results of 99mTc-HL91 imaging of 32 patients correlate well with radiotherapy response (P = 0.049) and also patient survival (P = 0.043). The average T/N value of 18 patients who receiving serial scanning was 1.57 ± 0.18, 1.44 ± 0.19 and 1.30 ± 0.14 respectively. There was significant statistic difference between these three groups (P = 0.000). Conclusions: HL91 SPECT imaging identified the hypoxia status and changes during radiotherapy in lung cancer. It was confirmed that hypoxia imaging with HL91 SPECT before treatment may predict radiotherapy response and patient survival. The relationship between T/N ratio and radiotherapy outcome in NSCLC [Table: see text] No significant financial relationships to disclose.

7044 Background: Radiation dose escalation is limited by the high incidence of pulmonary and esophageal toxicity, leading to calls for the omission of elective nodal irradiation (ENI) and the willingness to use involved-field radiotherapy (IFRT) in patients with stage III non-small cell lung cancer (NSCLC). Methods and Materials: Patients with inoperable stage III NSCLC were enrolled and patients with previous treatment were ineligible, as were those with supraclavicular nodal metastases, pleural effusion, the Karnofsky performance status of No significant financial relationships to disclose.