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Abstract #4106

Evaluation of Optimal Timing for Diffusion Weighted MR Imaging to Assess Early Tumor Response of Lung Cancer After Stereotactic Body Radiotherapy

Shigeaki Umeoka1, Yukinori Matsuo2, Tomohisa Okada1, Aki Kido1, Yusuke Iizuka2, Masahiro Hiraoka2, Kaori Togashi1

1Department of Diagnostic Imaging and Nuclear Medicine, Graduate School of Medicine, Kyoto University, Kyoto, Japan; 2Department of Radiation Oncology and Image-applied Therapy, Graduate School of Medicine, Kyoto University, Kyoto, Japan

Apparent diffusion coefficient (ADC) value of lung cancer calculated from diffusion-weighted imaging (DWI) has a potential for predicting early tumor response or predicting prognosis for patients who underwent radiotherapy. However, it has not been fully discussed appropriate timing for ADC to assess tumor response. Thus, we prospectively evaluated the optimal timing of DWI in patients with non-small lung cancer who underwent Stereotactic Body Radiotherapy (SBRT). Our study indicated that DWI at six months after SBRT seemed the best timing for assessing tumor response compared with DWI at pre-, three months after, nine months after, and twelve months after SBRT.