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.