PT - JOURNAL ARTICLE AU - Wouter van Elmpt AU - Michel Öllers AU - Anne-Marie C. Dingemans AU - Philippe Lambin AU - Dirk De Ruysscher TI - Response Assessment Using <sup>18</sup>F-FDG PET Early in the Course of Radiotherapy Correlates with Survival in Advanced-Stage Non–Small Cell Lung Cancer AID - 10.2967/jnumed.111.102566 DP - 2012 Oct 01 TA - Journal of Nuclear Medicine PG - 1514--1520 VI - 53 IP - 10 4099 - http://jnm.snmjournals.org/content/53/10/1514.short 4100 - http://jnm.snmjournals.org/content/53/10/1514.full SO - J Nucl Med2012 Oct 01; 53 AB - This study investigated the possibility of early response assessment based on 18F-FDG uptake during radiotherapy with respect to overall survival in patients with non–small cell lung cancer. Methods: 18F-FDG PET/CT was performed before radiotherapy and was repeated in the second week of radiotherapy for 34 consecutive lung cancer patients. The CT volume and standardized uptake value (SUV) parameters of the primary tumor were quantified at both time points. Changes in volume and SUV parameters correlated with 2-y overall survival. Results: The average change in mean SUV in the primary tumor of patients with a 2-y survival was a decrease by 20% ± 21%—significantly different (P &lt; 0.007) from nonsurvivors, who had an increase by 2% ± 22%. A sensitivity and specificity of 63% and 93%, respectively, to separate the 2 groups was reached for a decrease in mean SUV of 15%. Survival curves were significantly different using this cutoff (P = 0.001). The hazard ratio for a 1% decrease in mean SUV was 1.032 (95% confidence interval, 1.010–1.055). Changes in tumor volume defined on CT did not correlate with overall survival. Conclusion: The use of repeated 18F-FDG PET to assess treatment response early during radiotherapy is possible in patients undergoing radiotherapy or sequential or concurrent chemoradiotherapy. A decrease in 18F-FDG uptake by the primary tumor correlates with higher long-term overall survival.