RT Journal Article SR Electronic T1 18F-FLT PET During Radiotherapy or Chemoradiotherapy in Head and Neck Squamous Cell Carcinoma Is an Early Predictor of Outcome JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 532 OP 540 DO 10.2967/jnumed.112.105999 VO 54 IS 4 A1 Bianca A.W. Hoeben A1 Esther G.C. Troost A1 Paul N. Span A1 Carla M.L. van Herpen A1 Johan Bussink A1 Wim J.G. Oyen A1 Johannes H.A.M. Kaanders YR 2013 UL http://jnm.snmjournals.org/content/54/4/532.abstract AB This prospective study used sequential PET with the proliferation tracer 3′-deoxy-3′-18F-fluorothymidine (18F-FLT) to monitor the early response to treatment of head and neck cancer and evaluated the association between PET parameters and clinical outcome. Methods: Forty-eight patients with head and neck cancer underwent 18F-FLT PET/CT before and during the second and fourth weeks of radiotherapy or chemoradiotherapy. Mean maximum standardized uptake values for the hottest voxel in the tumor and its 8 surrounding voxels in 1 transversal slice (SUVmax(9)) of the PET scans were calculated, as well as PET-segmented gross tumor volumes using visual delineation (GTVVIS) and operator-independent methods based on signal-to-background ratio (GTVSBR) and 50% isocontour of the maximum signal intensity (GTV50%). PET parameters were evaluated for correlations with outcome. Results: 18F-FLT uptake decreased significantly between consecutive scans. An SUVmax(9) decline ≥ 45% and a GTVVIS decrease ≥ median during the first 2 treatment weeks were associated with better 3-y disease-free survival (88% vs. 63%, P = 0.035, and 91% vs. 65%, P = 0.037, respectively). A GTVVIS decrease ≥ median in the fourth treatment week was also associated with better 3-y locoregional control (100% vs. 68%, P = 0.021). These correlations were most prominent in the subset of patients treated with chemoradiotherapy. Because of low 18F-FLT uptake levels during treatment, GTVSBR and GTV50% were unsuccessful in segmenting primary tumor volume. Conclusion: In head and neck cancer, a change in 18F-FLT uptake early during radiotherapy or chemoradiotherapy is a strong indicator for long-term outcome. 18F-FLT PET may thus aid in personalized patient management by steering treatment modifications during an early phase of therapy.