18F-FLT PET during radiotherapy or chemoradiotherapy in head and neck squamous cell carcinoma is an early predictor of outcome.
This prospective study used sequential PET with the proliferation tracer 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-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 (18)F-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
(18)F-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 (18)F-FLT uptake levels during treatment, GTVSBR and GTV50% were unsuccessful in segmenting primary tumor volume.


CONCLUSIONS
In head and neck cancer, a change in (18)F-FLT uptake early during radiotherapy or chemoradiotherapy is a strong indicator for long-term outcome. (18)F-FLT PET may thus aid in personalized patient management by steering treatment modifications during an early phase of therapy.
Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
Bianca A W
BA
Hoeben
Esther G C
EG
Troost
Paul N
PN
Span
Carla M L
CM
van Herpen
Johan
J
Bussink
Wim J G
WJ
Oyen
Johannes H A M
JH
Kaanders
D000328:Adult; D000368:Aged; D001692:Biological Transport; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy / Q000628:therapy*; D015224:Dideoxynucleosides / Q000378:metabolism; D005260:Female; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy / Q000532:radiotherapy / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D013997:Time Factors; D016896:Treatment Outcome
D015224:Dideoxynucleosides; C002854:alovudine