• Masatoyo Nakajo, Masayuki Nakajo, Yoriko Kajiya, Megumi Jinguji, Nobuaki Nishimata, Shunji Shimaoka, Tohru Nihara, Kuniaki Aridome, Sadao Tanaka, Yoshihiko Fukukura, Atushi Tani, and Chihaya Koriyama.
• Department of Radiology, Kagoshima University, Graduate School of Medical and Dental Sciences, 8-35-1 Sakuragaoka, Kagoshima 890-8544, Japan. toyo.nakajo@dolphin.ocn.ne.jp
• Eur. J. Nucl. Med. Mol. Imaging. 2013 Aug 1; 40 (8): 1223-32.

PurposeTo examine the diagnostic performance of (18)F-fluorothymidine (FLT) PET/CT in primary and metastatic lymph node colorectal cancer foci in comparison with (18)F-fluorodeoxyglucose (FDG) PET/CT.MethodsThe study population comprised 28 patients with 30 newly diagnosed colorectal cancers who underwent surgical resection of the primary lesion and regional lymph nodes after both FLT and FDG PET/CT. The associations between SUVmax levels and pathological factors were evaluated using the Mann-Whitney U or Kruskal-Wallis test. Differences in diagnostic indexes for detecting nodal metastasis between the two tracers were estimated using the McNemar exact or χ(2) test.ResultsAll 30 primary cancers (43.0 ± 20.0 mm, range 14 - 85 mm) were visualized by both tracers, but none of the FLT SUVmax values exceeded the FDG SUVmax values in any of the primary cancers (6.6 ± 2.4 vs. 13.6 ± 5.8, p < 0.001). The sensitivity, specificity and accuracy for detecting nodal metastasis were 41% (15/37), 98.8% (493/499) and 94.8% (508/536) for FDG PET/CT, and 32% (12/37), 98.8% (493/499) and 94.2% (505/536) for FLT PET/CT, respectively. The sensitivity (p = 0.45), specificity (p = 0.68) and accuracy (p = 0.58) were not different between the tracers. Nodal uptake of FLT and FDG was discordant in 7 (19%) of 37 metastatic nodes. There were ten concordant true-positive nodes of which six showed higher FDG SUVmax and four showed higher FLT SUVmax, but the difference between FDG and FLT SUVmax was not significant (5.56 ± 3.55 and 3.62 ± 1.45, respectively; p = 0.22).ConclusionFLT has the same potential as FDG in PET/CT for the diagnosis of primary and nodal foci of colorectal cancer despite significantly lower FLT uptake in primary foci.

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