RT Journal Article
SR Electronic
T1 <sup>18</sup>F-FLT-PET/CT adds value to <sup>18</sup>F-FDG-PET/CT for diagnosing relapse after definitive radiotherapy in patients with lung cancer. Results of a prospective clinical trial
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP jnumed.120.247742
DO 10.2967/jnumed.120.247742
A1 Tine Noehr Christensen
A1 Seppo W Langer
A1 Gitte F Persson
A1 Klaus Richter Larsen
A1 Annika Loft
A1 Annemarie Gjelstrup Amtoft
A1 Anne Kiil Berthelsen
A1 Helle Hjorth Johannesen
A1 Sune Hoegild Keller
A1 Andreas Kjaer
A1 Barbara Malene Fischer
YR 2020
UL http://jnm.snmjournals.org/content/early/2020/10/09/jnumed.120.247742.abstract
AB Diagnosing relapse after radiotherapy for lung cancer is challenging. The specificity of both CT and 2-deoxy-2-[18F]fluoro-D-glucose (FDG)-PET/CT is low due to radiation-induced changes. 3’-deoxy-3’-[18F]fluorothymidine (FLT)-PET has previously demonstrated higher specificity for malignancy than FDG-PET. We investigated the value of FLT-PET/CT for diagnosing relapse in irradiated lung cancer. Methods: Patients suspected for relapse of lung cancer after definitive radiotherapy (conventional fractionated radiotherapy (cRT) or stereotactic radiotherapy (SBRT)) were included. Sensitivity and specificity were analysed within the irradiated high-dose volume (HDV) and patient-based. Marginal differences and inter-observer agreement were assessed. Results: Sixty-three patients who had received radiotherapy in 70 HDVs (34 cRT; 36 SBRT) were included. The specificity of FLT-PET/CT was higher than FDG-PET/CT (HDV: 96% [87-100] vs. 71% [57-83]; P = 0.0039; patient-based (90 % [73-98] vs. 55% [36-74]; P = 0.0020)). The difference between specificity of FLT-PET/CT and FDG-PET/CT was higher after cRT compared with SBRT. Sensitivity of FLT-PET/CT was lower than FDG-PET/CT (HDV: 69% [41-89] vs. 94% [70-100]; P = 0.1250; patient-based: 70% [51-84] vs. 94% [80-99]; P = 0.0078). Adding FLT-PET/CT when FDG-PET/CT was positive or inconclusive improved diagnostic value compared with FDG-PET/CT only. In cRT-HDVs, the probability of malignancy increased from 67% for FDG-PET/CT alone to 100% when both PETs were positive. Conclusion: FLT-PET/CT adds diagnostic value to FDG-PET/CT in patients with suspected relapse. The diagnostic impact of FLT-PET/CT was highest after cRT. We suggest adding FLT-PET/CT when FDG-PET/CT is inconclusive or positive within the previously irradiated volume to improve diagnostic value in patients where histological confirmation is not easily obtained.