Evaluation of thoracic tumors with 18F-fluorothymidine and 18F-fluorodeoxyglucose-positron emission tomography.
OBJECTIVE
18F-fluorodeoxyglucose (FDG) is the most widely used positron emission tomography (PET) imaging probe used for the diagnosis, staging, restaging, and monitoring therapy response of cancer. However, its specificity is less than ideal. A new molecular imaging probe (18F-deoxyfluorothymidine [FLT]) has been developed that might afford more specific tumor imaging. The aims of this study were as follows: (1) to compare the use of FDG-PET and FLT-PET for tumor staging, (2) to compare the degree of FDG and FLT uptake in lung lesions, and (3) to determine the correlation between PET uptake intensity and tumor cell proliferation.


METHODS
FDG-PET and FLT-PET scans were performed in 11 patients with solitary pulmonary nodules and another 11 patients with known non-small cell lung cancer (NSCLC). Tracer uptake was assessed quantitatively by standardized uptake values (SUVs). Histologic evaluation of tissue samples obtained from biopsy specimens or surgical resections served as the "gold standard." Tumor cell proliferation was assessed by Ki-67 staining.


RESULTS
Pathology verification was available from 99 tissue samples in the 22 patients (29 pulmonary lesions, 66 lymph node stations, and 4 extrapulmonary lesions). Thirty-three samples (33.3%) were positive for tumor tissue (22 pulmonary, 9 lymph node stations, and 2 extrapulmonary). FDG-PET findings were false-positive in three pulmonary lesions, while FLT-PET findings were false-positive in one lesion. There were two false-negative findings by FDG-PET and six false-negative findings by FLT-PET. FDG uptake of the malignant lesions was significantly higher than FLT (maximum SUV, 3.1 +/- 2.6 vs 1.6 +/- 1.2 [mean +/- SD]; p < 0.05). A significant correlation was observed between FLT uptake of pulmonary lesions and Ki-67 labeling index (r = 0.60, p = 0.02) but not for FDG uptake (r = 0.27, p = not significant).


CONCLUSIONS
Compared to FDG-PET, detection of primary and metastatic NSCLC by FLT-PET is limited by the relatively low FLT uptake of the tumor tissue. Thus, FLT-PET is unlikely to provide more accurate staging information or better characterization of pulmonary nodules than FDG-PET. Nevertheless, the correlation between FLT uptake and cellular proliferation suggests that future studies should evaluate the use of FLT-PET for monitoring treatment with cytostatic anticancer drugs.
Department of Molecular and Medical Pharmacology, Ahmanson Biological Imaging Center/Nuclear Medicine.
Cecelia S
CS
Yap
Department of Molecular and Medical Pharmacology, Ahmanson Biological Imaging Center/Nuclear Medicine.
Johannes
J
Czernin
Department of Pathology and Laboratory Medicine, Division of Cardiothoracic Surgery, UCLA School of Medicine, Los Angeles, CA.
Michael C
MC
Fishbein
Department of Surgery, Division of Cardiothoracic Surgery, UCLA School of Medicine, Los Angeles, CA.
Robert B
RB
Cameron
Department of Molecular and Medical Pharmacology, Ahmanson Biological Imaging Center/Nuclear Medicine.
Christiaan
C
Schiepers
Department of Molecular and Medical Pharmacology, Ahmanson Biological Imaging Center/Nuclear Medicine.
Michael E
ME
Phelps
Department of Molecular and Medical Pharmacology, Ahmanson Biological Imaging Center/Nuclear Medicine. Electronic address: wweber@mednet.ucla.edu.
Wolfgang A
WA
Weber
D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology; D015224:Dideoxynucleosides; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis; D008175:Lung Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals; D012680:Sensitivity and Specificity; D013899:Thoracic Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000473:pathology
D015224:Dideoxynucleosides; D019394:Ki-67 Antigen; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; C002854:alovudine