Quantitative assessment of SSTR2 expression in patients with non-small cell lung cancer using(68)Ga-DOTATOC PET and comparison with (18)F-FDG PET.
OBJECTIVE
Dynamic PET studies with(68)Ga-DOTATOC were performed in patients with non-small cell lung cancer (NSCLC) to assess the somatostatin receptor 2 (SSTR2) expression. Furthermore, dynamic(18)F-fluorodeoxyglucose (FDG) studies were performed in the same patients to compare the SSTR2 expression with the tumour viability.


METHODS
The study population comprised nine patients, examined with both tracers on two different days within 1 week. Standardised uptake values (SUVs) were calculated and a two-tissue compartment model was applied to the data. Furthermore, a non-compartment model based on the fractal dimension (FD) was applied to the data.


RESULTS
The DOTATOC uptake was generally lower than the FDG uptake. Moderately enhanced DOTATOC uptake was noted in seven of the nine tumours. All kinetic parameters except k (4) were lower for DOTATOC than for FDG. The mean SUV was 2.018 for DOTATOC, in comparison to 5.683 for FDG. In particular, k (3) was highly variable for DOTATOC and showed an overlap with the normal lung tissue. The fractional blood volume V (B) was relatively low for both tracers, not exceeding 0.3. The highest significant logarithmic correlation was found for the FD of the two tracers (r=0.764, p=0.017). The logarithmic correlation for SUVs was also significant (r=0.646, p=0.060), as was that forV (B) (r=0.629, p=0.069). In contrast, none of the eight metastases which were positive on FDG PET showed any DOTATOC uptake.


CONCLUSIONS
The results demonstrated moderate (68)Ga-DOTATOC uptake in primary NSCLC but did not provide any evidence for SSTR2 expression in metastases. This may be caused by loss of the gene expression in metastases as compared with the primary tumours.
Medical PET Group--Biological Imaging (E0601), Clinical Cooperation Unit, Nuclear Medicine, German Cancer Research Center, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany. ads@ads-lgs.com
Antonia
A
Dimitrakopoulou-Strauss
Vassilios
V
Georgoulias
Michael
M
Eisenhut
Felix
F
Herth
Sophia
S
Koukouraki
Helmut R
HR
Mäcke
Uwe
U
Haberkorn
Ludwig G
LG
Strauss
D014408:Biomarkers, Tumor / Q000378:metabolism*; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000378:metabolism*; D019788:Fluorodeoxyglucose F18 / Q000493:pharmacokinetics*; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D015282:Octreotide / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D009942:Organometallic Compounds / Q000493:pharmacokinetics*; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution
D014408:Biomarkers, Tumor; C499142:Ga(III)-DOTATOC; D009363:Neoplasm Proteins; D009942:Organometallic Compounds; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D019788:Fluorodeoxyglucose F18; C093733:somatostatin receptor 2; D015282:Octreotide