The expression of alpha(v)beta(3) and glucose metabolism are upregulated in many malignant lesions, and both are known to correlate with an aggressive phenotype. We evaluated whether assessment of alpha(v)beta(3) expression and of glucose metabolism with PET using (18)F-galacto-RGD and (18)F-FDG provides complementary information in cancer patients.
Methods: Eighteen patients with primary or metastatic cancer (non-small cell lung cancer [NSCLC], n = 10; renal cell carcinoma, n = 2; rectal cancer, n = 2; others, n = 4) were examined with PET using (18)F-galacto-RGD and (18)F-FDG. Standardized uptake values (SUVs) were derived by volume-of-interest analysis. (18)F-Galacto-RGD and (18)F-FDG PET results were compared using linear regression analysis for all lesions (n = 59; NSCLC, n = 39) and for primaries (n = 14) and metastases to bone (n = 11), liver (n = 10), and other organs (n = 24) separately.
Results: The sensitivity of (18)F-galacto-RGD PET compared with clinical staging was 76%. SUVs for (18)F-FDG ranged from 1.3 to 23.2 (mean +/- SD, 7.6 +/- 4.9) and were significantly higher than SUVs for (18)F-galacto-RGD (range, 0.3-6.8; mean +/- SD, 2.7 +/- 1.5; P < 0.001). There was no significant correlation between the SUVs for (18)F-FDG and (18)F-galacto-RGD for all lesions (r = 0.157; P = 0.235) or for primaries, osseous or soft-tissue metastases separately (P > 0.05). For the subgroup of lesions in NSCLC, there was a weak correlation between (18)F-FDG and (18)F-galacto-RGD uptake (r = 0.353; P = 0.028).
Conclusion: Tracer uptake of (18)F-galacto-RGD and (18)F-FDG does not correlate closely in malignant lesions. Whereas (18)F-FDG PET is more sensitive for tumor staging, (18)F-galacto-RGD PET warrants further evaluation for planning and response evaluation of targeted molecular therapies with antiangiogenic or alpha(v)beta(3)-targeted drugs.