Purpose: To explore the relationship between metabolic uptake of the 18F-ALF-NOTA-PRGD2 (18F-RGD) tracer on positron emission tomography/computerized tomography (PET/CT) and the antiangiogenic effect of apatinib in patients with solid malignancies.
Materials and patients: Patients with measurable lesions scheduled for second- or third-line single-agent therapy with apatinib were eligible for this prospective clinical trial. All patients underwent 18F-RGD PET/CT examination before the start of treatment. Standardized uptake values (SUVs) of contoured tumor lesions were computed and compared using independent sample t-tests or the Mann-Whitney U test. Receiver-operating characteristic (ROC) curve analysis was used to determine accuracy in predicting response. Survival curves were compared using the Kaplan-Meier method.
Results: Of 38 patients who consented to study participation, 25 patients with 42 measurable lesions met the criteria for inclusion in this response assessment analysis. The median follow-up time was 3 months (range, 1-10 months), and the median progression-free survival (PFS) was 3 months (95% confidence interval, 1.04-4.96). The SUVpeak and SUVmean were significantly higher in responding tumors than in non-responding tumors (4.98 ± 2.34 vs 3.59 ± 1.44, p = 0.048; 3.71 ± 1.15 vs 2.95 ± 0.49, P = 0.036). SUVmax did not differ between responding tumors and non-responding tumors (6.58 ± 3.33 vs 4.74 ± 1.83, P = 0.078). An exploratory ROC curve analysis indicated that SUVmean [area under the ROC curve (AUC) = 0.700] was a better parameter than SUVpeak (AUC = 0.689) for predicting response. Using a threshold value of 3.82, high SUVmean at baseline was associated with improved PFS (5.0 vs. 3.4 months, log-rank P = 0.036).
Conclusion: 18F-RGD uptake on PET/CT imaging pretreatment may predict the response to antiangiogenic therapy, with higher 18F-RGD uptake in tumors predicting a better response to apatinib therapy.
Keywords: 18F-RGD PET/CT; Antiangiogenic therapy; Integrin αvβ3; Malignancies.