Purpose: We report the effect of antiangiogenic therapy on the biodistribution of (18)F-FPPRGD2 (a surrogate biomarker of integrin αvβ3 expression), and the potential of (18)F-FPPRGD2 to predict the prognosis in patients with cervical cancer and ovarian cancer in this clinical scenario.
Methods: Data from six women, age range 30 - 59 years (mean ± SD 44.0 ± 12.5 years), who had undergone a (18)F-FPPRGD2 PET/CT scan and bevacizumab-containing therapy were prospectively collected and analyzed. We compared baseline (18)F-FPPRGD2 and (18)F-FDG uptake in the lesions and tumor-to-background (T/B) ratios. The maximum and mean (18)F-FPPRGD2 standardized uptake values (SUVmax and SUVmean) were recorded for 13 normal organs, as well as in all the identified malignant lesions on the pretreatment scan and the 1-week post-treatment scan. We also measured changes in (18)F-FPPRGD2 uptake from before to 1 week after treatment, and compared them to the changes in (18)F-FDG uptake from before to 6 weeks after treatment. Treatment outcomes were correlated with these changes.
Results: The uptake in lesions and T/B ratio of (18)F-FPPRGD2 were lower than those of (18)F-FDG (SUVmax 3.7 ± 1.3 vs. 6.0 ± 1.8, P < 0.001; SUVmean 2.6 ± 0.7 vs. 4.2 ± 1.3, P < 0.001; T/B ratio based on SUVmax 2.4 ± 1.0 vs. 2.6 ± 1.0, P < 0.04; T/B ratio based on SUVmean 1.9 ± 0.6 vs. 2.4 ± 1.0, P < 0.003). One patient did not return for the follow-up scan and in another patient no lesions were identified on the pretreatment scan. (18)F-FPPRGD2 uptake in lesions in the remaining four patients had significantly changed 1 week after treatment (SUVmean 3.3 ± 1.0 vs. 2.7 ± 1.0, P < 0.001), while uptake in all normal tissues analyzed was not affected by treatment. One patient with clinical disease progression had a decrease in lesional (18)F-FPPRGD2 SUVmean of 1.6 % and in (18)F-FDG SUVmean of 9.4 %. Two patients with a clinical complete response to treatment had decreases in lesional (18)F-FPPRGD2 SUVmean of 25.2 % and 25.0 % and in (18)F-FDG SUVmean of 6.1 % and 71.8 %. One patient with a clinical partial response had a decrease in lesional (18)F-FPPRGD2 SUVmean of 7.9 % and in (18)F-FDG SUVmean of 76.4 %.
Conclusion: This pilot study showed that (18)F-FPPRGD2 and (18)F-FDG provide independent information about the biology of ovarian and cervical cancers. Bevacizumab-containing therapy does not affect (18)F-FPPRGD2 uptake in normal organs, but does result in statistically significant changes in lesions. In addition, (18)F-FPPRGD2 may have potential for early prediction of response to such treatments. These preliminary findings have to be confirmed in larger studies.
Keywords: 18F-FPPRGD2 PET/CT; Bevacizumab; Cervical cancer; Ovarian cancer.