18F-FDG PET/CT evaluation of tumor response to the implantation of RENCA macrobeads (RMB) in phase I and II clinical trials [INDBB 10091] in advanced, treatment-resistant metastatic colorectal cancer (mCRC).

Abstract

e15046 Background: RMB, a cytostatic, biological system form of anti cancer therapy have been used in Ph I & II clinical trials in mCRC w/ evidence of improved survival benefit & QOL. Evaluation of metastatic tumor response by standard CT RECIST criteria however has been unsatisfactory. We hypothesized that using 18F FDG PET/CT scan to evaluate tumor anatomy & metabolism could provide a more accurate picture of tumor response to RMB Methods: 48 mCRC pts (14, Ph 1; 34, Ph 2a) who failed available treatments were implanted intraperitoneally w/ RMB (8mb/kg). Physicals, biomarkers & lab evaluation were obtained at baseline & days 14-90, with PET CT imaging at baseline & day 90. PET scan was acquired 1 hour after FDG injection of 9.4 mCi. CT was used for attenuation correction. Correlation between 18F FDG PET SUVmax findings & CEA & or CA19-9 responses was assessed. Positive response was defined as ≥20% decrease post implant in CEA, CA19-9 & SUV. Only tumors w/ SUVmax ≥ 2.5 were evaluated. SUV measurements were made by 1 radiologist experienced in PET-CT scanning & SUV determination Results: 123 FDG positive mCRC lesions (39, Ph 1; 84 Ph 2a) were detected in 37 evaluable pts (14 m, 23 f; mean age 58.2; SUVmax 2.5-17.5). Of the 37 pts, 28 (76%) showed stabilization & or decreased FDG uptake (4 w/ frank necrosis) as well as stable/decreased CT tumor measurements. Pts w/ pulmonary lesions showed greater responses than those w/ hepatic lesions. 9 (24%) of 37 pts showed increased SUVs. 23 pts (62%) showed decrease in CEA & or CA 19-9 ≥ 20%. 17 pts (74%; 13 decrease, 4 central & peripheral necrosis) had correlation between decreased SUVs/necrosis & biomarkers decrease Conclusions: We conclude SUVs are useful in monitoring mCRC lesions response to RMB therapy. Changes in SUVs correlate w/ CEA & CA 19-9 changes. Taken together the combined data indicate anti tumor effect in these Ph 1/2a trials & offer preliminary support for our hypothesis that 18FDG can be useful in evaluating cell system therapies. Issues of SUVmax standardization & effects of intra tumor heterogeneity however must be considered. Further studies are merited & ongoing, including a planned Ph 3 trial Clinical trial information: NCT01053013; NCT00283075.