18FDG-PET in targeted therapy with cetuximab in gastric or gastroesophageal junction (GEJ) adenocarcinoma: First results of the Italian FOLCETUX Study

Abstract

4061 Background: The aim of the study was to evaluate 18FDG-PET impact in gastric or GEJ cancer patients (pts) treated with cetuximab plus chemotherapy. Methods: Pts with stomach or GEJ unresectable/metastatic adenocarcinoma, not yet treated, EGFR+, were enrolled in the FOLCETUX study. Pts received cetuximab weekly at 400 mg/m2 iv loading dose, and then at 250 mg/m2 iv maintenance dose, weekly at 400 mg/m2 iv loading dose, and then at 250 mg/m2 iv maintenance dose, CPT11 180 mg/m2 iv d1, LFA 100 mg/m2 iv followed by 5FU 400 mg/m2 iv bolus and 600 mg/m2 iv continuous infusion 22h d1–2 (FOLFIRI) every 2 weeks, for a maximum of 24 weeks, then cetuximab alone was allowed in pts with CR/PR/SD. Anti-tumor activity was assessed by CT and PET scan at baseline and then every 6 weeks. A decrease in tumor FDG-uptake (metabolic response) was evaluated according to EORTC recommendations; objective response (OR) was evaluated with CT scan according to the RECIST criteria. Results: From November 2004 to December 2005, 22 pts (16M, 6F) performed at least 2 consecutive PET scans (at baseline and after 6 weeks), with a total of 91 PET scans (median per pts 4; range 2–8). PET was positive in 20 pts (90.9%); no FDG uptake was seen in 2 pts (9.1%) with signet ring cell carcinoma. A metabolic response correctly predicted: CR/PR in 10/12 pts (83%) after 6 weeks of therapy and in 11/12 (91.7%) after 12 weeks; SD in 4/8 pts (50%) after both 6 and 12 weeks. On the whole, response to therapy was predicted by PET after 6 weeks in 14/20 pts (70%). No correlation was demonstrated between median Standardized Uptake Value (SUV) at baseline PET and OR: 10.9 (3–29) in CR/PR pts and 9.6 (6.4–29.8) in SD pts. In the PET scan after 6, 12 and 18 weeks, the median SUV value respectively decreased to 4.4, 2.6 and <2.0 in CR/PR pts and to 7.5, 7.4 and 3.6 in SD pts. The percentage of SUV reduction after 6 weeks was 54.2 in CR/PR pts vs 30.3 in SD pts (p = 0.36); no difference was observed between intestina (55%) and non-intestinal (45%) subtypes. No significant correlation was observed between the Ki-67 and SUV value. Conclusions: These preliminary results suggest that PET can make an early prediction of the response to cetuximab plus FOLFIRI therapy. No significant financial relationships to disclose.