Is positron emission tomography (PET) with FDG an early predictor of the RECIST morphological response to chemotherapy in metastatic colorectal cancer patients (mCRC)-

Developmental Therapeutics: Cytotoxic Chemotherapy
Session Type and Session Title: 
Poster Discussion Session, Developmental Therapeutics: Cytotoxic Chemotherapy
Abstract Number: 


J Clin Oncol 27:15s, 2009 (suppl; abstr 2533)
A. Hendlisz, P. Emonts, A. Covas, L. Ameye, M. Paesmans, R. Castany Prado Maria del Rosario, G. Machiels, M. Van den Eynde, B. Vanderlinden, P. Flamen; Institut Jules Bordet, Brussels, Belgium; Institut Jules Bordet Université Libre de Bruxelles, Brussels, Belgium

Abstract Disclosures


Background: Reliable early assessment of response would help identify active treatments and avoid unnecessary side effects. Our hypothesis was that FDG-PET metabolic changes 2 weeks after the first dose of chemotherapy predict standard morphological response. Methods: 45 mCRC patients undergoing 1st or 2nd-line chemotherapy are planned to be included in a prospective trial comparing early metabolic changes, as measured by serial FDG-PET, with the standard RECIST- based response assessment using multi-slice CT. A signed informed consent was obtained in all cases. For the lesion-by-lesion analysis, according to the EORTC recommendations, a metabolic response was defined as a ≥ 15% decrease of the standardized FDG uptake (SUVmax) on day 14. A patient was classified as having overall metabolic responsive disease if the majority or all lesions observed on the baseline PET showed a metabolic response, without any progressive lesion ( ≥25% increase). Results: At interim analysis, 28 patients (median age 65.9 yrs) were available for comparative metabolic and morphological analysis of 88 lesions. Mean number of lesions per patient was 3 (range 1-8). Patients received FOLFOX (18), FOLFIRI (9), and capecitabine (1) as first- (19) or second-line (9) treatments. Metabolic assessment showed 49 (56%) responding and 39 (44%) nonresponding lesions. The morphological response rate in metabolically non-responding lesions (5/39; 13%) was lower than in responding lesions (22/49; 45%) (p = 0.001; Fisher's exact test). A mixed metabolic response, combining responding and non-responding lesions within the same patient, was seen in 21/28 (75%) pts. A RECIST response was observed in 6/14 (43%) PET responding and in 0/14 (0%) PET nonresponding patients (p = 0.02; Fisher's Exact test). Updated results of this ongoing trial will be presented. Conclusions: Serial FDG PET seems able to identify non-responding mCRC disease after one course of chemotherapy.