Setting of the candidate exposure conditions in an individualized tumor response testing (ITRT) toward an individual chemotherapy for esophageal cancer

Background  To apply the collagen gel droplet embedded culture-drug sensitivity test (CD-DST) technique to individualized tumor response testing (ITRT) in esophageal cancer, optimal exposure conditions that would permit us to predict the clinical response to the low-dose cisplatin (CDDP)/5-fluorouracil (5-FU) regimen and docetaxel (DOC) regimen were determined. Methods  CD-DST was performed on 35 surgical specimens and 27 endoscopic biopsy samples from patients with esophageal squamous cell cancer. The reported blood AUC values were reproduced, or an in vitro concentration-response curve was constructed, for each regimen to determine exposure conditions using surgical specimens. For endoscopic samples, we estimated the evaluation rate (of CD-DST) and compared in vitro sensitivity with clinical response in measurable lesions to validate the exposure conditions determined. Results  Overall, data were evaluated in 75.8% of the cases (94.3% in surgical specimens and 51.9% in endoscopic biopsy samples). Modeled exposure conditions were 5-FU 2.0 μg/ml/120 h with a cutoff inhibition rate (IR) of 50% for the low-dose CDDP/5-FU regimen and DOC 0.04 μg/ml/120 h with a cutoff IR of 50% for the DOC regimen. Conclusions  Although the study failed to compare in vitro results with clinical outcomes in measurable lesions, and the practical usefulness and applicability of the technique remain to be demonstrated, CD-DST might be a useful tool in selecting optimal chemotherapeutic agents.