Preliminary results of preoperative FOLFOX chemotherapy for locally advanced colon cancer patients with therapeutic drug monitoring of 5-FU

579 Background: Preoperative chemotherapy is an alternative approach undergoing active clinical research in patients (pts) with locally advanced colon cancer (LACC). The aim of this study was to assess the feasibility and preliminary evidence of activity of a direct monitoring of 5-FU levels based on pharmacokinetically (PK) guided dose adjustments. Methods: LACC pts (T4 or T3 with extramural depth >5mm) diagnosed after a colonoscopy and spiral CT were scheduled to receive 4 cycles of Oxalipatin (85mg/m²), Leucovorin (400 mg/m²), bolus 5-FU (400 mg/m2) and infusional 5-FU (initial dose of 2400mg/m² in 46h and then tailored according to PK monitoring to reach an area under the curve (AUC) between 25-30 mg·h·L-1). Surgery was planned 4 to 6 weeks after the completion of chemotherapy treatment. All pts were staged at baseline and before surgery. Pathological tumor regression was graded according to the MSKCC classification. Toxicity was reported according to the NCI-CTCAE 4.0. Results: From March 2011 to April 2013, 16 pts (M/F: 10/6; median age 56) with LACC were evaluated. Median dose of 5-FU was 4750 mg. 70.6% pts required a 5-FU dose increase to reach the target AUC. Median 5-Fu plasma clearance was 199,58 L/h. Side effect profile included G3 neutropenia (6 pts), G2 diarrhea (5 pts), G2 nausea (3 pts) and G2 asthenia (4 pts). Neoadjuvant treatment was discontinued in 2 pts due to small bowell obstruction requiring surgery. No progressive disease was observed during preoperative chemotherapy. A radiological dowstaging was achieved in 9 pts (56.25%). All pts underwent surgery (laparoscopy-assisted 50%) with an R0 resection rate of 93.75%. There were no treatment-related deaths. Pathological responses (MSKCC score) included grades 4, 3+ and 3 in 12.5%, 12.5% and 25% of pts, respectively. Median number of harvested nodes was 23.5 (7-51) with a ypN0 rate of 75%. Median time to hospital discharge was 7 days. After a median follow-up of 7 months (3-27), the 2-year actuarial median PFS and OS were 67.5% and 100%. Conclusions: Preoperative PK-adjusted FOLFOX in LACC pts achieves major pathological responses in almost 50% the pts and a remarkable R0 resection rate. Further research seems warranted.