Preliminary results of a phase I study of external beam radiation therapy (EBRT), oxaliplatin (OX), bevacizumab (BV), and capecitabine (CAP) for locally advanced or metastatic adenocarcinoma of the rectum

3543 Background: BV, a monoclonal antibody against vascular endothelial growth factor, increases survival when added to first and second line chemotherapy for metastatic colorectal cancer. Preclinical studies suggest BV may enhance tumoral radiation sensitivity. Preliminary studies of OX and 5-FU based chemoradiation therapy for rectal cancer have suggested improved pathologic CR rates compared to 5-FU/ radiation alone. CAP allows fluoropyrimidine treatment without the inconvenience of an infusion pump. We investigated CAP + BV + OX + EBRT for pts with rectal cancer to evaluate for the MTD and preliminary efficacy results. Methods: Pts with adenocarcinoma of the rectum and no prior pelvic irradiation received 5040 cGy EBRT (180 cGy/fx), CAP (625–825 mg/m2 PO BID on EBRT days), BEV (15 mg/kg d1 and 10 mg/kg d8 and d22), and OX (50–75 mg/m2/week during radiation, weeks 1–5) in dose-escalating fashion. DLT was defined as any grade 3 heme tox ≥ 7d, grade 4 heme tox, grade 4 non-heme tox during chemoradiation, or inability to deliver >85% of planned treatment. Pts eligible for surgical resection could have surgery 6–8 wks after treatment completion. After recovery from surgery, patients could be treated with CAP, BV, and OX. Results: 11 patients (5 men/6 women) have been enrolled. All have completed chemoradiation and resection. At dose level 1 (CAP 625 mg/m2 BID, OX 50mg/m2) there were no DLT’s in 3 pts. 1/3 pts had G3 subarachnoid hemorrhage during adjuvant chemotherapy. At dose level 2 (CAP 825 mg/m2, OX 50 mg/m2) 2/2 pts had DLT (1 G4 diarrhea; 1 G2 rectal pain, causing treatment hold for study-defined DLT). 6 more pts were treated at dose level 1. 1pt had DLT of G3 diarrhea. G2 toxicities included diarrhea (3/11), fatigue (2/11), skin changes (2/11), and pain (2/11). 9/11 patients were downstaged. 2/11 patients had pCR at surgery and 2/11 microscopic disease only. Conclusions: CAP + BEV + OX + EBRT is a well-tolerated, active regimen for the treatment of rectal cancer. MTD was determined to be CAP 625 mg/m2 BID + BEV 15 mg/kg d1 + 10 mg/kg d 8 and 22 + OX 50 mg/m2/week. Further study of efficacy at the MTD is warranted. [Table: see text]