Study of Panitumumab Given First With Capecitabine and Oxaliplatin (CAPOX) and Then With Capecitabine and Radiation of the Pelvis for Treatment of Patients With Rectal Cancers That May or May Not Have Spread Beyond the Rectum

Overview

Panitumumab is a monoclonal antibody. It works by attaching to a protein called epidermal growth factor receptor found on normal and cancer cells. When panitumumab attaches, it blocks another protein called epidermal growth factor (EGF) from attaching to the cell. This is important because, when EGF is blocked, a cell's growth slows down or stops. Panitumumab may also help radiation therapy work. Also because panitumumab is a fully-human antibody, it may be less toxic than other monoclonal antibodies made to block the EGF receptor. Chemotherapy, such as capecitabine and oxaliplatin, works to kill cancer cells directly. Capecitabine given during radiation helps radiation therapy work better. This study is being done to learn how rectal cancer tumors that are not removed surgically respond to treatment with panitumumab and chemotherapy given before radiation therapy begins followed by treatment with panitumumab and capecitabine given with radiation therapy.

Colorectal cancers express EGF and/or EGFR mRNA in 66% of primary tumors, 44% of adjacent mucosa, and up to 62% of positive lymph nodes. Patients enrolled in NSABP FR-1 will begin therapy with the anti-EGFR antibody panitumumab--which has shown single-agent activity in colorectal cancer patients--in combination with CAPOX, an effective treatment for patients with advanced colorectal cancer, with the convenience of using an oral fluoropyrimidine (capecitabine.) The intent with this first phase is to expose distant metastases to the agents early and to shrink the tumor before giving radiation therapy. After chemotherapy, radiotherapy with capecitabine and panitumumab will be given to destroy the primary tumor. Panitumumab is added to the radiochemotherapy regimen because data showed positive results when another anti-EGFR antibody was added to radiotherapy in patients with head and neck cancer. This approach aims to improve neoadjuvant combined modality therapy for rectal cancer; it should provide effective therapy for eligible patients and valuable information about clinical tumor response rates and treatment tolerability, which, if favorable, may be used to develop future Phase III trials.