e14036 Background: Metastatic or recurrent colorectal cancers generally become unresectable and will not respond to radio- or chemo-therapy. Studies showed that p53 has a synergic effect with radio- or chemotherapy. This study is to determine the efficacy and safety of recombinant adenoviral human p53 gene (rAd-p53) combined with standard FOLFOX4 regimen in treatment of advanced colorectal cancer. Methods: From July 2008 to Dec. 2011, 56 patients with an advanced colorectal cancer or local recurrent disease were treated with rAd-p53 and standard FOLFOX4 regimen. For local tumor, 1-4×1012 viral particles (VP) of rAd-p53 diluted into 5 ml of saline solution was injected into tumor at multiple directions, once a week for 6 weeks. If tumor spreading into abdominal cavity, 4×1012 VPs diluted in 500 ml of saline solution were injected inraperitoneally, twice in 2 weeks. If having lung or liver metastasis, 2×1012 VPs diluted into 100 ml of saline solution were given intravenously twice in 2 weeks. Three days after the first gene therapy, the standard FOLFOX4 regimen was given for six cycles. Results: The follow-up time was 3~38 months with a median of 19.5 months. Among these patients, 8 (14.3%) patients were assessed as complete response, 31 (55.4%) as partial response and 11 (19.6%) as stable disease. After the combined treatment, a radical resection was successfully performed in 18 cases with local recurrent disease. All these patients were still alive at the last follow-up. Common adverse events were 38.4~40.5 oC self-limited fever, occurring in 86% patients. No serious adverse events were observed. Conclusions: rAd-p53 combined with FOLFOX4 is a safe and effective treatment for advanced colorectal cancer or local recurrent disease.