Carbon Ion Radiotherapy for Patients with Locally Recurrent Rectal Cancer

The large intestine starts at the ascending colon, which is connected to the small bowel, and ends at the rectum, which extends from the sacral promontory to the anal canal. In 2008, approximately 43,000 patients died of colorectal cancer in Japan which is the third most common cause of cancer deaths, after lung and stomach cancers. Approximately 100,000 patients were diagnosed with colorectal cancer in 2004, thus making it the second most common type of cancer after stomach cancer. The analysis of the post-operative recurrence rates of colorectal cancer indicates a higher rate for rectal cancer than colon cancer. When compared by the site of recurrence, rectal cancer had a more than three times higher local recurrence rate than colon cancer. With the recent advances in surgical techniques and procedures, the pelvic recurrence rate of rectal cancer has been decreasing, however the post-operative recurrence rate is still 5% to 20% today. Surgical resection is the first choice for locally recurrent rectal cancer, although total pelvic extenteration or another highly invasive procedure is often required. In many cases, locally recurrent rectal cancers are not completely resectable so generally surgical resections are not selected. The comparison of resection rates by the type of tumors shows that the resection rates were in the range of 40% to 50% for liver metastases and 20% to 40% for lung metastases, whereas the rate was 10% to 40% for locally recurrent colorectal cancers (Table 1)1,2) Curative resection of thesetumors will lead to a survival rate similar to those for other types of recurrences and metastases. Radiation therapy is often indicated for unresectable cases of locally recurrent rectal cancer; most of the past studies on conventional x-ray radiotherapy reported a 12-month median survival and a 10% 3-year overall survival. The use of adjuvant chemotherapy elevated the local control rate up to around 20%, which is far from satisfactory. Heavy charged particle beams have been shown to exert potent anti-tumor effects against radioresistant adenocarcinomas. To improve both the long-term local control and survival of locally recurrentrectal cancer, we have initiated a radiation dose-escalation trial using heavy charged particles.