Study of Radiation Therapy in Combination With Xeloda, for Initially Metastatic, Low and Middle Rectal Cancer

In initially metastatic rectal carcinoma, a neo-adjuvant multi-drug chemotherapy is usually performed, followed by a pelvic chemoradiation. The surgical indications on both metastases and the pelvic site are then discussed: in the case where a complete (or near-complete) response (CR) of the rectal tumor is observed (10 to 40%), the local surgery may be omitted or poned ("wait-and-see") in a sphincter-sparing strategy, in order to minimize or avoid the surgical morbidity, to focus on metastatic disease by the continuation of chemotherapy, and to preserve a better quality of life. After 8 weeks of induction chemotherapy (mFolfox6 regimen, 4 cycles), the aim of our study is to optimize the chemoradiation step on the distal rectal tumor, thanks to Intensity-Modulated Radiotherapy (IMRT) with simultaneous integrated boost (SIB) (Phase-1 part of the study), concomitantly with oral capecitabine. According to a Fibonacci dose-escalation scheme, 3 radiation dose-levels are defined, up to the definition of the maximal tolerated dose (MTD), requiring the inclusion of a maximum of 20 patients. Further patients will be included at the recommended dose for phase-2 (RDP2) in a two-step phase-2 study, considering simultaneously as principal objective at 12 months, both the efficacy (local CR rate in the range of 10 to 25%) and the tolerance (pelvic radiation disease: grade 3-4 toxicities in the range of 30 to 10%). Overall 65 patients will be included in the phase-2 study at the RDP2 dose.