[R1 resection in the region of the lower gastrointestinal tract: relevance and therapeutic consequences].

Incomplete resection (R1) and local recurrence of colorectal cancer continue to be a significant surgical problem. Radical resection of bowel and lymph node bassin are clearly necessary after incomplete endoscopic resection or local surgical excision. However, the situation is more difficult after previous conventional surgery. Anastomotic recurrence following resection and lymph nodal recurrence can often precede curative reresection. Locoregional lymph node metastases due to incomplete surgical clearance of the lymphatic drainage of colonic cancer may also be cured by radical reresection. Despite application of neoadjuvant therapy, integration of modern surgical concepts such as the circumferential resection margin and advances in surgical technique, R1 resection of rectal cancer remains a major problem. Although primary surgical therapy may be considered in selected cases, this situation will require multimodal therapy in most instances.