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This thesis investigates less invasive treatments for large colon polyps and early-stage colon cancer. The focus on a new technique: the colonoscopy-assisted laparoscopic wedge resection (CAL-WR). This technique combines endoscopy (examination of the colon with a camera) and laparoscopy (minimal invasive surgery) to remove polyps and early-stage tumors.

In the past, patients often underwent major surgery in which a large part of the colon and the surrounding lymph nodes were removed. Research has shown, however, that for many patients the risk of lymph node metastasis is so low that removing only the tumor is oncologically safe. Not all polyps or tumors can be removed endoscopically, meaning major surgery is still necessary in some cases. These procedures often carry significant complications and, in some cases, can even be life-threatening. CAL-WR offers a less invasive alternative, with fewer complications and a shorter hospital stay. It serves as a bridge between endoscopic techniques and major surgery, allowing more patients to be treated with an organ preserving strategy.

The first part of this thesis examines the effects of CAL-WR on quality of life and costs. It shows that patients do not experience any disadvantages, while the treatment is safer and less expensive than major surgery. The second part evaluates whether CAL-WR is safe and effective for early-stage colorectal tumors (T1 carcinomas). Additionally, a protocol is presented for the nationwide LIMERIC-II study, which will further investigate long-term outcomes. The final part compares surgical outcomes of T1 and T2 tumors (tumors that grow slightly deeper into the bowel wall of the colon). A model was also developed to predict the risk of lymph node metastases in T2 tumors, helping determine which patients might be adequately treated by removing only the tumor instead of undergoing major surgery. Finally, the evidence for adjuvant chemotherapy in patients with T1- or T2 colorectal cancer and lymph node metastases is examined.