If I have a good doctor that I trust and I have a large mass in my colon that is cancerous, I want that thing out now.
The surgery is also important for a number of reasons. They can look for signs of spread (metastasis) in the surrounding tissue/omentum. They can grab some lymph nodes and then a pathologist can look at the lymph nodes and at the colon mass. He can determine if the cancer has spread regionally and also if it invaded all the way through the colon wall and how aggressive it is.
This isn't something to go shopping around for. General surgeons see this stuff all the time and it needs to come out. They will start the other treatment (chemo/radiation) as soon as they have tissue to help them with staging/grading.