Sept. 23, 2025
Removing colorectal cancer (CRC) can be challenging due to tumor location, size and stage. However, Mayo Clinic Surgery finds that more than 50% of colorectal tumors deemed unresectable are operable.
"A lot of our practice is referral based, and many patients come to us for a second opinion after being told their cancer is inoperable or that the tumor cannot be removed," says Amit Merchea, M.D., a colon and rectal surgical oncologist at Mayo Clinic in Jacksonville, Florida. "We take pride in our ability to resect many of these tumors because we know that resection leads to a far improved survival and a much better treatment course for these patients."
Challenges associated with removing primary, nonmetastatic colon and rectal tumors
Rectal cancer surgery can require advanced surgical expertise and techniques. Tumor size and location are important factors. Understandably, patients prefer to avoid an ostomy. Many times, Mayo Clinic surgeons can perform an anastomosis after tumor removal. Anastomosis is a procedure that many general surgeons may not be comfortable performing.
"Surgical resection of rectal tumors calls for a particular skill set to be able to operate within the confines of the pelvis," says Dr. Merchea. "Even when the operation itself is relatively simple, reconnecting the GI tract requires a high level of technical ability and specialization. Furthermore, cancer outcomes are highly dependent upon the surgical technique."
Cancer involving the colon is less likely to be considered unresectable. But if the cancer is inoperable, it's likely because the tumor is complex, metastatic or locally advanced, growing into the abdominal wall or involving the major blood vessels of the abdomen. However, in people with metastatic colon cancer, resection of the primary tumor and all known metastatic disease offers the best long-term survival, according to a study published in the Journal of Surgical Research. In these situations, chemotherapy is frequently administered before surgery, after surgery or both.
"A lot of our practice is referral based, and many patients come to us for a second opinion after being told their cancer is inoperable or that the tumor cannot be removed."
To remove large colon or rectal tumors growing into other structures, surgeons must collaborate with specialists outside the colorectal field. "When tumors get to be that size, we call on other surgical specialists and have them readily available to help remove the cancer in a single, multidisciplinary operation," says Dr. Merchea. Their surgical expertise helps ensure that the resection does not compromise nearby structures.
Minimally invasive approaches such as robotic surgery allow for quicker recovery and fewer complications. Robotics also provides the visualization and instruments needed to access areas of the body that would be more difficult to reach with open surgery. Using intraoperative radiation therapy in combination with robotics or other surgical modalities is valuable when there is concern that the margin of resection may be positive.
"Robotic surgery doesn't necessarily make a tumor resectable, but it certainly makes tumors easier to remove," says Dr. Merchea. "Better visualization and jointed, wristed instruments allow us to get into confined places, such as the small bony area of the pelvis, with a lower likelihood of needing a conversion or a large vertical incision. That shortens a patient's length of stay and allows the patient to get to other treatment therapies faster."
Resecting metastatic rectal tumors
Patients with CRC don't always realize that even though they have metastatic disease, the cancer may still be resectable and potentially curable, explains Dr. Merchea. A study published in Cancers reports that metastatic disease to the liver is identified in 20% of patients with CRC at diagnosis. Early-stage CRC is treated with resection. However, in the 40% of patients who present with metastatic disease, first line treatment often includes other options beyond surgery.
"We take out the primary cancer before the metastatic disease only if it is symptomatic or if a liver transplant is under consideration," says Dr. Merchea.
If local organs require resection and transplant is not indicated, Mayo Clinic surgeons collaborate to address all areas of the disease in a single operation under one anesthetic. The combined operation typically occurs after a few months of initial chemotherapy. Treating both sites surgically in the same operation involves only one recovery and less time under anesthesia compared with two separate surgeries.
For larger volume metastatic disease, liver transplantation is gaining momentum as a more viable treatment option. "We work closely with our liver transplant colleagues," says Dr. Merchea. "We resect the primary tumor and wait 3 to 6 months to see if the patient demonstrates new disease outside the liver. If not, we perform a liver transplant. This approach can give the patient a 50% to 70% five-year survival rate, which is better than surgical resection for liver metastatic disease. The ability to increase the survival rate like that is exciting."
For more information
Xu Z, et al. Treatments for stage IV colon cancer and overall survival. Journal of Surgical Research. 2019;242:47.
Torres-Jimenez J, et al. Local treatments in the unresectable patient with colorectal cancer metastasis: A review from the point of view of the medical oncologist. Cancers. 2021;13:5938.
Refer a patient to Mayo Clinic.