Sept. 16, 2025
Historically, surgeons and medical oncologists often deemed primary and recurrent colorectal cancers fixed to critical structures as unresectable. This has been particularly true for rectal and anal cancers involving pelvic structures, such as the sacrum, organs and neurovascular structures. Without the possibility of curative resection, treatment is palliative, and survival rates are low.
Over the past few decades, the definition of unresectable has changed, according to Eric J. Dozois, M.D., chair of Colon and Rectal Surgery at Mayo Clinic in Rochester, Minnesota.
"Advances in chemotherapy and radiation therapy have, in part, driven this change," says Dr. Dozois. "We've also developed new surgical techniques that allow us to achieve negative margin resection (R0). It's uncommon for us to consider a tumor unresectable."
For patients with locally advanced colorectal cancer, being evaluated at a specialized, experienced center is essential to determine if they are a candidate for curative resection surgery.
New surgical techniques improve oncological outcomes
The standard of care for locally advanced colorectal cancer includes total neoadjuvant therapy, such as chemotherapy and radiotherapy, followed by curative resection. The effectiveness of this multimodality treatment relies largely on the surgeon's ability to perform the surgery safely and obtain clear margins.
Dr. Dozois and his surgical colleagues have been at the forefront of developing procedures for resecting colorectal tumors involving the:
- Aortoiliac axis: Surgeons remove the tumor and sections of the aorta and iliac blood vessels. They work quickly to reconstruct the blood vessels, typically using deceased donor grafts to reduce the risk of infection. In an early study published in Diseases of the Colon and Rectum in 2013, R0 resection was achieved in seven of 12 patients. Overall and disease-free survival rates of patients four years following this procedure were 55% and 45%, respectively. These outcomes were comparable to those for tumors considered resectable.
- Lower spine and pelvis: This procedure involves various degrees of sacropelvic resection, up to lower lumbar vertebra L4. Hardware and, in some cases, bone grafts, are used to stabilize the spine when necessary. A 2014 publication in Diseases of the Colon and Rectum based on 30 patients reported an R0 rate of 93% and five-year overall and disease-free survival of 46% and 43%, respectively. Long term, 14 patients needed assistance with ambulation, including four patients who underwent lower extremity amputation.
- Pelvic sidewall: Previous attempts at resecting locally advanced colorectal tumors in this area of dense anatomy yielded an R0 resection rate of about 60%. To improve this rate, Mayo physicians developed a two-stage approach, accessing the tumor first from the back, called a posterior approach, to push it forward. This step made anterior resection easier and resulted in an R0 rate of 100%, according to a study of 10 patients published in Diseases of the Colon and Rectum in 2024.
An enhanced approach to multimodality therapy
At Mayo Clinic, intraoperative radiation therapy (IORT) also is part of multimodality treatment. The use of IORT during surgery to reduce recurrence for locally advanced colorectal cancers started in the 1980s.
A 2008 paper published in the Annals of Surgery reported the outcomes of 146 patients with locally unresectable colorectal cancer treated with this comprehensive approach. Surgical margins were negative in 68% of patients, and the five-year overall and disease-free survival rates were 52% and 43%, respectively. At the time, these patients would have had extremely poor prospects with other available treatment options.
Despite the improvements in IORT technology over the years, it is still available only at select centers. "At Mayo Clinic, we have access to the latest linear accelerator technology for IORT," says Dr. Dozois. "We use it during surgery for many locally advanced colorectal cancers."
Surgical collaboration drives care and innovation
When a colorectal tumor involves nearby structures, treatment is complex due to the many possible pathways for care. The presence of distant metastatic disease is also a consideration. Curative-intent surgery for locally advanced colorectal cancer is still possible if the metastatic lesions are resectable.
A multidisciplinary team of medical oncologists, radiation oncologists, surgeons and other specialists works together to plan each patient's treatment. Depending on the structures involved, the surgical team may include multiple areas of expertise, such as:
- Gynecologic surgery.
- Orthopedic surgery.
- Plastic surgery.
- Urologic surgery.
- Vascular surgery.
This collaboration between surgical specialties has been the driving force to overcome contraindications to curative surgery for these extensive tumors.
Counseling patients about the risks and benefits of surgery
Mayo Clinic surgeons are researching how to make these surgeries safer and reduce complications. Currently, however, they are long and intensive operations.
"We can increase survival, but patients need to determine whether the potential side effects are worth it," says Dr. Dozois. "We spend a lot of time talking to patients and sometimes bring in our cancer psychologists to assist with the decision-making process."
Mayo Clinic also offers a wide range of services after surgery to help with recovery, such as survivorship groups, rehabilitation, pain management and amputee care. For patients who travel for care, Dr. Dozois works with referring providers to ensure support is available at home. "Cancer treatment can significantly affect a patient's quality of life, and we are continually striving to improve the patient experience before, during and after surgery," he says.
For more information
Abdelsattar ZM, et al. Surgery for locally advanced recurrent colorectal cancer involving the aortoiliac axis: Can we achieve R0 resection and long-term survival? Diseases of the Colon & Rectum. 2013;56:711.
Colibaseanu DT, et al. Extended sacropelvic resection for locally recurrent rectal cancer: Can it be done safely and with good oncologic outcomes? Diseases of the Colon & Rectum. 2014;57:47.
Sakata S, et al. Improving R0 resection rates with a posterior-first, 2-stage approach for en bloc resection of locally advanced primary and recurrent anorectal cancers involving the deep pelvic sidewall. Diseases of the Colon & Rectum. 2024;67:90.
Mathis KL, et al. Unresectable colorectal cancer can be cured with multimodality therapy. Annals of Surgery. 2008;248:592.
Refer a patient to Mayo Clinic.