Endoscopic view of a self-expandable metal stent (SEMS). Source
Colorectal cancer affects the lower portion of the gastrointestinal system, including the large intestines (colon) and rectum. This type of cancer occurs more frequently in Western countries, including the United States and Canada, with approximately 140,000 new cases in the U.S. alone in 2010. Colorectal cancer kills approximately 50,000 Americans each year according to the National Cancer Institute. Treatment depends on the exact location of the tumor, whether metastasis has occurred, and the overall condition of the patient.
Radiation and chemotherapy may be pursued for inoperable tumors - those that cannot be safely removed due to proximity to other structures, extent of spread, and surgical risks outweighing the benefit of tumor removal in the case of advanced cancers. The treatments aim at reducing tumor size and preventing spread. As described by the British Columbia Cancer Agency, type IV colorectal cancer is usually considered incurable, and patients may opt to forego the rigorous treatment due to a lack of expected benefits. In either case, not being able to remove the tumor can allow it to obstruct the gastrointestinal outflow, causing blockage of the colon and/or rectum.
Surgery may be pursued to relieve obstruction via colostomy (creating a new outlet from the intestines above the blockage to a receptacle carried outside the body,) resection (slicing the obstruction open and reforming it.) and/or anastomosis (creating a bypass.) In recent years, stenting has given patients new non-surgical options for the relief of acute colorectal blockage due to inoperable cancer. As reviewed in Current Opinions in Gastroenterology in 2007, stenting can be a first attempt prior to surgery on the obstruction to avoid unnecessary invasive procedures.
Self-expanding metal stents, wire mesh that sits in the lumen of the smooth muscle, inserted into the rectum or colon to create an open duct to allow the passage of fecal matter was first described in 1991. The exact material, length, and method of placement depend on the needs and circumstances of the patient. Surgical departments evaluate the outcomes and performance of specific brands and methods, such as the pilot study conducted by Shim et al in 2003 and a clinical trial at Sloan-Kettering from 2002-2006, on an ongoing basis as new materials become available. In August 2010, recommendations were updated based on recent data. Stenting can allow the avoidance of emergency surgery in 90% of high-risk patients.
Risks and Outcome of Colorectal Stenting
Compared to surgery, stenting has a lesser anesthetization risk because general anesthesia is not used, usually only local. The hospital stay is also shorter, an important aspect for patients with inoperable cancer and a poor prognosis – only six percent of patients with stage IV colorectal cancer survive five years according to the American Cancer Society. Most risks associated with stent placement do not apply to cancer patients with a poor prognosis from the disease, as stent migration and stenosis (closure, tumor overgrowth) take time. More severe obstructions may have complications from stenting due to the introduction of air. Perforation and infection are two potential issues that require additional treatment or intervention.
Most reviews of the relatively recent surgical alternative to colorectal obstruction agree that no conclusive outcomes can be drawn because of the lack of comparable studies. However, being able to relieve bowel obstruction in a timely manner can be expected to increase the quality of life for any patient, especially one with a poor prognosis and short expected remaining life such as one with inoperable colorectal cancer. Morbidity and mortality have not been found to be increased by the procedure, and if anything, it carries fewer risks than surgical intervention, giving colorectal cancer patients a more comfortable first option without compromising future treatment options.