Post-treatment surveillance for rectal cancer patients is designed to detect treatable local recurrence and distant metastases in asymptomatic patients. As such, surveillance is appropriate for patients who are candidates for surgery and/or other treatment options such as chemotherapy. Surveillance is typically recommended for 5 years after treatment.[1],[2],[3] About 80% of recurrences are detected within 3 years, and 95% within 5 years of curative-intent rectal resection. Salvage resection of recurrent disease is possible in greater than 1/3 of patients following rectal cancer resection of the primary tumor with median survival of 3-5 years.[2],[3],[4],[5]

National Comprehensive Cancer Network (NCCN) and the American Society of Colon and Rectal Surgeons practice guidelines provide guidance for performing surveillance. Surveillance after curative-intent rectal cancer resection typically includes history with assessment of symptoms, physical examination including digital rectal exam, carcinoembryonic antigen (CEA) testing, and computed tomography (CT) imaging that may allow detection of recurrence amenable to intervention (Table 1).[1],[2],[3]

Table 1. Rectal Cancer Surveillance

As part of the history and physical exam, digital rectal exam with an experienced finger has an important role in rectal cancer surveillance because locoregional recurrence is of greater clinical import for rectal cancer than for colon cancer due to anatomic and biologic differences. Digital rectal exam allows palpation of a low anastomosis, the sphincter complex and pelvic floor muscles, presacral space, and pelvic side walls, and can be done at the same time as rigid or flexible proctoscopy. There is limited evidence to support surveillance proctoscopy, but some practices incorporate frequent proctoscopic exams into the surveillance schedule following low anterior resection or transanal excision due to the increased risk for luminal recurrence, especially in cases with close or incomplete margins, or other unfavorable pathologic features.[1],[2],[3],[4],[5],[6],[7]

CEA tests and CT scans are typically done for detection of systemic recurrence. Studies that show advantages for colorectal cancer surveillance include CEA in the regimen, though the test has only 65% positive predictive value and 15% of CEAs are falsely elevated in patients without recurrence.[2] Surveillance regimens that show modest survival benefit include both CEA testing and CT imaging.[4] CT may detect early liver and lung metastases that may be resectable for cure. Liver MRI and PET-CT imaging are not recommended for routine surveillance but may have some value in patients with equivocal CT findings or elevated CEAs without demonstrable CT abnormalities. The value of circulating tumor DNA levels (ctDNA) as markers for detecting response to neoadjuvant and operative therapy, and for surveillance after treatment in operative and non-operative pathways is currently under investigation.[8]

Colonoscopy is done prior to rectal resection to search for synchronous neoplasms. Colonoscopy should be done 3-6 months after rectal resection for those unable to have complete preoperative colonoscopy due to rectal luminal narrowing. Most recommend repeat colonoscopy 1 year after resection because most metachronous cancers are found within 2 years, and then every 1-5 years depending on surveillance colonoscopy findings.[1],[2],[3]

Most rectal cancer surveillance studies include patients with stage II-III disease and potentially curative stage IV disease. Because stage I disease is associated with 5-year survival > 90%, several guidelines recommend only endoscopic surveillance without imaging after rectal resection. However, stage I rectal cancer patients treated by local excision have higher risk for endoluminal and mesorectal local recurrence than those treated by rectal resection, especially those with positive margins, lymphovascular invasion, poorly differentiated histology, or T2 disease. For these patients, a surveillance schedule similar to stage II/III patients is performed in many centers.[1],[2],[3]

Surveillance strategies are modified for patients with genetic cancer syndromes and those who have organ-preserving non-operative treatment (“watch and wait”). Patients with genetic colorectal cancer syndromes such as Familial Adenomatous Polyposis and Lynch Syndrome require more frequent endoscopic exams and genetic counseling is offered to the patient and high-risk relatives.[1],[2],[3]

Some practices have adopted “watch and wait” non-operative management (NOM) programs for patients with a complete clinical response (cCR) to total neoadjuvant therapy.[1],[2],[3],[4],[5],[6],[7] For NOM patients, surveillance is more intense than for patients undergoing TME surgery, because the risk for recurrence is higher. The goal of surveillance in the NOM setting is the earliest possible detection of recurrence so that salvage surgery can be performed. While pelvic MRI is not currently recommended for routine postoperative surveillance after rectal resection, it is an important component of surveillance for rectal wall tumor regrowth in patients with cCR following TNT. Surveillance in the NOM pathway includes frequent digital rectal exams and proctosigmoidoscopy to assess luminal recurrence and frequent pelvic MRI for rectal wall and mesorectal recurrence (Table 1).[6],[7]

A randomized trial comparing induction (chemotherapy before chemoradiation) TNT with consolidation (chemotherapy after chemoradiation) TNT found that about 50% of patients receiving TNT had a cCR allowing placement in a NOM pathway. Disease-free survival (DFS) at 3 years was not significantly different between groups [induction 76% (95% CI, 69 to 84) vs consolidation 76% (95% CI, 69 to 83)] and both groups were not significantly different when compared to historical controls (DFS 75%) who had standard neoadjuvant chemoradiation, TME, and adjuvant chemotherapy.[6][9] A retrospective case series from the same group showed that 19.5% of 113 patients with cCR had tumor regrowths - 20 were salvaged with TME and 2 by transanal excision of the regrowth.[7] Intensive surveillance is key to early detection and salvage in the NOM setting.

Surveillance after rectal cancer treatment can be costly when considering the marginal survival advantage. Cost will need to be assessed in the future with the development of new screening methods.[2],[3] The cost of frequent nonoperative management testing for patients with a cCR after TNT will need to be compared to the cost of TME and associated complications, as well as the quality of life considerations in patients with low anterior resection syndrome after TME. Rectal cancer surveillance guidelines after rectal resection and for non-operative management may change with evolving evidence-based literature.