Kinichi Hotta, MD
Outcome measurements of endoscopic resection (ER) of colorectal neoplasms are divided into 3 phases: short-term, mid-term, and long-term. Short-term outcomes include R0 resection, en bloc resection, procedure time, and complications. En bloc with R0 resection is an especially reliable endpoint to estimate future local recurrences. R0 resection can be achieved in piecemeal fashion, but this significantly hinders the ability to accurately estimate the risk for local recurrence. Recently, residual tumors taken by biopsies of surrounding mucosa immediate after ER especially in cold polypectomy was used for a new outcome measurement. On the other hand, curative resection rate with negligible risk of metastasis and recurrences is also used as an important measurement of treatment outcome of T1 colorectal cancers (CRCs).
Mid-term outcome measures include local recurrence after ER. Local recurrence can be evaluated with follow-up colonoscopy up to 2 years after ER and is the primary endpoint of treatment in lesions with no risk of lymph node or distant metastasis. Local recurrence rate after ER is often evaluated when assessing mid-term treatment outcomes.
Recurrence and prognosis of T1 CRC are the most important long-term outcomes. Survival rate, mortality due to CRC, and treatment of recurrent disease are important long-term endpoints. In addition, the occurrence of metachronous colorectal neoplasms, ie, advanced neoplasm or invasive cancers, are also important measures that are followed during surveillance following ER.
Polypectomy has been widely applied for diminutive and small colorectal polyps. Since the introduction of this technique, hot-snare polypectomy (HSP) has become a time-proven established approach of ER. However, with advances in endoscopic techniques and devices, new polypectomy techniques other than HSP have been introduced over the years.
Cold-forceps polypectomy (CFP) is simple, easy, and a safe technique for the removal of diminutive polyps. However, CFP using standard forceps may not be adequate as previous studies have shown incomplete resection rates with this approach.1 Indeed, newly developed large-capacity forceps demonstrated better complete resection rates than standard capacity forceps based on a randomized, controlled trial.2 Draganov et al2 reported that complete visual eradication of the polyp ≤ 6 mm with one forceps bite was achieved in 78.8% of the jumbo forceps group and 50.7% of the standard forceps group.
The current European Society of Gastrointestinal Endoscopy Guidelines recommend cold-snare polypectomy (CSP) as an easy and safe method for the removal of diminutive and small polyps.3 There were no reports of perforation and postpolypectomy localized peritonitis with this approach. Moreover, when compared to standard HSP, removal of diminutive and small colon polyps via CSP appears to be associated with a lower rate of bleeding.4 Furthermore, based on data from randomized, controlled trials, ER with CSP yields a higher complete resection rate when compared to CFP5,6 and a similar histopathological residual rate when compared to HSP.7 Kawamura and colleagues7 reported that for a total of 796 polyps (4 to 9 mm) that were randomized, the complete resection rate for CSP was 98.2% compared with 97.4% for HSP.
Endoscopic mucosal resection (EMR) is a technique that involves injection of a lifting solution at the base of the lesion followed by snare resection. EMR has been commonly used for the removal of small and large sessile and depressed polyps.3 The deeper resection margins achieved with this approach vs conventional polypectomy also allow for the evaluation of possible submucosal invasion (SMI) if present in the resected specimen. For large lesions measuring more than 20 mm, piecemeal EMR is generally required.8 The drawback of this approach is the inability to accurately assess the lateral and deep resection margins. As such, this approach can be associated with the potential of overlooking the possibility of microscopic SMI given the fragmented nature of the resected specimens.
Several other variants of the standard EMR technique have been introduced for the ER of colorectal lesions. Underwater EMR9 is a simple technique for the resection of large sessile polyps, with some studies suggesting a higher complete resection rate when compared with standard EMR, although randomized, controlled trials are lacking.10 The endoscopic submucosal resection with ligation method has also been reported for the management of small neuroendocrine tumors in the rectum and has demonstrated sufficient pathological complete resection rate, particularly of the deep margins.11,12 Furthermore, additional modified EMR methods have also been developed with the aim of increasing the en bloc and R0 resection rates. Precutting EMR is a technique of circumferential or semicircumferential mucosal incision prior to snaring.13 Precutting EMR has been shown to have better en bloc resection and R0 resection rates when compared to historical controls of standard EMR. Tip-in EMR is a simple modified method in which the tip of the snare is anchored to one margin of the lesion by making a small incision with electrocautery prior to snaring.14 This method reduces the risk of slippage of the snare, particularly when working with flat lesions, and has been shown to be effective for the en bloc resection of lesions as large as 30 mm. However, current data are still limited with no large case series or controlled trials available.
Endoscopic submucosal dissection (ESD) was developed for the en bloc and R0 resection large of large colorectal neoplasms.15,16 When compared to EMR, pathological assessment of ESD specimens is more accurate, and hence ESD is the preferred ER method for low-risk T1 CRC.17,18 A Japanese multicenter, nonrandomized prospective study of 1845 colorectal lesions (≥ 20 mm) confirmed a significantly higher en bloc resection rate with ESD (94.5%) when compared to EMR (56.9%) (P < .01).19 These findings have been corroborated in subsequent studies. A recent meta-analysis revealed that the en bloc resection rate was 89.9% for ESD vs 34.9% for EMR patients (RR 1.93, P < .001) and the R0 resection rate was 79.6% for ESD vs 36.2% for EMR patients (RR 2.01, P < .001) based on 4678 patients in 11 studies.20 Moreover, ESD is also an effective technique for the resection of lesions (ie, those extending over several folds, nonlifting) that are difficult with conventional EMR.21 Additional studies have also shown that ESD may be favorable when attempting ER of colorectal lesions in particularly difficult locations, such as at the anorectal junction,22 ileocecal valve,23 and appendiceal orifice.24
Local recurrence is an important issue of ER of colorectal tumors (Figure 29-1). Local recurrence rates8,25–30 after piecemeal EMR have been estimated to between 10% and 23% (Table 29-1). Based on our retrospective study of 572 colorectal neoplasms (≥ 10 mm), local recurrence is significantly higher with piecemeal resection (23.5%) vs an en bloc approach (0.7%) (P < .001).28 To reduce the risk of local recurrence after piecemeal EMR, careful observation of the resection margins and base of the EMR site with image-enhanced endoscopy may be important. Tanaka et al demonstrated that magnified observation using image-enhanced endoscopy after piecemeal EMR is useful to reduce local recurrences.31 The use of argon plasma coagulation (APC) following EMR has been mainly studied in Western countries with some conflicting data. A nonrandomized, controlled trial suggested that APC decreases local recurrence after piecemeal EMR for large sessile colorectal neoplasms,32 whereas a separate prospective, uncontrolled study did not show differences in recurrence rate with or without APC after piecemeal EMR.33
As previously discussed, the rate of en bloc and R0 resection is significantly higher with ESD compared to EMR in the treatment of large colorectal lesions,20 thereby resulting in a lower risk for local recurrence. Based on a large-scale, multicenter cohort study conducted in Japan, local recurrence of ESD and EMR were 1.4% and 6.8% (P < .01), respectively.30 On multivariate logistic regression analysis, piecemeal resection was identified as the most significant risk factor for local recurrence. On the other hand, a large-scale, multicenter cohort study conducted in Australia demonstrated an excellent endoscopic management rate for large colorectal neoplasms.8 However, their strategy required intensive surveillance at 4 and 16 months, and the need for repeat endoscopic therapy for local recurrence was 16% at the time of first surveillance and 2% during second surveillance. Only 1% after widefield EMR required surgical treatment.