Gastrointestinal endoscopy is used in the surveillance of patients after radical treatment of rectal cancer to identify and verify LR in order to increase the ultimate success rate. This method also enables clinicians to identify and remove metachronous tumors and precancerous lesions. Current guidelines recommend this examination as one of the foundations of surveillance. However, much of the evidence that forms the basis of these recommendations originates from outdated literature reported when patients were treated with various treatment regimens.
The vast majority of published studies on postoperative surveillance has included patients with 2 separate entities: colon cancer and rectal cancer [13–15]. Differences between these cancers include anatomical location (rectal cancer: retroperitoneal), diagnostic requirements (magnetic resonance imaging [MRI], transrectal ultrasound), and therapies used (RT), which in turn may affect the diagnostic and therapeutic processes of the LR. Recurrent tumors located up to 8 cm from the sphincters are usually available by digital rectal examination and, above all, they show earlier clinical symptoms (altered bowel habits, hematochezia, abdominal pain).
Currently, less than 10% of patients who undergo radical treatment experience LR [17–19], owing to the use of an appropriate surgical technique (TME), the radical nature of the procedures (R0, circumferential resection margins: negative), and the combined treatments based on the RT schedule delivering a biologically effective dose above 30 Gy [20, 21]. Several studies have shown that about half of LRs are isolated, with no distant metastatic lesions [22, 23].
The risk of LR is associated with the following factors (among others): more advanced disease stage (American Joint Committee on Cancer/TNM), more distal location of the tumor, and perioperative treatment used. Preoperative RT reduces LR by approximately 50%-70% and postoperative RT by approximately 30%-40% in all locations of the rectum [24, 25]. This effect may be enhanced by the use of concurrent computed tomography (CT) [26, 27]. Some studies reported a significant reduction in the risk of LR in anastomosis after anterior rectal resection after the use of preoperative 5 × 5 Gy sRT [25].
In patients with CRC, an estimated risk of the presence of synchronous neoplastic lesions is 2%-4% [28, 29]. Epidemiological data show that after radical treatment, patients with CRC have a 1.5- to 2-fold increased risk of developing metachronous lesions compared with that in a healthy population, as well as an increased risk (1%-2%) of developing a second primary CRC [30–32], especially in the first years after resection [29, 31]. The risk of developing metachronous adenoma after CRC resection can be estimated at less than 10% [33, 34], which is similar to that of developing adenomatous changes after polypectomy in the general population [35, 36].
Improvement of overall survival in patients under postoperative surveillance after resection was confirmed in studies in which carcinoembryonic antigen testing, imaging (such as CT or MRI), and clinical visits were regularly performed in addition to endoscopic examination [37]. Close monitoring of asymptomatic cancer patients allows for earlier detection of recurrence compared with a diagnosis based solely on the presence suspicious symptoms [38]. Nevertheless, the importance of extensive postoperative surveillance for recurrence after rectal cancer resection remains controversial. More recent publications indicate that intensified surveillance after surgery does not improve treatment outcomes [39–41].
Endoscopic examination remains only part of a multidisciplinary approach. A few studies that have investigated the effects of intensified follow-up endoscopy have consistently showed that, despite more frequent detection of asymptomatic recurrences and thus more frequent qualification for radical treatment, there was no improvement in overall survival in groups subjected to frequent endoscopic examinations [42].
Earlier guidelines for post-rectal cancer surveillance included frequent endoscopic checkups of at least once every 6–12 months [43, 44]. The currently recommended schemas, based on current publications on surveillance after radical treatment of rectal cancer, advocate examinations at least 2–3 times over a 5-year follow-up period [45–47], that is, much less often than previously recommended (Table 6).
Our study has some limitations because of its single-center and retrospective nature. However, the fact that patients were analyzed in one center contributes to the standardization of therapeutic and diagnostic procedures. The percentage of LRs in our analysis, including those located directly in the anastomosis, remained low (6.5%, including 5 patients with anastomosis) and is similar to that reported by other studies [48–50]. The low recurrence rates are not conducive to reliable statistical analyses, although endoscopic examination is known to have a low sensitivity in detecting recurrences. Nonetheless, high specificity and the ability to sample biological material make endoscopy the preferred method for confirming the presence of recurrent lesions and verifying them histopathologically. Diagnosis of relapse is most often based on physical or imaging examinations (CT, MRI). Factors that increase the value of regular imaging tests as an alternative to endoscopy are the possibility of a simultaneous diagnosis of a lesion located outside the intestinal lumen and distant (systemic) lesions, as well as the diagnosis of possible consequences of radical treatment: postoperative fistulas, radiation-induced changes, and pelvic insufficiency fractures [51]. In addition, the invasiveness of endoscopic examinations should be taken into account, as they often result in poor patient tolerance associated with an increased risk of serious complications (including gastrointestinal perforation) [52]. Although small doses of radiation from X-rays that patients receive during imaging examinations (CT) have an impact on the body, the levels are too low to contraindicate even frequent examinations [41].
Our results do not confirm the advantage of endoscopic examinations in detecting recurrences in patients who are not receiving RT. This finding may have resulted from the small number of LRs detected (although a low rate of LR is the current standard). Given the results of other studies, however, a higher percentage of LRs and those located in the anastomosis can be suspected in this group of patients [25]. Although on the one hand, the use of RT reduces the number of local recurrences, on the other hand, it is recommended in more advanced tumors: in patients who are in general characterized as having a higher risk of LR, frequently located outside the bowel lumen. Thus, it remains debatable as to whether diagnostic indications for endoscopy in postoperative surveillance after rectal cancer treatment depend on the use of RT.