Oncological outcome after local treatment for early stage rectal cancer

Management of early stage rectal cancer continues to be a challenge for many multidisciplinary cancer teams. Decision-making post polypectomy, assessing the risk of luminal and mesorectal recurrence, not to mention distal disease, provokes considerable discussion. In this study, we primarily aimed to capture the outcomes after following the management of early stage rectal cancer by a selection of approaches available to all MDTs. We considered endoscopic treatment of early cancer by EMR/ESD/standard polypectomy, along with to surgical treatment, which included either TEM/TAMIS or major surgery. The decision to adopt a particular treatment strategy is often subtle and based on several different factors including the location of the tumour, patient comorbidity and patient/surgeon preference. In our study, the three groups of patients showed similar patient and tumour characteristics. Our findings suggest that, in selected patients, long-term oncological outcomes after endoscopic excision of the polyp by EMR or ESD are no different to local excision and major resection surgery. Furthermore, it highlights that if endoscopic excision has been performed successfully, as defined by healthy scar at site check, further resection of the rectum by either TEM/TAMIS or major surgery may not be required unless there are adverse features that have been identified. This study reflects the reality of current clinical practice in a centre where all three options are available at expert level and describes the dilemmas encountered at MDT.

Several previous studies have examined oncological outcomes after local excision and radical surgery [3, 11‐13, 15]. However, most of these studies have included both colonic and rectal cancer making it difficult to draw conclusions about rectal cancer specifically [13]. Others have investigated outcomes across all stages of cancer where local excision may not be sufficient to ensure complete removal of the tumour [3]. Reports of TEM/TAMIS surgery often include different histological types of cancer aside from adenocarcinoma or report other non-oncological outcomes making it difficult to draw conclusions about cancer-specific survival in these patients [18].

The results of our study suggest that oncological outcomes are similar across all three groups. A recent study has also examined local excision with TEM/TAMIS and compared outcomes to major surgery [19]. Patient characteristics, surgical outcome and survival rates were comparable to our study, as radical resection rates were 84% for TEM/TAMIS and 99% for major surgery; 5-year cancer-specific survival rates were 95% and 94%, respectively [19]. This demonstrates that, if oncological safety can be ensured, local excision with only a polypectomy could be considered sufficient treatment for early stage rectal cancer and may be attractive in patients who are not fit for surgical excision. Furthermore, our results highlight that a TEM/TAMIS resection of the polypectomy site or major surgical resection may be unnecessary if the scar is healthy with no evidence of regrowth and the MRI scan shows no distant lymphatic spread [14].

Despite the findings of this study showing promising outcomes for local therapy in rectal cancer, it is important to realise there are several limitations. Firstly, the number of patients in each treatment group is small and further investigation in larger cohorts of patients in a multicentre setting would be necessary to ensure the results can be generalised. Secondly, there will be selection bias as nearly half of the patients were referred from surrounding hospitals to our institution as it is a tertiary referral centre for TEM/TAMIS surgery and advanced endoscopic resection. Thus, bias for local therapy could have been introduced at an early stage in the decision-making process with patients opting for local excision instead of major surgery [1‐3]. There is also a bias based on the age and comorbidity of the patient. A healthy patient, particularly if younger, is more likely to be offered major surgery, whereas an elderly patient with comorbidity may opt for local excision or a watch and wait policy to avoid the morbidity of major surgery. The vast majority of patients, however, fall in between these two extremes and are subjected to a detailed conversation in clinic where they are actively encouraged to participate in the final decision about treatment [4, 5, 20‐22]. Hence, this study reflects the reality of current clinical practice where the decisions regarding surgery or local excision involve consideration of the patient’s wishes, the clinician’s expertise and the characteristics of the tumour. Thus, we did not seek to determine which factors contributed to decisions regarding which treatment arm the patient entered as it would be an impossible task when performed retrospectively. Prospective studies are already investigating these treatment modalities to determine the optimal treatment strategy [23].

Unfortunately, because of a heterogeneity in endoscopic and histology reports and as half of these patients were referred from another hospital, we were not able to analyse polyp features in the patients that were only treated with an endoscopic polypectomy. This is an important consideration for future studies and would allow comparison of outcomes based on polyp features if recording of endoscopy and histology reports could be standardised [24, 25]. Protocolised documentation would also help to inform the MDT discussion, especially when the discussion is about management after R1 polypectomy, where the treatment is usually tailored based on the available information [1].

Our study supports the notion that major surgery should be reserved for those with an incomplete excision, especially macroscopically incomplete and if adjuvant therapy cannot be given [14, 26‐30]. However, local excision does not allow complete staging of the tumour as there is no reliable way to detect histologically positive lymph nodes [18, 31]. In our study, 7% of patients who had a polypectomy and 4% of TEM/TAMIS patients developed metastatic disease which is comparable to studies on major resection surgery with T1 disease where 10% patients develop distant metastases [32]. Close follow-up of all cohorts remains mandatory.

Amongst the patients found to have recurrent disease, three out of five patients (60%) developed metastatic disease without local recurrence. Interestingly, one of these patients who had a radical polypectomy developed a liver metastasis 14 months after the procedure. Our patient was unfit for liver surgery; however, there have been reports in the literature where a similar case presentation of a patient developing liver metastasis nine months after ESD was successfully treated with a liver resection and anterior resection [33]. However, no residual tumour was detected in the rectal cancer resection specimen nor in lymph nodes highlighting that these patients may have tumours that behaves differently, and local excision may not necessarily impair outcome. This most likely reflects inherent differences in tumour biology. However, as the overall recurrence rate in our study is low, we are not able to examine differences in outcome based on tumour biology.

In conclusion, this study demonstrates that it is possible to achieve good oncological outcomes in selected patients presenting with early stage rectal cancer with a polypectomy procedure, similar to patients with a TEM/TAMIS or major resection. If there is a wide involved margin after polypectomy, it may be possible to perform a wider local excision with TEM/TAMIS surgery, though often there is no residual tumour in the specimen, and therefore, this may not be always necessary. A local excision by TEM/TAMIS resection is, therefore, not warranted after a successful polypectomy. Further prospective studies need to determine which features of the tumour help to predict tumour biology and enable identification of patients who may require a more aggressive approach with major surgery.