International validation of a risk prediction algorithm for patients with malignant colorectal polyps

Applicability of the Scottish screen-detected polyp cancer study (SSPoCS) algorithm in a multicentric cohort in the management of malignant colorectal polyps

BACKGROUND/OBJECTIVES

Robust evidence regarding the management after endoscopic resection of malignant colorectal polyps (MCP) is lacking. Inconsistencies in reporting on potential prognostic factors hinder the decision process. To address these issues, the Scottish Screen-detected Polyp Cancer Study (SSPoCS) introduced an algorithm based in two easily obtainable variables: resection margin and lymphovascular invasion. This study aims to assess the applicability of the SSPoCS algorithm in a Portuguese multicentric cohort.

METHODS

Endoscopically resected MCP in five centers were included. The main outcome was residual/recurrent malignancy (RRM), defined as any of the following: (1) residual intramural or lymph node malignancy in the surgical specimen after completion surgery; (2) local or systemic recurrent disease in conservatively managed patients.

RESULTS

Two-hundred and eleven patients were included (mean age: 68.6 ± 10.4 years; male participants: 65.4%); 121 underwent completion surgery while 90 remained in surveillance. Thirty-two patients (15.2%) experienced RRM: 27 displayed residual malignancy in the surgical specimen and five developed recurrent disease. According to the SSPoCS algorithm: 120 patients were classified as having low-risk of residual disease, six of whom displayed RRM (5.0%); 10 as medium-risk, with one having RRM (10.0%); and 81 as high-risk, 25 of whom experienced RRM (30.9%). Lesions classified as low risk showed a negative predictive value (NPV) of 95.0% to exclude RRM. The algorithm demonstrated good accuracy in predicting RRM in a Receiver Operating Characteristic curve analysis (AUC: 0.74; 95% CI: 0.65-0.83; p < 0.001).

CONCLUSIONS

The SSPoCS algorithm revealed good accuracy in predicting residual/recurrent malignancy with a NPV of 95.0% to exclude RRM in low-risk lesions.

Factors affecting treatment decisions for endoscopically resected low- and high-risk malignant colorectal polyps in a screening setting

INTRODUCTION

The European Guidelines for colorectal cancer screening of 2006 state that only high-risk endoscopically resected malignant colorectal polyps (MCPs), defined as poor/no differentiation or positive resection margins or lymphovascular invasion, require colonic resection.

METHODS

A multicentre series of 954 patients with screen-detected MCP (northern Italy, 2005-2016, age 50-69) was studied to identify (1) the factors affecting the choice of colonic resection, and (2) the factors associated with deviation from the European Guidelines for low- and high-risk patients. Data analysis was based on multilevel logistic regression models.

RESULTS

Five hundred sixty-four (59.1 %) patients underwent colonic resection. The factors significantly associated with surgical referral included: distal and rectal versus proximal tumour site (inverse association); sessile and flat versus pedunculated morphology (direct association); tumour size (direct); moderate/poor versus good differentiation (direct); adenocarcinoma of not otherwise specified type versus adenocarcinoma with a residual adenoma component (direct); positive versus negative resection margins (direct); lymphovascular invasion (direct); and high-grade versus low-grade/absent tumour budding (direct). In low-risk MCPs, tumour budding encouraged strongly the decision for surgery. In high-risk MCPs, a distal/rectal tumour site encouraged the follow-up option.

CONCLUSION

The identification of factors associated with treatment choices other than those currently recommended may help prioritise the clinical questions in the development of future guidelines.

Sporadic Polyps of the Colorectum

Colorectal polyps are common, and their diagnosis and classification represent a major component of gastrointestinal pathology practice. The majority of colorectal polyps represent precursors of either the chromosomal instability or serrated neoplasia pathways to colorectal carcinoma. Accurate reporting of these polyps has major implications for surveillance and thus for cancer prevention. In this review, we discuss the key histologic features of the major colorectal polyps with a particular emphasis on diagnostic pitfalls and areas of contention.

Pathological features associated with metastasis in patients with early invasive (pT1) colorectal carcinoma in colorectal polyps

AIMS

Colorectal carcinoma (CRC) arising in a colorectal polyp with invasion limited to the submucosa is sufficiently treated by complete endoscopic resection alone in many cases. Histological features of the carcinoma including tumour size, vascular invasion and poor tumour differentiation or evidence of de-differentiation, such as tumour budding, are associated with a higher risk for metastasis such that oncological resection is recommended. However, most malignant polyps with these features do not have lymph node metastases at the time of resection, so there is a need for better refinement of the histological risk features.

METHODS AND RESULTS

A total of 437 consecutive colorectal polyps with submucosal invasive carcinoma from a single centre, 57 of which had metastatic disease, were supplemented by 30 cases with known metastatic disease from two additional centres. Clinical and histological features of the polyp cancers were reviewed looking for differences between the 87 cancers with metastatic disease and the remaining cases without metastasis. A subgroup of 204 polyps removed intact was also analysed to ensure maximum histological accuracy.

CONCLUSIONS

This study confirmed larger invasive tumour size, vascular invasion and poor tumour differentiation as adverse predictive features. Prominent peritumoral desmoplasia and high cytological grade were additional adverse features. A predictive logistic regression model comprised of (i) presence of any form of vascular invasion; (ii) presence of high tumour budding (BD3); (iii) width of invasive tumour component > 8 mm; (iv) depth of invasive tumour > 1.5 mm; and (v) the finding of prominent expansile desmoplasia located within and beyond the deep invasive edge of the carcinoma, showed excellent performance in predicting metastatic disease.

Resection margin involvement after endoscopic excision of malignant colorectal polyps: definition of margin involvement and its impact upon tumour recurrence

AIMS

Malignant polyps are examined to assess histological features which predict residual tumour in the unresected bowel and guide surgical decision-making. One of the most important of these features is resection margin involvement, although the best definition of margin involvement is unknown. In this study we aimed to investigate three different definitions and determine their impact on clinical outcomes.

METHODS AND RESULTS

One hundred and sixty-five malignant polyps removed endoscopically were identified and histological features correlated with either residual tumour in subsequent surgical resections or tumour recurrence following a period of clinical follow-up. Involvement of the polyp margin by cancer was defined in three different ways and outcomes compared. Tumour recurrence was associated with tumour grade, mucinous histology and resection margin involvement. All three definitions of margin involvement separated polyps into clinically significant categories; however, a margin ≤ 1 mm identified 73% of polyps as 'high-risk' compared with 59.1% when involvement was defined as tumour within the zone of coagulation artefact at the polyp base or 50% when tumour was present at the margin. All three 'low-risk' groups had a locoregional recurrence rate < 6.5%.

CONCLUSIONS

Definitions of margin involvement for endoscopically removed malignant polyps in the colon and rectum vary between health-care systems, but a 1-mm clearance is widely used in Europe and North America. Our results suggest that a 1-mm margin is unnecessary and should be replaced by a definition based on tumour at the margin or within coagulation artefact at the polyp base.

Decision making in the management of adults with malignant colorectal polyps: An exploration of the experiences of patients and clinicians

AIM

A diagnosis of colorectal polyp cancer presents a treatment dilemma. The decision between segmental resection versus endoscopic surveillance is difficult due to a lack of good quality clinical evidence for either option. The aim of this study was to understand the decision making experiences of both clinicians and patients when faced with such a diagnosis.

METHODS

Qualitative, semi-structured interviews were undertaken with 10 clinicians involved in the care of patients diagnosed with polyp cancer and five patients who had experience of a diagnosis of polyp cancer. All clinicians and patients were from four hospital trusts across the north of England. Interviews were audio-recorded, transcribed verbatim and analysed using the principles of interpretative phenomenological analysis.

RESULTS

Analysis of the interview transcripts evidenced that clinicians and patients were supportive of a shared approach to treatment decision making in the context of a diagnosis of colorectal polyp cancer. Uncertainty, influences and information were among the themes identified to be preventing this happening at present. This study identified themes which were common to both groups. These were complexity of the risk information, lack of patient information resources, and system factors and time.

CONCLUSION

This research study has evidenced several factors such as uncertainty, complexity of risk information and influences on decisions which are preventing patients being involved in treatment decisions following a diagnosis of colorectal polyp cancer. Recommendations for improvements in practice, including a framework to assist treatment decision making in the future, are highlighted.