TBA (22W103)

Title: Histopathological Characteristics of Screening-Detected Colorectal Cancers. An Eight-year Single Institution Experience.

Author(s)

C Ward1, D Gibbons1, M Cotter1, N Swan1, N Nolan1, S Martin2, A Hanly2, D Winter2, R Kennelly2, A White1, B Nolan1, G Cullen3, G Doherty3, K Sheahan2

Department(s)/Institutions

1. Department of Histopathology, St. Vincents University Hospital, Dublin 2. Department of Colorectal Surgery, St. Vincents University Hospital, Dublin 3. Department of Gastroenterology, St. Vincents University Hospital, Dublin

Introduction

Colorectal cancer (CRC) screening detects cancers at an earlier stage, improving overall survival. However, when adjusted for stage the survival benefit in comparison to symptomatically presenting CRCs persists. The characteristics of screen-detected CRCs which contribute to a more favourable prognostic profile remain unclear.

Aims/Background

We aimed to evaluate the histopathological features of screen-detected cancers with comparison to a cohort of symptomatic cases.

Method

We analysed a database of all screen-detected CRCs in our institution since screening began in 2012. A cohort of symptomatic patients from 2020 was used for comparison. Histopathological reports were reviewed for prognostic factors such as lymphovascular invasion, perineural invasion and tumour budding. For neoadjuvant rectal cancer cases, the radiological stage pre-neoadjuvant therapy was also recorded.

Results

194 screen-detected CRCs were identified from January 2013 to December 2021. 176 symptomatic presentations were identified for comparison. There was a significant increase in early stage (stage I+II) detection in the screening group (61%vs39%, p=<0.001), largely driven by detection of T1 cases in both colon (31%vs14%, p=0.003) and rectal cancers (38% vs 12%, p=0.003). Screen-detected rectal cancers undergoing neoadjuvant chemotherapy had significantly higher complete response rates (42%vs17%, p=0.012). Rates of lymphovascular invasion were significantly higher in the symptomatic group (45%vs34%, p=0.007), predominantly due to extramural venous invasion (28%vs11%, p<0.001). Perineural invasion was also more frequent (16%vs7%, p=0.002). Rates of tumour budding and mismatch-repair protein status were similar.

Conclusions

Population screening for CRC results in cancer detection at an earlier stage. Screen detected CRCs have a more favourable risk profile, with lower rates of adverse prognostic factors such as venous and perineural invasion.