Histological reporting of locally excised pT1 colorectal cancer in the English Bowel Cancer Screening Programme: national audit and cohort description.

[AIMS] Colorectal cancer (CRC) is increasingly detected at an early stage through national screening programmes, including tumours confined to the submucosa (pT1). Many pT1 CRC are managed by local endoscopic excision, and histological risk assessment is central to determining the need for further treatment.

[METHODS] Clinical and pathology data were analysed for screen-detected pT1 CRC removed by local excision within the English Bowel Cancer Screening Programme (BCSP) between 2021 and 2022. The completeness of data recorded in the Bowel Cancer Screening System (BCSS) was audited against national pathology guidance. Clinicopathological features and subsequent management were described.

[RESULTS] 1267 pT1 CRC from 1260 patients were identified. BCSS data were available for all cases, although some histological fields were incomplete or coded as 'not assessable'. Most tumours were adenocarcinoma, not otherwise specified (NOS) (95.7%) and well-moderately differentiated (90.4%). Venous, lymphatic and perineural invasion were recorded in 8.9%, 9.2% and 1.0% of cases, respectively. Complete local resection (R0) was documented in 643 tumours. Following local excision, 342 pT1 CRC (27.0%) received further treatment, most commonly colorectal resection (287 cases) or repeat local excision (23 cases). Lymph node metastases were reported histologically in 33 patients.

[CONCLUSIONS] This large, contemporary cohort demonstrates that the English BCSP holds rich clinical and histological data suitable for audit and research. The audit highlights parameters where assessment is constrained by specimen-related factors and where data entry could be improved. These data characterise the histological features of locally excised pT1 CRC and their subsequent management and provide a foundation for future outcome-focused studies.