Quality markers in colorectal cancer surgery: what is the evidence?

Abstract

Validating metrics of surgical quality against survival outcomes remains essential to accurately predict prognosis in colorectal cancer (CRC). This thesis explores the complexities in defining, measuring, and assessing surgical quality in CRC.

Three major factors are examined: (i) plane of excision, (ii) extent of lymphadenectomy (EoL), and (iii) the appropriateness of lymphadenectomy—particularly in areas of watershed blood supply. Historically, emphasis has been placed on achieving the correct plane of excision to ensure an intact mesorectal/mesocolic fascia and prevent tumour transection.

By contrast, EoL has received comparatively less attention, largely due to the difficulty in objective measurement, often limited to crude assessments such as lymph node (LN) yield. However, recent interest in central vascular ligation (CVL), or D3 lymphadenectomy, highlights a shift in focus. CVL involves high vascular ligation at the origin of feeding arteries to enhance central LN clearance. It is associated with improved mesocolic plane integrity, reduced local recurrence, and better survival in some cohort studies. Despite ongoing debate over its routine use—due to technical difficulty and potential complications—CVL is increasingly viewed as a benchmark for high-quality CRC surgery. Yet, verifying whether CVL has been achieved remains reliant on intraoperative assessment, as the level of pedicle transection cannot be confirmed by pathology alone.

The appropriateness of lymphadenectomy based on targeted vascular pedicles—especially in regions with variable blood supply like the splenic flexure (SF)—is another underexplored area. Applying CVL and CME principles in such regions is complex, given the uncertainty around dominant lymphatic pathways.

Chapters II–IV address lymphadenectomy extent, while Chapters V–VI examine ‘appropriate’ lymphadenectomy in the context of SF cancers.