Predictive model for sphincter preservation in lower rectal cancer

Abstract

Background: Low rectal cancer poses a significant surgical challenge because of its close proximity to the anal sphincter, often requiring radical resection with permanent colostomy to achieve oncological safety. Revisited rectal anatomy, advances in surgical techniques and neoadjuvant therapies have enabled the possibility of sphincter-preserving procedures, however, it is uniformly not applicable. Selecting appropriate candidates for sphincter preservation is crucial, as an ill-advised approach may compromise oncological outcome or lead to poor functional outcomes. Currently there is no consensus - which clinical, anatomical, or molecular factors most accurately predict the feasibility of sphincter-preserving surgery (SPS) in this subset of patients. By identifying these predictors, the study seeks to support improved patient selection, enhance surgical planning, and ultimately contribute to better functional and oncological outcomes in patients with low rectal cancer.

Aim: To identify predictive factors that determine the feasibility of SPS in patients with low rectal cancer.

Methods: A comprehensive literature search was conducted using PubMed/MEDLINE databases. The search focused on various factors influencing the feasibility of SPS in low rectal cancer. These included patient-related factors, anatomical considerations, findings from different imaging modalities, advancements in diagnostic tools and techniques, and the role of neoadjuvant chemoradiotherapy. The relevance of each factor in predicting the potential for sphincter preservation was critically analyzed and presented based on the current evidence.

Results: Multiple studies have identified a range of predictive factors influencing the feasibility of SPS in low rectal cancer. Patient-related factors include age, sex, preoperative continence status, comorbidities, and body mass index. Anatomical considerations, such as tumor distance from the anal verge, involvement of the external anal sphincter, and levator ani muscles, also play a critical role. Additionally, a favourable response to neoadjuvant chemoradiotherapy has been associated with improved suitability for sphincter preservation. Several biomarkers, such as inflammatory markers like interleukins and C-reactive protein, as well as tumor markers like carcinoembryonic antigen, are important. Molecular markers, including BRAF and KRAS mutations and microsatellite instability status, have been linked to prognosis and may further guide decision-making regarding sphincter-preserving approaches. Artificial intelligence (AI) can further add in to select an ideal patient for sphincter preservation.

Conclusion: SPS is feasible in low rectal cancer and depends on patient factors, tumor anatomy and biology, preoperative treatment response, and biomarkers. In addition, tools and technology including AI can further help in selecting an ideal patient for long term optimal outcome.

Keywords: Factors; Low rectal cancer; Predictive model; Sphincter preservation; Surgery.

Figure 1

Predictive factors for sphincter preservation in low rectal cancer.

Figure 2

Surgical options for low rectal cancer. A: Low anterior resection; B: Ultra-low anterior resection; C: Partial inter-sphincteric resection; D: Subtotal inter-sphincteric resection; E: Total inter-sphincteric resection; F: Abdominoperineal resection. LAR: Low anterior resection; UL-LAR: Ultra-low anterior resection; ISR: Inter-sphincteric resection; APR: Abdominoperineal resection; IS: Internal sphincter; ES: External sphincter; DL: Dentate line; ARJ: Ano-rectal junction.