Anterior tumour location as a risk factor for local recurrence after laparoscopic surgery for stage I ultra-low rectal cancers: exploratory analysis of the Ultimate trial.

BACKGROUND

Anterior tumour location is an established risk factor for local recurrence (LR) in advanced rectal cancer, but its significance in stage I ultra-low rectal cancer remains unclear.

METHODS

This exploratory supplemental analysis used data from Ultimate trial, a multicentre prospective phase II study across 47 Japanese institutions (2014-2017). Patients with cT1-2 N0 M0 ultra-low rectal cancer (≤ 5 cm from the anal verge) underwent laparoscopic resection. Tumour location was categorized as anterior (10-2 o'clock) or non-anterior (2-10 o'clock). The primary endpoint was LR; secondary endpoints included recurrence-free survival, overall survival, and stoma-free survival.

RESULTS

Of 300 enrolled patients, 297 were analysed (median follow-up 37.2 months); 93 tumours (31.3%) were anterior. Baseline characteristics, operative outcomes, and pathological findings were similar between the two groups. The 3-year cumulative LR rate was 11.9% for anterior tumours and 3.0% for non-anterior tumours (hazard ratio (HR) 4.46; 95% confidence interval (c.i.) 1.67 to 11.89; P = 0.001). Multivariable analysis showed an independent association between anterior location and LR (HR 4.68; 95% c.i. 1.72 to 12.74); subgroup analysis revealed no difference in clinical (c) T1 patients, but a significantly higher LR rate for anterior tumours in cT2 patients (25.3% versus 4.7%; P < 0.001). Three-year recurrence-free survival (83.9% for anterior tumours versus 88.9% for non-anterior tumours; P = 0.222), overall survival (> 95%), and stoma-free survival were comparable between the two groups.

CONCLUSION

Anterior tumour location in the ultra-low rectum was associated with an increased risk of LR, particularly in cT2 patients, highlighting the need for a more refined treatment strategy and vigilant monitoring.