Excision Depth Versus Margin Status After Large Loop Excision of the Transformation Zone (LLETZ): Which Predicts Cure?

Background Large loop excision of the transformation zone (LLETZ) is the standard treatment for high-grade cervical intraepithelial neoplasia (CIN). Adequate excision depth and complete margin clearance are considered important for disease eradication; however, deeper excisions may increase obstetric morbidity. Identifying which surgical factors most strongly predict successful treatment is clinically important. Methods We conducted a retrospective cohort study of women undergoing LLETZ in our colposcopy unit. Data collected included age, referral cytology, excision depth, margin status, histology, and test of cure (high-risk human papillomavirus (hrHPV) and cytology). Successful treatment was defined as hrHPV negativity with no reflex cytology. Excision depth was categorised as ≤7 mm or ≥8 mm. Associations between depth, margin status, and outcomes were analysed using odds ratios (ORs). Results A total of 143 women who underwent LLETZ (mean age 39.6 years) were involved in this study. Most referrals were for high-grade cytology (76.9%). Histology confirmed CIN2+ in 65.0%, with occult invasive carcinoma and glandular neoplasia identified in 2.1% and 2.8%, respectively. The mean excision depth was 9.9 mm; 74.1% measured ≥8 mm. Clear margins were achieved in 67.8%, involved in 19.6%, and indeterminate in 12.6%. Test-of-cure results were available for 121/143 (84.6%). Overall, 73.6% achieved hrHPV negativity. Deeper excisions showed modestly higher cure rates compared with shallow excisions (75.6% vs. 67.7%; OR 1.47). In contrast, margin status strongly predicted outcomes: cure was achieved in 85.4% with clear margins compared with 50.0% with involved margins, corresponding to nearly sixfold higher odds of failure with margin involvement (OR 5.8, 95% confidence interval (CI) 2.2-15.3). Most failures reflected isolated HPV persistence, while high-grade cytological recurrence was uncommon (4%). Conclusion Margin clearance is the principal determinant of successful treatment following LLETZ. Excision depth demonstrated only a modest association with cure, whereas involved margins markedly increased the risk of persistent disease. Optimising excision technique to achieve complete clearance, rather than simply increasing cone depth, may improve outcomes while minimising unnecessary cervical tissue loss.