Rim Mandibulectomy: Safe, even in the face of understaging?

Background:
Bony invasion in oral squamous cell carcinoma (SCC) is a poor prognostic factor. It is diagnosed preoperatively utilising staging scans and periosteal stripping. Tumours with invasion into the medulla typically require segmental mandibulectomy (SM) to ensure oncological clearance. A more conservative rim/marginal mandibulectomy (RM) may be performed in cases of close tumour proximity to bone or cortical erosion. However, this procedure may risk under-treatment if the preoperative assessments underestimate the extent of bone invasion.
This retrospective cohort study explores the suitability of RM as a conservative alternative to SM in select patients.
Methods:
Patients undergoing mandibulectomy for SCC at a UK OMFS centre between 2018-2023, with >24months follow-up, were identified. Primary outcomes are survival and recurrence, analysed using multivariate regression. Subgroup analysis will be performed on RM patients who subsequently demonstrate histological medullary involvement.
Results:
RM (n=26) and SM (n=30) patients met inclusion criteria. Regression modelling did not identify RM or SM procedures as a significant factor in patient outcomes (p>0.9). Histological medullary involvement was found in 6 RM patients (23%). Survival outcomes and recurrences in these patients were not significantly different to the wider RM group. Presence of bone margin clearance of 5mm was significantly related to survival outcomes.
Conclusions:
Findings continue to support RM as a safe surgical option, even with inherent risk of under-staging. However, preoperative diagnostic accuracy is key to reducing the risks. A further 10 patients have been identified for analysis and will also be presented in the dataset.