Prognostic implications of mandibular invasion in oral cancer

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Abstract
Background Mandibular invasion alters the clinical staging and management of oral epidermoid carcinoma on the assumption that underresection of mandibular bone invaded by tumor can result in disease progression and poor outcome. Methods Cox's proportional hazard model was used to assess the effect of mandibular invasion on recurrence-free survival in 107 patients with squamous cell carcinoma of the oral cavity after controlling for the potential confounding effect of positive margins, tumor size, nodal status, and type of resection. Results Mandibular invasion was characterized as none (n = 59), focal (n = 25), or deep (n = 23). Relapse-free survival at 60 months by the Kaplan Meier product limit method for the none, focal, and deep invasion groups was 61%, 73%, and 46% respectively (p = .28). Variables influencing disease recurrence were positive margins, size >2 cm, N2 and N3 nodal disease, and marginal vs segmental mandibular resection. Mandibular invasion was not a significant risk factor for disease recurrence with an adjusted hazard ratio for deep invasion vs focal or no invasion of 1.0 (95% CI = 0.5, 2.2; p = 1.00). Conclusions Detection of bone invasion, particularly in small tumors, may not be as critical to surgical planning as previously expected. The necessity for and extent of bone resection should be determined by the objective of achieving an adequate surgical margin and not the presence of bone invasion per se. © 2000 John Wiley & Sons, Inc. Head Neck 22: 794–798, 2000.