Abstract
Purpose/objective(s)In early-stage, node negative oral tongue cancer, there is limited data supporting tumor depth of invasion (DOI) as an indication for post-operative radiotherapy (PORT) to the primary site. The primary aim of this study is to examine the effect of tumor DOI and PORT on overall survival (OS).Materials and methodsThe National Cancer Database (NCDB) was used to query patients with AJCC stage I and II oral tongue cancer (2006-2013). Patients were stratified by receipt of PORT, elective neck dissection (ND), and DOI (≤4 mm or >4 mm). Kaplan-Meier analysis was performed to compare OS (using the log-rank test) between PORT versus no-PORT. Multivariable Cox proportional hazards regression model performed to evaluate the independent effect of PORT and neck dissection on OS.ResultsAmong 939 patients, 69.3% were clinical stage I, 67.4% received ND, 23.4% had DOI >4 mm, and 10.4% received PORT. The addition of PORT did not improve OS with tumor DOI ≤4 mm (p = 0.634) or >4 mm (p = 0.816). The addition of elective neck dissection improved OS for DOI >4 mm (p = 0.010), but not for ≤4 mm (p = 0.128). On multivariable analysis, ND improved OS if DOI >4 mm (HR, 0.37; 95% CI, 0.17-0.81 [p = .012]), when also controlling for age, sex, PORT status, clinical stage, and pathological stage.ConclusionTumor DOI should not be used as a sole indication for PORT in early stage oral tongue cancers. Elective neck dissection at the time of excision of the primary tumor results in higher OS for tumors with DOI >4 mm.
Highlights
Depth of invasion (DOI) is defined as the length measured from the tumor surface to the deepest point of invasive tumor in a paraffin embedded section [1]
neck dissection (ND) improved overall survival (OS) if DOI >4 mm (HR, 0.37; 95% CI, 0.17-0.81 [p = .012]), when controlling for age, sex, post-operative radiotherapy (PORT) status, clinical stage, and pathological stage
DOI is an important prognostic factor for nodal metastasis in oral tongue cancer, with increasing DOI associated with nodal involvement and worse prognosis [3,4,5,6,7]
Summary
Depth of invasion (DOI) is defined as the length measured from the tumor surface to the deepest point of invasive tumor in a paraffin embedded section [1]. DOI is an important prognostic factor for nodal metastasis in oral tongue cancer, with increasing DOI associated with nodal involvement and worse prognosis [3,4,5,6,7]. O'steen et al retrospectively evaluated the outcomes of 32 patients with stage N0-2b oral tongue or floor of mouth cancers with the primary tumor not crossing the midline who underwent PORT. At a median follow-up of 5.5 years among patients alive at the end of the study, there were no isolated nodal recurrences despite the majority of tumors possessing of DOI >4 mm. The authors concluded that the risk of nodal recurrence when omitting CL neck RT was very low if the primary tumor did not cross the midline, irrespective of other risk factors [5]
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