Abstract
Depth of invasion (DOI) can be calculated preoperatively by MRI, and whether MRI-determined DOI can predict prognosis as well as whether it can be used as an indicator of neck dissection in cT1N0 tongue squamous cell carcinoma (SCC) remains unknown. The main goal of the current study was to answer these unknowns. A total of 151 patients with surgically treated cT1N0 tongue SCC were retrospectively enrolled, and MRI-determined DOI was measured based on T1-weighted layers with a 3.0T scan. The Chi-square test was used to evaluate the association between clinical pathologic variables and neck lymph node metastasis, and the factors that were significant in the Chi-square test were then analyzed in a multivariate logistic regression analysis model to determine the independent predictors. The main study endpoints were locoregional control (LRC) and disease-specific survival (DSS), and the Kaplan-Meier method (log-rank test) was used to calculate the LRC and DSS rates. The factors that were significant in univariate analysis were then analyzed in the Cox model to determine the independent prognostic factors. A value of p < 0.05 was considered significant, and all statistical analyses were performed with SPSS 20.0. Occult neck lymph node metastasis was noted in 26 (17.2%) patients, and the ROC curve indicated that the optimal cutoff value of MRI-determined DOI was 7.5 mm for predicting neck lymph node metastasis, with a sensitivity of 86.9%. The factors of lymphovascular invasion, MRI-determined DOI, pathologic DOI, and pathologic tumor grade were significantly associated with the presence of neck lymph node metastasis in univariate analysis, and further logistic regression analysis confirmed the independence of lymphovascular invasion, MRI-determined DOI, and pathologic DOI in predicting neck lymph node metastasis. The 5-year LRC and DSS rates were 84% and 90%, respectively. Cox model analysis suggested the MRI-determined DOI was an independent prognostic factor for both LRC and DSS. Therefore, elective neck dissection is suggested if MRI-determined DOI is greater than 7.5 mm in cT1N0 tongue SCC, and MRI-determined DOI ≥ 7.5 mm indicates additional risk for disease recurrence and cancer-related death.
Highlights
Depth of invasion (DOI) can be calculated preoperatively by MRI, and whether MRI-determined DOI can predict prognosis as well as whether it can be used as an indicator of neck dissection in cT1N0 tongue squamous cell carcinoma (SCC) remains unknown
MRI-determined DOI is significantly different from MRI-determined tumor thickness, but whether MRI-determined DOI has the same effect as MRI-determined tumor thickness and whether it can be used as an indicator of elective neck dissection (END) in cT1N0 tongue SCC remain unknown; the main goal of the current study was to clarify these unknowns
The most valuable finding in the current study was that MRI-determined DOI was significantly associated with the presence of neck lymph node metastasis, which added a nearly 3-fold risk of neck lymph node metastasis if MRI-determined DOI was greater than 7.5 mm, and MRI-determined DOI was an independent prognostic factor for locoregional control (LRC) and disease-specific survival (DSS)
Summary
Depth of invasion (DOI) can be calculated preoperatively by MRI, and whether MRI-determined DOI can predict prognosis as well as whether it can be used as an indicator of neck dissection in cT1N0 tongue squamous cell carcinoma (SCC) remains unknown. Owing to a wide range of occult metastasis rates[2,3], either elective neck dissection (END) or the watchful waiting policy has been the favored treatment for cT1N0 tongue SCC4,5. Investigators favoring END have commented that it allows accurate disease staging and decision making for the need for adjuvant therapies, and the resection of metastatic lymph nodes can potentially reduce the recurrence risk[6,7]; the main concern according to the traditional watchful waiting policy is the associated surgical complications, which include shoulder dysfunction and over-treatment, in patients with no pathologic metastases[8]. MRI-determined DOI is significantly different from MRI-determined tumor thickness, but whether MRI-determined DOI has the same effect as MRI-determined tumor thickness and whether it can be used as an indicator of END in cT1N0 tongue SCC remain unknown; the main goal of the current study was to clarify these unknowns
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