Is preoperative ultrasonography accurate in measuring tumor thickness and predicting the incidence of cervical metastasis in oral cancer?

The need for elective neck dissection in patients with early stage oral cancer is controversial. A preoperative predictor of the risk of subclinical nodal metastasis would be useful. Studies have shown a strong correlation between histological tumor depth and the risk of nodal metastasis. To determine if preoperative ultrasonography is an accurate measure of tumor depth in oral carcinoma. To assess if preoperatively measured tumor depth predicts an increased risk of subclinical metastatic neck disease and thus the need for elective neck dissection. Twenty one consecutive patients with biopsy proven squamous cell carcinoma of the tongue/floor of mouth were analyzed prospectively. Each patient received a preoperative ultrasonography to assess tumor depth which was compared to histological measures. Univariate analysis was used to correlate tumor thickness and T stage with neck metastasis. There was a significant correlation between the preoperative ultrasonography and histological measures of tumor depth (correlation coefficient 0.981, P<0.001). The overall rate of lymph node metastasis was 52%. The rate of metastasis was 33% in N0 necks. In the group with tumors<5mm in depth, the neck metastatic rate was 0%, as compared with 65% in the group 5mm. Using univariate analysis tumor depth and T stage were significant predictors of cervical metastasis (P=0.0351 and P=0.0300, respectively). Preoperative ultrasonography is an accurate measure of tumor depth in oral carcinoma. Tumor thickness is a significant predictor of nodal metastasis and elective neck dissection should be considered when this thickness is 5mm.