A novel tumor: specimen index for assessing adequacy of resection in early stage oral tongue cancer

Purpose: Surgical margin status frequently affects decisions regarding adjuvant treatment; however, reporting and interpretation of surgical margins is subject to considerable subjectivity because of many factors including the adequacy of resection. We developed a novel measure of the adequacy of surgical resection, the tumor: specimen index (TSI), and tested its utility at predicting clinical outcomes in a retrospective cohort study.

Patients and methods: An institutional database was queried to identify previously untreated patients with T1 and T2 oral tongue cancer who underwent surgery during 1985-2009 (n=433). The TSI, a geometric mean representing the percentage of the surgical specimen that is occupied by the tumor in average single dimension, was calculated from the largest measured lengths, widths, and heights of the tumor in relation to the entire surgical specimen. Multivariate analyses of locoregional recurrence-free probability (LRRFP) and disease-specific survival (DSS) were performed with commonly accepted prognosticators in addition to TSI and surgical margins status.

Results: The mean TSI was 41 (range 11-90; SD 14). Surgical margin status was associated with TSI; margins were negative in 84% of patients with TSI<45 and in 63% of patients with TSI⩾45 (p<0.001). TSI⩾45 was associated with worse LRRFP (57% vs. 76%, p<0.001) and worse DSS (68% vs. 85%, p<0.001). In a multivariate analysis that did not include TSI, surgical margin status independently predicted LRRFP (p=0.014) but not DSS. When TSI was included, only TSI, and not surgical margin status, was an independent predictor of both LRRFP (p=0.002) and DSS (p=0.011).

Conclusion: The tumor: specimen index is an easily-calculated metric for estimating the adequacy of 3-dimensional resection in T1 and T2 oral tongue cancer that independently predicts oncologic outcomes.