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Depth of Invasion Addition to Tumor Guidelines Can Result in a Higher Tumor Stage in More Than 20% of Patients

by Amy E. Hamaker •

COMMENT: This was a retrospective analysis of 85 oral cavity tumors with greatest dimension and thickness assessed via ultrasound and MRI and then compared to histopathology. Staging via AJCC7 and AJCC8 were also compared. Tumor thickness was more reliably measured with ultrasound; greatest dimension was more reliable with MRI. AJCC8 resulted in higher staging approximately 20% of the time. As a rhinologist, using ultrasound was not even on my radar to assess tumor thickness for oral cavity tumors. —Jennifer A. Villwock, MD

How accurate are tumor dimension measurements on ultrasound (US) and magnetic resonance (MR) imaging compared to histopathology, and how does this affect tumor staging according to the 8th edition of the AJCC/UICC cancer staging system (AJCC8)?

BOTTOM LINE: For preoperative tumor staging, the tumor thickness (TT) is best estimated by the use of US. The incorporation of depth of invasion (DOI; proximity to underlying lymph-vascular structures) in the AJCC8 can result in a higher tumor stage in more than 20% of patients, with an associated worse prognosis.

BACKGROUND: A tumor’s greatest dimension (GD) and TT can be measured on preoperative imaging and can be very different from each other. Before AJCC8, TT and DOI measures were often incorrectly used interchangeably; now their definitions have become more specific.

STUDY DESIGN: Retrospective analysis of 83 oral cavity cancer patients, including 85 oral cavity tumors, treated between 2011 and 2016.

SETTING: The Netherlands Cancer Institute, Amsterdam, the Netherlands.

SYNOPSIS: TT was measured on US and histopathology in 76 of the 85 tumors and using MR on 46 of the 85 tumors. GD was measured on US and histopathology for 44 of 85 tumors, and on MR and histopathology for 47 of 85 tumors. Mean TT measured on US images and associated histopathology sections was 5.1 mm. TT measures for the MR dataset, using different data, showed a mean TT of 7.4 mm found on MR and a mean TT of 6.1 mm found on histopathology. GD was reported on US images with associated histopathology sections (mean GD: 15.9 mm); using a different data set, GD was reported from MR images (mean GD: 18.8 mm) and associated histopathology (mean GD: 17.6 mm). Compared to US, GD measured on MR showed a higher correlation and agreement with histopathology. AJCC7 and AJCC8 agreed in 67 out of 85 tumors (48 as T1, 19 as T2); however, 18 tumors were classified into a higher T class when staging with AJCC8. No tumors were classified in a lower category. Limitations included speculation over use of histopathology.

CITATION: Brouwer de Koning SG, Karakullukcu MB, Lange CAH, Ruers TJM. The oral cavity tumor thickness: Measurement accuracy and consequences for tumor staging. Eur J Surg Oncol. 2019;45:2131-2136.