Can Computed Tomography Characteristics of the Oropharynx in Cancer of Unknown Primary Predict Primary Tumor Site?

Abstract

Objectives:

(1) Measure axial and coronal parapharyngeal space area (PPSA) and parapharyngeal mucosal thickness (PMT) in patients who present with cancer of unknown primary (CUP). (2) Determine if PPSA and PMT differences between affected and unaffected sides of the oropharynx were found based on site of primary (tonsil vs base of tongue [BOT]) or body mass index (BMI).

Methods:

Institutional review board–approved retrospective chart and preoperative computed tomography (CT) review of consecutive patients presenting between 2007-2013 with CUP to a tertiary university hospital. Subjects did not have an identified primary on clinical or imaging examinations including positron emission tomography/CT but did have an identified primary after surgery. Two blinded radiologists reviewed CT scans. Measurements of PPSA and PMT at defined levels in the axial and coronal planes and prediction of the primary site were made. Independent variables were primary tumor site and BMI. Comparisons were made using Student t test.

Results:

There was no significant difference in PPSA or PMT between the affected and unaffected sides of the oropharynx for the entire group (n = 17, ΔPPSA axial 0 mm², P = .5; ΔPPSA coronal 16 mm², P = .2; ΔPMT 0.3 mm, P = .2) or for subgroups based on primary site (tonsil vs BOT) or BMI (≤25, >25). Blinded examiners correctly predicted the primary site in 7/17 (41%) of cases.

Conclusions:

Differences in axial PPSA and PMT were not useful to predict the primary site in patients with CUP. Although not statistically significant, coronal PPSA in subjects with BMI >25 may be useful in identifying the primary tumor site.