Radiographic extracapsular extension (ECE) and treatment outcomes in locally advanced oropharyngeal carcinoma (OPC).
6019 Background: Pathologic ECE (pECE) of tumor through lymph node (LN) is a poor prognosticator for OPC and typically diagnosed upon surgical LN removal. At our institution, experienced radiologists routinely identify ECE on pretreatment CT. The prognostic value of radiographic ECE (rECE) is less clear and may prove clinically useful. In this study, we evaluate rECE as an independent prognosticator in OPC. Methods: Retrospective review of 185 patients with locally advanced OPC treated in our department from 2006-2012. 109 patients had accessible pretreatment CT reports clearly stating the presence or absence of rECE. Patients were treated with definitive concurrent chemoradiation therapy (CCRT) (30%), induction chemo then CCRT (47%), or surgery with adjuvant CCRT (14%) or RT (9%). Kaplan-Meier survival analysis compared these cohorts for locoregional control (LRC), distant control (DC), and progression-free (PFS) and overall survival (OS); log-rank tests were performed for significance. Multivariate analysis was conducted via cox-regression. Results: Median follow-up of the 109 patients was 31 months (range: 1-80 months). 61 patients had rECE(+) and 48 had rECE(-) scans. There was no significant difference between the cohorts in terms of median age, stage, treatment type, smoking history, or tumor HPV status. There was a difference in nodal stage with 83% of rECE(+) patients having N2-3 disease versus 67% of rECE(-) patients (p=0.02). On univariate analysis, there were differences between the rECE(-) versus rECE(+) cohorts in OS (4yr: 92% vs 72%, p=0.01), PFS (4yr: 92% vs 62%, p=0.002), and DC (4yr: 98% vs 76%, p=0.006), with no difference in LRC (4yr: 95% vs 91%, p=0.35). On multivariate analysis factoring in age, smoking history, stage, and treatment type, rECE presence was a negative predictor of OS (hazard ratio, 0.26; 95% CI, 0.07 to 0.95) and PFS (hazard ratio, 0.23; 95% CI, 0.06 to 0.81), with DC approaching significance (hazard ratio, 0.13; 95% CI, 0.02 to 1.05). Conclusions: While pECE is an established risk factor for locally advanced OPC, this study suggests that rECE may be an independent poor prognosticator of PFS, OS and DC with potential importance in guiding clinical management.