Retrospective Analysis Suggests Benefit of Adding Cetuximab to Radiotherapy Irrespective of p16 Status in Oropharyngeal Carcinoma


Key Points

  • In patients with locoregionally advanced oropharyngeal squamous cell carcinoma of the head and neck, p16-positive disease was associated with improved outcome both among those receiving radiotherapy alone and those receiving cetuximab and radiotherapy.
  • The addition of cetuximab appeared to be of benefit in both p16-positive and p16-negative patients.

A retrospective analysis of the phase III registration trial IMCL-9815 of cetuximab (Erbitux) reported in the Journal of Clinical Oncology by Rosenthal et al suggests that the addition of cetuximab to radiotherapy was of benefit irrespective of p16 expression in patients with locoregionally advanced oropharyngeal squamous cell carcinoma of the head and neck.

Effect of p16 Status

The analysis included 182 patients with evaluable tumor p16 status from the trial, in which previously untreated patients received radiotherapy alone or with weekly cetuximab. Among these patients, 41% were p16-positive.

Patients who were p16-positive had longer overall survival whether they received radiotherapy alone (hazard ratio [HR] = 0.40, 95% confidence interval [CI] = 0.21–0.74) or with cetuximab (HR = 0.16, 95% CI = 0.07–0.36). Locoregional control and progression-free survival were also improved among p16-positive vs p16-negative patients.

Effect of Cetuximab

Compared with patients receiving radiotherapy alone, outcomes were at least numerically better in those receiving cetuximab and radiotherapy among both p16-positive patients (eg, hazard ratio [HR] = 0.31, 95% CI = 0.11–0.88, for locoregional control; HR = 0.38, 95% CI = 0.15–0.94, for overall survival) and p16-negative patients (HR = 0.78, 95% CI = 0.49–1.25, for locoregional control; HR = 0.93, 95% CI = 0.59–1.48, for overall survival). There was no significant interaction between p16 status and treatment effect for locoregional control (P = .087) or overall survival (P =.085). Similar trends were observed among 49 patients with p16-positive/human papillomavirus–positive disease and 14 who were p16-positive/human papillomavirus–negative.

The investigators concluded: “p16 status was strongly prognostic for patients with [oropharyngeal cancer]. The data suggest that the addition of cetuximab to [radiotherapy] improved clinical outcomes regardless of p16 or HPV status versus [radiotherapy] alone.”

The study was supported by ImClone Systems, Eli Lilly, Bristol-Myers Squibb, and Merck KGaA.

James A. Bonner, MD, of University of Alabama at Birmingham Comprehensive Cancer Center, is the corresponding author of the Journal of Clinical Oncology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.