Prognostic value of p16 status on the development of a complete response in involved oropharynx cancer neck nodes after cisplatin based chemoradiation – a secondary analysis of NRG Oncology RTOG 0129

Publication date: Available online 28 May 2016
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Thomas J. Galloway, Qiang (Ed) Zhang, Phuc Felix Nguyen-Tan, David I. Rosenthal, Denis Soulieres, André Fortin, Craig L. Silverman, Megan E. Daly, John A. Ridge, J Alexander Hammond, Quynh-Thu Le
PurposeTo determine the relationship between p16 status and the regional response of patients with node positive oropharynx cancer treated on Study XXXX.Materials and MethodsPatients with N1-N3 oropharynx cancer and known p16 status who underwent treatment on Study XXXX were analyzed. Pathologic complete response rates in patients treated with a post-chemoradiation neck dissection (with p16-positive or p16-negative cancer) were compared by Fisher's exact test. Patients managed expectantly were compared to those treated with a neck dissection.ResultsNinety-nine of 292 (34%) of patients with node positive oropharynx cancer and known p16 status underwent a post-treatment neck dissection (p16-positive: n=69 and p16-negative: n=30). The remaining 193 patients with malignant lymphadenopathy at diagnosis were observed. Neck dissection was performed a median of 70 (range 17 - 169) days after completion of chemoradiation. Neither the pre-treatment nodal stage (p=0.71) nor the post-radiation, pre-neck dissection clinical/radiographic neck assessment (p=0.42) differed by p16 status.A pathologic complete response (pCR) was more common among p16-positive patients (78%) than p16-negative patients (53%, p=0.02) and was associated with a reduced incidence of local-regional failure (HR 0.33, p = 0.003). On multivariate analysis (MVA) of local-regional failure a test for interaction between pCR and p16 status was not significant (p = 0.37).One-hundred-ninety-three of 292 (66%) of initially node positive patients were managed without a post-treatment neck dissection. Development of a clinical CR was not significantly influenced by p16-status (p = 0.42). Observed patients with a clinical nodal CR had disease control outcomes similar to patients with a pCR neck dissection.ConclusionsPatients with p16-positive tumors had significantly higher complete pathologic response and locoregional control rates than those with p16-negative tumors.

Teaser

This second analysis of XXXX investigates the role of post-treatment neck dissection in the management of node positive oropharynx cancer managed with primary chemoradiation. Patients treated on protocol were imaged 6-8 weeks after the completion of chemoradiation and post-treatment neck dissection was recommended for those with advanced stage (N2-N3) at diagnosis. p16-positive tumors are significantly more likely to develop a complete pathologic response. Many patients were ultimately observed, without increased regional failure.


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