Use of FDG-PET/CT Response Evaluation after Chemoradiotherapy in HPV+ Oropharyngeal Cancer

Abstract

Objectives:

Evaluate the use of 3-month positron emission tomography (PET)/computed tomography (CT)–response assessment post-chemoradiotherapy (CRT) in predicting locoregional failure (LRF) in HPV+ oropharyngeal cancer (OPC).

Methods:

101 consecutive patients with stage III/IV HPV+ OPC who received definitive carboplatin/paclitaxel-based CRT from 2005-2010 and underwent PET/CT pre-treatment and at 3-months post-therapy were retrospectively identified. PET/CT-response was reported as complete (CR), near-complete (nCR), or partial (PR); nCR was classified as CR at the primary site and as PR in the neck. CT-response for the neck was graded per RECIST-1.1. Test characteristics for predicting 3-year local failure (LF) and regional failure (RF) were calculated.

Results:

Among 98 patients with an evaluable primary, LF occurred in 2/67 patients with CR, 0/20 with nCR, and 1/11 with PR. For LF, PET/CT demonstrated 88% accuracy, 33% sensitivity, 90% specificity, 9% positive predictive value (PPV), and 98% negative predictive value (NPV). Among 91 patients with evaluable necks by RECIST, RF occurred in 6/67 with CR, 2/11 with nCR, and 0/7 with PR. For RF, PET/CT demonstrated 76% accuracy, 25% sensitivity, 81% specificity, 11% PPV, and 92% NPV, which compared favorably with CT characteristics of 56%, 38%, 45%, 6%, and 88%, respectively. Quantitative SUVmax thresholds did not improve the predictive accuracy of 3-month PET/CT for LRF. Overall, PET/CT surveillance was 92% and 89% accurate for detecting LF and RF.

Conclusions:

In this largest reported study to-date of post-CRT response assessment by PET/CT for HPV+ OPC, 3-month PET/CT demonstrated high negative predictive value for LRC. PET/CT surveillance was highly accurate for detecting LRF.