Retrospective Review of Positron Emission Tomography With Contrast-Enhanced Computed Tomography in the Posttreatment Setting in Human Papillomavirus–Associated Oropharyngeal Carcinoma

Abstract

Objective To determine the value of positron emission tomography (PET) with contrast-enhanced computed tomography (CT) in assessing the need for neck dissection by retrospectively reviewing the pathology reports of patients with human papillomavirus (HPV)- associated oropharyngeal squamous cell carcinoma (SCC). Design Retrospective cohort study. Setting Tertiary medical center. Patients Seventy-seven patients with HPV-related SCC. Main Outcome Measures Seventy-seven consecutive patients with a diagnosis of HPV-related SCC who were treated with radiotherapy as the primary treatment between August 2007 and October 2010 were retrospectively evaluated for radiologic and pathologic rate of persistence of nodal metastasis after completion of definitive radiotherapy. Pretreatment and posttreatment imaging included contrast-enhanced CT and PET. Response to treatment was measured on CT, PET at standardized uptake value (SUV) thresholds of 2 and 2.5, and PET/CT by a neuroradiologist in a blinded fashion. Then, the pathology report of the patients who underwent neck dissections was reviewed for nodal status after resection and correlated with the imaging findings. Results Of the 77 patients, 67 met the study criteria, with an average follow-up PET/CT scan at 90.5 days after completion of radiotherapy. Ten patients did not undergo follow-up PET/CT imaging. Twenty patients underwent neck dissections after completion of radiation therapy. Of these 20 patients, 4 had persistent tumor and 16 did not have viable tumor. Using the final pathology report to correlate with imaging responses, CT had a negative predictive value (NPV) of 85.7% (95% CI, 48.7%-97.4%), PET with SUV thresholds of 2 had an NPV of 91.7% (95% CI, 64.6%-98.5%), PET with a cutoff SUV of 2.5 had an NPV of 85.7% (95% CI, 60.1%-96.0%), PET/CT with an SUV of 2 had an NPV of 100% (95% CI, 59.8%-100.0%), and PET/CT with an SUV of 2.5 had an NPV of 85.7% (95% CI, 48.7%-97.4%). The 47 patients who did not undergo neck dissection had a median follow-up of 26 months without an isolated neck failure. Analysis of all 67 patients in the cohort revealed the following values: CT had an NPV of 95.7% (95% CI, 85.8%-98.8%), PET with an SUV of 2 had an NPV of 98.2% (95% CI, 90.4%-99.7%), PET with an SUV of 2.5 had an NPV of 95.0% (95% CI, 86.3%-98.3%), PET/CT with an SUV of 2 had an NPV of 100.0% (95% CI, 92.0%-100.0%), and PET/CT with an SUV of 2.5 had an NPV of 95.7% (95% CI, 85.8%-98.8%). Conclusions Positron emission tomography combined with contrast-enhanced CT has a better NPV than either imaging modality alone in patients with HPV-associated oropharyngeal SCC. Furthermore, PET/CT with an SUV threshold of 2 used in patients with HPV-related SCC offers an imaging modality with a high NPV that may obviate the need for unnecessary neck dissections.

Long-term results of positron emission tomography-directed management of the neck in node-positive head and neck cancer after organ preservation therapy

“…A high rate of complete pathological response in this group causes a lower PPV which to some extent is consistent with our findings. However, the PPV is still superior to CT [26] and more importantly, the NPV remains high which supports an observation policy regarding the neck in PET-negative patients [24].…”

Lessons from a standardized program using PET–CT to avoid neck dissection after primary radiotherapy for N2 squamous cell carcinoma of the oropharynx

“…Five of the studies in Table 3 do not explain if salvage was attempted in the patients with a neck recurrence [8][9][10][11][12]. Our results following PET-CT, and most of the other studies with data on salvage rate, confirm the conclusions of our 1999 report that patients who recur in the neck after RT are unlikely to be salvaged [13].…”

“…Our study has the lowest PPV of 0%-meaning that we had no case in which a patient with a positive PET-CT failed in the neck. The study by Chan and colleagues reports a PPV of 15%, which is also very low [8].…”

“…(7) No history of neck surgery before RT that could disrupt the cervical lymphatics. (8) No history of prior RT to the head and neck. (9) No history of other cancers that could confound evaluation of treatment for oropharyngeal cancer.…”

PET/CT Imaging and Human Papilloma Virus–Positive Oropharyngeal Squamous Cell Cancer: Evolving Clinical Imaging Paradigm

“…Chan et al (66) studied 77 patients with HPV-positive OPSCC who underwent contrast-enhanced PET/CT after radiotherapy as the primary treatment. The authors showed that enhanced PET/CT has a better negative predictive value than either enhanced CT or nonenhanced PET/CT alone in patients with HPV-positive OPSCC.…”