Prognostic Significance of Post-Treatment PET/CT Following Salvage Re-irradiation of Head and Neck Cancers

Tawee Tanvetyanon, MD, MPH; Tapan A. Padhya, MD; Judith C. McCaffrey, MD; Julie A. Kish, MD; Jimmy J. Caudell, MD, PhD; Andy Trotti, MD; and Edward A. Eikman, MD
Published: Monday, Mar 07, 2016
Tawee Tanvetyanon, MD, MPH

About the lead author:

Tawee Tanvetyanon, MD, MPH
Moffitt Cancer Center
Tampa, FL

Expert’s Perspective

Megan E. Daly, MD
Megan E. Daly, MD
Department of Radiation Oncology
UC Davis Medical Center


Why is this article contemporary?

Re-irradiation is an increasingly employed strategy for locally recurrent head and neck cancer, and in select cases may result in long-term disease-free survival. However, disease surveillance following re-irradiation poses several unique challenges. Following de novo radiation for primary head and neck cancer, the utility of imaging modalities that may augment physical exams is well-studied. Positron emission tomography and computed tomography (PET/CT) scanning has a negative predictive value in excess of 90% in this setting, and provides valuable prognostic information to patients and physicians. Although it is tempting to extrapolate these results, the increased tissue inflammation and necrosis, and the increased risk of distant metastases following re-irradiation, could complicate imaging interpretation, and the performance of PET/CT following re-irradiation has not been thoroughly evaluated.

In the present study, the authors explore the prognostic significance of PET/CT following re-irradiation in a cohort of recurrent head and neck cancer patients. They identify a positive predictive value for PET/CT of >95%, suggesting PET/CT may be a valuable component of surveillance in this setting. Evidence-based surveillance algorithms are lacking for many cancer types, and in an era of value-based care, well-designed studies that demonstrate the value of specific imaging studies are needed. This study is an important first step in assessing the utility of PET/CT following re-irradiation for recurrent head and neck cancer.

Abstract

Objective

Positron emission tomography/computed tomography (PET/CT) has been widely used to assess tumor response following chemoradiotherapy of head and neck cancer. In general, a negative post-treatment PET/CT is associated with a good prognosis. Nevertheless, in the setting of re-irradiation, an increasingly adopted salvage treatment modality, this association remains unclear. In this report, we explored the prognostic significance of PET/CT following re-irradiation.

Materials and Methods

The records of patients who underwent re-irradiation for recurrent or new primary head and neck cancer as well as PET/CT scans before and at 1.5 to 4.0 months after treatment were reviewed. Re-irradiation was given with intensity-modulated radiation therapy at a median dose of 60 GY with a cumulative dose of 130 GY. Concurrent chemotherapy was given in all but three patients. Semi-quantitative analyses of PET/CT were re-performed. Metabolic response was assessed using PET response criteria in solid tumors (PERCIST) criteria.

Results

Included for analyses were 54 patients; 16 patients (30%) had a negative post-treatment PET/CT and 38 patients (70%) had a positive scan. At a median follow-up time of 55 months, 44 patients had died. Among those with negative PET/CT, the median overall survival was 38.7 months, compared with 9.4 months among those with positive PET/CT (P <.001), corresponding to estimated 5-year survival rates of 42.2% and 3.6%, respectively. The positive predictive value of PET/CT for 5-year mortality was 96.4%, while the negative predictive value was 42.2%. By PERCIST criteria, a statistically significant survival advantage was observed only among patients with a complete metabolic response, but not partial metabolic response.

Conclusions

Based on our limited experiences, PET/CT after re-irradiation can be useful for prognostic purposes. Although a negative post-treatment PET/CT may not reliably portend a good prognosis, a positive PET/CT practically rules out the possibility of long-term survival.

Introduction

Re-irradiation is a well-recognized salvage therapy for head and neck cancer patients who develop recurrent disease or new primary cancer in a previously irradiated area. In the absence of distant metastatic disease, about 10 to 20% of such patients may become long-term survivors after re-irradiation, with or without salvage surgery.1-3 Data from a randomized phase III study has shown that, after a salvage surgery, treatment with adjuvant re-irradiation along with concurrent chemotherapy improves progression-free survival (PFS) when compared with observation alone.4 For this clinical scenario, therefore, the National Comprehensive Cancer Center Guideline currently recommends that re-irradiation be considered as one of the limited treatment options including additional surgery, palliative chemotherapy, or best supportive care.5


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