By Bhisham Chera MD, FASTRO, Medical University of South Carolina
Investigators from the University of Michigan presented data from a phase II trial evaluating the utility of mid-treatment FDG-PET/CT to guide the use of de-intensified chemoradiotherapy. Patients with AJCC 8th edition stage I-II HPV-associated OPSCC with pre-treatment FDG-PET-avidity were enrolled. Over 50% of patients were smokers. All patients had a radiation plan for 70 Gy and 35 fractions with concurrent weekly carbo/taxol and at 20 Gy had a mid-treatment PET/CT. Those patients who had ≥50% reduction in metabolic tumor volume stopped treatment at 54 Gy and the others completed the entire course of 70 Gy. The primary endpoint was non-inferiority of two-year locoregional recurrence (LRR) in the entire cohort compared to an institutional historic control; the two-year LRR for the entire cohort was 6.8% and the trial did meet its primary endpoint. The two-year LRR for the two different cohorts was 4.6% in the 70 Gy cohort and 9.4% in the 54 Gy cohort; however, this represents only two and three failures, respectively. In general, toxicity was lower in the 54 Gy cohort, and the DHT rate was low and similar between both cohorts.
Not included in the abstract but presented in the podium presentation was that early patient reported outcomes at one month were better in the 54 Gy cohort with most patients returning to baseline at one year.
The authors conclude that “FDG-PET based de-escalated chemoradiation appears feasible and may improve both objective and subjective toxicity metrics.” Better patient selection by using multimodality imaging (e.g., FDG, FMISO, MRI) and companion biomarkers (e.g., ctHPVDNA) may also improve the efficacy of de-intensification.
Abstract 16 - FDG-PET-based Selective De-escalation of Radiotherapy for HPV-Related Oropharynx Cancer: Results from a Phase II Trial was presented during the Plenary II session at the 2024 Multidisciplinary Head and Neck Cancers Symposium on March 1, 2024.
