PHOENIX, Arizona — Positron emission tomography (PET) can identify patients with p16-positive oropharynx cancer (OPC) who are suitable for therapy de-escalation, according to a recent prospective study.
After 2 weeks of treatment, about half of patients demonstrated a reduction in metabolic tumor volume (MTV) of 50% or more on fluorodeoxyglucose (FDG) PET and had their radiotherapy de-escalated.
The research, presented at the 2022 Multidisciplinary Head and Neck Cancers Symposium on February 24, showed that de-escalation was associated with a notable reduction in adverse events: less weight loss, reduced need for a feeding tube, and improved swallowing over a 3-month follow-up.
"Advanced imaging helps physicians personalize therapy based on patients' individual tumor characteristics and response to treatment," Steven Allen, MD, PhD, Department of Radiation Oncology, University of Michigan, Ann Arbor, said in a release. "By incorporating FDG-PET scans before and midway through treatment, we were able to adjust the radiation dose for about half of our patients and reduce their short-term side effects while still focusing on tumor control."
The idea of radiotherapy de-escalation for oral cancer patients has long been a topic of debate.
A 2021 phase 3 trial reported by Medscape Medical News showed that radiotherapy de-escalation for patients with oral cancer can result in robust responses and lower toxicity. This finding aligned with the results of another recent trial that found, following successful surgery, patients can reduce adjuvant radiotherapy and skip chemotherapy altogether while still maintaining excellent 2-year progression-free survival.
Previous studies have also demonstrated that markers on FDG-PET taken pre- and mid-treatment are prognostic for treatment response in patients with p16-positive OPC.
However, the current phase 2 trial of patients with p16-positive OPC receiving standard radiotherapy plus chemotherapy is the first trial to assess FDG-PET as a mid-treatment imaging marker for de-escalation.
The authors recruited 59 patients with stage I or II p16-positive OPC who had avid FDG uptake and excluded those with matted lymph nodes or a history of head and neck surgery.
Participants had a median age of 60 years, 88% were male, and about half were never smokers. All patients received weekly carboplatin/paclitaxel chemotherapy alongside standard 70 Gy radiotherapy given over 35 fractions.
Those with a low MTV on pre-treatment FDG-PET and a reduction in MTV of at least 50% after 2 weeks of treatment were de-escalated to a total radiotherapy dose of 54 Gy in 27 fractions.
The team found that almost 50% of the patients (n = 28) met the criteria for de-escalation, and received about 25% less radiation exposure compared with those who stayed on the standard dose.
Compared with baseline, de-escalated patients lost significantly less weight than those who remained on the standard dose, at 6% vs 11% (P < .001), and required fewer feeding tube placements, at 1 vs 7 (P = .037).
The team reported that, compared with baseline, patients in the reduced-dose group showed significant improvements in swallowing function at 3 months (P = .036).
The researchers also observed improvements in scores on 4 patient-reported outcome surveys, but those did not reach statistical significance.
Overall, "we anticipated long-term improvements in side effects, but the short-term improvements were better than expected," senior author Michelle L. Mierzwa, MD, also from the University of Michigan, said in a press release.
The study is supported in part by an NIH/NCI grant. The authors have disclosed no relevant financial relationships.
2022 Multidisciplinary Head and Neck Cancers Symposium: Abstract 1. Presented February 24, 2022.
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Cite this: Liam Davenport. Imaging Identifies Candidates for Oropharynx Cancer De-escalation - Medscape - Mar 01, 2022.