6012 Background: The excellent prognosis of patients with low risk HPV associated oropharyngeal squamous cell carcinoma has led to concerns about overtreatment and excessive toxicity with radiotherapy and cisplatin, leading to interest in de-intensification trials. We investigated whether cetuximab, an EGFR targeting antibody, when combined with radiotherapy would result in a decrease in symptom burden and toxicity with similar efficacy when compared to weekly cisplatin. Methods: TROG 12.01, a randomised, multicentre trial involving 15 sites in Australia and New Zealand enrolled patients with HPV associated oropharyngeal squamous cell carcinoma, AJCC 7th edition Stage III (excluding T1-2N1) or stage IV (excluding T4 and/or N3 and/or N2b-c if smoking history >10 pack years and/or distant metastases). Patients were randomised (1:1) to receive radiotherapy (70Gy in 35 fractions) with either weekly cisplatin, 7 doses of 40mg/m2 or cetuximab, loading dose of 400mg/m2 followed by 7 weekly doses of 250 mg/m2. The primary outcome was symptom severity assessed by the MD Anderson Symptom Inventory Head and Neck Symptom Severity Scale from baseline to 13 weeks post completion of radiotherapy using the area under the time-severity curve (AUC). Sample size was 170 evaluable patients to provide at least 90% power to detect an effect size of 0.5, using a 2-sided test at 0.05 level of significance. Trial was registered on ClinicalTrials.gov: NCT01855451. Results: Between 17th June 2013 and 7th June 2018, 189 patients were enrolled and 182 were evaluable, with 92 on cisplatin arm and 90 on cetuximab included in the main analysis. The median follow-up was 4.1 years (0.4 - 5.3). Analyses were performed in all eligible randomised patients that commenced treatment (modified intention-to-treat population). There was no difference in the primary endpoint of symptom severity; difference in AUC cetuximab – cisplatin was 0.05 (95%CI: -0.19, 0.30), p= 0.66. The T-score (mean number of > grade 3 acute adverse events) was 4.35 (SD 2.48) in the cisplatin arm and 3.82 (SD 1.8) in the cetuximab arm, p= 0.108. The 3 -year failure-free survival rates were 93% (95% CI: 86-97%) in the cisplatin arm and 80% (95% CI: 70-87%) in the cetuximab arm (hazard ratio = 3.0 (95% CI: 1.2-7.7); p=0.015. The increase in failures in the cetuximab arm was evenly split between distant and locoregional failures. Conclusions: For patients with low risk HPV associated oropharyngeal cancer, radiotherapy and cetuximab had inferior failure-free survival without improvement in symptom burden or toxicity compared to radiotherapy and weekly cisplatin. Radiotherapy and cisplatin remains the standard of care. Clinical trial information: NCT01855451.
Initial Results from a Phase 2 Prospective Trial of De-intensified Chemoradiation therapy for Low-Risk HPV-associated Oropharyngeal Squamous Cell Carcinoma
