Main Session
Sep
28
SS 09 - Head and Neck 1: Highest-Rated Abstracts for Virally-Mediated Head and Neck Cancer
156 - Long-Term Outcomes Following Substantial De-Escalation of Elective Radiotherapy Dose and Volume in Patients Treated with Definitive Chemoradiotherapy for HPV-Associated Oropharyngeal Cancer
Presenter(s)
Amir Safavi, MD, MSc - Memorial Sloan Kettering Cancer Center, New York, NY
A. H. Safavi1, E. C. Dee1, C. J. Tsai2, Y. Wu3, S. McBride1, D. Gelblum1, Y. Yu1, L. Chen1, K. Zakeri1, A. Shamseddine1, J. J. Kang4, J. Cracchiolo5, R. J. Wong5, M. Cohen5, I. Ganly5, L. Dunn6, A. Ho6, E. Sherman6, N. Riaz1, and N. Y. Lee1; 1Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 2Princess Margaret Cancer Centre, Toronto, ON, Canada, 3Memorial Sloan-Kettering Cancer Center, New York, NY, 4Yale University Department of Radiation Oncology, New Haven, CT, 5Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, 6Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s):
Major de-escalation of elective radiotherapy (RT) dose and volume for human papillomavirus (HPV)-associated oropharyngeal cancer (OPC) maintains two-year disease control while achieving excellent quality-of-life profiles. We sought to determine if this approach sustains oncologic efficacy and favorable swallowing ability five years following definitive concurrent chemoradiotherapy (CCRT).Materials/Methods:
This single-institution retrospective cohort study included consecutive patients treated at least five years prior to this analysis. All patients underwent PET-CT and MRI staging. HPV diagnosis was confirmed by both p16 immunohistochemistry and HPV-RNA in-situ hybridization. Elective volumes consisting of nodal levels and at-risk regions surrounding gross disease were treated to 30 Gy in 15 fractions. Cone-down volumes (gross disease without expansion) were sequentially boosted to 70 Gy in 35 fractions. Level VII in the node-negative neck and uninvolved levels IB and V bilaterally were omitted. Locoregional control (LRC) was the primary outcome estimated using cumulative incidence functions with death as a competing risk. Overall (OS), progression-free (PFS), and distant metastasis-free survival (DMFS) were secondary outcomes estimated using Kaplan-Meier method. MD Anderson Dysphagia Index (MDADI) scores were obtained at each visit where available and compared to baseline using sign test; a clinically meaningful change (CMC) was 10 points.Results:
From 2017-2019, 276 patients underwent CCRT; 172 (62.3%) received 300 mg/m2 high-dose cisplatin. Stage distribution included 87 (31.5%) patients with cT3-4 and 65 (23.5%) with cN2-3 disease (AJCC 8th Edition). With 64 months (IQR 50-74) median follow-up, 60-month LRC was 97.0%; OS 90.8%; PFS 85.9%, and DMFS 91.2%. No locoregional (LR) failures occurred after 18 months or in omitted nodal levels. One solitary elective nodal failure (1/276 patients [0.4%]) occurred at 6 months; this involved node, present but unidentified at diagnosis, received 30 Gy elective instead of 70 Gy gross disease dose. All remaining LR failures occurred within 70 Gy volumes. Two patients (0.7%) were feeding-tube dependent for 12+ months. Mean (SE) MDADI composite scores were: baseline 90.1 (0.86); 6 months 79.1 (1.1); 12 months 85.7 (1.3); 24 months 88.2 (1.3); 36 months 90.9 (1.7); 48 months 91.0 (1.8); and 60 months 92.2 (1.5). Long-term MDADI scores returned to baseline (p>0.05), following a decline at 6 months (p<0.001 and CMC).Conclusion:
Long-term outcomes affirm durable oncologic efficacy and return to baseline swallowing ability following substantially de-escalated elective RT. Confirmatory phase III data will help establish this approach as the new standard-of-care with definitive CCRT for HPV-associated OPC.