3574 - Ablative Thoracic Radiotherapy in the Context of Systemic Therapy for HPV-Positive HNSCC Distant Metastases
Presenter(s)
M. H. Nehmeh1, Z. Zhang2, A. Horn1, D. Y. Gelblum3, A. Shamseddine3, Y. Yu3, N. Riaz3, S. M. McBride3, C. B. Simone II4, A. J. Wu3, D. Billing3, T. L. Chaunzwa3, P. Iyengar3, D. R. Gomez3, N. Shaverdian3, N. Y. Lee3, and J. Ma3; 1Memorial Sloan Kettering Cancer Center, New York City, NY, 2Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, 3Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 4New York Proton Center, New York, NY
Purpose/Objective(s): Thoracic metastases are a common site of distant failure in HPV-positive head and neck squamous cell carcinoma (HNSCC) and increasingly managed with radiotherapy (RT), yet optimal RT dose and fractionation regimens remain unclear. We hypothesized that ablative thoracic RT (BED =100 Gy) would improve failure-free survival and investigated the impact of systemic therapy (ST) on outcomes.
Materials/Methods: Retrospective single-institution analysis was performed for patients with treated with RT for lung metastases from HPV+ OPC with 3-month landmark after RT completion. Univariable and multivariable Cox analyses were performed for composite endpoints (recurrence/progression or death) of lesion-level in-field RFS (IFRFS), intrathoracic recurrence-free survival (ITRFS), and distant metastasis (DM).
Results: We identified 71 patients with 127 irradiated intrathoracic lesions. Median KPS 80 (IQR 80, 90), median RT dose 45 Gy (IQR 27-50) and median BED 59 Gy (IQR 51, 100). Most patients (67%) had intrathoracic disease only at time of RT. ST was delivered within 3 weeks of RT in 51 patients (40%) and 35 patients (28%) received ST within 3 months post-RT. Median follow-up was 19.5 months (IQR 9, 31) and median overall survival was 31 months. On multivariable Cox analysis, receipt of post-RT chemotherapy was independently associated with worse outcomes (HR 4.67, p<0.001), whereas delivery of BED =100 was associated with improved outcomes (HR 0.51, p=0.029). Additionally, patients with lung/mediastinal lymph node–only metastases at the time of RT had significantly improved outcomes (HR 0.39, p<0.001). On landmark analysis, BED=100 was associated with significantly better outcomes: ITRFS HR 0.41 (0.20–0.82, p=0.013), IFRFS HR 0.35 (0.23–0.61, p<0.001). Post-RT ST was linked to worse outcomes: DM HR 2.89 (1.04–8.05, p=0.042), ITRFS HR 3.46 (1.76–6.80, p<0.001), IFRFS HR 3.20 (1.98–5.17, p<0.001).
Conclusion: In this HPV+ HNSCC thoracic metastasis cohort, ablative BED=100 was consistently associated with improved in-field and intrathoracic recurrence free survival. Post-RT systemic therapy use and nodal metastases was associated with poorer outcomes, while patients with lung-only metastases had better outcomes. The role of ablative RT (BED =100) within the broader context of systemic therapy sequencing warrants further study to optimize patient selection.