Factors associated with detection of oligometastatic recurrence and outcome following definitive (Chemo)radiotherapy for oropharyngeal carcinoma

PURPOSE/BACKGROUND: We aim to describe characteristics and patterns of detection of distant metastasis (DM) and subsequent outcomes following definitive (chemo)radiotherapy [(C)RT] for oropharyngeal cancer (OPC). MATERIAL/METHODS: OPC patients who developed DM after initial complete response to (C)RT from 2010 to 2020 were included. DM were classified as oligometastases (≤5 lesions) vs polymetastases. Interval from prior normal surveillance imaging to DM detection was recorded. Multivariable analysis (MVA) was performed for overall survival (OS) after DM. RESULTS: A total of 124 patients were eligible. Most (116/124, 94 %) developed DMs within the thorax, of whom 72 (58 %) had thorax only DM. Oligometastases (n = 46) vs polymetastases (n = 78) were more commonly detected without DM-related symptoms (76 % vs 55 %, p = 0.003) and identified with shorter interval from previous normal imaging (median 7.9 vs 12.7 months, p = 0.030). Median follow-up from DM diagnosis was 31.5 months. Three-year OS after DM was higher for patients with oligometastases vs polymetastases (32 % vs 5 %, p < 0.001). Patients with oligometastases who received salvage therapy had a longer 3-year OS (vs not) (63 % vs 7 %, p < 0.001). On MVA, salvage therapy (Hazard Ratio [HR) 0.32, p = 0.005), HPV + status (HR 0.50, p = 0.002) and thorax only distant metastases (HR 0.64, p = 0.034) were associated with longer OS. CONCLUSIONS: Nearly one-third of first DM in OPC following initial complete response to (C)RT are oligometastases and most occur within the thorax. Most oligometastases are asymptomatic and more commonly detected following a shorter surveillance scan interval. DM-targeted salvage therapy for oligometastases is associated with longer OS. Prospective studies refining surveillance algorithms to increase detection of oligometastases in asymptomatic high-risk OPC patients are indicated.