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PURPOSE/OBJECTIVE(S): Frameless Gamma Knife stereotactic radiosurgery (GKSRS) has become an effective supplement to frame-based, which is however sensitive to patient’s involuntary motions and prone to prolonged treatment duration. Such delays during treatment inevitably result in patient discomfort and the inability to complete intended treatment. The purpose of this study is to investigate whether active coaching during frameless GKSRS can reduce actual treatment duration. MATERIALS/METHODS: Patients treated at a single institution with frameless GKSRS from 2017 to 2020 were retrospectively identified. Beginning in 2019, all patients treated with frameless GKSRS were actively coached to prevent treatment interruptions. Patient characteristics and treatment plans were compared between the cohorts of patients treated with and without active coaching. Linear regressions between the planned and actual treatment duration of treatment sessions were performed on either cohort. ANOVA and Wilcoxon tests were used for statistical analyses with a p-value less than 0.05 considered as significant. RESULTS: Of the total 43 patients and 105 treatment sessions identified, 27 patients underwent 51 treatment sessions of frameless GKSRS with active coaching. There was no significant difference in patient characteristics and treatment plans between the two cohorts. Patients treated with active coaching underwent significantly fewer CBCTs during treatment. The median planned and actual treatment durations were 31.4 and 51.7 min for the non-coached cohort, and 38.6 and 49.8 min for the coached cohort. The results of linear regressions showed that the actual treatment duration was 1.29 and 1.56 times longer with and without active coaching, respectively, which indicated a significant reduction in the actual treatment duration with active coaching. CONCLUSION: Our results suggest that active coaching was associated with significant reductions of actual treatment duration. This simple intervention can be clinically implemented to prevent unnecessary treatment interruptions, improve patient comfort and ensure completion of treatment as prescribed during frameless GKSRS.

Traditionally, patients treated with chemoradiotherapy for node-positive oropharyngeal squamous cell carcinoma (N+ OPSCC) have undergone a planned neck dissection (ND) after treatment. Recently, negative post-treatment positron-emission tomography (PET)/computed tomography (CT) imaging has been found to have a high negative predictive value for the presence of residual disease in the neck. Here, we present the first comprehensive analysis of a large, uniform cohort of N+ OPSCC patients achieving a PET/CT-based complete response (CR) after chemoradiotherapy, and undergoing observation, rather than ND. From 2002 to 2009, 302 patients with N+ OPSCC treated with 70 Gy intensity-modulated radiation therapy and concurrent chemotherapy underwent post-treatment clinical assessment including PET/CT. CR was defined as no evidence of disease on clinical examination and post-treatment PET/CT. ND was reserved for patients withCR on either PET/CT, clinical examination, or other imaging. 260 patients (86.1%) had clinical and radiographic CRs, and underwent neck observation (rate of regional control, 97.7%; 5-year overall survival, 79.8%). The four observed patients experiencing neck recurrence had initial staging of N1 (n = 2), N2b (n = 1), and N2c (n = 1). Three of four were successfully surgically salvaged. There was no association between N stage and rate of neck recurrence (p = 0.74). 52 and 25% of patients undergoing ND had viable tumor in the neck after positive and negative PET/CT, respectively. We conclude that patients achieving CRs after chemoradiation, based on clinical and PET/CT assessment, have a high probability of regional control, with a 2.3% regional failure rate, and may be safely observed without planned ND.