Stereotactic Post-operative Radiotherapy for Intraparotid Metastatic Cutaneous Squamous Cell Carcinoma

This study is a phase II randomized trial where patients will be randomized in a 1:2 ratio to standard of care treatment with conventional fractionation PORT (Arm 1) vs. ultrahypofractionated stereotactic PORT (Arm 2). Patients will be stratified by pathologic nodal status (pN1 vs. pN2-pN3) per the American Joint Committee on Cancer (AJCC) 8th edition staging and use of immunotherapy (classified as neoadjuvant immunotherapy (with or without adjuvant immunotherapy) vs. planned for adjuvant immunotherapy only vs. no immunotherapy. Patients randomized to Arm 2 will be also compared to historical control data for primary endpoint of tumor local control at 2-years. The objective of this study is to assess the clinical efficacy, toxicity and QOL of ultra-hypofractionated SABR compared to conventional fractionation for adjuvant radiation following resection of locally advanced, node-positive cutaneous SCC of the head and neck. Primary endpoint \- Tumor control within the irradiated field at 2 years following adjuvant radiation completion defined as absence of clinical, radiographic or biopsy-proven recurrence within the irradiated field Secondary endpoints * Regional recurrence * Disease-free survival (DFS) * Overall survival (OS) * Rate of salvage treatment (surgery in the ipsilateral neck) and freedom from unsalvageable recurrence in the ipsilateral parotid gland or neck * Radiation-associated toxicity based on the Common Terminology Criteria for Adverse Events(CTCAE) version 5.0 * Patient-reported outcomes using the MD Anderson Symptom Inventory for Head and Neck Cancer (MDASI-HN) and the EuroQOL 5-Dimension 5-Level (EQ-5D-5L) questionnaires