Introduction: Oropharyngeal squamous cell carcinoma (OPSCC) incidence has increased over the past two decades largely because of an increase in human papilloma virus (HPV)-related OPSCC. We report here outcomes of definitive radiation therapy for OPSCC with simultaneous integrated boost intensitymodulated radiotherapy (IMRT) in a regional Australian cancer centre. Methods: We retrospectively reviewed electronic medical records (EMR) of all patients treated with IMRT for head and neck cancer. We included patients who received a curative intent IMRT for OPSCC (2010)(2011)(2012)(2013)(2014). Results: Of 61 patients, 80% were men, and the median age was 57 years. Ninety percent of our patients received concurrent systemic therapy, and 68% were p16 positive. The median radiotherapy dose received was 70 Gy in 35 fractions. The median follow up for surviving patients was 22 months. Twenty-four month actuarial data show that the loco-regional recurrence free, metastasis-free MFS, cancer-specific (CaSS) and overall survival percentages were 98.3%, 92.6%, 91% and 90.3%, respectively. We did not observe grades 4 or 5 acute or late toxicities, and 10 patients (16.2%) exhibited persistent grade 3 toxicity 6 months after completing the treatment. Conclusion:The results from curative IMRTs for OPSCC delivered in a regional cancer centre are comparable with results published by tertiary referral centres. A long-term follow up of this patient cohort will continue for further analyses and comparisons with tertiary centres.

Introduction: Evidence-based Australian guidelines (eviQ) recommend adjuvant supraclavicular fossa irradiation after axillary lymph node dissection (ALND) in node-positive breast cancer patients. Disparity between surgically determined versus computed tomography (CT) determined nodal volumes may result in discontiguous nodal volumes and untreated nodal tissue. We examine the extent of untreated nodal tissue in women with breast cancer post-level II or III ALND and adjuvant radiation therapy (RT) using ESTRO contouring guidelines. Methods: Female breast cancer patients who underwent level II and III ALND with apical clip placement from 2016 to 2020 and CT simulated in supine position were included. CT-defined axillary level II-IV volumes were contoured using ESTRO guidelines. The distance between the apical clip and RT nodal volumes was measured to indicate extent of untreated tissue. Results: Of 34 eligible patients treated by 7 surgeons, 76% had level II ALND and 24% level III ALND. Only 5.9% of clips entirely encompassed the corresponding RT nodal volumes. 55.9% of clips fell within and 44.1% fell inferolaterally outside the corresponding RT nodal volumes. A median 3.6 cm (range 0-7.5 cm) of undissected nodal tissue would not be included within standard RT target volumes following eviQ recommendations. Conclusion: There is a disparity between surgically determined versus CT determined axillary nodal volumes, leading to discontiguous nodal volumes and untreated axillary nodal tissue, despite following standard radiation contouring guidelines. Intraoperatively placed apical axillary clips may assist radiation oncologists to accurately delineate undissected nodal tissues at risk.