ESTRO 2021 Abstract Book

S819

ESTRO 2021

Conclusion The study presents 33 fractions with SIMB using IG-IMRT helical approach may be a practical option in treating nasopharyngeal carcinoma and it showed comparable results in terms of survival, treatment related side effect and response compared with the standard 35 fractionation. PO-0986 Radiotherapy versus Surgery in Early Stage HPV-positive Oropharyngeal Cancer D. KIM 1 , H. Wu 1 , J.H. Kim 1 , S. Ahn 2 , E. Chung 2 , K. Eom 3 , Y.H. Jung 4 , W. Jeong 4 , T. Kwon 5 , S. Kim 6 , C.W. Wee 6,6 1 Seoul National University Hospital , Radiation Oncology , Seoul, Korea Republic of; 2 Seoul National University Hospital , Otorhinolaryngology-Head and Neck Surgery, Seoul, Korea Republic of; 3 Seoul National University Bundang Hospital , Radiation Oncology , Seongnam, Korea Republic of; 4 Seoul National University Bundang Hospital , Otorhinolaryngology-Head and Neck Surgery, Seongnam, Korea Republic of; 5 SMG-SNU Boramae Medical Center, Otorhinolaryngology-Head and Neck Surgery, Seoul, Korea Republic of; 6 SMG-SNU Boramae Medical Center, Radiation Oncology , Seoul, Korea Republic of Purpose or Objective To compare the outcomes of upfront radiotherapy (RT) versus surgery in early stage human papilloma virus- positive oropharyngeal squamous cell carcinoma (hpv+OPC), and investigate for preoperative clinical factors that can predict requirement for postoperative adjuvant treatment. Materials and Methods A multicenter study including 166 patients with AJCC 8 th ed. stage I–II hpv+OPC was conducted. Patients who received induction chemotherapy or cetuximab-based concurrent chemoRT (CCRT) were excluded. Patients with a single lymph node (LN) metastasis >3cm or multiple LN metastases treated with RT without chemotherapy were also excluded. Sixty (36.1%) and one-hundred six (63.9%) patients received upfront (CC)RT and surgery, respectively. Seventy-eight (73.6%) patients in the surgery group received postoperative (CC)RT. Results With a median follow-up of 45.6 months for survivors, the 2-year overall survival (OS), progression-free survival (PFS), and locoregional control (LC) for (CC)RT/surgery were 97.8%/96.4% ( P =0.755), 91.1%/92.0% ( P =0.810), and 92.9%/93.3% ( P =0.721), respectively. In multivariate analyses, patients showing synchronous radiologic extranodal extension and conglomeration (ENEcong) of metastatic LNs showed significantly poor OS ( P =0.047), PFS ( P =0.001) and LC ( P =0.003). In patients undergoing upfront surgery, the number of 2 or more clinically positive LN metastases (OR, 5.15; P =0.004) and LN metastases with ENEcong (OR, 3.75; P =0.009) were predictors for postoperative CCRT. No patient in the (CC)RT group demonstrated late severe toxicity whereas 3 (2.8%), 1 (0.9%), and 1 (0.9%) patients in the surgery group showed grade 3 dysphagia, grade 3 xerostomia, and fatal oral cavity bleeding. Conclusion We found no differences in OS, PFS, and LC between (CC)RT vs. surgery as initial treatment in stage I–II hpv+OPC which warrants comparison via a prospective trial in the treatment de-escalation era. However, most early stage hpv+OPC patients undergoing surgery received adjuvant (CC)RT. Pretreatment LN findings were prognostic, and also predictive for adjuvant treatment. PO-0987 Evaluation of swallowing function using PSS-HN scale for head-neck cancer patients undergoing IMRT P. Mukherjee 1 , S. Agarwal 2 , N. Kalyani 3 , M. Roy 4 , A. Doshi 5 , S. Kommineni 5 , R. Patel 6 1 Jaslok Hospital and research centre, Radiation Oncology, mumbai, India; 2 Jaslok Hospital and Research centre, Radiation Oncology, mumbai, India; 3 Jaslok Hospital and Research , Radiation Oncology, MUMBAI, India; 4 Jaslok Hospital and Research Centre, Radiation Oncology , Mumbai , India; 5 Jaslok Hospital and research Centre, Radiation Oncology, Mumbai, India; 6 Jaslok Hospital and Research Centre, Radiation