Abstract Book

S139

ESTRO 37

measures include 2 year local control (LC), regional control (RC), distant metastasis free survival (DMFS), and overall survival (OS), and patient reported symptoms (PRO-CTCAE) and quality of life (EORTC QLQ-C30 & H&N35). Data analysis was peformed for patients with a minimum of 1 year of follow-up. Results 113 patients have enrolled with 82 having a minimum follow-up of 1 year. Smoking status was as follows: 49% never, 35% ≤ 10 pack years, and 16% > 10 pack years. Forty-four percent were HPV and p16 positive and 56% were HPV negative/unknown and p16 positive. Post- treatment PET/CT complete response rate was 97% at the primary site and 81% in the neck. Eight patients had planned neck dissection with 1 having pathological residual disease. Two year PFS, LC, RC, DMFS, CSS, and OS were the following: 93%, 98%, 99%, 95%, 96%, and 95%. 16 patients were treated with RT alone and all remain in cancer control. Mean pre- and 1-year post-treatment EORTC QOL scores were: Global 79/82 (lower worse), Swallowing 8/12 (higher worse), Dry Mouth 15/55 (higher worse), and Sticky Saliva 10/33 (higher worse). 39% of patients required a feeding tube (none permanent) for a median of 10.5 weeks (range 3-42 weeks). Mean pre- and 1 year post-treatment PRO-CTCAE (0 to 4 scale, higher worse) scores were: Swallowing 0.5/0.9 and Dry mouth 0.5/1.6. There were no ≥ Grade 3 late adverse events. Conclusion Initial clinical outcomes with highly de-intensified CRT are excellent in favorable risk OPSCC with evidence of better preservation of quality of life as compared to standard therapies (ClinicalTrials.gov, NCT02281955). OC-0274 Effect of radiotherapy technique/fractionation on 2-year primary local control in the PET-NECK study C.T.K. Fong 1 , C. McConkey 2 , P. Sanghera 1 , A. Hartley 1 , J.K. Rahman 2 , C. Nutting 3 , H. Al-Booz 4 , M. Robinson 5 , H. Mehanna 6 1 Queen Elizabeth Hospital Birmingham, Hall-Edwards Radiotherapy Research Group, Birmingham, United Kingdom 2 University of Warwick, Clinical Trials Unit, Warwick, United Kingdom 3 Royal Marsden Hospital, Cancer Institute, London, United Kingdom 4 Bristol Haematology and Oncology Centre, Oncology, Bristol, United Kingdom 5 Weston Park Hospital, Oncology, Sheffield, United Kingdom 6 University of Birmingham, Institute of Head and Neck Studies and Education, Birmingham, United Kingdom Purpose or Objective The randomised phase 3 PET-NECK study demonstrated that PET-CT scan surveillance resulted in similar survival but was more cost-effective than planned neck dissection for squamous cell carcinoma of the head and neck (SCCHN) with N2 or N3 stage. In addition, the similar outcomes in overall survival and global quality of life seen in the study between the permitted radiotherapy techniques [intensity modulated radiotherapy (IMRT) vs 3D conformal radiotherapy (3D-CRT)] and between the permitted fractionations [7 week (68-70Gy/34-35# over 45-46 days) vs 6 week (60-66Gy/30# over 39 days) vs 4 week (55Gy/20# over 25 days)] has already been presented. The predominance of hypofractionated accelerated regimes and the use of synchronous chemotherapy in all patients makes the primary local control data from this study of particular radiobiological interest for ongoing and future randomised studies. Material and Methods In the 532 (94%) patients where data on technique was available: 200 (38%) received 3D-CRT and 332 (62%) received IMRT. In the 525 patients where fractionation

data was available: 181 (34%), 288 (55%), and 56 (11%) patients received 68-70 Gy in 34-35 fractions (#), 60-66 Gy in 30#, and 55Gy in 20# respectively. Baseline characteristics including treatment arm, timing of neck dissection, chemotherapy regime, age, sex, T stage, N stage, performance status, smoking status, and alcohol status were not significantly different between the two treatment technique cohorts and between the three fractionation cohorts. However, there were significantly fewer 3D-CRT patients with oropharyngeal cancer (79% vs 88% p=0.014) and there were significantly more patients in the 55Gy/20# cohort when compared with the 6 and 7 week cohorts (48% vs 16% vs 30%). 2-year local control was examined by each of the technique and fractionation cohorts, and by p16 status which was available in 424 (80%) of the 532 patients with available data on technique and 417 (79%) of the 525 patients with available data on fractionation. Results 2-year primary local control in p16+ve patients was 95% (95% confidence intervals: 91-99%) vs 93% (89-97%) for 3D-CRT (n=118) vs IMRT (n=206). The corresponding figures for p16-ve patients were 78% (66-91%) vs 76% (63- 88%), (n=45 vs n=55). In p16+ve patients receiving 4 week (n=25) vs 6 week (n=193) vs 7 week (n=98) fractionations, the 2-year primary local control was 87% (74-100%) vs 95% (92-98%) vs 92% (86-97%). The corresponding figures for p16-ve patients were 85% (69-100%) vs 80% (66-93%) vs 74% (59-88%) (n=23 vs n=37 vs n=41). No significant differences were observed in any of these comparisons. Conclusion The 2-year primary local control outcomes seen in this study support the continued examination of accelerated hypofractionation in the ongoing CompARE and HYPNO prospective randomised trials. This data may also be useful in further modifying radiobiological models for the addition of synchronous chemotherapy to radiotherapy. OC-0275 Comprehensive toxicity profiles in HN cancer patients treated with radiotherapy: a benchmark study L. Van den Bosch 1 , A. Van der Schaaf 1 , H.P. Bijl 1 , J.G.M. Vemer-van den Hoek 1 , O. Chouvalova 1 , M.C.A. Kramer 1 , R.J.H.M. Steenbakkers 1 , J.A. Langendijk 1 1 University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands Purpose or Objective The purpose of this prospective cohort study was to determine comprehensive toxicity risk profiles (CITOR) in head and neck cancer (HNC) patients treated with primary radiotherapy with or without systemic treatment. Material and Methods This population-based prospective cohort study was composed of 750 HNC patients treated between 2007 and June 2016. All patients were enrolled into a prospective data registry in which physician-rated toxicities (CTCAE v4.0) were prospectively collected weekly during treatment and at regular intervals up to 5 years thereafter. Toxicity prevalence for all patients as well as for 4 subgroups was analyzed. Subgroups were defined based on stage (early: stage I-II vs. advanced: stage III-IV) and tumor location (proximal: nasopharynx, oropharynx, oral cavity vs. distal: hypopharynx and larynx). Toxicity patterns of individual patients were identified as persistent low (grade 0-1), decreasing, persistent high (≥ grade 2) or progressive, by comparing the toxicity grade near the end of treatment with the last recorded toxicity grade during follow up. The recovery percentage was calculated as the number of patients with a decreasing pattern divided by the number of patients with a decreasing, persistent high or progressive pattern. Results The compliance rate was high, i.e. 96% for acute (week 1 to 12) and 88% for late (month 6 to 60) toxicity scoring.