ESTRO 2020 Abstract Book

S458 ESTRO 2020

were alive. At the time of last evaluation, complete remission was assessed in 46 cases (67.6%). Locoregional relapse was recorded in 19 patients with a median time of 11 months. Distant metastases were developed in 6 patients with a median time of 7 months. The 5- and 10-year PFS were 62.7±6.5% and 53.2±8.7%, respectively. The 5- and 10-year OS were 78.9±5.5% and 61.4±9.2%, respectively. Good performance status PS, lower TNM stage, concomitant chemotherapy were significantly improving PFS. High grade (≥G2) mucositis and dysphagia, and the treatment technique with 3DCRT, although not significant, presented a deterioration of the PFS. In the multivariate Cox analysis remained significant: TNM stage, concomitant chemotherapy, PS. Good PS, concomitant chemotherapy, absence of late dysphagia were significant predictors of improved OS. Age, high TNM stage, absence of induction chemotherapy, 3DCRT technique, although not significant, resulted in an OS reduction. In the multivariate Cox analysis, concomitant chemotherapy, late dysphagia and PS remained significant. Regarding acute toxicity (mucosal, salivary, dysphagia, skin) presented a clear improvement with VMAT, with the high grade acute toxicities (≥G2) significantly most prominent in 3DCRT treated patients. The reason of the acute toxicity improvement with VMAT was supported by the dosimetric parameters of organs at risk. For example, the mean dose to the parotids averaged over the patients presenting G0-1 salivary toxicity was 35.4±2.0 Gy, to compare with the 44.6±4.8 Gy to the patients developing ≥G2 acute toxicity. The mean dose to the parotids in the 3DCRT and VMAT patients was 61.4±1.8 Gy and 28.4±0.8 Gy, respectively. The odd ratio for acute salivary toxicity, between VMAT and 3DCRT was 4.67 (p=0.02). Conclusion Significant improvement in toxicity profile was shown in patients treated with VMAT technique. Outcome significantly improved with concomitant chemotherapy and good PS, but also in patients treated with advanced technology. PO-0850 Proton Beam Reirradiation In Head And Neck Patients at CNAO: preliminary results. S. Ronchi 1 , B. Vischioni 1 , M. Bonora 1 , V. Vitolo 1 , M.R. Fiore 1 , A. Iannalfi 1 , A. Barcellini 1 , S. Molinelli 1 , S. Russo 1 , D. Maestri 1 , M. Ciocca 1 , L. Preda 2 , F. Valvo 1 1 National Center of Oncological Hadrontherapy, Radiotherapy Unit, Pavia, Italy ; 2 National Center of Oncological Hadrontherapy, Diagnostic Imaging Unit, Pavia, Italy Purpose or Objective To evaluate our initial experience in terms of clinical outcomes and toxicity in patients (pts) who underwent head and neck (H&N) reirradiation with proton therapy (PT) at National Center of Oncological Hadrontherapy (CNAO). Material and Methods Patients were treated in the phase II protocol CNAO 05/2011. Inclusion criteria were: 1) Karnofsky Performance Status ≥ 70; 2) relapse after at least 6 months from the first radiation treatment; 3) expected survival of at least 6 months; 4) no therapeutic alternatives with radical intent available; 5) no severe co-morbidities; 6) age between 14 and 75 years; 7) no distant metastases. Pts without prior documentation of H&N radiation therapy (RT) and pts treated with palliative intent were excluded. Local response and toxicity (tox) were respectively evaluated using RECIST and CTCAE v.4.0 criteria. MRI and clinical evaluation were performed after treatment every 3 months (mo.) in the first 2 years, every 6 mo. in the third year, then once a year. Results From January 2014 to July 2018, 44 N&H patients (pts) received PT reirradiation with curative intent at CNAO.

Median age was 64 years (yrs) (range 37-81 yrs). Histology was squamous cell in 24 pts (54.6%), undifferentiated in 10 pts (22.7%), adenoid cystic in 6 pts (13.6%), other histologies in 4 pts (9%). Median time from first RT was 26 months (mo.), (range 6-279). Median dose of previous RT was 66.8 Gy (range 25-76 Gy). Mean GTV was 45.9 cc (range 2.2-75.3). Median prescription dose for PT was 61 Gy[RBE] (range 45-70) in 30.5 fractions (range 15- 35). Median follow-up (FU) time was 13.2 mo. (range 3- 44). At last follow-up (FU), 20 pts were alive with disease, 8 with no evidence of disease, 12 died of disease and 3 died for other causes. At last FU, local control (LC) was maintained in 27 pts (63%). The 1-year LC, progression free survival (PFS) and overall survival (OS) were 71.6%, 62.2% and 82.6%, respectively. The 2-year LC, PFS and OS were 50.4%, 41.2% and 52.8%, respectively. 3 pts (7%) experienced acute grade 3 tox. Late tox was G0 in 20 (45%), G1-G2 in 17 (39%), G3 in 5 (11%) and G5 with carotid blow-out in 2 (5%) pts, respectively. Conclusion In our experience, PT showed good local control and acceptable rates of toxicity. However, in the reirraidation setting, the risk of severe late toxicity should be always considered and previously discussed with the patient. A larger series of patients and a longer follow-up are warranted. PO-0851 Impact of Adjuvant Radiation Therapy for Advanced Cutaneous Squamous Cell Carcinoma of Head and Neck V. Atallah 1 , G. Poissonnet 2 , E. Roxanne 3 , M. Chand 4 , S. Anne 3 , G. Pauline 4 , S. Renaud 5 , C. Dorian 3 , B. Alexandre 3 , J. Sicurani 4 , R. Natale 4 , J. Hannoun-Levi 4 , K. Benezery 4 1 universitary hospital, radiotherapy, Pointe-a-pitre, Guadeloupe ; 2 Centre Antoine Lacassagne, Surgery, France, France ; 3 Centre Antoine Lacassagne, Surgery, Nice, France ; 4 Centre Antoine Lacassagne, Radiotherapy, Nice, France ; 5 Centre Antoine Lacassagne, biostatistics, Nice, France Purpose or Objective Cutaneous squamous cell carcinoma (CSCC) is one of the most common malignant tumors worldwide. There is conflicting evidence regarding the indications for and benefits of adjuvant radiation therapy (ART) for head and neck cutaneous squamous cell carcinoma (HNCSCC). New evidence-based risk stratification system as Brigham and Women’s tumor classification (BWH) may optimize identification of patients who benefit from ART compare to ancient classification. Our objective was to compare outcomes between patients who underwent surgery alone with those who received ART to identify ART indications. Material and Methods All patients undergoing primary surgery with or without adjuvant radiation therapy with curative intent for HNCSCC treated from April 2007 to December 2018 in our center were included. We made a retrospective monocentric study and collected major patient data and tumor characteristics (including American Joint Committee on Cancer, 8th edition (AJCC-8) staging system and BWH classification). Results A total of 290 HNCSCCs were included in this study, of which 241 (83.1%) were men with the mean age of 78.3 (36-100) years. Twenty-one (7.2%) patients were immunosuppressed, 41 (14.2%) patients were nodes- positive (N+) , 105 (36.2%) patients were treated for recurrent disease, 28 (9.65%) patients were margin- positive and 82 (28.3%) patients received post-operative ART. According to BWH classification, 88 (30.3%) patients were T1, 76 (26.2%) were T2a, 100 (37.9%) were T2b and 16 (5.5%) were T3. The 3-year Kaplan-Meier estimates were 50.2 %for Disease- Free Survival (DFS) and 76.0%for Overall Survival (OS).