ESTRO 2020 Abstract book

S481 ESTRO 2020

To investigate the effectiveness and safety of reirradiation (re-RT) for recurrent head and neck cancer patients who were previously treated with curative aim. Material and Methods Patients were included for this study who underwent re- RT for recurrent head and neck cancer between 2007– 2019. The overlapping volume should have received ≥45Gy for initial irradiation and also received ≥45Gy for re-RT. Patients treated with stereotactic body radiotherapy were excluded. Medical records and dosimetric data were retrospectively reviewed. Overall survival (OS), progression-free survival (PFS), severe late toxicities, and prognostic factors were analyzed. Results A total of 55 patients were analyzed. The median follow- up after re-RT was 13.8 months (range, 3.7–130.0). The median dose of initial irradiation and re-RT were 67.5 Gy (range, 54–72) and 63 Gy (range, 45–67.5), respectively. The median interval between the radiotherapy courses was 22 months (range, 4.6–123.4). The most frequently reirradiated cancer were nasopharyngeal carcinoma (25.5%) followed by major salivary gland cancers (16.4%). The median OS and PFS were 12.2 and 8.6 months, respectively. The 2-year local failure-free survival and distant metastasis-free survival were 70.0% and 67.9%, respectively. Multivariate analysis showed that good performance (ECOG 0 or 1), complete surgical resection of tumor, longer time interval (≥18 months) between radiotherapy courses, and higher re-RT dose (≥60Gy) were statistically significant factors for favorable OS. Longer time interval between radiotherapy courses and higher re- RT dose were also significantly associated with prolonged PFS. Grade≥3 late toxicity were reported in 10 (18.2%) patients. The median toxicity-free survival was 10.7 months. Re-RT dose ≥65Gy and surgery were a significant predictor of grade≥3 late toxicity. Conclusion Re-RT is a feasible and effective treatment for recurrent head and neck cancer when used with caution. However, since higher re-RT dose resulted in both better prognosis and higher toxicity, administration of re-RT should be individualized. PO-0804 Adjuvant radiotherapy in the management of major salivary gland tumors – Retrospective analysis A. Florindo 1 , S. Saraiva 1 , T.C. Tomás 2 , A. Abrunhosa- Branquinho 1 , V. Mendonça 1 , M. Filomena de Pina 1 1 Hospital de Santa Maria, Serviço de Radioterapia, Lisboa, Portugal ; 2 Hospital Professor Doutor Fernando Fonseca, Serviço de Oncologia, Lisboa, Portugal Purpose or Objective National Cancer Care Network (NCCN) guidelines suggest surgery with neck dissection (ND) for cN+ disease and for high grade and/or T3-4 major salivary gland tumors (mSGT). This study aims to evaluate the long-term survival outcomes of patients who underwent surgery (with or without ND) and adjuvant radiotherapy (AR) for mSGT, as well as, prognostic factors that affect clinical outcomes. Material and Methods Retrospective analysis was performed on patients (pts) who underwent post-operative radiotherapy for mSGT between 2006 and 2018. Palliative pts were excluded. Kaplan-Meier curves for disease-free survival (DFS) and overall survival (OS) were calculated, Cox regression was used for uni- and multivariate analysis to assess prognostic factors. Log-rank tests were used to compare survival outcomes according to ND status, stratified by stage and by histopathological risk (HPR) according to “Risk Stratification of World Health Organization (WHO) Recognized Salivary Gland Malignancies”. Results 41 of 77 pts were eligible for analysis (Table1). The median follow-up was 36.75 months (range 3.2-151.2 months) and the median AR dose was 66 Gy (range 54 – 70 Gy).

Purpose or Objective To evaluate the prognostic role of the methylation levels of “ Long interspersed nucleotide element-1 ” (LINE-1) repetitive elements in patients (pts) with Oropharyngeal Cancer (OPSCC) in locally advanced stages treated with definitive intent. Material and Methods We retrospectively reviewed a cohort of 156 pts with stage III–IVB (AJCC TNM 7 th Ed.) OPSCC. Patients were included if treated with definitive purpose. Genomic DNA was extracted from OPSCC formalin-fixed paraffin-embedded tissues. Human Papillomavirus 16 (HPV16) DNA was quantified with real-time quantitative Polymerase Chain Reaction (PCR) using specific primers for the amplification of a region spanning the E6 genes of the HPV16 genome, whereas real-time quantitative Methylation-Specific PCR evaluated the methylation status of LINE-1 repetitive sequences. The impact of LINE-1 methylation on progression-free survival (PFS) and overall survival (OS) was assessed using Kaplan-Meier analyses. Optimal cut-points for LINE-1 were searched through a recursive algorithm that estimated the predictive value for PFS (Harrell's c-index) for each possible couple of LINE-1 values; optimal cut-points were defined as those that maximized Harrell's c-index. This study was supported by a grant from the Centro di Riferimento Oncologico, IRCCS-National Cancer Institute (Intramural Grant 5 × 1000 to EF and GF). Results The median follow up was 33 months (interquartile range: 17-75 months). HPV DNA was detected in 45 pts (28,85%) and 109 pts (69.9%) were male. Definitive surgery (followed by adjuvant therapy) or (chemo-) radiotherapy was performed in 71 (45,5%) and 85 (54,5%) pts, respectively. On the whole cohort, PFS and OS were respectively 64.6% and 71.8% at 2 years, and 49.5% and 53.7% at 5 years. Three patterns of LINE-1 methylation status were indentified according to PFS and OS: high≥55%, intermediate 35-54%, low<35%. Analyzing all patients, PFS at 2 years was 75.9% in the high methylation group, 62% in the intermediate group, 41,6% in the low methylation group (p<0.0001). Furthermore, OS at 2 years was 82.1% in the high methylation group, 73% in the intermediate group, 46% in the low methylation group (p=0.0003) (Fig. 1). The level of methylation of LINE-1 remained prognostic for both PFS (p= 0.0042) and of OS (p=0.0112) in the subgroup of HPV-negative pts. In HPV-positive group, respect to patients with LINE-1 <55%, cases with a LINE-1 ≥55% have had better trend in terms of PFS and OS, but this difference was not statistically significant as shown in Table 1. Only one had a methylation of LINE-1 < 35%. Conclusion In our cohort, LINE-1 methylation levels identified three groups of OPSCC pts with different PFS and OS. In particular, LINE-1 hypomethylation associated with a worse prognosis in the subgroup of HPV-negative pts, suggesting its role as prognostic biomarker for risk stratification for OPSCC pts. However, future investigations on a larger cohort are needed to further support the prognostic potential of LINE-1 methylation in OPSCC, especially in HPV-positive pts. PO-0803 Outcomes of reirradiation in head and neck cancers: Two institutional experience H. Lee 1 , H. Wu 1 , I.A. Kim 2 , K. Eom 2 , C.W. Wee 2 , J.H. Lee 1 , J.H. Kim 1 1 Seoul National University Hospital, Radiation Oncology, Seoul, Korea Republic of ; 2 Seoul National University Bundang Hospital, Radiation Oncology, Seongnam, Korea Republic of Purpose or Objective