ESTRO 38 Abstract book

S365 ESTRO 38

M. Kenji 1 , Y. Hamamoto 2 , Y. Urashima 1 , N. Takata 2 , K. Kikuchi 1 , M. Miyagawa 2 , T. Mochizuki 2 1 Matsuyama Red Cross Hospital, Radiology, Matsuyama city, Japan ; 2 Ehime University Graduate School of Medicine, Radiology, Toon City, Japan

dose was 50 Gy followed by 24 Gy for C12 boost. Median follow-up was 40 months. Results Median 5-years overall survival (OS), progression free survival (PFS) and local disease free survival (LDFS) rates were 85.5%, 57.4% and 74.9%. Median time until progression was detected was 32 months (range: 2 – 205 months). Early grade > 3 mucositis, dermatitis and dysphagia were detected in 52.2%, 7.5% and 11.9%. Besides common toxicities two patients (3.0%) developed grade 3 toxicities with osteoradionecrosis of the jaw after 18 and 66 months. Higher-grade late toxicity (CTCAE grade 4) was not detected. There was no treatment related death. Conclusion Our results demonstrate that postoperative bimodal radiotherapy with IMRT plus C12 boost seem to be feasible and effective treatment method in ACC of MiSGs of oral cavity with good control and survival rates and tolerable toxicity. PO-0711 Second Primary Cancer in Salivary gland cancer in South Korea: A Nationwide Population-based Study J. Heo 1 , Y. Oh 1 , O.K. Noh 1 , M. Chun 1 , O. Cho 1 1 Ajou University School of Medicine, Radiation Oncology, Suwon, Korea Republic of Purpose or Objective The aim of this study was to evaluate the prevalence of second primary cancer (SPC) among salivary gland cancer (SGC) patients by using nationwide claims data in South Korea. Material and Methods The nationwide cohort assessed in this study patients who were diagnosed with SGC from January 1, 2010, to December 31, 2014. We analyzed cancer incidence according to the time sequence. Additionally, we evaluated standardized incidence ratios (SIRs) to estimate the risk of SPC in SGC patients. Results A total of 1,614 patients (868 male and 746 female subjects) who were diagnosed with SGC and received surgery were confirmed, and 829 patients received radiotherapy. Of these patients, one-hundred and fifty- five patients (9.6%) developed an SPC, and the most common cancer site was the thyroid (13.5%). Patients with SGC had a high risk of SPC (SIR 4.39, 95% CI: 3.73 – 5.14), particularly nasopharynx cancer (SIR 79.43), Non-Hodgkin lymphoma (SIR 14.95) and tonsillar cancer (SIR 66.67). Female had a higher risk of malignancy than male (SIR 5.14 for women and SIR 3.73 for men). Age was a significant predictive factor for SPC (P = 0.024) among clinical factors, and patients over 54 years were at a higher risk for mental disorders (hazard ratio: 1.43, P = 0.031). Conclusion SGC patients with surgery had a longer life expectancy and a higher risk of SPC than the general population did. Therefore, close surveillance for SPC is important in elderly patients with SGC. PO-0712 A new prediction model for patient reported xerostomia; external validation in postoperative setting H.P. Van der Laan 1 , L. Van den Bosch 1 , A. Van der Schaaf 1 , R.J.H.M. Steenbakkers 1 , H.P. Bijl 1 , M. Dieters 1 , J.G.M. Van den Hoek 1 , S. Both 1 , E. Schuit 2 , J.A. Langendijk 1 1 University of groningen- University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands ; 2 Utrecht University- University Medical Center Utrecht, Julius Center for Health Sciences and Primary Care, Utrecht, The Netherlands

Purpose or Objective To evaluate the outcomes of external beam radiotherapy (EBRT)

for

metastatic

lesions (MLs) of differentiated thyroid cancer (DTC). Material and Methods Between August 1997 to March 2018, 73 lesions in 36 patients (male/female = 15/21; age 35-87 years, median 62 years)received EBRT and were followed up by CT, MR images, and/or FDG-PET/CT in our institution. Median follow-up time was 14 months (range, 1-110 months). Among assessed 73 lesions, 56 lesions were distant metastases (bone/lung/other sites = 45/5/6)and 17lesions were neck/mediastinallymph- node metastases. Doses of EBRT were 8-70 Gy (median 40 Gy). Seventeen patients received radioactive iodine therapy (RAIT) after EBRT. Results One- and 3-year overall survival rates were 87% and 63%, respectively. One- and 3-year control rates of lesions received EBRT were 79% and 45%, respectively. Three- year control rates were 0% for lesions received <30 Gy (n=7), 35% for lesions received 30- 49Gy (n=38), and 82% for lesions received 50 Gy< (n=28). There were statistically significant differences of control rates between <30 Gy and 30-49 Gy (p=0.0002), and <50 Gy and >50 Gy (P=0.00374). Three-year control rates according to sites of lesions were as following; 55% for neck/mediastinal lymph-nodes, 33% for the bone metastasis, and 65% for the lesions in other organs (P = 0.2201). Three-year control rates were 67% for lesions received RAIT after EBRT (27 lesions), and 30% for lesions received no RAIT after EBRT (46 lesions) (p=0.0093). There were no significant differences in control rates by age, sex, and pathological subtype (papillary carcinoma vs. follicular carcinoma). EBRT doses of >50 Gy and addition of RAIT after EBRT were statistically significant independent factors for the good control of lesions received EBRT on multivariate analysis. Conclusion Because a significant proportion of patients with MLs of DTC requiring EBRT survived for a long time, long-term control of irradiated lesions is required even in palliative intent radiotherapy. EBRT doses of >50 Gy and addition of RAIT after EBRT seemed to be useful for long-term control of lesions received EBRT. PO-0710 IMRT+Carbon Ion Boost for Adenoid Cystic Carcinoma of the Minor Salivary Glands of the Oral Cavity K. Lang 1 1 University Hospital Heidelberg- Radiooncology, Radiooncology Heidelberg, Heidelberg, Germany Purpose or Objective Adenoid cystic carcinomas (ACCs) are more frequently located in the minor salivary glands (MiSGs) of the oral cavity than in the major salivary glands and they are characterized by slow tumor progression and frequently local recurrence. Main treatment option is surgery followed by combined radiotherapy. This study summarizes our institution`s experience with bimodal postoperative RT in ACCs of the minor salivary glands of the oral cavity to evaluate survival and toxicity. Material and Methods The retrospective analysis contained 67 patients with ACC of MiSGs of the oral cavity who underwent surgery followed by radiotherapy. The median cumulative IMRT

Purpose or Objective