ESTRO 37 Abstract book

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ESTRO 37

tomography was performed for NPC diagnosis and evaluation of neck lymph node metastasis in 488 patients (96 %). Magnetic resonance imaging was associated for 61 of them (12%). Seventy seven percent of cases had locally advanced tumors (T3 T4 /N2 N3). Tumor and lymph node necrosis were found in 11% and 14% of cases respectively. Radiotherapy was delivered for 506 patients and combined to chemotherapy in 75.6% of them. Survival analyses were calculated using the Kaplan Meier method and compared according to the presence or not of necrosis with the Log-Rank test for the univariate study, and with the Cox model for the multivariate study. Results After a median follow-up of 67.8 months (range 2-276), the overall survival at 5 and 10 years of our patients were 59.4% and 49.8% respectively. In univariate analysis, patients with no tumor necrosis on imaging had a significantly better overall survival (p = 0.03). In fact, the 5-year and 10-year survival were 60.7% and 50.6% vs 47.1% and 33.3% respectively for patients without and with tumor necrosis. However, there were no significant differences in overall survival at 5 and 10 years for patients with or without lymph node necrosis on imaging (p = 0.7). In multivariate analysis, detection of tumor necrosis on imaging did not appear to have an impact on NPC patients’ survival Conclusion To our knowledge, there are no studies specifically addressing the prognostic impact of tumor necrosis for NPCs in contrast to lymph node necrosis. Our work suggests the importance of taking into account this prognostic factor in the therapeutic management of NPC. EP-1182 Relation of Parotid Shrinkage to Acute Xerostomia During Adaptive Radiation for Head and Neck Cancer E. Healy 1 , B. Willen 2 , A. Ayan 1 , J. Eckstein 3 , J. Wobb 1 , D. Mitchell 1 , E. Miller 1 , J. Grecula 1 , D. Blakaj 1 , A. Bhatt 1 1 The Ohio State University, Radiation Oncology, Columbus- Ohio, USA 2 Wright State University, School of Medicine, Detroit, USA 3 University of Toledo, School of Medicine, Toledo, USA Purpose or Objective Purpose: Xerostomia is a very common toxicity after head and neck radiation therapy (RT). Prior studies have correlated the parotid gland (PG) dose to xerostomia, and also parotid dose to gland shrinkage that occurs after RT. The purpose of our study was to correlate acute moderate to severe (≥ grade 2) xerostomia that develops during RT to dose and gland shrinkage. Material and Methods Methods: We analyzed 100 patients who underwent adaptive re-planning (200 plans) between December 2014 to August 2017. Volumetric Modified Arc Therapy (VMAT) based IMRT was used in all. All patients had an initial CT simulation scan used for radiation planning and a subsequent new CT simulation for adaptive replan. Dose- volume histograms were used to measure mean doses to the PG. We then correlated the mean doses to PG and volume changes noted at the time of replan to grade of xerostomia noted at time of replan. Lyman–Kutcher– Burman (LKB) NTCP model was used to correlate mean dose to xerostomia (Fig 1). Generalized logistic regression model (GLM) was used to analyze various levels of PG (%) shrinkage (5%, 10%, 15%, 20%, 25%, 30%) that predicted for ≥ grade 2 xerostomia at a given mean dose. Results Results: Median total RT dose was 70 Gy (60-70 Gy in 30- 35 daily fractions). Median time to performing replan was at fraction #21 (42 Gy) and around day 37 of therapy (13- 66 days). Mean dose received at time of replan with corresponding volume change: Right PG = 1548 cGy, - 13.6%; Left PG = 1647 cGy, There was a significant

correlation noted for the dose received by the L PG and volume changes noted (p<0.05). The LKM model yielded a mean dose ~12 Gy predictive of TD50 for ≥ grade 1 xerostomia and ~32 Gy for ≥ grade 2 (fig 1). The GLM model showed a convergence of ≥ grade2 toxicity vs total PG volume shrinkage of >20% to L PG mean dose (p < 0.01). Conclusion Conclusions: Acute moderate to severe xerostomia occurring during active head and neck RT is significantly correlated to mean dose and shrinkage of the parotid glands. Adaptive replanning has the potential to reduce salivary gland doses and thus ultimately may reduce the severity of xerostomia. EP-1183 Age distribution and age-related outcomes of olfactory neuroblastoma: a population-based analysis W. Wang 1 , Z. Yin 1 1 Tianjin Medical University Cancer Hospital & Institute, Department of Radiation Oncology, Tianjin, China Purpose or Objective Olfactory neuroblastoma (ON) is a rare and uncommon disease arising from the upper nasal cavity and ethmoid sinus.In order to describe the age distribution and to evaluate the role of prognostic value of age on survival in patients diagnosed with olfactory neuroblastoma (ONB), a population-based retrospective analysis was conducted. Material and Methods The population-based study of patients in the Surveillance, Epidemiology, and End Results (SEER) tumor registry, who were diagnosed with ONB from 1973 to 2014 were retrospective analyzed.The diagnosis code of 9522/3 was queried and all records were found in the following sites: C30.0 (nasal cavity), C31.0 (maxillary sinus), C31.1(ethmoid sinus), C31.2(frontal sinus), C31.3 (sphenoid sinus), C31.8 (overlapping lesion of accessory sinus) and C31.9 (accessory sinus, NOS). Information for race, age, gender, year at diagnosis, primary site, SEER stage, treatment (including surgery, radiotherapy and chemotherapy) were included in this study. Results The cohort included 876 patients with a median age of 54 years. The age distribution is in unimodal, and most frequently occurred in the 5 th to 6 th decades of life. Kaplan-Meier analysis demonstrated an overall survival (OS) and cancer-specific survival (CSS) rate of 69% and 78% at 5 years. Multivariable Cox regression analysis showed that age, SEER stage and surgery were independent prognostic factors for CSS. The risk of overall death and cancer-specific death increased 3.1% and 1.6% per year, respectively. Patient aged >60 presented significantly worse OS and CSS than patients aged ≤60 years, even in patients with loco-regional disease or in those treated with surgery. Conclusion This study highlights the growing evidence that there is a uni-modal age distribution of olfactory neuroblastoma, and that age is an important adverse prognostic factor.

Electronic Poster: Clinical track: CNS

EP-1184 Elderly patients with Glioblastoma Multiforme treated with radiotherapy: a single institution study A.M. Glynn 1 , G. Rangaswamy 1 , J. O’Shea 1 , M. Dunne 1 , R. Grogan 2 , S. McNally 2 , D. Fitzpatrick 1 , C. Faul 1 1 Beaumont Hospital-Dublin-Ireland, St Luke's Radiation Oncology Network, Dublin, Ireland 2 Beaumont Hospital-Dublin-Ireland, Department of Neurosurgery, Dublin, Ireland