ESTRO 38 Abstract book

S666 ESTRO 38

EP-1201 Outcomes in young patients (<40) treated for oral cavity squamous cell carcinoma in the modern era A. Billfalk Kelly 1 , L. Lin 2 , W. Xu 2 , S.H. Huang 1 , R. Wu 1 , A. Bayley 1 , S. Bratman 1 , J. Kim 1 , M. Giuliani 1 , J. Ringash 1 , J. Waldron 1 , B. O''Sullivan 1 , J. Cho 1 , D. Goldstein 3 , A.A. Hosni 1 , A. Hope 1 1 Princess Margaret Cancer Centre, Radiation Oncology, Toronto, Canada ; 2 Princess Margaret Cancer Centre, Biostatistics, Toronto, Canada ; 3 Princess Margaret Cancer Centre, Surgery, Toronto, Canada Purpose or Objective Outcomes of oral cavity squamous cell carcinoma (OSCC) tend to be worse than other head and neck squamous cell carcinomas (HNSCC) despite modern surgical and radiation techniques and the use of postoperative concurrent chemotherapy in high risk OSCC. Anecdotal evidence has suggested that OSCC patients under the age of 40 have aggressive disease. We evaluated the outcomes of OSCC patients <40 treated in the modern IMRT era at our institution. Material and Methods After obtaining REB and institutional approval, OSCC patients under 40 were identified from our prospectively collected database. Details were collected in relation to tumor and treatment factors. Oncologic outcomes including overall survival, disease free survival, and loco- regional control were determined for this sub-set. Overall survival (OS) and disease-free survival (DFS) were analyzed using Kaplan Meier method and loco-regional control was evaluated using competing risk analysis. Results From 1183 consecutive patients with OSCC treated with curative intent between 2005 and 2017, 57 patients (5%) under the age of 40 were identified. The median age was 33 years (range 18-39). In the study cohort 42% of patients were female and 58% male; 61% of patients were lifelong non-smokers, with only 23% current smokers, and 16% ex- smokers; 44% were non-drinkers. ECOG performance status was 0-1 in 92.9% ( one 2, 3 missing data). Surgery was to the primary lesion only in 26%, to the primary with an ipsilateral neck dissection in 53%, and 21% had surgery to the primary with bilateral neck dissections. Only 5% of patients had positive microscopic resection margins. Lymph node involvement with extra-nodal extension was seen in 17% of patients, 5% had LVI and 37% had PNI. Almost 60% received definitive surgery alone, while in 40% surgery was followed by adjuvant radiotherapy; among these, 65% received concurrent chemotherapy. The adjuvant radiotherapy dose received ranged from 56Gy in 40 fractions to 70.72Gy in 35 fractions; 26% of patients received 60Gy in 30 fractions, and 52% receiving 66Gy in 33 fractions. Almost half, 44%, had stage I disease, 10.5% stage II, 16% stage III, 28% stage IV; 1 patient’s biopsy showed CIS despite a large tumor. Serious comorbidity was present in 8 patients: 6 with previous malignancies (10.5%), 1 with Fanconi’s Anaemia, and 1 with severe SLE causing renal failure. With a median follow-up of 4.27 (5.03 in survivors) years, 1-year OS was 94% (0.88-1), 3-year OS 84% (0.75-0.95) and 5-year OS 82% (0.71-0.93). DFS was 84% (0.74-0.94) at one year, and 66% (0.54-0.81) at 5 years. Event free survival was 87% at 1 year (94-74), 79% at 3 years (88-65) and 74% at 5 years (84-57) . Conclusion The clinical impression of poor outcomes for patients aged under 40yrs may represent recall bias. Such treated curatively for OSCC in our institution appear to have acceptable OS and DFS. EP-1202 Associations between smoking cessation after radiotherapy for larynx cancer and patient outcomes A. Srivastava 1 , J. Contreras 1 , M. Daly 1 , H. Gay 1 , W. Thorstad 1 , A. Apicelli 1

1 Washington University School of Medicine, Radiation Oncology, Saint Louis, USA Purpose or Objective Continued tobacco use is known to be a poor prognostic factor among patients undergoing radiation therapy (RT) for cancers of the head and neck. However, this relationship is not well characterized for carcinomas of the larynx/hypopharynx (LNX/HPX), which are almost exclusively associated with tobacco use. Therefore, in this study we sought to evaluate whether there was a disease control and survival benefit to smoking cessation after RT for cancers of the LNX/HPX. Material and Methods An institutional database of patients with squamous cell carcinoma of the LNX/HPX treated with definitive intent RT between 2012 and 2017 was reviewed. Patients were eligible for inclusion if they had a documented history of tobacco use at the beginning of RT and were planned to undergo definitive therapy. Following completion of therapy, patients were stratified into two cohorts based on continued tobacco use. The student’s t-test and Fisher exact test were utilized to compare baseline clinical and demographic covariates. The Kaplan-Meier method and log-rank test were used to estimate and compare locoregional control (LRC), distant control (DC), and overall survival (OS) between the cohorts, and Cox regression tests were used to identify predictors of these outcome metrics. Results A total of 102 patients were eligible, and 34 (33.3%) continued smoking following definitive therapy. Most patients (52/102, 51%) underwent surgery, and the majority (71/102, 70%) received concurrent chemotherapy with RT. Median follow-up time was 26 months (range 1- 64). Baseline demographic and clinical characteristics were similar between the groups, but smoking cessation was less common among African Americans (p=0.03). At two years of follow up, actuarial LRC rates were 63% for patients who continued to smoke and 79% for patients who stopped (p=0.02) while DC rates were 86% and 90%, respectively (p=0.53). There was a survival benefit in patients who stopped smoking (92% v. 78%, p= 0.01). On multivariate analysis, smoking status post RT (hazard ratio [HR]: 2.6, 95% confidence interval [CI]: 1.8-3.9; p = 0.01), higher performance status (HR: 2.3, 95% CI: 1.4-4.2, p= 0.03), and advanced tumor stage (HR: 2.9, 95% CI: 1.7-5.8, p=0.02) were predictive of worse OS. Notably there was no association between number of pack-years previously smoked and disease outcome (p=0.21). Conclusion Smoking cessation after definitive treatment of larynx/hypopharynx cancer is associated with a significant increase in OS regardless of extent of smoking history, underscoring the importance of smoking cessation. EP-1203 Characterization of DCE-MRI parameters associated with advanced mandibular osteonecrosis A.S.R. Mohamed 1 , R. He 1 , Y. Ding 1 , J. Wang 1 , B. Elgohari 1 , H. Elhalawani 1 , J. Johnson 1 , J. Stafford 1 , J. Bankson 1 , V. Sandulache 2 , C. Fuller 1 , S. Lai 1 1 The University of Texas- MD Anderson Cancer Center, Radiation Oncology, Houston, USA ; 2 Baylor College of Medicine, Otolaryngology, Houston, USA Purpose or Objective We aim to characterize the quantitative DCE-MRI parameters associated with advanced mandibular ORN following definitive radiotherapy for head and neck cancer patients. Material and Methods Patients with advanced ORN after curative-intent radiation treatment of head and neck cancer were prospectively enrolled in an observational imaging study after institutional-review board approval and study-