ESTRO 36 Abstract Book

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Data and tumor tissue from 815 patients enrolled in 4 trials (DAHANCA 6-7, RTOG 9003, ARTSCAN, RTOG 0129) was available for analysis: 350 (43%) HPV-neg and 465 (57%) HPV-pos. Patients with HPV-pos tumors were significantly younger (mean: 56 vs 59 years, p=0.0002), in better performance status (PS=0: 74% vs 50%, p<0.0001), had smaller tumors (T1-2: 46% versus 33%, p<0.0001) and more advanced N-stage (N+: 87% versus 76%, p<0.0001) compared with the HPV-neg subgroup. HPV-status significantly influenced prognosis and HPV-pos patients had favorable PFS (HR=0.42 [95% CI: 0.34-0.51] with a 42% absolute increase at 10 years) and OS (HR=0.40 [0.32-0.49] with a 40% absolute increase at 10 years) compared to the HPV-neg subgroup. Smoking independently influenced outcome and never/former smokers had better prognosis than current smokers with HR of 0.61 [0.50-0.75] and 0.58 [0.47-0.72] for PFS and OS, respectively. A further analysis of the impact of smoking was performed classifying smoking as former/current vs never smokers. This consequently led to the exclusion of 166 patients from the ARTSCAN trial where this information was not available. Compared to the HPV-neg smoking subgroup, HPV-pos never smokers were found to have significantly better outcomes (PFS: HR: 0.20 [0.14-0.31] and OS: HR: 0.20 [0.13-0.31]). Similar, although less pronounced, survival benefits were observed for HPV-pos smokers (PFS: HR: 0.41 [0.33-0.51] and OS: HR: 0.38 [0.30-0.47]) when compared with HPV-neg smokers. There was no significant interaction between HPV-status and fractionation effect, whatever the coding for smoking. Conclusion HPV status was not found to be predictive of outcome after altered fractionated RT in this pooled analysis of OPC. However, the strong prognostic impact of HPV was confirmed and especially HPV-pos never smoking patients have superior outcome after RT. Supported by the French Ministry of Health (PHRC) OC-0334 Prospective MR assessment of dose-response kinetics of non-target muscles in head and neck cancer A.S.R. Mohamed 1 , R. Davuluri 1 , S. Frank 1 , Y. Ding 1 , S. Lai 1 , J. Wang 1 , C. Fuller 1 , K. Hutcheson 1 1 The University of Texas- MD Anderson Cancer Center, Radiation Oncology, Houston, USA Purpose or Objective We have recently demonstrated the role of Magnetic Resonance Imaging (MRI) in characterizing radiotherapy (RT)-induced changes in non-target swallowing related musculature in a retrospective head and neck cancer cohort treated with definitive RT. We aim to validate the longitudinal dose-response changes of normal-muscle quantitative MRI signal kinetics in a prospective and well curated institutional dataset. Material and Methods A total of 39 patients were enrolled as part of an ongoing prospective clinical trial after obtaining study specific signed consent. All patients underwent three MRI studies: pre-, mid-, and post-RT. The mean T1, T1+ contrast (T1+C), and T2-weighted signal intensities (SI) for superior pharyngeal constrictors (SPC), middle pharyngeal constrictors (MPC), intrinsic tongue muscles (ITM), geniohyoid (GH), genioglossus (GG), mylohyoid (MH), masseters, medial/lateral pterygoids, anterior/posterior digastrics (ADM, PDM), and buccinators were recorded in the three time points and delta SI changes were calculated. Trapezius muscle was segment as a control due to negligible dose received. The SI changes were correlated to RT dose to the segmented structures after deformable image registration to planning CT and dose. Results All patients were stage III-IV HPV-positive oropharyngeal cancer. Median age was 58 years (range 39-80), 35 (90%) were men, and 35 (90%) were white race. Tonsillar fossa was the area of tumor origin in 20 patients (51%) and base

of tongue in 19 (49%). Prescription dose was 70 Gy in 33 fractions. At mid-RT; significant increase in mean T1+C SI was noted in the following muscles: ADM, ITM, GHM, and MPC (p=0.005, 0.01, 0.04, and 0.002, respectively) and significant increase in mean T2 SI was noted only in MPC (p=0.0005). At post-RT; significant increase in mean T1+C SI was detected in all studied muscles (p<0.05 for all). After Bonferroni correction for multiple comparisons, all remained significant except buccinators, pterygoids, and masseter. Post-RT increase in T2 SI was detected only in pharyngeal constrictors and medial pterygoids (p<0.05) and remained significant after Bonferroni correction for pharyngeal constrictors. No significant changes in mean T1 SI was detected in all tested muscles in both time points. There were no dose-parameter relationship in all muscles with increased T1+C and T2 SIs in all studied time points. Mean dose to muscle groups with significant increase in T1+C after Bonferroni correction was significantly higher compared to other muscle groups (52.7 vs. 37.5 Gy, p<0.0001). Simultaneously, mean dose to pharyngeal constrictors that showed significant T2 increase was significantly higher compared to other muscle groups (63.2 vs. 41.2 Gy, p<0.0001). Conclusion Significant dose-dependent increase in mid-RT and post- RT T1+C and T2 signal intensities is noted in non-target swallowing muscles particularly in pharyngeal constrictors due to higher beam-path dose to these muscles. The Global Task Force on Radiotherapy for Cancer Control (GTFRCC) has not only highlighted the urgent need for addressing the inequity gap in access to radiotherapy globally, it has also demonstrated that judicious investment in radiotherapy infrastructure and training is both effective and cost-effective. Indeed, in addition to preventing millions of cancer deaths in the decades to come, investing in radiotherapy has also been shown to bring value for money and a positive return on investment to the societies involved. The GTFRCC has articulated five calls-to-action in order to remedy the radiotherapy shortage and to make sure that radiotherapy is included into the multidisciplinary approach to cancer care. To ascertain a global impact by 2035, the time is now to build upon the GTFRCC results. ESTRO and the stakeholders involved in the GTFRCC have decided to join forces by establishing a new collaborative group with the aim of identifying timely, effective, and achievable responses to the GTFRCC’s calls-to-action, and of positioning radiotherapy as an essential component of effective cancer care globally. It is our pleasure to launch this initiative at ESTRO 36! SP-0336 Costs and needs of radiotherapy: a regional perspective E.H. Zubizarreta - zubi 1 1 IAEA, Applied Radiation Biology and Radiotherapy, Wien, Austria This analysis presents the resources needed and costs at the present time globally and by region to give full access to RT. The variables and methodology were the same used by the GTFRCC. The GTFRCC reported the resources needed and costs to reach full access to RT in 2035 by income group, but not per region (Atun R et al. Expanding global access to radiotherapy. Lancet Oncol 2015; 16(10)). The division in regions adopted by the IAEA was used: Africa (AF), North America (NA) only includes USA and Symposium: GTFRCC SP-0335 GTFRCC: where to go from here? Y. Lievens 1 1 University Hospital Ghent, Department of Radiation Oncology, Gent, Belgium