ESTRO 2023 - Abstract Book

S964

Digital Posters

ESTRO 2023

M. O'Connell 1 , T. Ermongkonchai 1 , D. Xing 2 , C.E. Cardenas 3 , B. Harris 4 , C. Barbon 5 , R. Khor 6 , H. Bahig 7 , A.S.R. Mohamed 8 , C. Fuller 9 , S.P. Ng 2 1 Austin Health, Radiation Oncology , Melbourne , Australia; 2 Austin Health, Radiation Oncology, Melbourne , Australia; 3 University of Alabama at Birmingham, Radiation Oncology, Alabama , USA; 4 Austin Health , Radiation Oncology, Melbourne , Australia; 5 MD Anderson Cancer Centre, Speech-Language Pathology, Houston, USA; 6 Austin Health, Radiation Oncology, Melbourne , Australia; 7 Centre hospitalier de l'Université de Montréal (CHUM), Radiation Oncology, Montreal, Canada; 8 MD Anderson Cancer Centre, Radiation Oncology, Houston, USA; 9 MD Anderson Cancer Centre , Radiation Oncology, Houston, USA Purpose or Objective Patients undergoing radiotherapy treatment for head and neck cancer experience acute and late toxicities relating to inflammation and subsequent fibrosis of masticatory muscles. This study aims to analyse the changes in apparent diffusion co-efficient (ADC) in muscles of mastication in patients undergoing radiotherapy treatment for head and neck cancer. Materials and Methods This is a secondary analysis of imaging obtained on the PREDICT-HN study. All patients had a pre- and post- radiotherapy MRI scan and weekly MRI scans during radiotherapy treatment. Pterygoid and masseter muscles were contoured on 50 images and an autocontouring model was generated. Contours for the muscles were autogenerated for other timepoints. These contours were checked by 2 radiation oncologists. The volume of each muscle and ADC values were extracted. Results Twenty one patients were included in the analysis. 80% of patients had oropharyngeal cancer. Mean ADC in muscles of mastication (masseter and pterygoids) dropped dramatically between the pre-treatment and week 1 MRI scans, and continue to be low during radiotherapy. The ADC in masseters increase in week 5/6 and post-treatment. The median ADC remained lower than baseline for the duration of treatment in both left and right masseter muscles and increased rapidly on the post-treatment MRI imaging (2-months following treatment) . The median ADC in pterygoid muscles initially decreased but overall increased throughout treatment. Conclusion ADC MRI changes observed in muscles of mastication of patients undergoing radiotherapy treatment for head and neck cancer has a non-linear trajectory. The degree of ADC changes observed during these on-treatment and post-treatment MRI scans should be correlated with patients' late effects to assess if ADC could be an early marker to predict for trismus and fibrosis. V. Ghosh 1 , A. Biswas 1 , A. Binjola 1 , S. Roy 1 , S. Bhasker 1 , M. Tripathi 2 , A. Kakkar 3 , S. Ghose 4 , R. Pramanik 4 , A. Sharma 4 , A. Thakar 5 , K. Rangarajan 6 , C. S.H. 6 , S. Kumaran 7 , C. Bal 2 , R.K. Malhotra 8 1 All India Institute of Medical Sciences (AIIMS), New Delhi, Radiation Oncology, New Delhi, India; 2 All India Institute of Medical Sciences (AIIMS), New Delhi, Nuclear Medicine, New Delhi, India; 3 All India Institute of Medical Sciences (AIIMS), New Delhi, Pathology, New Delhi, India; 4 All India Institute of Medical Sciences (AIIMS), New Delhi, Medical Oncology, New Delhi, India; 5 All India Institute of Medical Sciences (AIIMS), New Delhi, Otorhinolaryngology, New Delhi, India; 6 All India Institute of Medical Sciences (AIIMS), New Delhi, Radiodiagnosis, New Delhi, India; 7 All India Institute of Medical Sciences (AIIMS), New Delhi, Nuclear Magnetic Resonance, New Delhi, India; 8 All India Institute of Medical Sciences (AIIMS), New Delhi, Delhi Cancer Registry, New Delhi, India Purpose or Objective We herein report the results of the interim analysis of a phase 2 clinical trial to assess the overall response rate(ORR) to gemcitabine & cisplatin(GC) based neoadjuvant chemotherapy(NACT) followed by dysphagia optimised intensity modulated radiotherapy(Do-IMRT) with concurrent weekly cisplatin in patients with locally advanced nasopharyngeal carcinoma(LA NPC). Materials and Methods We hypothesised that compared to historical control, the use of NACT followed by cisplatin-based Do-IMRT in stage II-IVA NPC will improve the complete response(CR) rate from 70% to 90% & the ORR from 80% to 95% at 3 months after completion of CRT. The target sample was 25. Patients with stage II-IVA NPC received 3 cycles of 3-weekly NACT with cisplatin(80mg/m ² IV divided over D1,D2) & gemcitabine(1g/m ² IV D1,D8) followed by Do-IMRT (65Gy,60Gy,54Gy/30fractions/6weeks to high, intermediate & low risk PTVs respectively by simultaneous integrated boost) with concurrent cisplatin(40mg/m ² IV weekly). Clinicoradiological response assessment was done at 3 weeks post-NACT & 3 months post-CRT using RECISTv1.1. PFS & OS were assessed by Kaplan-Meier method. Swallowing evaluation was done by using MD Anderson Dysphagia Inventory(MDADI) questionnaire at baseline, immediately and 3 & 6 months post-CRT. Serial changes in MDADI composite scores(CS) at all time points were analysed by Friedman test & pair wise comparison was done by Wilcoxon signed rank test. Serial plasma EBV-DNA titres were assessed by real-time PCR. Results Out of a total of 30 screened patients, 23 were eligible and recruited in this study from 25-Sep-2020 to 01-Jan-2022. The database was locked on 15-June-2022. The median age at diagnosis was 34 years (range:15-65 years). 82.6% of the patients had undifferentiated NPC & 91.3% stained positive for EBV-LMP1. 21 out of 23 patients completed NACT with 9.1% & 95.5% CR rate & ORR to NACT, respectively. 20 out of these 21 patients had been started on CRT & 18 had completed CRT. The CR rate & ORR after CRT were 78.6% & 92.9% respectively. 1 patient had locoregional progressive disease(PD) and 1 had PO-1206 NACT followed by cisplatin-enhanced dysphagia-optimised IMRT in nasopharyngeal cancer-phase 2 trial