ESTRO 2020 Abstract book

S973 ESTRO 2020

Furthermore, the significant difference between ADC r and ADC s in before RT is in agreement with more contribution of parotid for saliva production after stimulation compared to rest that is confirmed with the score 0 of xerostomia for all patients. Non-significant difference between ADC r and ADC s during RT can be consistent with parotid function loss as confirmed by scores of 2 and 3, whereas significant difference between ADC r and ADC s after RT may justify some possible recovery but smaller percentage changes of ADC s compared to ADC r at this time in comparison with before RT is accorded with late morbidity scores of 1 and 2 after 6 months (Table1). Further investigations will provide more insight into the correlation between ADC values and xerostomia at different time intervals. PO-1676 Blood biomarkers for cognitive damage after PCI; an exploratory analysis of the HA-PCI phase 3 trial I. Compter 1 , E. Oldoni 2 , R. Houben 1 , L. Van der Weijst 3 , M. De Ruiter 4 , A. Goris 2 , M. Holt 5 , S. Deprez 6 , M. Lambrecht 7 , Y. Lievens 3 , J.P. Van Meerbeeck 8 , S.B. Schagen 9 , J.S.A. Belderbos 10 , D.K.M. De Ruysscher 1 1 MAASTRO clinic- GROW- School for Oncology and Developmental Biology- Maastricht University Medical Centre, Dept. of Radiation Oncology, Maastricht, The Netherlands ; 2 KU Leuven, Laboratory for Neuroimmunology- Department of Neurosciences, Leuven, Belgium ; 3 Ghent University Hospital and Ghent University, Department of Radiation Oncology, Ghent, Belgium ; 4 The Netherlands Cancer Institute- Antoni van Leeuwenhoek, Division of Psychosocial Research and Epidemiology, Amsterdam, The Netherlands ; 5 KU Leuven, VIB-KU Leuven Center for Brain and Disease Research, Leuven, Belgium ; 6 KU Leuven, Department of Imaging and Pathology, Leuven, Belgium ; 7 Leuven Kanker Instituut- UZ Gasthuisberg, Department of Radiotherapy Oncology, Leuven, Belgium ; 8 Antwerp University Hospital UZA, Department of Pulmonology & Thoracic Oncology, Edegem, Belgium ; 9 The Netherlands Cancer Institute - Antoni van Leeuwenhoek, Division of Psychosocial Research and Epidemiology, Amsterdam, The Netherlands ; 10 The Netherlands Cancer Institute - Antoni van Leeuwenhoek, Department of Radiation Oncology, Amsterdam, The Netherlands Purpose or Objective An important adverse effect of prophylactic cranial irradiation (PCI) is cognitive decline. There is a need for the identification of blood biomarkers in order to detect and predict neuronal damage resulting in neuro-cognitive decline after cranial irradiation. Neurofilament light chain (NfL) is associated with neuro-axonal damage in multiple neurological disorders. Here, we report on an exploratory analysis of blood biomarkers measured over time with neuro-cognition in the hippocampus avoidance PCI (HA- PCI) phase III trial (NCT01780675) in SCLC Material and Methods Blood samples were available from 48/168 patients. Serum neurofilament light chain levels were measured with an electrochemiluminescence immunoassay. Angiogenesis, chemokine, cytokine, vascular and pro-inflammatory biomarkers were analysed using the Meso Scale Discovery multiplex ELISA platform. The samples were taken before PCI (T1), at the end of PCI (T2) and 4 months post-PCI (T3). Changes in biomarkers at end of radiotherapy (T2) and at four months follow-up (T3) were calculated and in both cases compared to baseline. Verbal memory was measured at baseline, 4, 8, 12, 18 and 24 months after completion of PCI with the Hopkins Verbal Learning Test‐Revised (HVLT‐R). A decline in score on the total recall of ≥ 5 points compared to baseline was considered to be clinically relevant. As this is an explorative analysis on a small subgroup of the randomized patients, only descriptive statistics were applied Results

Purpose or Objective To evaluate the functional variation of irradiated parotid in acute and late treatment phases using diffusion-

weighted MRI (DWI). Material and Methods

This study enrolled 15 Head and Neck Cancer (HNC) patients (Table1) who treated with 3D conformal radiotherapy underwent DWI at rest and after gustatory stimulation, with intraoral administration of 2 mL lemon in three time points as follows: before, during (one day after receiving the mean dose 26 Gy) and 6 months after the end of radiotherapy (RT). Apparent diffusion coefficient (ADC) maps were constructed from DWIs. Mean ADCs were extracted at rest and after stimulation (ADC r , ADC s ) from selected regions of interest (ROI) for three time points. Evaluation of xerostomia was done based on RTOG/EORTC acute and late morbidity scores at the same time points as imaging that are presented in Table1. Finally, Wilcoxon paired samples test was used to compare the changes of ADC over time as well as at rest and after stimulation in each time point.

Results The ipsilateral parotid glands received a mean dose of 47.1 Gy (14.9–63.5 Gy). Difference between mean ADC r in before RT and during RT was not significant ( p =0.12). The ADC r values were significantly higher after RT than before RT ( p =0.003) and during RT (after dose 26 Gy) ( p =0.001) (Figure1). Additionally, the difference between ADC r and ADC s in each time point was assessed. The results showed that there is significant difference between ADC r and ADC s in before RT ( p =0.005). Difference between these parameters after RT was also significant ( p =0.05) and the percentage changes of ADC s compared to ADC r at this time was smaller in comparison to before RT. Non-significant difference ( p =0.21) between ADC r and ADC s in during RT was also observed.

Conclusion Non-significant difference between ADC r in before RT and during RT may indicate that no immediate cell death takes place but Salva-producing cells lose their function during the first two weeks of RT and water or salvia content may change up to the dose constraint of 26 Gy. A significant increase of ADC r values after 6 months of RT (late phase) in comparison to before and during RT could be related to the recovery of baseline production of saliva or cell death.