Low incidence of RT-induced MRI changes and stable QoL following proton irradiation
Carola Luetgendorf-Caucig,
Austria
OC-0442
Abstract
Low incidence of RT-induced MRI changes and stable QoL following proton irradiation
Authors: Carola Luetgendorf-Caucig1, Maciej Pelak1, Birgit Flechl1, Piero Fossati1, Markus Stock2, Christian Reschl1, Petra Georg3, Eugen Hug1
1MedAustron, Radiation Oncology, Wiener Neustadt, Austria; 2MedAustron, Medical Physics, Wiener Neustadt, Austria; 3MedAuston , Radiation Oncology, Wiener Neustadt, Austria
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Purpose or Objective
Irradiation of intracranial tumors may induce endothelial damage in the surrounding normal brain tissues, resulting in an increase of capillary permeability. These changes can be depicted on MRI as a new contrast non-tumoral contrast enhancement. Radiation-induced contrast enhancement (RICE) occur after photon as well as proton therapy (PT). This study evaluated the incidence of RICE after PT and their impact on Quality of Life (QoL).
Material and Methods
421 patients treated between 01/2017 and 06/2021 were included. All patients participated in a prospective registry study. Follow-up evaluations including MRIs were at 3,6,12 months after treatment completion and annually thereafter. QoL parameters were assessed by EORTC-C30 questionnaires. All follow-up MRIs underwent an independent second look evaluation by a radiation oncologist and diagnostic radiologist. Images were reviewed with focus on response and on onset of new intra-parenchymal contrast enhancement outside GTV but inside the irradiated volume.
Results
49% (n=206) patients received therapy for intracranial non-CNS tumors (meningioma, pituitary adenoma, and other), 27% (n=113) for head and neck cancer with skull base involvement, 15% (n=61) for primary CNS tumors and 10% (n=41) for skull base tumor.
Median follow-up was 24 months (range 6-54), 352 (86%) patients had proton therapy as primary treatment, 59 (14%) had salvage treatment with proton re-irradiation (ReRT).
Median prescribed dose was 58.5 GyRBE (range 40-78 GyRBE), median D1% of brain tissue was 54.3 GyRBE (range 30-76 GyRBE).
Local control and overall survival were 91% and 95% at 2 years.
The cumulative RIBL incidence was 15% (n=63), with significantly lower occurrence in the primary RT group vs. the ReRT group (13% vs. 27%; p<0.001). According to Grade, the distribution was 10.5% (n=44) Grade I (asymptomatic, MRT finding only), Grade II RIBL, 13 (3%) (moderate symptoms) (grade 2) and 1% (n=6) developed Grade 3 toxicity. Actuarial 2-year RIBL incidence was 18% for the all Grades and the entire, 16% following primary radiation and 34% after ReRT.
All RICE developed outside the residual tumor, but inside the Planning Target Volume (PTV), median D1% was 60GyRBE (range 46- 122GyRBE), median time to development was 11.8 months (range 2.7-37 months) in the total cohort, for primary RT 14.2mo (4mo -37mo) and 6mo (3mo -19mo) following ReRT. At the time of analysis 26 of the 63 RICE had resolved (41.3%).
Following proton radiation, general QoL was not compromised. In a matched-pair analysis of 54/50 patients with/without RICE, functioning scales and symptoms’ scales remained stable. Only at the 12-month patients with RICE had stable global health score, whereas patients without RICE improved (p<0.05). At 24 months the score for RIBL patients improved without difference between the groups.
Conclusion
Overall incidence of RICE after proton radiotherapy is very low - even for skull base tumors requiring high total doses and it had no significant negative impact on long term QoL.