ESTRO 2020 Abstract Book

S69 ESTRO 2020

et al. reported on the first 46 BM patients randomized to HA-WBRT or WBRT in a single blind randomized controlled trial. Neurocognitive function (NCF) was assessed through a standardized neurocognitive test battery, with both patients and examiners blinded to the allocated treatment. The primary endpoint was the difference in changes of HVLT-R delayed recall at 4 months between HA- WBRT and WBRT. First differences were observed at 6 months, with a mean change of HVLT-R total recall of +2 ± 1.26 vs. -1 ± 0.97, ( p =0.08), and of HVLT-R recognition of 0.6 ± 0.54 vs. -1.4 ± 0.62, ( p =0.03) in patients receiving HA-WBRT and WBRT, respectively. The phase III PREMER study compared HA-PCI to PCI in 118 SCLC patients, with NCF as primary end-point, assessed by the Free and Cued Selective Reminding Test. HA-PCI significantly prevented 3- and 6-months memory disorders (rate of free delayed recall drop: 21.7 vs 5.1%; p 0.01; 32.6 vs 7.3%; p 0.008; 18.5 vs 3.8%; p 0.09 at 3, 6, and 12 months, respectively, in PCI vs PCI-HA arm. The NRG Oncology CC001 phase III trial randomized 518 BM patients to WBRT + Memantine (M) or HA-WBRT+M. Both multidimensional cognitive tests and patient-reported symptoms (PRS) were recorded. HA was associated with a 26%-reduction of cognitive decline (adjusted HR=0.74, 95% CI: 0.58-0.95, p=0.02). Time to NCF failure was significantly longer in the HA-WBRT arm. PRS also favored HA. Toxicity, overall survival, and intracranial progression were similar between the treatment arms. Lehrer et al. conducted a meta-analysis of five randomized prospective trials to quantify and compare the cognitive benefits derived from SRS, WBRT + M, and HA-WBRT, relative to WBRT. Three to four-months cognitive failure rates were 53.2% (95%CI: 48.5%-57.8%), 43.7% (95%CI: 37.7%-49.8%), 33.3% (95%CI: 28.6%-52%), 20.9% (95%CI: 15.7%-26.7%), in patients treated with WBRT, WBRT + M, HA-WBRT, and SRS, respectively. SRS, WBRT + M, and HA-WBRT had all statistically lower rates of cognitive failure than WBRT. Despite a large trend toward the use of SRS in patients with BMs, WBRT still retains value in patients unfitted for SRS or systemic BM treatment due to BM presentation. These patients are not necessarily at the end of the course of their disease and deserve attention to their neurocognitive outcome. HA-WBRT showed its cognitive preservation ability in three randomized trials and in a meta-analysis, as well as no additional toxicity and an acceptable recurrence rate in the HA area. Taken together, these data should lead to the routine use of HA when considering WBRT. SP-0146 Against the motion: This house believes that hippocampus avoiding WBI is the current standard of care C. Le Pechoux 1 , A. Levy 1 , A. Botticella 1 , O. Henry 2 , G. Auzac 2 , S. Bolle 1 , F. Dhermain 1 1 gustave Roussy Cancer Campus, Radiation Oncology, Villejuif Cedex, France ; 2 gustave Roussy Cancer Campus, Radiation Oncology Physics, Villejuif Cedex, France Abstract text Because of advances in the management of several solid tumours such as NSCLC, breast cancer, melanoma, the risk of developing brain metastases (BM) seems to increase as survival is prolonged. Their management represents a real challenge because Symptomatic BM can cause life- threatening symptoms and serious impairment of quality of life. In the last 15 years, there has been development and widespread use of stereotactic radiotherapy (SRT), but this concerns a subgroup of patients who have a limited number of brain lesions, for whom brain SRT and/or surgery can be proposed. This strategy provides better results than whole-brain irradiation (WBI) with median survival exceeding 12 months. WBI is still regarded as standard treatment for multiple symptomatic BM, not accessible to SRT even though a randomised trial does not seem to support the use of this approach versus best

supportive care in NSCLC. There is strong concern about the toxicity of such treatment. Acute toxicity is generally manageable but long-term sequelae such as neurocognitive toxicity and ataxia, are deleterious to the quality of life of patients. There are areas of active research that hold great potential to reduce the risk of neurocognitive decline after WBI such as hippocampal- sparing radiotherapy and the use of neuroprotective agents. As neurocognitive toxicity from WBI related to damage to neural progenitor cells in the subventricular zone and hippocampus and the induction of inflammation in the brain, several studies have been performed assessing hippocampus avoiding irradiation, considering that BM in the hippocampal region seem rare (about 5%), Promising results have been reported in patients having undergone WBI to treat BM. Another challenging area is evaluating prophylactic cranial irradiation with hippocampus avoidance, with contrasting preliminary results. The cause of radiation injury to the brain is likely to be multifactorial, and reducing radiation dose to the hippocampus may not be the only way to reduce neurotoxicity. Furthermore we need more mature results to conclude that it should the new standard of care. Abstract text Surface guided radiation therapy (SGRT) is a technique which uses optically visible light (and potentially other sources, such as thermal imaging) in order to position the patient during treatment according to the position during CT simulation. While positioning the patient according to skin marks and in-room lasers is the current standard practice, this method suffers from potential inaccuracies due to patient rotations, which are hardly detectable and accounted for, and misalignments of body regions, where no skin marks are drawn on. The same precision as with spatial lasers is achieved using SGRT-based positioning. For some body regions, SGRT has the potential to decrease the number of CBCT-based setups, resulting in the reduction of unnecessary radiation exposure to the patient, if it is assured that setup uncertainties are in the same range as CBCT positioning with SGRT. For treatment sites in the abdominal or pelvic region, this seems not to be the case: For example bladder and/or rectum filling set a limit to patient (or tumor) position using solely the surface as a surrogate. In addition, the accuracy of SGRT patient positioning decreases from cranial to abdominal regions (as well as for laser-based patient setup). The tube-like shape of (most) abdominal regions causes any registration algorithm to be less effective and reliable. Using internal organs or bones (and therefore techniques such as 2D, 3D, 4D MV/kV imaging, ultrasound, or marker tracking, etc.) in these cases cannot be neglected. With a (relatively) novel technique like SGRT, there remain many potential improvements in the workflows. One is that (even close to unnoticeable) time delays in patient setup can decrease the acceptance of therapists. In addition, more focus must be drawn upon staff training. As most commercially available systems are standalone systems, there is a lack of integration in the clinical workflows (e.g. CBCT-based positioning and 6DoF couch tops). The positioning of abdominal/thoracic (internal) tumor sites is one of the major future applications for SGRT, as internal-external correlation models are still missing on a broad basis. The selection of the region-of-interest (ROI) is another Symposium: Surface guided radiation therapy SP-0147 Surface imaging for patient positioning: current status and scope for improvements P. Freislederer 1 1 University Hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany