P14.69 Trends in postoperative chemoradiotherapy for Glioblastoma patients: a Danish cohort study

Abstract

Abstract BACKGROUND Postoperative chemoradiotherapy (CRT), using conventional radiotherapy (convRT), has a key role in the treatment of glioblastoma (GBM) supported by level 1A evidence. In the past decade, evidence supporting hypofractionated radiotherapy (HFRT) has emerged. However, GBM patients in clinical trials are highly selected. Consequently, real-world patients may not be able to undergo evidence-based treatments. The aim of this retrospective Danish cohort study was to evaluate the utilisation of and compliance with postoperative CRT in real-world GBM patients over time. MATERIAL AND METHODS All adults (≥18 years) with newly diagnosed GBM (histology confirmed) between 2011 and 2018 were identified via the Danish Neuro-Oncology Registry, which was furthermore used to extract all data. Radiotherapy (RT) was classified as convRT (≤2 Gy/fr, planned dose 44–66 Gy) or HFRT (>2 Gy/fr, planned dose 34 or 40 Gy). The utilisation of and compliance with CRT (only concomitant treatment assessed) was measured by intended and administered treatment, respectively. To assess trends, patients were grouped per year of diagnosis. Multivariable logistic regression was used to analyse the association of age (</≥70), sex, performance status (PS) before surgery and RT, tumour focality, extent of surgery, concomitant chemotherapy (CT), hospital (4 University Hospitals), and year of diagnosis, with convRT or HFRT. RESULTS The cohort consisted of 2153 patients. For the entire period, postoperative RT was planned in 1743 patients: utilisation of 81%, over time fluctuating between 77 and 84%. ConvRT was planned in 1428 patients (66%), with a steadily decreasing utilisation from 73% in 2011 to 52% in 2018. Of those, 1346 (94%) could complete RT as planned (over time fluctuating between 88–97%). In this group, the utilisation of and compliance with concomitant CT was 86% (fluctuating between 80–93%) and 73% (fluctuating between 47–84%), respectively. HFRT was planned in 315 patients (15%), with a utilisation of up to 26% in 2018, after a more pronounced increase since 2014. The compliance with HFRT was 93%, fluctuating between 85–100%. In this group, the utilisation of and compliance with concomitant CT was 33% (fluctuating between 0–47%) and 78% (fluctuating between 33–100%), respectively. The utilisation of HFRT compared to convRT was significantly associated with higher age, poorer PS before RT, multifocal tumour, less extensive surgery, less frequent concomitant CT, one hospital of RT treatment, and more recent diagnosis years. CONCLUSION The increased utilisation of HFRT is in line with emerging evidence during the cohort period. However, while HFRT was developed as a more convenient schedule for those with a poorer PS and older age, the overall utilisation of postoperative RT did not increase. Nor did the compliance with CRT increase in real-world Danish GBM patients.