THE LANDSCAPE OF SECOND LINE (AND BEYOND) TREATMENTS FOR GLIOBLASTOMA (IDH WILDTYPE) IN THE UK IN 2021: AN UPDATE FROM THE HISTO-MOL GBM COLLABORATIVE

Abstract AIMS First line treatment for glioblastoma has been standardised for the last 20 years. However, there is signifi- cant variation in choice of second (and subsequent) line treatments. In particular the role of re-resection and re-irradiation are unclear. Using a large individual patient database, we sought to describe the landscape of subsequent lines of treatment. METHODS Using the Histo-Mol GBM Collaborative database, a large individual patient database of patients diagnosed with pathologically confirmed glioblastoma in the UK in 2021, we investigated choice and outcomes of subsequent lines of treatment. RESULTS To date, 1481 patients from 43 oncology centres are included in the Histo-Mol GBM Collaborative database. From this cohort, 1078 (73%) demonstrated confirmed progressive disease (PD), of whom 476 (44%) received second line treatment. Systemic therapy (SACT) was the main second line treatment, provided in 336 patients (71%), followed by surgery (84 patients, 18%) and radiotherapy (30 patients, 6%). Only 13 patients (3%) were documented as being enrolled in a clinical trial. SACT was lomustine in 180 patients (54%), PC/PCV in 72 patients (21%), and Temozolomide in 68 (20%). Confirmed second progression occurred in 320 (67%), of whom only 123 (38%) went on to have 3rd line treat- ment. This was primarily systemic therapy (92 patients, 75%), with a minority receiving radiotherapy (15 pa- tients, 12%) or surgery (12 patients, 10%). 4th (28/71 patients, 39%) and 5th (4/16 patients, 25%) line treatments were rarely offered. In total, only 100 patients (9% of all patients with PD) received re-resection, whilst 48 patients received re- irradiation (4% of all patients with PD). Re-irradiation fully overlapped the initial PTV in 25 patients (52%), had marginal overlap in 9 patients (19%), and no overlap in 14 patients (29%). CONCLUSION Less than half of all patients receive second line treatment at progression. Re-resection and re-irradiation are infrequently used across all subsequent treatment lines.