OC-0408 Higher-dose radiotherapy for metastatic spinal cord compression: First results of a phase II trial

Purpose or Objective To evaluate the outcomes after high-precison RT (preferably VMAT) with increased doses (EQD2 for tumors >40 Gy) when compared to 10x3 Gy (EQD2=32.5 Gy) for metastatic spinal cord compression (MSCC) in patients with favorable survival prognoses. Materials and Methods Since 08/2019, 29 (of 65) patients (9 female, 20 male) with motor deficits due to MSCC and a favorable survival prognosis according to a validated score have been included in a phase II trial (RAMSES-01). Median age is 68 (48-90) years, and most common tumor types are prostate cancer (n=10), breast cancer (n=7) and myeloma (n=6). RT regimens include 18x2.333 Gy (EQD2=43.2 Gy, n=10), 15x2.633 Gy (41.6 Gy, n=17;fewer fractions due to Covid-19 pandemic) and 12x2.663 Gy + 3x2.333 Gy (40.5 Gy, n=2;due to concurrent immunotherapy). Primary endpoint is local progression-free survival (LPFS=no progression of motor deficits during RT and no in-field recurrence following RT). Secondary goals include effect on motor function [improvement, overall response (OR) = at least no further progression] and sensory deficits, pain relief, overall survival (OS) and toxicity. Follow-up (FU) is performed until death or for 12 months. Results Three patients are currenty under treatment, one patient died after 14 Gy. Thus, 25 patients are evaluable for LPFS and response. LPFS is 100% at the end of RT (currently n=25), and at 1 month (n=21), 3 months (n=16), 6 months (n=9), 9 months (n=5) and 12 months (n=3) following RT. Considering best response during FU, OR and improvement rates are 100% and 60%, respectively. Sensory function normalized in 5 of the 9 patients (55.6%) with pre-RT sensory dysfunction. Of 21 patients with pain (median score 8, range 4-10), 18 (86%) achieved pain relief [complete in 7 patients (33%)]. OS-rates at 6 and 12 months are 71% and 71%, respectively. Six patients died (3 sepsis, 2 pneumonia, 1 tumor progression);death was not related to RT. RT-related grade 3 toxicity occurred in 2/25 (8%) patients (1 esophagitis, 1 diarrhea). Conclusion First results of high-precision RT with increased doses for MSCC in patients with favorable survival prognoses appear very promising with high response and LPFS rates and very few grade 3 toxicities. Updated information will be presented at the meeting.