Introduction: The Viable Allograft Supplemented Disk Regeneration in the Treatment of Patients With Low Back Pain (VAST) trial (NCT03709901) evaluated the safety and efficacy of disc tissue allograft injection (VIA Disc®) into degenerated lumbar discs in patients with discogenic chronic low back pain (N=218; Beall et al. Pain Physician 2021). At 12 months, clinically meaningful improvements in pain, assessed via a visual analog scale (VAS), and in function, based on Oswestry Disability Index (ODI) score, were achieved in the investigational allograft and saline groups. An open-label extension study is in progress. Here, we report outcomes in patients who completed the 24-month follow-up.

Methods: The prospective, randomized, controlled VAST trial was conducted in patients with 1- or 2-level degenerative lumbar disc disease and chronic low back pain refractory to nonoperative treatments. At 12 months, patients could continue in an open-label extension study for up to 36 months, with an interim visit at 24 months. In this interim analysis, we assessed mean change from baseline in VAS and ODI scores and categorical responder status. To minimize confounding, we compared these 24-month data with results from prior timepoints in this completer population only.

Results: Nine of 12 sites participated in the VAST extension; outcome data were entered for 83 patients at 24 months (allograft-treated, n=70; saline-treated, n=13). The 24-month completer population within each study arm was similar to the intent-to-treat population in age, sex, race, ethnicity, body mass index, and smoking status. In the allograft-treated group, change from baseline in VAS score (mean [95% CI]) at month 24 was -26.4 (-34.29 to -18.41) versus -16.2 (-36.4 to 3.68) in the saline-treated group (Figure 1A). The proportion of patients achieving ≥50% reduction in VAS score at 24 months was 47% versus 31% in the allograft- versus saline-treated group (Figure 1B). From month 6 to 24 there was a steady decline in benefit in the saline-treated group; in the allograft-treated group there was improvement from month 6 to 12 followed by a decline from month 12 to 24 to just below the benefit at month 6 (Figure 1AB). The longitudinal trends for ODI (not shown) were similar to those for VAS score.

Between month 12 and 24, 9/66 allograft-treated patients demonstrated ≥50% reduction in VAS scores and 26/66 attained a VAS score ≤20 points, versus 1/13 and 2/13, respectively, of those receiving saline. Similarly, between months 12 and 24, reduction in ODI score of ≥10 points was seen in 22% of allograft-treated patients versus none in the saline group.

Discussion: This interim analysis of an open-label extension of the VAST trial suggests that viable disc tissue allograft might be a beneficial nonsurgical treatment for patients with chronically painful degenerated lumbar discs. These 24-month data showed durable pain relief and functional improvement in treated patients, whereas initial benefits in patients receiving saline injections diminished by 24 months.

Fig 1. Improvement in Pain Over 24 Months in the Completer Population. A, VAS score change versus baseline. B, proportion of patients with ≥50% reduction in VAS score