Bone morphogenetic proteins in spinal surgery: what is the fusion rate and do they cause cancer?

Abstract

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: The aim of this study was to determine the fusion rate using recombinant human bone morphogenetic protein (rhBMP) in spinal surgery and to estimate the risk of cancer subsequent to their use. SUMMARY OF BACKGROUND DATA: rhBMP may obviate the need for iliac crest bone graft harvest and provides similar or higher fusion rates than autologous bone graft. Recently, there are concerns that rhBMPs may either cause cancer or accelerate progression. METHODS: Patients were treated by 2 spine surgeons between 2002 and 2012. Inclusion criteria were patients who resided in the state of Victoria, Australia, undergoing lumbar fusion (anterior, lateral, posterior, and posterolateral) with rhBMP [either rhBMP-2 (Infuse) or rhBMP-7 (OP-1)]. Exclusion criteria were patients who reported having an invasive cancer diagnosis before the spinal fusion procedure. The occurrence of incident cancers was obtained from record linkage to the Victorian Cancer Registry. RESULTS: A total of 527 patients were included in the cohort, with a mean follow-up of 4.4 years (1.8-11.5). Patients received Infuse in 77% of cases and OP-1 in 23%. The mean Infuse does was 10.2 mg (2.5-48.0) and 3.3 mg (1.7-6.6) for OP-1. There was no significant difference in fusion rates between Infuse (90.1%) and OP-1 (91.9%) (P = 0.42). The overall success of interbody fusion with rhBMP was 93.5% at 12 months. Twenty-seven patients were diagnosed with an invasive cancer since treatment (20 Infuse and 7 OP-1 patients). Comparing the observed numbers in our study cohort with those expected on the basis of the Victorian population's age and sex-specific rates, we observed that the study cohort was not at a significantly increased risk of cancer. The standardized incidence ratio for cancer overall (of any type) was 0.84 [95% confidence interval (95% CI) 0.56-1.21]. CONCLUSION: Off-label use of rhBMP provided high fusion rates with no evidence of a significantly increased risk of cancer.