‘No evidence’ that bone-growth agent for spinal fusion increases cancer risk

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A new study has found no significantly higher risk of cancer in patients who underwent lumbar spinal fusion surgery using recombinant human bone morphogenetic protein (rhBMP) than in the general population. The study appears in November 15 issue of Spine.

“Our study provides further evidence of rhBMP’s efficacy as a fusion agent with no evidence of a significantly increased risk of cancer,” write Gregory M Malham of Epworth Hospital, Melbourne, Victoria, Australia, and colleagues. But they emphasise that additional, larger studies will be needed to definitively establish the safety and effectiveness of using rhBMP products to promote bone growth for spinal fusion surgery.

The researchers analysed 527 patients who underwent lumbar spinal fusion surgery using rhBMP between 2002 and 2011. All procedures were performed by Malham or co-author Graeme A Brazenor. Fusions were performed using rhBMP alone (ALIF and LLIF) or a combination of rhBMP and local bone (PLIF and posterolateral fusions).

The patients (average age 58) had no previous history of invasive cancer. The risk of developing new cancer after spinal fusion with rhBMP was independently assessed by Graham Giles and Roger Milne of Cancer Council Victoria by linking patient data to a population-wide mandatory cancer registry.

In the analysis, Malham and Brazenor found high rates of successful spinal fusion surgery using rhBMP. Follow-up CT scans showed fusion rates between 90 and 95%, depending on which operative approach was used. After one year, the overall rate of successful fusion was 93.5%.

At an average follow-up of 4.4 years, 27 of the 527 patients were diagnosed with some form of invasive cancer. Based on the cancer registry, this was not significantly different from the number observed in a population of the same age and sex.

There was no increased prevalence of any one type of cancer. The study also found low rates of other rhBMP-related complications, such as ectopic bone growth.

“Our study represents the first retrospective review of patients treated with rhBMP using verified cancer prevalence from a compulsory state cancer registry,” says Malham. But he notes that the results can’t definitively rule out a small increase in cancer risk. “It is still possible that much longer follow-up may ultimately detect a tendency toward one or more cancers.” The authors note that their study was performed “independently of industry.” 

The researchers also point out that rhBMP does not require grafting of the patient’s own bone. Using rhBMP instead of harvested bone graft may avoid pain and a substantial risk of additional complications. Malham notes that he and Brazenor have not used iliac crest bone for spinal fusion since they began using rhBMP.