In this month's issue of the Lancet Neurology, the PD SURG trial results (conducted by a multicenter team of collaborative investigators from all over Britain) are including a one year follow-up of Parkinson's disease deep brain stimulation (DBS) patients. The trial was randomized, and it compared DBS to best medical therapy. The primary outcome variable was quality of life, and interestingly, patients in the best medical therapy arm had access to apomorphine pumps. Though sites were allowed to use the subthalamic nucleus (STN) target, the globus pallidus internal target, and even lesion therapy (e.g. pallidotomy), 174/178 (98%) of patients in the surgery group were implanted with subthalamic nucleus DBS. There was a five-point improvement noted in quality of life scores in the surgical compared to medical group. Although compared to other studies the quality of life improvement was less robust, this may have reflected a longer study duration, or potentially even disease progression. There were unmistakable improvements in dyskinesias, and on time in the surgical group, although diaries were not utilized.
Though, not a perfect trial, its large size and use of a medical control group along with unique access to apomorphine made it unique among available DBS publications. The results underscored the powerful influence that DBS can have on motor fluctuations. Additionally, these SURGE investigators plan in the future a long term (9 year) follow-up, and this will surely enlighten the field as to disease progression, and other issues potentially important to DBS cohorts.
One unique and hidden aspect of this trial was the report of the "reasons why patients sought DBS surgery." Severe off periods, dyskinesia and tremor were far and away the most common indications cited for DBS therapy. As DBS moves into a tailoring phase (the right target and approach for a particular symptom or symptom cluster) this type of information will be very useful to clinicians.
People may criticize the lower total motor change scores reported in PD SURG when comparing pre- and post-operative operative outcomes to other trials, however they must remember that as many randomized blinded DBS trial results emerge from international centers (VA PADRECC study, Cleveland Clinic/Emory Study, UF COMPARE trial), that the open label improvements previously documented will almost certainly be shown to be a study bias. The results of the PD SURG trial may offer a look at what DBS outcomes may realistically look like as the therapy migrates to centers with less expertise (remember they used a multitude of centers all over Britain).
It is fascinating to see that 98% of implants were placed in the subthalamic nucleus in this study, despite the option for surgeons to use a different target. Though the subthalamic target has many strengths, it also has relative weaknesses. Emerging data is now strongly suggestive that the motor outcomes in pallidum and subthalamic nucleus are actually similar, and that targets in the future should be tailored for individual patients and individual symptoms.
In conclusion can we say the PD SURG trial was a surge forward for the PD community? The answer is certainly yes, as the publication of more carefully controlled DBS trials will be important in guiding DBS therapy into the future.
You can find out more about our National Medical Director, Dr. Michael S. Okun, by also visiting the Center of Excellence, University of Florida Health Center for Movement Disorders and Neurorestoration. Dr. Okun is also the author of the Amazon #1 Parkinson's Best Seller 10 Secrets to a Happier Life and 10 Breakthrough Therapies for Parkinson's Disease.