Objective: To conduct a secondary analysis of the EARLYSTIM study¹ to 1: Quantify the meaning of HRQoL outcomes and 2: Evaluate the changes of disease properties associated with HRQoL Changes.

Background: The EARLYSTIM study compared deep brain stimulation (DBS) with best medical treatment (BMT) over 2-years and showed a between group difference in the mean change of 8.0 from baseline in favor of DBS in health-related quality of life (HRQoL), measured with the PDQ-39 SI (summary index). Generally, biometrical interpretation of studies does not weigh the changes the patient or statistical distribution-based views, leadings to limitation in understanding which changes matter to the patient.

Method: Information using the Minimally Important Change (MIC) of the PDQ-39 SI was obtained through anchor-based techniques (Patient Global Impression of Change) and distribution-based techniques (magnitude of change, effect size, thresholds, distribution of benefit) were applied to the data from EARLYSTIM. Multiple regression was used to identify determinants of change in HRQoL.

Results: Anchor based techniques showed a PDQ-39 SI difference (follow-up–baseline) for patients who declared “minimal improvement” of -5.7 [-9.9, -1.6] (mean [95%CI]) in the DBS group vs -2.9 [-9.0, 3.1] in the BMT group. As the vast majority (80.8%) of DBS patients improved declared “much or very much improvement”, while the PDQ-39 SI difference was -8.7 [-11.4, -5.9] for the DBS and -6.5 [-10.8, -2.2] in the BMT group.
Distribution-based techniques showed the relative change and effect size provided a moderate benefit in the DBS group on the HRQoL, whereas a slight worsening was observed in the BMT group. The observed PDQ-39 SI change in the DBS group (-7.8) was higher than the MIC estimated value (-5.7 by the anchor; -6.3 by triangulation of thresholds), but not in the BMT (0.2 vs. -2.9 to -5.4), respectively. Almost 90% of the patients in the DBS group declared some improvement (approximately 57% beyond the estimated MIC), which was significantly different from the BMT group whose proportions were just over 30%. The number needed to treat (NNT) to improve ≥1 MIC by DBS vs BMT was 3.8. Change in depression, disability and pain influenced improvement of the DBS group

Conclusion: DBS improved HRQoL in a high proportion of patients to a significant and moderate degree, at 2 years follow-up.

References: 1Schuepbach WM, Rau J, Knudsen K, et al. Neurostimulation for Parkinson’s disease with early motor complications. N Engl J Med. 2013;368:610-622.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/interpretation-of-health-related-quality-of-life-outcomes-from-the-earlystim-study/