Identifying patients with non-response for an extension of TMS treatments for depression: A retrospective analysis of clinical response conversion.

Introduction: Transcranial Magnetic Stimulation (TMS) is an FDA-approved treatment for Major Depressive Disorder (MDD) which traditionally consists of 30 sessions of daily treatment followed by a taper phase of 6 sessions. Generally, over 50 % show a significant improvement in MDD symptoms; however, there are many patients who show a trend of improvement but have not have yet crossed that threshold defining meaningful clinical response. Extending the acute course with more sessions may optimize outcomes for the treatment course, however little data exist to inform which patients would benefit from treatment extension. In a retrospective analysis of naturalistic treatment data, we examined variables association with "conversion" of patients from nonresponder to responder status following extension of the acute course by at least 5 sessions. Methods: Response was defined as ≥ 50 % reduction from baseline score on the Inventory of Depressive Symptomatology-Self Report (IDS-SR). Of 485 treatment courses reviewed, we identified 40 patient series where a course extension (≥41 treatments) was given to patients who had not achieved response at treatment 30. In 21 treatment series, the patient "converted" to responder status by end of the course. Mixed model ANOVAs of IDSSR scores were used to compare the groups and identify features associated with conversion to response with additional sessions. Results: In 21 treatment series (representing 17 unique individuals), patients converted from nonresponse to response with additional treatment sessions beyond 30. Greater degree of IDS-SR improvement from baseline to treatment 30 was significantly associated with conversion to responder status. A 26 % reduction in IDS-SR total by treatment 30 showed 77.5 % accuracy in classifying whether or not a patient would ultimately respond to a 10-session course extension. Conclusion: Extension of the acute TMS course beyond 30 sessions is effective in converting a subset of nonresponding patients into treatment responders. The patients that were most likely to benefit from extension were those that improved the most by treatment 30. While these data may begin to inform extension criteria research, further study is needed to determine a clinically reliable threshold for selection of patients for an extension.