Transcranial Magnetic Stimulation for Psychological Distress in Patients With Advanced Illness

Patients with advanced illness commonly experience symptoms of depression, anxiety, loss of autonomy, hopelessness, and diminished meaning and purpose. Often referred to as existential distress, these symptoms are associated with poor outcomes, including reduced medication adherence, lower quality of life, increased desire for hastened death, and suicide risk. Affecting up to 19% of patients with advanced cancer, existential distress is also a leading reason individuals pursue medical assistance in dying (MAiD), underscoring its impact at the end of life.

Treatment options for existential distress in palliative care (PC) are limited. Antidepressants and anxiolytics have modest evidence of benefit, may take weeks to work, and can cause adverse effects such as falls and confusion. Psychotherapeutic interventions have also shown limited efficacy in randomized trials and are often too time consuming for patients with limited life expectancy. Given the prevalence and consequences of existential distress, there is an urgent need for brief, scalable, and rapidly effective interventions for patients receiving PC.

Repetitive Transcranial Magnetic Stimulation (rTMS) is a Health-Canada- and FDA-approved safe and non-invasive brain stimulation intervention used to treat major depression, post-traumatic stress disorder, and other mood and anxiety disorders where medication has been ineffective. The technique uses trains of powerful, focused magnetic pulses, applied via a handheld inductor placed against the scalp, to induce changes in the activity of frontal lobe circuits responsible for regulating cognition and emotion. The most common stimulation protocols target the dorsolateral prefrontal cortex (DLPFC), using high-frequency (10-20 Hz) to the left DLPFC or low-frequency (1 Hz) to the right DLPFC, or both. With therapeutic rTMS, multiple sessions of treatment are delivered daily over 20-30 visits, to achieve durable symptomatic improvements. Clinical studies have shown rTMS can achieve a response (>50% symptom reduction) in half of patients and sustained remission rates in approximately 1/3 of patients whose depression has been refractory to 2 or more medications.

rTMS is generally well-tolerated with very few complications; about 95% of patients are able to complete a full course of treatment. However, there are obvious barriers to using traditional rTMS in the terminal population. First, the need to come to an rTMS clinic for a 60-minute session daily for 4-6 weeks is too great a time commitment for most patients nearing the end-of-life. Second, rTMS was only recently approved for public funding in many Canadian provinces, limiting the availability of rTMS to research settings and private clinics until now. Third, rTMS devices have been historically costly and difficult to transport, making it unfeasible for inpatient PC facilities to purchase an rTMS device or share one with a psychiatric clinic nearby. All of these factors have changed in the past couple years. New protocols of patterned rTMS have shortened treatment sessions yet preserve efficacy. Other "accelerated rTMS" protocols have given up to 10 sessions per day and shown symptom remission in just 2-5 days. The cost of these devices has also decreased dramatically in recent years (~$25,000 CAN), while the portability and availability have also improved, to the point that it is now feasible to use them in palliative settings.

The current body of literature presented above has studied the effectiveness of rTMS in patients with treatment-refractory depression and other mental illness. Essentially, the current treatment protocols have been designed to be effective in populations who are the most difficult to treat clinically. As such, there is no evidence as to whether or not patients with clinically less severe psychological distress (depression and anxiety), would require the same intensity and duration of treatment to achieve a clinically relevant therapeutic effect.

Objectives

Among patients with advanced illness followed by a PC provider:

1. Identify the lowest and range of therapeutic rTMS dose to relieve psychological distress, including an analysis of clinical predictors of response.
2. Test the feasibility and preliminary efficacy of accelerated rTMS for the treatment of psychological distress including: 1) ease of recruitment; 2) completion of follow-up; 3) effect size and variance estimates of treatment for primary and secondary outcomes; and 4) patient satisfaction with treatment.

Trial Design

The study is a phase 2a dose-finding open-label clinical trial, followed by a phase 2b prospective, sham-control or sham-crossover study, depending on the therapeutic dose identified in phase 2a.

Intervention and Control

The rTMS intervention will be performed in a dedicated rTMS patient room on an inpatient PC unit, where the patient can remain in their bed seated upwards at a 45 degree angle, or seated comfortably in a chair.

The stimulation intensity for the treatment will be determined by measuring the resting and active motor threshold (rMT and aMT) using single pulse TMS over the motor cortex using standard techniques as in previous trials. Investigators will use left-sided intermittent theta burst stimulation (iTBS) because it appears to achieve greater reductions in depressive symptoms and suicidal thoughts. The trained team member will locate the left DLPFC using the BeamF3 technique, which does not require neuroimaging and achieves comparably accurate positioning. For the phase 2a open-label dose-finding study, this region will be stimulated intermittently at 3 TMS pulses every 200 milliseconds for 2 seconds (i.e. 30 stimulations). This procedure is repeated every 10 seconds for 3 minutes during which 600 total pulses are delivered. Participants will receive up to 8 3-minutes sessions daily at 45 minute intervals for 5 days (consecutively or in a seven-day window if need be).

The results of this dose-finding study will inform the appropriate therapeutic dose to be provided to treatment-group participants in the phase 2b feasibility and preliminary efficacy trial. For example, if the dose-finding study demonstrates patients have a clinical response after just 3 days of treatment or 24 total doses, this will be the new treatment protocol for the phase 2b feasibility study.

For the sham intervention in the phase 2b feasibility and preliminary efficacy trial, the active coil will be replaced by a "sham" coil, which produces similar sound and scalp sensations as the active coils, but delivers no effective cortical stimulation.

Should the results of the dose-finding study demonstrate a low dose and minimal time is required to achieve therapeutic effect (e.g. 15 sessions over 3 days), the investigators will proceed with a sham-crossover study in which each patient will receive either the treatment or sham intervention first, followed by a 4-day washout period, after which they will receive either the treatment or sham intervention (whichever they did not receive the first round). Each patient thus serves as their own control. Alternatively, should the results demonstrate a high dose and time commitment (e.g. 40 sessions over 5 days) is required to achieve therapeutic effect, investigators will proceed with a sham-control design in which each patient will be randomized to receive either rTMS only or the sham control only. This decision is based on the rationale that it would be too cumbersome to ask patients to dedicate a minimum of 2 full weeks (5 days of treatment or sham, followed by a 4 day washout period, followed by another 5 days of treatment or sham) to this study, given these individuals are experiencing advanced illness.

Sample Size

To facilitate dose-finding in the phase 2a open-label trial, investigators will enroll patients until a clear threshold for therapeutic effect is identified, up to a maximum of 15 patients.

For the phase 2b feasibility and efficacy trial, investigators will aim to recruit 25 patients for the sham-crossover design, or 40 patients (n=20 treatment and n=20 control) for the sham-control design.

Recruitment

Each patient admitted to the PC unit will automatically be screened for eligibility by a research staff member and the treating PCU physician. Research staff will look at each newly admitted patient's Edmonton Symptom Assessment System (ESAS) score in the medical chart. A score of 7 or greater on the Depression, Anxiety or Well-being subscale of the ESAS will trigger research staff to approach the patient's physician to ensure the patient has an expected >1 month to live and is capable (physically and cognitively) of participating in the study. Both prospective participants and their physician will complete a screening questionnaire to ensure no contraindications to rTMS treatment.

Potential participants from the community will be identified by a member of their regional palliative care team (RPCT). A score of 7 or greater on the Depression, Anxiety or Well-being subscale of the ESAS and an expectation that the patient has an expected >1 month to live while being capable (physically and cognitively) of participating in the study will trigger an RPCT member to approach the patient to determine whether they are interested in the study. Both prospective participants and their health care provider will complete a screening questionnaire to ensure no contraindications to rTMS treatment.

For the phase 2b feasibility and preliminary efficacy trial, controls will be recruited in the same manner.

Allocation and Blinding

Investigators will use a random sequence generator for clinical trials. Information about allocation sequence will only be available to the trained research staff member who is administering the rTMS.

During the phase 2b feasibility and preliminary efficacy clinical trial, participants will be randomized to treatment versus sham (either order of treatment vs. sham is randomized in a sham-crossover, or the receipt of treatment or sham is randomized in a sham-control design). Participants will not be made aware of their randomization status and treatment allocation (i.e. participant blinding).

Study investigators will also be blinded to intervention allocation. The only individual who will have knowledge of the participant's intervention allocation is the trained rTMS operator who will be delivering the intervention.

Statistical Methods

Analysis of study results for the dose-finding study will be descriptive and correlational. Investigators will use descriptive statistics to examine the characteristics of participants who had a positive response to rTMS/ responded the quickest compared to the characteristics of participants who did not respond to rTMS treatment/had a slower response. We will also use descriptive measures (mean, median and respective confidence estimates) to evaluate the dose when 50% of participants, for example, experienced an improvement in symptoms.

Main analyses for the feasibility outcomes in both the dose-finding and phase 2b trial study will include calculation of outcomes using descriptive statistics with 95% confidence intervals. As the main aim is one of estimation rather than hypothesis testing, variance estimates and effect sizes with 95% confidence intervals will be calculated for primary and secondary efficacy measures in favour of significance testing.

Analysis for the phase 2b trial specifically will adopt an intention to treat approach. Assessment for a crossover effect should we use a sham-crossover design will employ a statistical analysis comparing the change in symptoms from before to after treatment in each patient over the sham period versus the active period. Assessment for a between-groups difference will be done should a sham-control design be employed.