Use of a Decision Aid to Resolve Uncertainty About Radioactive Iodine Treatment in Patients With Intermediate Risk Thyroid Cancer

Background Information Differentiated thyroid cancer (DTC) presents with a spectrum of disease severity, which is associated with varying recurrence rates. Radioactive iodine (RAI) treatment is often considered for moderate to high recurrence risk cases. Patients with low-risk DTC typically have very low recurrence rates, and RAI is generally not used. In contrast, patients with high-risk DTC commonly receive RAI due to a substantial risk of recurrence. The intermediate-risk group experiences uncertainty regarding the potential benefit of RAI in reducing recurrence risk. This study is designed to evaluate the effect of a decision aid (DA) on the decision-making process among patients with intermediate-risk DTC.

Rationale In 2020, an estimated 860,000 individuals in the United States were living as thyroid cancer survivors, with approximately 55% classified as having low-risk disease. Use of RAI in patients with high-risk DTC has been associated with extended survival and reduced recurrence. Among patients with intermediate-risk DTC, 15-year survival rates remain high at 85% to 93%. However, the benefits of RAI in this population may apply only to certain subgroups, such as older individuals or those with larger tumors.

The study intervention consists of a web-based decision aid called RAI Decisions. Eligible patients are randomized to either the DA arm or a usual care (UC) arm. The UC arm receives standard educational material from the American Cancer Society (ACS) website.

Decisions regarding RAI in intermediate-risk DTC are more complex due to several factors: variability in disease severity, limited data on risk and benefit, and differences among physicians and institutions in treatment recommendations and communication practices. Additional factors influencing decision-making may include age, comorbidities, and fertility considerations. Current clinical practice guidelines recommend consideration of RAI in this group, rendering the decision one of personal preference. These guidelines have contributed to a shift away from over treatment of DTC.

RAI usage within the intermediate-risk category is often influenced by disease severity markers (e.g., number of lymph nodes involved, thyroglobulin levels), physician specialty and perceptions, geographic proximity to care, and institutional practices such as multidisciplinary tumor board discussions. Standard of care currently ranges from minimal patient engagement to robust shared decision-making. The decision aid used in this study does not intend to direct or alter clinical decisions regarding RAI use. Instead, it is designed to support informed, value-based decisions through balanced educational content. The decision aid clearly states that it does not provide medical advice and that treatment decisions should be made in consultation with the patient's clinical team.

This research addresses a documented gap in informational support for patients with intermediate-risk DTC making decisions about RAI. The web-based DA seeks to promote informed choice through evidence-based content, interactive tools, and guidance for communicating with healthcare providers. Previous research suggests that patients who understand the trade-offs of treatment options are more likely to make decisions consistent with their values and experience less regret.

Study Design This is a multi-site randomized controlled trial (RCT) conducted at three hospital systems in the Washington, DC metropolitan area. A total of 713 newly diagnosed intermediate-risk DTC patients will be screened to enroll and randomize 408 participants, specifically 204 in the DA arm and 204 in the UC arm. Participants will be assessed at four timepoints: baseline, 1 week, 4 weeks, and 6 months post-randomization. Retention of 85%, calculated as 346 participants, at 6 months is expected.

The primary outcome is informed choice, assessed at 4 weeks. Secondary outcomes include knowledge, decisional conflict, regret, and treatment satisfaction, assessed at 4 weeks and 6 months. Additional analyses will examine whether self-efficacy and satisfaction with physician communication mediate the DA's effect. Exploratory outcomes include quality of life (QOL), treatment choice, and intermediate indicators of cancer recurrence (e.g., serum thyroglobulin levels, lymph node characteristics via ultrasound, and clinician concerns noted during routine care).

Although treatment decisions will be recorded, the DA is not designed to encourage or discourage RAI use. Instead, the focus is on whether patients make informed decisions aligned with their personal values. Because intermediate-risk DTC is generally an indolent condition, the trial will assess surrogate markers of recurrence risk rather than long-term clinical outcomes.

Participants will complete study assessments via phone or online, according to their preference. Assessors will be blinded to randomization status. Satisfaction with the assigned website (DA or UC) will be measured at the end of each follow-up survey. It is hypothesized that the DA will increase rates of informed choice compared to UC among patients with intermediate-risk DTC.

Inclusion criteria

• Patients aged 18 and older
• Patients diagnosed with intermediate risk DTC < 6 months ago and who are making a decision about RAI treatment
• Ability to understand the information conveyed in the informed consent form, pose questions and process answers (e.g., no cognitive impairment per direct consultation with the patient's physician), and, finally, provided informed consent to participate.
• Participants willingness to be contacted and remain available to complete study activities throughout the duration of the study.

Exclusion criteria

• Diagnosis of low risk or high risk DTC
• Prior history of RAI
• Clinical contraindications that prevent consideration of RAI (e.g., pregnancy, lactation, neutropenia if considering high dose of RAI)