Fear of cancer recurrence (FCR) is one of the most prevalent, persistent, and disruptive sources of distress for adult cancer survivors. Prevalence rates for FCR have been estimated at up to 89%, with approximately half of cancer survivors reporting clinically significant levels of FCR. Despite the recognized prevalence, persistence, and suffering associated with FCR, effective and accessible treatments for FCR are lacking and urgently needed. Our long-term goal is to develop, evaluate, and implement effective behavioral interventions for cancer survivors suffering with FCR.

The proposed randomized pilot study will assess the effects of a novel therapeutic intervention-Acceptance and Commitment Therapy (ACT)-for breast cancer survivors (BCS) with clinically-significant FCR. ACT is a spiritually-sensitive behavioral therapy that has shown efficacy in the treatment of anxiety in non-cancer populations, and preliminary efficacy in improving a variety of outcomes among adults with cancer. ACT uses mindfulness and acceptance processes, along with committed behavior change in service of an individual's deeply held values to enhance psychological flexibility and encourage adaptive coping with life challenges, such as cancer.

The primary objective of the proposed 3-arm randomized controlled pilot trial is to assess the feasibility/acceptability and determine preliminary effect size estimates of ACT in preparation for a fully-powered efficacy trial. To allow for potential drop out (15% attrition) and ensure we have a minimum of 78 completers through the end of the trial, we will enroll approximately 91 BCS with clinically significant FCR (defined by score ≥ 13 on Fears of Cancer Recurrence Inventory-Short Form). Participants will be randomized to one of three groups: (1) a 6-week ACT intervention group (n=26); (2) a 6-week survivorship education group (SE; n=26); or (3) enhanced usual care (EUC; n=26). The impact of ACT, SE, and EUC on survivors' FCR and associated psychological, spiritual, and biological (telomere length) outcomes will be examined at baseline (T1), post-intervention (T2), and at 1-month (T3) and 6-month follow-up (T4) with the following specific aims:

Aim 1: Evaluate feasibility and acceptability of ACT, SE, and EUC according to the:

1. Percentage of eligible BCS who consent to participate in the trial;
2. Attendance rate across 6 sessions of ACT and SE;
3. Retention rate through T4 in the ACT, SE, and EUC arms;
4. Mean ratings across groups for intervention satisfaction and helpfulness for managing FCR.

Aim 2: Determine pairwise effect size estimates of ACT, SE, and EUC effects at each time point (T2, T3, T4) adjusted for T1 on the:

1. Primary outcome: reducing FCR;
2. Secondary psychological outcomes: cancer-related experiential avoidance, cognitive avoidance, anxiety, depression, post-traumatic stress symptoms, vitality, breast cancer self-efficacy, and quality of life;
3. Secondary spiritual outcomes: spiritual well-being and mindfulness;
4. Secondary biological outcome: telomere length.

Inclusion Criteria: Participants in this study will be eligible if they are:

1. ≥18 years old,
2. have been diagnosed with non-metastatic breast cancer (stages I-III),
3. have completed curative treatment for breast cancer,
4. have not experienced a cancer recurrence, and
5. report a clinically significant level of FCR (Fear of Cancer Recurrence Inventory-Short Form score of ≥ 13)

Exclusion Criteria: Participants in this study will be ineligible if they are:

1. severe depression (PHQ-8 score of ≥ 20),
2. past participation in ACT or formal mindfulness training, and
3. limited English proficiency.

Participants were blinded to study hypotheses.