Changes in fatigue interference were measured using the validated 7-item interference scale of the Fatigue Symptom Inventory scale. Interference items assessed the degree to which fatigue interfered with general levels of activity, ability to bathe and dress, normal work activity, ability to concentrate, relations with others, enjoyment of life, and mood. Fatigue interference was scored on an 11-point scale, ranging from 0 (no interference) to 10 (extreme interference). Interference items were summed to obtain a total perceived interference score, with higher scores indicating greater fatigue interference.

The Fatigue Symptom Inventory (FSI), is a 14-item self-report measure designed to assess the severity, frequency, and daily pattern of fatigue as well as its perceived interference with quality of life. Severity is measured on separate 11-point scales (0=not at all fatigued; 10=as fatigued as I could be) that assess most, least, and average fatigue in the past week as well as current fatigue. Frequency is measured as the number of days in the past week (0-7) that respondents felt fatigued as well as the extent of each day on average they felt fatigued (0=none of the day; 10=the entire day). Perceived interference is measured on separate 11-point scales (0=no interference; 10=extreme interference) that assess the degree to which fatigue in the past week was judged to interfere with general level of activity, ability to bathe and dress, normal work activity, ability to concentrate, relations with others, enjoyment of life, and mood. Higher FSI scores are associated with worse outcomes.

The Fatigue Symptom Inventory (FSI), is a 14-item self-report measure designed to assess the severity, frequency, and daily pattern of fatigue as well as its perceived interference with quality of life. Severity is measured on separate 11-point scales (0=not at all fatigued; 10=as fatigued as I could be) that assess most, least, and average fatigue in the past week as well as current fatigue. Frequency is measured as the number of days in the past week (0-7) that respondents felt fatigued as well as the extent of each day on average they felt fatigued (0=none of the day; 10=the entire day). Perceived interference is measured on separate 11-point scales (0=no interference; 10=extreme interference) that assess the degree to which fatigue in the past week was judged to interfere with general level of activity, ability to bathe and dress, normal work activity, ability to concentrate, relations with others, enjoyment of life, and mood. Higher FSI scores are associated with worse outcomes.

Emotional distress was assessed using the Generalized Anxiety Disorder 7-Item (GAD-7), which is a reliable and validated self-report measure to assess anxiety symptoms. For the GAD-7, respondents rated how often they have been bothered by 7 anxiety symptoms over the past 2 weeks using the following scale: 0 = Not at all; 1 = Several Days; 2 = Over half the days; and 3 = Nearly every day. Respondents also answer a question to assess the duration of their anxiety symptoms. The scale is scored 0-21, where 0-4 is minimal anxiety, 5-9 is mild anxiety, 10-14 is moderate anxiety, and scores >15 is severe anxiety. Using a cut-off of 8 the GAD-7 has a sensitivity of 92% and specificity of 76% for diagnosis generalized anxiety disorder.

Fear of cancer recurrence will be measured using the 42-item Fear of Cancer Recurrence Inventory (FCRI). This survey has been validated across diverse cancer populations, has strong psychometric qualities, and is the most comprehensive multidimensional scale of FCR available.[36, 37] Items are scored on a Likert scale ranging from 0 ("not at all" or "never") to 4 ("a great deal or "all the time"). Higher scores indicate higher FCR. The FCRI is both internally consistent (Cronbach's α=0.75 to 0.91 across subscales) and stable over a two-week interval (ρ = 0.58 to 0.83 across subscales). It also has convergent validity with other standardized measures of FCR (ρ = 0.66 to 0.77) and discriminant validity with QOL amongst a large sample (n = 600) of Canadian cancer patients with varying tumor types.

Participants' quality of life (QOL) was assessed with the Functional Assessment of Cancer Therapy-Ovarian Cancer (FACT-O), which has demonstrated internal consistency, reliability, and validity. This measure is composed of the Functional Assessment of Cancer Therapy-General scale, with an ovarian cancer-specific subscale (OCS) included. The measure is divided into five primary QOL domains: physical well-being (7-items, scored 0-28), social/family well-being (7-items, scored 0-28), emotional well-being (6-items, scored 0-24), functional well-being (7-items, scored 0-28), and additional concerns (OCS subscale, 12-items, scored 0-44). Participants rated each QOL domain item based on the past 7 days as: 0) Not at all; 1) A little bit; 2) Somewhat, 3) Quite a bit, and 4) Very much. Subscales can be analyzed separately or aggregated to produce a total score which is scored 0-152 with higher scores signifying better quality of life.

We assessed emotional distress with the 8-item Patient Health Questionnaire (PHQ-8), which is a reliable and validated self-report measure to assess depressive symptoms. For the PHQ-8, respondents rated how often they have been bothered by 8 symptoms of depression over the past 2 weeks using the following scale: 0 = Not at all; 1 = Several Days; 2 = Over half the days; and 3 = Nearly every day. The scale is totaled (range 0-24) where total scores of 5, 10, 15, and 20 represent cutpoints for mild, moderate, moderately severe and severe depression, respectively.

We examined the number of participants who required reductions in the dose of their PARP inhibitor during the trial.

We assessed participants tendency to catastrophize about their fatigue using the Fatigue Catastrophizing Survey (FCS). Patients rate each question on a 5-point scale (1=never true to 5=all of the time) to indicate how often each item is true for them when they've experienced fatigue. The scale is scored by totaling the 10 items (range 10-50, where higher scores mean more severe fatigue catastrophizing). In prior research, more catastrophizing (as indicated by higher scores on the FCS) were associated with significantly greater fatigue.

Self-efficacy concerning fatigue (i.e. the belief in one's capabilities to execute behaviors) was measured with the 7-item Self-Efficacy Scale (SES28). Items are scored on a 4-point Likert scale, and total scores range from 4 to 28. Higher scores indicate a greater sense of control over fatigue.

We will measure changes in psychological flexibility (ACT processes) using the Acceptance and Action Cancer questionnaire, which is a 18-item measure adapted from the widely validated AAQ-II and diabetes-adapted AAQ towards cancer specific items. Numerous adaptations of the AAQ towards specific clinical targets have been shown to produce valid measures that mediate ACT outcomes for the specific population. The scale is scored by totaling the individual items (scale: 18-126). Lower scores reflect more psychological flexibility.

Experiential avoidance will be measured using the Brief Multidimensional Experiential Avoidance Questionnaire (BEAQ) which only includes 15-items and covers all dimensions of experiential avoidance, including: behavioral avoidance, distress aversion, procrastination, distraction and suppression, repression and denial, and distress endurance. The scale is scored by totaling individual items (range 15-90), where higher scores reflect more avoidance. This measure is internally consistent and has been broadly associated with psychopathology and quality of life.

We will use the 10-item Valuing Questionnaire (VQ) to assess personal values enactment during the past two weeks. Respondents rate on a 6 point scale (0 "not at all true" to 6 "completely true") how often each item was true for them during the past two weeks and evaluate using a two-factor scale; the Progress scale and Obstruction scale. The scale is scored by totaling 5 individual items (scored 0-30), where higher progress scores are associated with positive affect, satisfaction with life, purpose in life and mastery and self-acceptance.

We will use the 10-item Valuing Questionnaire (VQ) to assess personal values enactment during the past two weeks. Respondents rate on a 6 point scale (0 "not at all true" to 6 "completely true") how often each item was true for them during the past two weeks and evaluate using a two-factor scale; the Progress scale and Obstruction scale. The VQ Obstruction subscale is scored by totaling the sum of 5 items (scored 0-30) Higher VQ Obstruction scores are associated with more depressive symptoms and negative affect.