Participants were YA cancer survivors aged 15‐39 years at the time of initial cancer diagnosis and aged 18‐39 years at the time of participation in this study. All participants had completed curative treatment at least 1 month but no more than 5 years before enrollment. Participants were also fluent in English, able to give informed consent, and not currently experiencing a psychiatric or neurological disorder that could impair their participation. YAs were recruited from the University of Arizona Comprehensive Cancer Center and community-based cancer advocacy groups in Tucson, Arizona.

Study procedures were reviewed and approved by the University of Arizona Institutional Review Board (IRB #STUDY00000717). All participants provided written informed consent.

To build the initial version of the TOGETHER website, we leveraged an existing digital platform developed by BrightOutcome Inc. [24]. The platform is a customizable, Health Insurance Portability and Accountability Act–compliant, mobile-friendly, password-protected website designed to facilitate remote delivery of course-based supportive care interventions and host live group videoconference sessions. We began by inputting the TOGETHER content into the platform’s infrastructure. Subsequently, we held 3 waves of usability testing with 3 participants per wave (n=9 total) based on prior research showing that 9 usability testers are needed to find moderately hard-to-find problems with 75% certainty [25].

Individual usability testing sessions were held in person and each lasted approximately 60 minutes. During these sessions, participants were introduced to a prototype of the TOGETHER website and asked to think aloud while completing a series of prescribed tasks (eg, log in, navigate from the home dashboard to session content). Participants were then asked to provide feedback on the appeal, clarity, comprehensibility, and aesthetic of the website. After each wave of testing, participant feedback was integrated into the website, and testers in the subsequent wave were shown the modified version. We iteratively incorporated stakeholder feedback in this way to maximize user engagement with TOGETHER [26]. Usability testing participants were compensated US $30 for their time.

Participants completed the 11-item Ease of Use subscale and 4-item Ease of Learning subscale from the Usefulness, Satisfaction, and Ease of Use (USE) questionnaire [27,28]. Items are rated on a 7-point scale ranging from 1 (Strongly Disagree) to 7 (Strongly Agree) and averaged to yield a total score. Higher scores indicate better usability. Usability testing participants also self-reported demographic and medical information.

Audio recordings of the usability testing sessions were transcribed verbatim by a third-party service (GMR Transcription Services, Inc.). Each transcript was reviewed by at least 2 reviewers using an analytic approach similar to Gale and colleagues’ [29] rapid qualitative analytic method to identify actionable feedback. Reviewers identified suggested changes to the website and supporting quotes using an analysis template in Microsoft Excel. The audio recordings were revisited as needed for content and wording clarifications. After independent review, coders compared and discussed results to achieve consensus. This process was completed after each round of usability testing, and changes to the website were implemented rapidly in response to participant feedback. In addition, descriptive statistics were used to summarize the demographic and clinical characteristics of study participants and to describe website usability per the USE individual items and subscale scores.

Information about usability testers’ demographic and medical characteristics can be found in Table 1. Participants were an average of 27 years old (range 23‐37) at the time of study participation and predominantly White (n=8, 89%), with two-thirds identifying as Hispanic or Latine (n=6, 67%). Slightly more than half were female, had completed some college or specialized training, and were working full-time (n=5, 56% each). The most common cancer diagnoses reported were breast cancer (n=3, 33%) and leukemia (n=2, 22%), and the average age at diagnosis was 24 (range 19‐34) years.

The frequency and means of item-level usability ratings for both USE subscales can be found in Table 2. Mean scores on the Ease of Use subscale of the USE questionnaire (mean 5.94, SD 1.27) and each of the 10 items contained therein (means ranged from 5.22 to 6.33) supported the website’s usability. Results for the Ease of Learning subscale demonstrated it was also easy to learn based on both the overall subscale score (mean 6.50, SD 0.89) and the 4 individual item scores (means ranged from 6.44 to 6.56).

A screenshot of the TOGETHER website can be found in Multimedia Appendix 1. YA cancer survivors described the website as “clean,” “neat,” “visually pleasing,” “user-friendly,” “straightforward,” “organized,” “intuitive,” and “easy to navigate.” Participants particularly valued that there were multiple ways to access or complete various website functions. For example, participants expressed appreciation that program exercises and home practices could be completed digitally within the website or downloaded as a PDF to be completed offline. Participants identified several strengths related to the aesthetics, content, function, and structure of the website, as well as recommendations for how to improve the platform. Table 3 lists the modifications made to the website in response to these recommendations. Of note, not all feedback led to immediate changes to the website. For example, some participants requested a progress tracking feature that would enable them to quickly visualize which aspects of the program had already been completed. This change was not feasible immediately following usability testing; however, it has since been implemented in subsequent iterations of the website.

Eligibility and recruitment for the feasibility trial mirrored that of usability testing, although feasibility trial participants were also required to have access to internet or cellular connectivity with sufficient bandwidth to participate in videoconferences. Participants who completed usability testing were permitted to enroll in the feasibility trial if desired. In such cases, participants provided informed consent for each stage of the study.

The feasibility trial was preregistered on ClinicalTrials.gov (NCT05597228) [30] and consisted of a single instance of the 10-week TOGETHER group intervention. After providing informed consent, participants completed a 1-time website orientation videoconference meeting with a member of the research team. Participants were also mailed a physical copy of the TOGETHER participant workbook. The physical copies were provided because YAs who contributed to the development of the intervention content [17] recommended providing both physical and digital copies of intervention materials to program users.

Participants then completed a full administration of the facilitator-led TOGETHER group intervention delivered via the adapted website. All intervention sessions were held on a Health Insurance Portability and Accountability Act–compliant version of Zoom. The link to join each week’s session was visible on the website beginning 36 hours before the session was scheduled to start and remained visible until 2 hours after the session was scheduled to end. Sessions each lasted approximately 2 hours and occurred on the same day of the week at the same time for the duration of the program. Immediately following each session, participants in attendance were sent a unique link to complete a brief electronic survey assessing the acceptability of that session’s content and group dynamics. Participants completed a similar survey postintervention assessing the acceptability of the overall program. Participants completed an individual exit interview with a member of the research team postintervention to provide qualitative feedback on their experience. Participants also completed a battery of patient reported outcome measures at baseline and postintervention. The battery was consistent with the planned assessment protocol for a future, larger-scale trial; however, given the small sample size, we were not powered to detect effects and therefore did not analyze these data. Participants were compensated US $50 for completing the baseline and post-intervention assessment batteries, US $20 for completing the exit interview, and US $5 for each of the 10 weekly surveys completed. In total, feasibility trial participants had the opportunity to earn up to US $170.

Details of the TOGETHER intervention have been previously published [17]. Briefly, each TOGETHER session consists of 3 main sections: learn and practice relaxation skills (first 30 min), practice skills derived from cognitive behavioral therapy principles (middle 60 min), and discuss YA-relevant health education topics (remaining 30 min). During each session, a facilitator guides participants through new content and leads interactive activities designed to reinforce the content and skills. Facilitators also create opportunities for participants to discuss their personal experiences and develop group rapport. Between sessions, participants complete home practice assignments to promote mastery of the intervention skills, and each session begins with a review of the prior week’s home practice. For this feasibility trial, sessions were facilitated by a predoctoral clinical psychology trainee (TKT) under the supervision of the study Principal Investigator (RSF). Sessions were video- and audio-recorded and reviewed during weekly supervision meetings to ensure intervention fidelity.

Feasibility was measured by calculating study recruitment and retention rates and tracking session attendance [31]. Feasibility was defined as achieving a 50% recruitment rate, a 70% retention rate, and average attendance of ≥ 6 of the 10 sessions. These benchmarks were based on rates observed in past studies of similar behavioral interventions in diverse cancer survivors [19,32,33] and in accordance with our prior investigation of the feasibility of TOGETHER content [17]. Acceptability was measured with study-specific weekly and postintervention surveys our team previously developed to assess the acceptability of the TOGETHER content [17]. Survey items assessed participant satisfaction with multiple aspects of TOGETHER and were rated on a Likert scale ranging from 0 (strongly disagree) to 4 (strongly agree). For this study, a new item was added to the postintervention acceptability survey assessing the acceptability of the study website. The study was considered acceptable if average scores on the weekly and postintervention survey items were ≥2 (ie, neutral or better). Participants also completed the Satisfaction subscale of the USE questionnaire [27,28] postintervention and self-reported demographic and medical information at baseline.

Descriptive statistics were used to summarize feasibility and acceptability metrics.

Seven YA cancer survivors enrolled in the single-arm feasibility trial, 6 of whom had also participated in usability testing due to practicality reasons. Information about feasibility trial participants’ demographic and medical characteristics can be found in Table 1. On average, feasibility trial participants were 25 years old at the time of participation (range 18‐33) and were 22 years old at the time of incident cancer diagnosis (range 17‐32). The majority were female (n=5, 71%), non-Hispanic White (n=4, 57%), and had never been married (n=4, 57%). The most well represented cancer types included bone and soft tissue (n=2, 29%) and breast (n=2, 29%).

All feasibility metrics were met. Of 12 seemingly eligible YA cancer survivors who were approached for participation, 7 (58%) consented and enrolled in the study (Multimedia Appendix 2). All 7 participants attended the first group session, after which 1 withdrew, and 1 was lost to follow-up. Of the remaining 5 participants, all were retained through the postintervention assessment (71% of enrolled). Across all 7 participants, the average attendance was 7.1 of the 10 intervention sessions (SD 4.2); however, among the 5 participants who attended at least 2 sessions, the average attendance was 9.6 of the 10 sessions (SD 0.5).

All acceptability metrics were met. Tables 4 and 5 show the average acceptability ratings for each of the 10 weekly sessions and for the overall program, respectively. Pooled average satisfaction with the individual weekly sessions was ≥3 for all items. Participants agreed to strongly agreed that they liked the sessions, the content was relevant and helpful, they felt confident with the content, and they felt comfortable and respected in the group. Similarly, at postintervention, the means for all items assessing overall program satisfaction were ≥3, with the exception of an item assessing satisfaction with the website. Based on feedback gathered in exit interviews, low ratings for satisfaction with the website were due to a timing feature that prevented participants from viewing data they had entered (eg, responses to home practice prompts) in subsequent weeks even though the data had been saved. This led some participants to express frustration with the website, particularly when reviewing the prior week’s home practice assignments at the start of each session. For example, when asked to share additional information about their experience in the program during exit interviews, one participant stated, “everything was great besides the homework assignments not saving” and another specified, “I would have liked using the website even more if it wouldn’t have erased the data. Besides that glitch it seemed quite self-explanatory and would’ve been used more.” This feature has since been fixed.

The Satisfaction subscale of the USE questionnaire supported the acceptability of the program website. The mean score on the overall subscale was 5.06 (SD 1.64), with individual item means ranging from 3.80 to 5.80. The item with the lowest average rating assessed if the website worked as desired, and no items received the lowest possible rating from any participant. When asked to identify the website’s most negative aspect(s), multiple participants identified the website not displaying past work properly. Conversely, when asked to identify the website’s most positive aspect(s), participants identified the “clean, friendly interface,” and described the website as “easy to navigate,” and “straight to the point.” Some participants also highlighted strengths of the overall program, including the exercises and home practice assignments as well as the value of meeting other YA cancer survivors and learning new tools and skills.