Clinical trials test new ways to identify, prevent, and treat cancer via diagnostic, behavioral, medical, surgical, and other types of interventions (eg, gene therapy) [1,2]. Over time, increased attention has been focused on improving clinical trial participation [3] and increasing age, sex, and racial or ethnic representation in clinical trials [4-6].

While many factors contribute to differences in general clinical trial participation, lack of knowledge and awareness about clinical trials is a significant barrier to recruitment [1,7-9]. That is, people cannot participate in a clinical trial if they do not know about the option of joining a clinical trial in the first place or do not have some level of health literacy to support informed decision-making about clinical trial participation. Healthy People 2030 defines personal health literacy as “the degree to which individuals have the ability to find, understand, and use information and services to inform health-related decisions and actions for themselves and others” [10]. Prior research on cancer information seeking has demonstrated that patient-provider communication scores, self-efficacy in managing one’s own health, difficulty understanding information, concern about the quality of information, and frustration during the search for information are associated with self-efficacy for obtaining cancer information [11,12].

Naturally, health literacy and cancer information-seeking skills can directly influence knowledge about clinical trials, especially because many clinical trial opportunities are posted online. Strategies to enhance general clinical trial knowledge about cancer and other medical conditions include media campaigns [13,14], clinical trial registries such as ResearchMatch [15], websites and online databases such as ClinicalTrials.gov [16], decision aids [17,18], tailored and targeted messages about research participation [19,20], direct-to-consumer and direct-to-patient invitations [21-23], patient education materials [24,25], and group-based information sessions [26,27].

Regarding cancer survivors’ knowledge of clinical trials and willingness to participate in research, differences by race or ethnicity have been observed. Using cross-sectional data from 147 Black and White cancer survivors who took the “Minority Patient Participation in Cancer Clinical Trials” survey, Kumar et al [28] found that Black cancer survivors were less likely than White cancer survivors to be aware of cancer clinical trials, express willingness to participate in cancer clinical trials, and participate in cancer clinical trials. Using data from the 2020 Health Information National Trends Survey, Commaroto et al [1] described cancer survivors’ (n=553) knowledge of clinical trials and prior invitations to participate in clinical trials. They found that cancer survivors with a high school diploma were less likely to have any knowledge of clinical trials than those with a baccalaureate degree or higher. However, no statistically significant differences were found in clinical trial knowledge or prior invitation to participate by sex, age, or race or ethnicity. Lastly, Cho et al [29] evaluated data from 958 cancer survivors from the 2021 Health Information National Trends Survey-Surveillance, Epidemiology, and End Results (SEER) Program and found that having 1 or more comorbidities was significantly associated with lower rates of clinical trial discussions but not clinical trial participation. While these studies provide useful information, it is also important to explore the correlates of clinical trial knowledge of cancer survivors that include but extend beyond sociodemographic factors.

The purpose of this study was to evaluate the associations between knowledge of clinical trials among US cancer survivors and perceived quality of patient-centered communication, cancer information seeking, emotional support, and watching health-related videos on YouTube. A priori, we proposed 2 main hypotheses:

Hypothesis 1: Cancer survivors with a higher perceived quality of patient-centered communication would have greater knowledge of clinical trials than those with a lower perceived quality of patient-centered communication.

Hypothesis 2: Cancer survivors who were “completely confident” that they could get advice or information about cancer if they needed it would have a greater knowledge of clinical trials than those who are less than completely confident.

Greater insights into ways to enhance clinical trial awareness among cancer survivors can support ongoing efforts to improve equitable participation and inclusion in cancer clinical trials.

The Health Information National Trends Survey (HINTS) regularly collects nationally representative data on the American public’s knowledge of, attitudes toward, and use of cancer and health-related information [30]. The HINTS data collection program was created to monitor changes in the rapidly evolving field of health communication [31]. In 2021, the National Cancer Institute undertook a pilot project to oversample cancer survivors for the HINTS using 3 cancer registries from the SEER Program as a sampling frame for cancer survivors: Iowa Cancer Registry, Greater Bay Area Cancer Registry, and New Mexico Tumor Registry [32]. HINTS-SEER data can be accessed by submitting a data request through the HINTS website, where comprehensive methodology details are also available. All HINTS-SEER data are deidentified. HINTS-SEER data were collected from January 11, 2021, through August 20, 2021. Eligibility criteria were as follows: cancer diagnosis specified to invasive cancers, 18 years of age and older, last contact no earlier than January 1, 2016, and a diagnosis date prior to 2018 based on certified data. Survivors who were only diagnosed with nonmelanoma skin cancer were excluded. However, survivors diagnosed with nonmelanoma skin cancer, in addition to other cancers, were included.

The present study used HINTS SEER data to cross-sectionally explore the associations between knowledge of clinical trials and various sociodemographic factors. A total of 27 of the 1234 responses were removed from the data analysis because of a missing response on the dependent variable of interest (knowledge of clinical trials), leaving a final sample size for analysis of 1207.

This study used publicly available, de-identified HINTS-SEER data to conduct a secondary analysis. The data contain no personal identifiers. Because the dataset is publicly available and deidentified, this research does not involve human subjects as defined by federal regulations (45 CFR 46.102) and is exempt from institutional ethics review. Accordingly, Institutional Review Board (IRB) review at the first author’s institution was not required. It should be noted that a formal Micro-Data Dissemination Policy for the Health Information National Trends Survey: HINTS SEER data use agreement between the author’s home institution and HINTS was signed on October 23, 2023. The parent HINTS-SEER pilot study underwent expedited review by the Westat IRB and was approved as an amendment to HINTS 5 on May 22, 2020 (Project Number 6048.14, Amendment ID #3212). The participating SEER registries obtained independent IRB approvals for their participation in the study. The full details of the selection of registries, the sampling and consenting procedures, and compensation can be found in the methodology report [33].

The following survey items were used to conduct the analysis for this study.

Knowledge of Clinical Trials (primary outcome). First, participants read the following prompt: “Clinical trials are research studies that involve people. They are designed to compare new kinds of health care with the standard healthcare people currently get. For example, a new drug or a new way for patients to track their diets.” Next, participants were asked, “How would you describe your level of knowledge about clinical trials?” The response options were (1) I don’t know anything about clinical trials, (2) I know a little bit about clinical trials, and (3) I know a lot about clinical trials. For the primary analysis, we compared “I don’t know anything about clinical trials” with “know a lot” and “know a little bit” combined. As a secondary analysis, we compared survivors who reported that they know “a lot” with those who reported that they know “a little bit” about clinical trials.

Age was evaluated continuously and by group (18‐64 y, 65‐74 y, and 75+ y). Race or Ethnicity was evaluated as non-Hispanic White versus all other racial or ethnic categories combined: Black or African American, Hispanic, Asian, and Other. Sex Assigned at Birth options were male and female. Education was evaluated as college graduate versus not college graduate.

Feelings about Household Income were assessed with the question, “Which one of these comes closest to your own feelings about your household’s income?” The response options were (1) living comfortably on present income, (2) getting by on present income, (3) finding it difficult on present income, and (4) finding it very difficult on present income. We consolidated the difficulty-related answers such that 3 groups were evaluated in the analysis: “living comfortably” versus “getting by” versus “finding it difficult” or “finding it very difficult on present income.”

Cancer Information Seeking. Participants were asked if they had ever looked for information about cancer from any source. Response options were yes and no.

Confidence to Get Cancer Health Information was assessed with the item, “Overall, how confident are you that you could get advice or information about cancer if you needed it?” The response options were completely confident, very confident, somewhat confident, a little confident, and not confident at all. We compared “completely confident” responses with all other responses combined.

Health Information Seeking on Social Media. First, participants read the prompt, “Sometimes people use the Internet to connect with other people online through social networks like Facebook or Twitter.” This is often called “social media.” Next, they were asked, “In the last 12 months, have you used the Internet for any of the following reasons?” Response options were (1) to visit a social networking site, such as Facebook or LinkedIn; (2) to share health information on social networking sites, such as Facebook or Twitter; (3) to participate in an online forum or support group for people with similar health or medical issues; and (4) to watch a health-related video on YouTube. Given that YouTube is the most widely used social media platform [34] and a common way for people to get health information [35], we only evaluated responses to watching health-related videos on YouTube in this analysis.

Trust Information From Doctor. Participants were asked how much they would trust information about cancer from a doctor. The response options were a lot, some, a little, and not at all. We compared “a lot” responses to all the others combined.

Understanding Information in Online Medical Records. Participants were asked how easy or difficult it was to understand the health information in their online medical record. The response options were very easy, somewhat easy, somewhat difficult, and very difficult. We compared “very easy” with all other categories combined.

Patient-Centered Communication Scale. The Patient-Centered Communication Scale variable was created using 7 items related to communication. Specifically, participants were asked how often doctors, nurses, or other health professionals they saw during the past 12 months were as follows: (1) give you the chance to ask all the health-related questions you had, (2) give the attention you needed to your feelings and emotions, (3) involve you in decisions about your health care as much as you wanted, (4) make sure you understood the things you needed to do to take care of your health, (5) explain things in a way you could understand, (6) spend enough time with you, and (7) help you deal with feelings of uncertainty about your health or health care. The response options included always=1, usually=2, sometimes=3, and never=4. The values of these 7 variables were reverse-scored, such that never=1 and always=4. The mean of these 7 variables (if at least half of the variables had valid values) was generated. Finally, the mean value was transformed to a 0‐100 scale.

Odds ratios (ORs), 95% CIs, and P values were calculated using SAS (version 9.4; SAS Institute Inc, Cary, NC, USA) proc surveylogistic with jackknife weighting, including the overall weight and 50 replicate weights, and the Newton-Raphson algorithm. The results are presented as odds ratios [95% CIs] for the odds of having knowledge about clinical trials and P values. Due to the small sample size (<25), some response categories were combined. Factors that had a corresponding P<.10 in univariable models were attempted in the multivariable model. In univariable analyses, all available data were used for each factor. Surveys that were missing a response were simply excluded from consideration for that factor’s univariable analysis. Using backward elimination, factors were removed one by one until all the remaining factors in the model were significant (P<.05). It should be noted that a higher percentage of the California registry respondents had knowledge of clinical trials than respondents from the New Mexico registry. Therefore, we adjusted for registry in the final models. When interpreting ORs, CIs that do not include the value 1 are considered significant. Data were analyzed using SAS (version 9.4) and SAS/STAT (version 14.1; SAS Institute Inc). Given that we first compared (primary analysis) “I don’t know anything about clinical trials” with “know a lot or know a little bit” combined and secondarily compared “know a lot” versus “know a little bit,” the sample sizes varied across analyses.

The objective of this study was to evaluate associations between knowledge of clinical trials among US adult cancer survivors and key correlates of interest. In the primary analysis comparing those who know “a lot” or a “little bit” combined versus those who did not know anything about clinical trials, we found that White race, a 4-year college education, and health information seeking including having watched a health-related video on YouTube were associated with increased odds of having knowledge of clinical trials, whereas female sex assigned at birth was associated with lower odds of having knowledge of clinical trials. Our first hypothesis that cancer survivors with a higher perceived quality of patient-centered communication would have greater knowledge of clinical trials than those with a lower perceived quality of patient-centered communication was not supported by the results. Moreover, our second hypothesis that cancer survivors who were “completely confident” that they could get advice or information about cancer if they needed it would have greater knowledge of clinical trials than those who are less than completely confident about finding cancer information if needed was also not supported by the results.

In the secondary analysis comparing those who know “a lot” versus “a little bit” about clinical trials, we found slightly different trends. In summary, those who were college graduates, those who looked for cancer information from any source, and those who understood health information in their online medical records had higher odds of knowing “a lot” about clinical trials.

A novel finding was that cancer survivors who watched health-related videos on YouTube had higher odds of clinical trial knowledge. Given YouTube’s broad reach, including among older adults [34], video-based education may be a scalable avenue for improving awareness of clinical trial opportunities. Several mechanisms may explain why watching health-related videos on YouTube is associated with greater clinical trial knowledge. First, YouTube provides a dynamic, visually engaging format that can simplify complex topics such as trial design, consent, and risks or benefits, potentially improving comprehension and retention. Second, YouTube’s algorithm can create an “information cascade,” where viewing 1 cancer-related video leads to recommendations of related content including clinical trial education [36]. Third, YouTube allows for peer-to-peer storytelling. Accordingly, testimonials from survivors or clinical trial participants may build trust and normalize clinical trial participation, which could be particularly impactful compared to static text-based resources that are often used to describe clinical trials. Finally, unlike passive browsing, intentionally watching health-related videos likely reflects higher digital health literacy and proactive health engagement; these traits may predict greater awareness of clinical trial opportunities.

Our results related to watching health-related videos on YouTube complement Nutbeam’s conceptualization of health literacy as not merely functional (basic reading and numeracy) but also interactive and critical [37,38]. Survivors who actively sought cancer information and who watched health-related videos on YouTube may be engaging in interactive or critical health literacy, leveraging digital platforms to deepen their understanding of research opportunities. Future interventions could therefore focus on improving survivors’ critical health literacy, particularly among those with lower educational attainment, to reduce disparities in clinical trial knowledge [39]. Clinicians and cancer centers could incorporate curated video content into survivorship care, and policies that encourage evidence-based digital health communication may help ensure content quality. Future research should identify optimal video characteristics (eg, length, storytelling approaches) that most effectively promote informed decision-making.

Other health information-seeking findings were that cancer survivors who ever looked for information about cancer from any source had higher odds of clinical trial knowledge, further underscoring the importance of health information-seeking skills. Health systems and patient navigators could play a key role in training survivors to locate and evaluate credible information, while policies supporting digital health literacy initiatives may help reduce disparities. Research should examine which strategies best sustain long-term information-seeking engagement.

Our finding that female sex assigned at birth was associated with lower clinical trial knowledge compared with male sex assigned at birth warrants further consideration. Although speculative, individuals assigned female at birth may engage more frequently with preventive and routine health care services yet experience different communication patterns during oncology visits, including shorter discussions about clinical research opportunities or lower referral rates to clinical trials. In addition, structural factors such as caregiving responsibilities and time constraints may limit opportunities to participate in research discussions or to seek supplemental information. Addressing these multifaceted factors through patient-centered communication strategies, tailored educational materials, and flexible clinical trial designs may help mitigate sex- and gender-related disparities in clinical trial knowledge and participation.

We observed that non-Hispanic White survivors were more likely to have clinical trial knowledge. Knowledge of clinical trials is needed before a cancer survivor can make an informed decision about participation. While many studies have shown that willingness and intent to participate in clinical trials do not vary across racial or ethnic groups if a clinical trial is explicitly offered to a person [20,40-42], it is imperative that health care systems and health professionals ensure equitable opportunities for cancer patients to be aware and knowledgeable about the clinical trials for which they may be eligible [43]. For example, oncologists can routinely present clinical trial opportunities to cancer survivors during medical encounters. eHealth interventions may also play a role in enhancing clinical trial knowledge [44], while direct-to-patient invitations via patient portals may enhance awareness of clinical trial opportunities without relying on health professionals to be gatekeepers of information [23]. Additionally, policies could support funding for inclusive recruitment and education campaigns.

Our finding that survivors with a college degree were more likely to report higher clinical trial knowledge underscores the relationship between educational attainment and health literacy. General information seeking and health-specific information-seeking models posit that sociodemographic characteristics (eg, education) shape both the motivation to seek information and the skills required to evaluate and apply it [39,45-47]. Higher educational attainment is associated with stronger critical appraisal skills, greater self-efficacy for information seeking, and more frequent use of diverse information channels. These factors likely enhance survivors’ ability to locate and interpret complex information about clinical trials, aligning with evidence that health literacy mediates the effect of education on knowledge and decision-making [43]. Higher educational attainment being linked to greater clinical trial knowledge may also reflect better access to academic medical centers that offer more clinical trial opportunities than community hospitals or federally qualified health centers. Additionally, cancer survivors with more education may proactively seek clinical trial options on health system websites, the National Cancer Institute website, or ClinicalTrials.gov, which may enhance their general knowledge of clinical trials. Strengthening health literacy and providing simplified, accessible trial information across care settings may help mitigate this gap. Future work could evaluate interventions that promote trial awareness among survivors with less formal education.

Our study complements the research by Gerdes et al, who explored clinical trial knowledge, discussions, and participation among cancer survivors using HINTS-SEER data [48]. In summary, they found that approximately 78% of cancer survivors reported having little or a lot of clinical trial knowledge and that those who discussed clinical trials with a health care provider had 8.71 higher odds of clinical trial knowledge than those who did not discuss clinical trials with a health care provider. Additionally, they found that clinical trial knowledge was lower for Hispanic versus non-Hispanic White participants. This study builds on the work of Gerdes et al by providing new insights into clinical trial knowledge among cancer survivors through our comprehensive evaluation of different correlates, including general patient-centered communication, emotional support, cancer information-seeking behaviors, and the use of YouTube to watch health-related videos. Additionally, while other studies have used HINTS data to evaluate associations between watching health-related videos on social media and correlates, including perceived patient-centered communication [49] and human papillomavirus awareness [35], to our knowledge, no studies have exclusively evaluated the relationship between watching health-related videos on YouTube and clinical trial knowledge among cancer survivors.

The strengths of this study include the large sample of cancer survivors recruited from 3 SEER registries and the breadth of the HINTS survey items, which allowed for a comprehensive analysis of variables that may be associated with knowledge of clinical trials. Despite these strengths, some limitations must be noted. First, although we assessed knowledge of clinical trials, we do not know whether cancer survivors who took the HINTS were knowledgeable about specific clinical trials (ie, those that were actively recruiting participants) versus general knowledge that clinical trials are possible options for cancer survivors. People who were knowledgeable about a specific clinical trial may have had more knowledge about clinical trials overall because they received information about what to consider when joining a clinical trial (eg, time demand, risks, benefits). Second, the question regarding clinical trial knowledge was broad and not limited to cancer-specific clinical trials. Third, it is unclear what knowing “a lot” about clinical trials meant to participants, and how that knowledge may have translated into actual enrollment in cancer clinical trials or other clinical trials beyond cancer (eg, mental health, diabetes, hypertension). Fourth, each of the 3 SEER registries had a different process for consenting cancer survivors to the HINTS-SEER survey, which may have affected those who were aware of the HINTS-SEER survey opportunity and ultimately participated. Lastly, this study represents survivors from only 3 SEER registries (Iowa, Greater Bay Area, and New Mexico), which may not be representative of all US cancer survivors.

Future work should explore specific domains of clinical trial knowledge among cancer survivors (eg, where to find them and different phases of clinical trials) and areas of greatest concern regarding clinical trial participation (eg, side effects and time commitment). Additionally, more research is needed regarding patient-provider communication regarding clinical trials and how the topic is typically introduced to cancer survivors. Finally, determining which attributes of health-related videos are most likely to appeal to cancer survivors warrants further research (eg, length, content, and types of people featured in videos).

In summary, sociodemographic factors and health information-seeking behaviors including engagement with online health videos were associated with clinical trial knowledge among US cancer survivors. These results suggest that enhancing digital health literacy, supporting evidence-based video education, and ensuring equitable clinician-patient discussions are promising strategies for increasing clinical trial awareness. Policies that fund digital outreach and promote equitable trial communication, along with research to identify the most effective educational approaches, will be critical to translating these findings into practice.