Cancer clinical trials span treatment, diagnosis, prevention, screening, supportive care, and health-services research. The latest annual NCI-Designated Cancer Center submission table published April 30, 2024 counted thousands of open studies and hundreds of thousands of accrued patients. Survey estimates from 2020 and 2021 show a narrower path from awareness to enrollment, while focused caregiver studies describe the practical work and burden surrounding participation.
Contents
- How many cancer trials are open by study source?
- What research categories attract patients?
- How are trials distributed across phases?
- What are the primary purposes of cancer studies?
- What do awareness and participation statistics show?
- What do caregiver studies measure?
How many cancer trials are open by study source?
The NCI Clinical Research Studies: Data Table 4 reports combined submissions from NCI-Designated Cancer Centers. The display is fiscal-year data, but the accessible table does not expose the selected fiscal year, so the figures below are identified by the table’s latest publication date: April 30, 2024. “Open trials” and “accrued patients” are different measures: the first describes study count, while the second describes people accumulated in the reported center submissions.
| Study source | Open cancer trials | Accrued patients |
|---|---|---|
| Industry-sponsored | 7,544 | 26,580 |
| Externally peer-reviewed | 2,330 | 105,486 |
| Institutional | 7,375 | 195,477 |
| National Cooperative Group | 5,796 | 13,416 |
| Other or unknown | 705 | 198,686 |
Industry-sponsored studies accounted for 7,544 open trials and accrued 26,580 patients. Externally peer-reviewed studies accounted for 2,330 open trials and accrued 105,486 patients. Institutional studies accounted for 7,375 open trials and accrued 195,477 patients. National Cooperative Group studies accounted for 5,796 open trials and accrued 13,416 patients. The other-or-unknown classification accounted for 705 open trials and accrued 198,686 patients. These categories describe the source classifications in the center table; they should not be read as a ranking of trial quality or patient benefit.
What research categories attract patients?
The same April 30, 2024 NCI table separates cancer research by category. Interventional studies accounted for 17,635 open trials and accrued 104,869 patients. Observational studies accounted for 3,177 open trials and accrued 362,410 patients. Ancillary or correlational studies accounted for 2,925 open trials and accrued 72,275 patients. Thirteen studies had no reported research category and accrued 91 patients.
The patient counts illustrate why study counts alone can be misleading. Observational research represented 3,177 open studies in this table, yet its reported accrued-patient figure was 362,410. Interventional research had 17,635 open studies and 104,869 accrued patients. Ancillary or correlational research had 2,925 studies and 72,275 patients. The no-category group was much smaller in both measures, with 13 studies and 91 patients.
For families and caregivers, the category label matters because it can signal how participation is organized. The supplied center data do not say that every interventional study involves treatment, nor that every observational study requires less time. They provide counts by research category, not a schedule, eligibility assessment, or prediction for an individual patient.
How are trials distributed across phases?
Development phase is another way the NCI table describes open cancer studies and accrued patients. The figures below retain the source’s phase labels and measurement context.
| Development phase | Open trials | Accrued patients |
|---|---|---|
| Phase 0 | 79 | 680 |
| Phase I | 3,098 | 10,976 |
| Phase I/II | 1,654 | 6,245 |
| Phase II | 5,731 | 22,037 |
| Phase II/III | 444 | 959 |
| Phase III | 4,549 | 17,072 |
| Phase IV | 128 | 720 |
Phase 0 studies accounted for 79 open trials and accrued 680 patients. Phase I studies accounted for 3,098 open trials and accrued 10,976 patients. Phase I/II studies accounted for 1,654 open trials and accrued 6,245 patients. Phase II studies accounted for 5,731 open trials and accrued 22,037 patients. Phase II/III studies accounted for 444 open trials and accrued 959 patients. Phase III studies accounted for 4,549 open trials and accrued 17,072 patients. Phase IV studies accounted for 128 open trials and accrued 720 patients.
The table is descriptive rather than predictive. It does not establish that a later phase is available to every person, that a phase has a particular outcome, or that the number of open studies equals the number currently recruiting. It does show that the April 30, 2024 center-submission display included studies across early, middle, combined, and later development phases.
What are the primary purposes of cancer studies?
Primary purpose gives another view of the research landscape in the Clinical Research Studies: Data Table 4. Basic-science studies accounted for 2,412 open trials and accrued 65,147 patients. Diagnostic studies accounted for 823 open trials and accrued 12,076 patients. Health-services-research studies accounted for 358 open trials and accrued 202,673 patients.
Prevention studies accounted for 439 open trials and accrued 28,132 patients. Screening studies accounted for 307 open trials and accrued 16,045 patients. Supportive-care studies accounted for 1,051 open trials and accrued 14,287 patients.
Supportive-care research is especially relevant to caregiver support because it is a named category in the center data, but the table does not break those 1,051 studies into caregiver interventions, family outcomes, symptom management, or other subtopics. The 14,287 accrued patients are therefore a count for supportive-care cancer studies as classified by the source, not a count of caregivers.
The purpose figures also show why cancer clinical trial statistics should be read across several dimensions. A study can be counted by source, research category, phase, and primary purpose, and those views answer different questions. None of the supplied figures provides a patient-level estimate of access, benefit, risk, travel time, cost, or caregiver time.
What do awareness and participation statistics show?
The Clinical Trial Knowledge, Discussion, and Participation Among Cancer Survivors reports weighted survey estimates from the 2021 HINTS-SEER sample, drawn from three SEER registries. In that 2021 sample, 77.9% of cancer survivors reported knowing at least a little about clinical trials. However, 15.2% said their medical team discussed clinical trials as a treatment option, and 7.5% reported ever participating in a clinical trial for their cancer.
The same source summarizes published estimates in 2025 and places adult cancer clinical-trial participation between 2% and 8%. That range is a published estimate summarized by the source, not a new measurement of the 2021 HINTS-SEER respondents. The 7.5% estimate belongs specifically to the 2021 HINTS-SEER sample.
For broader context, the Clinical Trial Invitation, Participation, and Preferred Sources of Clinical Trial Information among American Adults reports results from the 2020 HINTS national adult sample. In that sample, 9% of Americans reported ever being invited to participate in a clinical trial. Among Americans who reported an invitation, 47% reported participating.
These figures measure different stages and populations. Knowing about trials is not the same as receiving a treatment discussion; a discussion is not the same as an invitation; and an invitation is not the same as participation. The 2020 national adult estimates and the 2021 cancer-survivor estimates should not be combined into a single funnel or treated as interchangeable rates.
What do caregiver studies measure?
Caregiver-focused evidence in the supplied sources comes from small, focused studies rather than population prevalence surveys. The Patient and Caregiver Perceptions of Caregiving Contributions During Cancer Clinical Trials: A Mixed-Methods Study included 21 patient-caregiver dyads in its final analysis. About 75% of participants were enrolled in trials involving several weeks of radiation, often with chemotherapy. Eighteen of the 21 caregivers were spouses or partners, representing 85% of caregivers, and 18 of 21 dyads lived in the same household, also representing 85%.
Patients reported that caregivers helped in an average of 3.14 of seven assessed contribution domains during cancer clinical-trial participation. Emotional support was reported by 100% of patients and caregivers in the study. These results describe the participants in that interview study; they are not estimates of the percentage of all cancer caregivers who provide those forms of support.
A separate Benefits and Burdens of Participation For Caregivers of Cancer Patients in Hospice Clinical Trials: A Pilot Study covered referrals made between June 2019 and February 2020. The study recorded 400 caregiver referrals. After initial screening, 203 contacted referrals remained, and 74 declined consent. The study received consent from 129 referrals: 87 clinical-trial participants and 42 pilot-study participants.
Mean caregiver burden was 4.05 among hospice clinical-trial participants, compared with 7.16 among pilot-only participants. Those are study-group means from the hospice research sample, not a general burden score for caregivers of people with cancer. The figures nevertheless show why participation statistics need a caregiver lens: enrollment decisions can involve emotional support, shared household responsibilities, trial schedules, and the burden associated with different research settings.
For readers considering a conversation about a cancer clinical trial, these statistics provide context rather than medical advice. The supplied research does not establish eligibility, expected results, or an individual caregiver’s likely burden. It does establish that cancer research is broad in type and purpose, that awareness and participation are measured separately, and that caregiver contributions and burdens have been documented in focused clinical-trial studies.