Clinical research directed towards understanding variations in cancer outcomes across different ethnicities is essential for understanding risk factors and enabling accurate interpretation of treatment efficacy, safety and tailored management with novel therapies [32]. In the evolving era of precision medicine within oncology, variables such as ethnic pharmacogenomic differences, individual patient characteristics and lifestyle factors should be considered in clinical trials to optimise the accuracy of outcomes [33].

Our analysis revealed significant differences in the characteristics of clinical trials conducted with sites in Asia versus those without. Trials with sites in Asia tend to have more locations and larger target enrolments, and are more often funded solely by the industry. They also exhibit a higher proportion of phase 3 trials and greater female representation. These findings are comparable to a previous study analysing industry-sponsored clinical research registered on CT.gov conducted between 2006 and 2014, showing that countries in Asia were the most likely to recruit exclusively outside high-income countries, and studies tended to be larger, of longer duration, and later phase interventions than studies performed solely in high-income countries [34].

We also found that trials without sites in Asia show a higher prevalence of phase 2 trials, a non-randomized design and a greater representation of older adults. These differences could be influenced by various factors, such as regional health policies, demographic characteristics, disease prevalence and industry strategies. Our data also indicate that global corporations play a dominant role in the sponsorship of oncology clinical research in Asia. Regional Asian biotechnology firms, although active, have a considerably smaller footprint in this regard. Understanding these discrepancies can provide valuable insights for future research planning and policy-making to ensure more equitable and representative clinical trials across different regions [35, 36].

Our analysis of the types of cancers studied in clinical trials also revealed a varied landscape depending on whether the trials include sites in Asia. Notably, lung and stomach cancer studies were significantly more common in trials with Asian sites than in those without (p < 0.001 and p = 0.0026, respectively). Myeloma also showed a significant difference, with less representation in trials with sites in Asia (p = 0.0375). These findings highlight the potential influence of regional disease prevalence and research focus on selecting cancer types studied in clinical trials which however does not match with the demographic trend in cancer incidence [37,38,39]. The higher prevalence of stomach cancer in Asia is mirrored in the types of trials conducted; the same was not found for liver cancer. This clearly suggests a research gap and possibly competing priorities in cancer research funding and focus in Asia.

The CAGR data suggest a general downward trend in the number of clinical trials conducted both in and outside of Asia over the 5-year period analysed. The overall downward trend in the number of clinical trials conducted in Asia was uniform and did not vary irrespective of whether the trials  were carried out exclusively in Asia or in conjunction with other countries. However, this trend is contrary to previous analyses of registered clinical trial information investigating the participation of Asian countries. A study of phase 2 and phase 3 global clinical trials registered on CT.gov between 2008 and 2015 showed larger increases in East Asia than in the United States and Europe [40]. Similarly, clinical trial information from the WHO’s ICTRP between 2008 and 2017 showed a sevenfold increase in the number of registered clinical trials in Asia over the 10-year period and the average annual increase in the number of registered trials was generally higher in Asia than in the USA, Canada, EU countries, or Australia [41]. This has also been demonstrated specifically for oncology clinical trials in China, India, Japan and South Korea, where the annual number of registered cancer trials from 2005 to 2018 in the ICTRP increased substantially, with an almost two-fold increase of registered interventional trials between 2005 and 2018 [18]. Only the study analysing industry-sponsored clinical research with countries categorised by income as used in the Global Burden of Disease project showed a stable rate of industry-funded clinical studies outside high-income countries over the 7-year investigation period (2006–2014) [34]. The declining trend identified in our analysis could reflect the impact of the global COVID-19 pandemic, which has disrupted research activities worldwide, particularly during 2020 and 2021 [42, 43].

Our study further demonstrated a less pronounced decline in the number of trials conducted at Asian sites. Despite a general downtrend in the overall trial count, the proportion of trials taking place in Asia witnessed a relative upward swing, as revealed by a 0.81% spike in the CAGR from 2020 to 2021. This observation is in harmony with earlier research that also signalled a more pronounced upward movement for clinical trial sites in Asia [18, 34, 41]. This increase could potentially signify a revitalisation of clinical research activities in the region after the disruptions caused by the COVID-19 pandemic. It might also reflect the increasing recognition of the importance of including diverse populations in clinical trials and the substantial patient pools and improved clinical trial infrastructure in many Asian countries. This positive trend underscores the growing role of Asia in the global clinical trials landscape.

Although the median for the number of sites was higher for trials with sites in Asia, we found a concentration of clinical trials primarily in East Asia, with China leading among trials with sites in Asia. Conversely, the United States dominates the trials without sites in Asia. This uneven distribution indicates a significant geographical disparity in the global conduct of clinical trials, with East Asia, particularly China, being highly represented, and without a significant contribution from other regions in Asia. This highlights an opportunity to expand the scope of clinical trials to encompass more diverse regions in Asia, fostering a more representative and inclusive research landscape. Such an expansion could provide richer and more generalised data, potentially enhancing the efficacy and safety of oncology treatment strategies across diverse populations.

Market considerations and regulatory obligations might account for the higher prevalence of clinical trial sites in East Asian countries, especially China. The National Medical Product Administration (NMPA) in China encourages early clinical trial participation in China or including China in multi-regional clinical trials and implementing an ethnic sensitivity analysis in the drug development plan [44, 45]. The preference and requirement for local patient data in new oncology drug applications is also a norm in Japan, South Korea and Taiwan, albeit with varying regulations based on the trial phase and scale and existing FDA/European medicines Agency (EMA) approval [46]. Simultaneously, participation in global phase 3 studies and demonstrating consistency with the overall study population can facilitate smooth approval timelines, enabling swifter access to innovative oncology medicines in Asia [47]. This aligns with the recent FDA guidance that provides recommendations and techniques to clinical trial sponsors for enhancing the diversity of clinical trial populations [48, 49].

Several barriers, however, often limit the execution of clinical trials in Asia. These include the potentially lengthy duration associated with obtaining regulatory approval for trials [50], along with regulatory differences in review processes, and inconsistencies in dossiers and other document requirements and management procedures [46]. In the field of oncology, various personal and geographical hurdles may interfere with the successful execution of clinical trials. Personal barriers include a need for more experienced healthcare personnel capable of conducting trials. Geographical challenges may arise due to the concentration of specialised centres in cities, making them inaccessible to individuals residing in rural areas [51]. Additionally, variations in health literacy across Asia can also pose challenges. This may manifest as a cautious approach towards enrolling in a trial due to unfamiliarity or misconceptions and a cultural tendency to lean on family support when making healthcare decisions [51].

Despite the barriers faced in conducting clinical trials in Asia, there are noteworthy opportunities in conducting oncology clinical trials in Asia that warrant exploration. These include potentially lower trial costs [52], higher chances for recruiting subjects for cancers with a higher prevalence in Asia (like gastric cancer) [50], higher representativeness for characteristics of cancers in Asia that differ from non-Asian populations [53, 54] and an availability of a larger pool of treatment-naïve patients for recruitment [55]. These concerted factors may have also contributed to the higher proportion of randomised trials in Asia, as observed in our study. Notably, conducting oncology clinical trials, including industry-sponsored studies, leads to the strengthening of local research capability [50, 51], enhancing regional research network capabilities [56] and establishing local clinical trial databases [57, 58]. These advancements ultimately support local oncologists in making referrals for patient enrolment, which not only advances the field of clinical research in the region but also facilitates early access to innovative therapies for life-threatening diseases.

The approval of cancer treatments marks a significant milestone; however, the lack of racial and ethnic representation in clinical trials poses barriers to developing evidence-based medicines. As shown in our study, studies with sites in Asia have a significantly higher rate of industry involvement as sole funder. This also puts the onus on the pharmaceutical industry to collaborate with the broader oncology community to implement effective changes [32, 59]. Several best practices for biopharmaceutical companies for enhancing ethnic diversity in clinical trials have also been discussed [7]. These include forming partnerships with diversity-focused professional bodies, selecting investigators and sites where diverse populations exist, creating referral maps that incorporate census data on diversity, consulting specialised advisory boards for diversity improvement, and implementing telemedicine approaches for broader participation. By working together in implementing these solutions, we can make significant strides in addressing systemic race-related barriers and promoting more equitable healthcare outcomes for all individuals, irrespective of their racial or ethnic background [60,61,62].

Our study has limitations, including reliance solely on entries from CT.gov, potentially leading to a sample bias that could affect the accuracy and generalizability of our results. Despite these limitations, we believe that they have not significantly impacted our overall findings regarding industry-sponsored trials. While the WHO-ICTRP includes some datasets from CT.gov, it often excludes many industry-sponsored clinical trials. Thus, our reliance on CT.gov primarily ensures the inclusion of these industry-sponsored studies in our analysis.