Background

Prostate cancer (PCa) is the most prevalent type of cancer in men in the UK, with approximately 55,100 confirmed new cases each year and a further 1.4 million worldwide [1, 2]. Effective treatments for localised and metastatic PCa are recognised to have side effects which may be associated with negative impacts on patients’ quality of life, functional status and physical and mental health [3,4,5,6]. Despite advances in PCa management and improvements in outcomes driven by clinical trials, it is recognised that significant PCa health disparity remains due to a poorly understood, complex interplay of factors [7]. It is well documented that Black men are at a 2.1 times greater risk of being diagnosed with PCa (23.5–37.2%) compared to individuals of White (13.2–15.0%) or Asian (6.3–10.5%) ethnicity [8, 9]. Black men are more likely to be diagnosed at a younger age and with a more advanced stage PCa compared to men of other ethnicities. Advanced PCa can have a significant impact on patients’ survival, quality of life and ability to carry out activities of daily living effectively [10].

Exercise has been demonstrated to improve the health outcomes and quality of life of men with PCa [11,12,13]. The evidence supporting the benefits of exercise in men with PCa has become more compelling over the past decade, to the extent that exercise is recommended in current national and international PCa guidelines [14, 15]. The effect of aerobic, resistance and flexibility exercise on patients’ outcomes at different stages of the pathway and in multiple settings for example home, community and hospital has been researched over varying durations [16, 17]. Exercise during and after PCa treatment is safe and effective at improving important health outcomes, including improved aerobic capacity and body composition [6, 11, 18]. Varying exercise modalities have been shown to improve body composition, strength, blood pressure, blood biomarkers such as plasma triglycerides and fasting plasma glucose, aerobic capacity, quality of life and attenuate fatigue [11, 12, 19,20,21]. Interventions involving combined exercise modalities, such as aerobic and strength training concurrently, have been demonstrated to improve bone density [6].

Exercise opportunities should be easily accessible to men with PCa regardless of racial or ethnic minority status. Recent reports have highlighted that diversity and representation are poor in PCa clinical trials, with approximately 96% of men participating in PCa research being White [22]. There is a need to understand whether the present evidence base for exercise interventions is representative and inclusive of racial and ethnic minority men with PCa and, if not, explore the barriers and seek tailored acceptable interventions or strategies which are more inclusive. The aim of this systematic review is to examine current reporting of race and ethnicity data and strategies to increase inclusivity and demographic representation within PCa and exercise trials.

Methods

Protocol and registration

The preferred reporting items for systematic review and meta-analyses (PRISMA) guidelines were followed when conducting and reporting this prospectively registered systematic review (PROSPERO ID: CRD42022384373) [23].

Eligibility criteria

We included trials published in the English language that studied exercise interventions in PCa patients. Manuscripts were excluded if they were protocols, reports, conference abstracts, position statements or case series reports. Participants must have been aged > 16 years and have been diagnosed with PCa. Studies could include any form of exercise intervention in isolation or combined with other lifestyle factors such as nutritional supplementation or smoking cessation. Studies that included either details of participants’ ethnicity or strategies to ensure inclusion and representation were eligible.

Search strategy

The MEDLINE Ovid, Cochrane Library and PubMed databases were searched from inception to July 2024. The search strategy keywords and MeSH terms used included the following: (1) exercise, (2) training, (3) prostate cancer, (4) ethnic and (5) diversity. Reference lists of all relevant systematic reviews identified were searched for additional studies. All searches were conducted by the same author (RA), with search results collated using Rayyan software [24], and duplicates were removed. All titles, abstracts and full texts were screened by one reviewer (RA). Any uncertainty of a manuscript was resolved by a second reviewer (MF).

Data extraction

One author (RA) extracted data using Microsoft Excel which was checked by a second author (MF). Any disagreements were resolved via consensus with a third party (CR). Extracted data included study design, participant demographics, intervention details and data for all outcomes.

Results

Seven hundred and seventy-eight records were retrieved from database searches, of which 15 records were duplicates. A further 649 were eliminated following a screening of titles and abstracts. After the full-text screening of 186 articles, 28 manuscripts were found to be eligible for inclusion in this review (Fig. 1) with an increase in the volume of papers published over the last three decades (Fig. 2).

Fig. 1
figure 1

PRISMA flow diagram

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Fig. 2
figure 2

Volume of peer-reviewed academic articles published per year included in the screening

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Characteristics of studies

The 28 studies included comprised 15,946 participants, with sample sizes ranging from 11 to 7328 per study. Summary details of the included studies and populations are presented in Table 1.

Table 1 Characteristics of included studies
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The majority of studies (21/28) were performed in North America. Eleven studies (12/28) were conducted at a single site and another 11/28 recruited patients from multiple sites with the remaining 5/28 not stating the number of recruiting sites. The trial enrolment duration varied from 1 day to 14 years with 3/28 studies stating a range of lengths depending on the patient and 6/28 studies not stating the trial duration.

Narrative synthesis

All studies included reported the ethnicity of participants. Four studies 4/28 (14.3%; [28, 34, 44, 47]) only reported including Caucasian individuals and one study 1/28 (3.6%; [46]) reported only including African American patients. The remaining studies 23/28 (82.1%; [11, 25,26,27, 29,30,31,32,33, 35,36,37,38,39,40,41,42,43, 45]) all recruited patients from multiple ethnicities. No studies included a statement regarding inclusivity as part of the published manuscripts.

Fifteen studies 15/28 (53.6%; [11, 25, 26, 29,30,31, 33, 38,39,40, 42, 43, 45, 47, 50]) adopted a randomised control trial design, four 4/28 (14.3%; [36, 41, 46, 51]) cross-sectional, two 2/28 (7.1%; [31, 49]) cohort, two prospective 2/28 (7.1%; [44, 48]), two feasibility 2/28 (7.1%; [27, 28]), laboratory analysis 1/28 (3.6%; [34]), secondary analysis 1/28 (3.6%; [35]) and case–control study 1/28 (3.6%; [37]). Ten studies 10/28 (35.7%; [25, 28, 32, 33, 35, 38, 43, 44, 47, 48]) only recruited patients on androgen deprivation therapy (ADT), nine studies 9/28 (32.1%; [29,30,31, 34, 37, 41, 46, 49, 50]) involved patients on any form of treatment and six studies 6/28 (21.4%; [11, 26, 40, 42, 45, 51]) recruited those who had undergone radical prostatectomy. One study 1/28 (3.6%; [27]) recruited those receiving radiotherapy only, one study 1/28 (3.6%; [39]) recruited either radical prostatectomy or radiotherapy and a single study 1/28 (3.6%; [36]) involved either ADT, radical prostatectomy or radiotherapy patients.

The exercise elements of the studies varied, and individual study exercise details are presented in Table 2. Seven studies 7/28 (25%; [26, 28, 30, 43,44,45, 49]) involved home-based or unsupervised exercise. Six studies 6/28 (21.4%; [27, 29, 34, 40, 42, 50]) reported exercise sessions that were supervised by an exercise trainer or exercise physiologist and a further six studies 6/28 (21.4%; [11, 25, 32, 33, 38, 47]) had a mix of supervision over the trial period. Nine studies 9/28 (32.1%; [31, 35,36,37, 39, 41, 46, 48, 51]) did not explicitly state whether exercise was supervised or unsupervised. Three studies 3/28 (10.7%; [11, 35, 50]) included resistance exercise interventions, two 2/28 (7.1%; [40, 42]) included aerobic exercise interventions and a further two studies 2/28 (7.1%; [27, 29]) included yoga or flexibility programmes. Eleven studies 11/28 (39.3%; [25, 26, 28, 32, 33, 36, 38, 43,44,45, 47]) investigated an intervention which used a mix of exercise modalities (i.e. aerobic, resistance and flexibility). Ten studies 10/28 (35.7%; [30, 31, 34, 37, 39, 41, 46, 48, 49, 51]) were physical activity-based and primarily involved activity tracking.

Table 2 Intervention and ethnicity data from included studies
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Risk of bias

Risk of bias was assessed on all randomised studies and conducted by one author (RA). The Cochrane Risk of Bias tool [52] was used with risk of bias on the study level classified as ‘low’, ‘unclear’ or ‘high’ risk [53]. Table 3 shows a summary of the risk of bias for each of the included studies.

Table 3 Risk of bias
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Discussion

Summary of findings

This review highlights the lack of reporting of patient ethnicity in PCa clinical trials involving exercise. Only 28 manuscripts reported ethnicity and none of the studies included a statement regarding strategies for ensuring inclusion or representative sampling. For example, studies may want to consider who the under-served groups are within the delivery area and barriers they face, plan for digital exclusion, recruit a sample who represents those who live with the specific condition, use language carefully or involve those under-served in the planning phase [54]. In the papers included in this review, it is evident that there is inconsistency in how ethnicity is reported making the results of the studies difficult to apply to the general PCa population. Accordingly, there is a greater need for those developing and running clinical trials in PCa and subsequently academic research outputs to adopt standardised terminology when it comes to describing and reporting the race and ethnicity of participants in exercise research, for example using those listed on countries official websites [55, 56]. To the authors’ knowledge, this is the first systematic review investigating ethnicity reporting in PCa and exercise trials and it therefore acts as a baseline for future practice.

Only one pilot trial has been included in this review that specifically recruited black men and this was in an African American community population. This mixed-methods study explored the quality of life, dietary and physical activity habits of African American PCa survivors [46]. The findings suggest that exercise interventions involving supervised strength training that are group-based; increase knowledge, skills-building and social support; address financial challenges and are easily accessed; these exercise interventions will help address some of the barriers in this underserved population [46]. Recognising that black men are at an increased risk of PCa, there is a clear need to design trials to fulfil the needs of black men, or at the very least further investigate qualitatively their views on exercise interventions and barriers. A study in 2017 explored the acceptability, barriers and facilitators to lifestyle interventions in African Caribbean PCa survivors and found that a PCa diagnosis, alongside ageing, heightened men’s awareness of their health [57]. They concluded that lifestyle interventions which enhance men’s independence and are framed as helping to regain fitness and aid post-treatment recovery are appealing and acceptable to African Caribbean PCa survivors [57].

Some of the barriers to research participation have been explored in other clinical populations and include a lack of childcare, mistrust, financial constraints, relatives’ influence and beliefs, lack of communication and cultural awareness between research staff and patients [58, 59]. The under-representation of ethnic minority groups in clinical trials affects the generalisability of study findings and ultimately contributes to exacerbating bias and inequities in access to healthcare if public health policies based on such evidence are implemented. It is possible that different ethnic groups respond in distinct ways to an intervention due to variations in physiology and/or disease state. Therefore, by studying the effects of an intervention in multiple ethnic groups, we can be sure that the outcomes are applicable to all.

Strengths and limitations

This systematic review has been conducted rigorously with regard to methodology and in line with the PRISMA guidelines. However, the main findings of this systematic review need to be considered in the context of some key limitations. For example, it is difficult to ascertain reasons for low recruitment numbers and, even when ethnicity was reported, recruitment strategy was not acknowledged in the manuscripts. Additionally, we must acknowledge that the lack of diversity may be due to the single centre studies being conducted in predominantly Caucasian areas, however, it is important that this is considered in their limitations section. More work is needed therefore to understand the barriers and facilitators of different ethnic groups to exercise research. Furthermore, recruitment strategies to ensure an inclusive sample need to be employed alongside reporting of participant ethnicities needs to be improved,

Implications for research and practice

The findings from this systematic review demonstrate that whilst there are many studies into the benefits of exercise within PCa patients, there are clear disparities between studies on the reporting of participants’ ethnicities and overall low numbers of ethnic minority men included. This systematic review suggests that representation is achieved in a few trials. Work needs to be performed to understand why representation is lacking in PCa exercise trials in the UK and action is needed to address this. Future studies may want to explore the barriers patients from different ethnic groups face when taking part in clinical trials and any potential bias within the recruitment process. Studies should include defined strategies to recruit a representative study sample and report this within the methods section of the manuscript in accordance with NIHR INCLUDE [54] to ensure the results are applicable and representative of the patient group. Additionally, authors should clearly report the ethnicity of participants within the demographic information of manuscripts to allow the reader to properly interpret the results in the context of the patients included.

Conclusion

This systematic review highlights that there is high heterogeneity in the reporting of participants’ ethnicity within PCa trials involving exercise. Additionally, it has also demonstrated that there are low numbers of ethnic minority men included in PCa and exercise studies in the UK and a lack of reporting of ethnicities in published papers. As such, further work is required to understand why representation is lacking within PCa exercise trials in the UK and strategies are needed to achieve representation. Future studies should seek to explore the barriers PCa patients from different ethnic groups face when taking part in clinical trials in the UK.