A recent international consensus definition for advance care planning (ACP) states that ACP is “the ability to enable individuals to define goals and preferences for future medical treatment and care, to discuss these goals and preferences with family and health-care providers, and to record and review these preferences if appropriate” (1). Ultimately the goal of ACP is to align the treatment a person receives with their preferences for care (2). Despite practice guidelines recommending ACP for people with cancer, results from the Australia National Advance Care Directive Prevalence study (2017) suggested that only 27% of people with cancer had documented their ACP preferences in an advance care directive (3). This finding is consistent with low rates of ACP discussion and documentation reported internationally (4–6).

In Australia, the terms used in advance care planning differ by state. Nationally, the term ‘substitute decision maker’ is used to denote the person who makes medical decisions if a person loses medical decision-making capacity. ‘Advance care directive’ is the umbrella term for documents expressing the person’s preferences for future health care in the event that they lose medical decision-making capacity. Internationally there is considerable variation in terminology used for ACP. However, the principles of appointing a surrogate decision maker, having conversations about preferences and values, and recording a written advance care directive are generally applicable. In the USA, physician orders such as Do Not Attempt Resuscitation (DNAR) are included in ACP documentation (1). In Europe, concepts and laws regarding ACP differ, with some countries having legally binding frameworks and others not (1). Some examples from English-speaking countries and Europe are presented in Supplementary File 1 (Advance care planning terms of reference). Often, laws regarding ACP are made at a state or provincial, rather than at a national, level. The lack of consistency in terms and definitions used can be confusing for patients and health providers.

Literature proposes a range of benefits of ACP across various populations. However, it is uncertain from the literature on cancer patients if proposed benefits of ACP have been empirically identified. Studies have found that the values and needs of cancer patients in response to ACP are different to other patient populations (7). For example, patients with cancer placed greater emphasis on decisions on their preferences for site or care rather than intervention-based treatment decisions (7). Also unknown from the literature is whether interventions to support uptake of ACP are targeting the most frequently reported barriers and enablers of ACP, and if so are they effective in improving uptake.

With several published reviews identifying barriers to ACP (8–10) and interventions to support uptake of ACP (11, 12), the aim of this overview of reviews is to clarify and consolidate the evidence base in oncology settings to inform recommendations for improving uptake of ACP. This overview took a systematic approach to searching, appraising, and synthesizing the review literature to address the following research questions (13):

This systematic overview of reviews used a standardized protocol prepared according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines (14). The protocol was registered with Prospero; registration number: CRD42021288825 (https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021288825).

Content analysis identified three categories of proposed and empirically supported benefits of ACP: patient benefits, family benefits, and healthcare service benefits, presented in Table 2 .

A misalignment was found between the proposed and empirically supported benefits of ACP, with many proposed benefits for patients, families, and healthcare providers not empirically supported within the same review. In terms of patient benefits, only ‘quality care’, ‘patient information’ and ‘care alignment’ had both proposed and empirically supported benefits (27, 28, 31, 41). For families, only ‘satisfaction with care’ was proposed as a benefit and empirically supported in the same review (28). Assessment of health care service benefits identified reduced hospitalization, reduced aggressive care, and reduced cost of care, as both proposed and empirically supported (28, 30, 39).

A deductive analysis identified barriers and enablers of ACP across 12 of the 14 Theoretical Domains Framework domains from 15/18 reviews (12, 27–29, 32–35, 37–43). Table 3 presents frequencies of the barriers and enablers by Theoretical Domains Framework domain, and content themes identified within each domain from the patient, healthcare provider, and healthcare service perspectives. More barriers of ACP were associated with healthcare providers (n=60) in comparison to patients (n=40) and healthcare services (n=3). Enablers of ACP were more frequently identified for patients (n=17) compared to healthcare providers (n=15) and healthcare services (n=3).

As described in the method, we assessed importance in relation to three previously published criteria: domain frequency, level of elaboration within each domain, and authors’ explicit statements about importance (22, 23). Of 14 possible domains, the most frequently coded across the 15 reviews were: knowledge (66%); environmental context and resources (66%); emotion (66%); skills (60%); social/professional role and identity (53%); beliefs about consequences (46%); and social influences (40%). High levels of elaboration were found in the most frequently coded domains, except for those where minimal themes are to be expected: for example, skills whereby communication and training were predominant.

Evidence of importance was further supported by the authors of reviews articulating specific barriers or enablers as important in influencing ACP; for example, “Health professionals’ knowledge of and attitudes towards ACP was also consistently found to be an important factor in their willingness to initiate or participate in ACP” (27). Importance was also inferred in statements that articulated the patient’s voice; for example, “Patients generally preferred to do ACP with the physician who knows them best, preferred that their physicians initiated discussion regarding ACP, and were more likely to participate in ACP or draw up an advance directive (AD) if they had discussed this with their oncologist” ( 27).

Statements of expressed importance were identified in seven reviews (27, 29, 32, 35, 39, 42, 43) and these aligned with the seven most frequently coded domains with the greatest level of elaboration: knowledge (n=5); skills (n=4); environmental context and resources (n=4); social influences (n=3); beliefs about consequences (n=2); social/professional role and identity (n=2); and emotion (n=1). High frequency content themes within these domains also aligned with expressed statements of importance. Details on domains of importance and example quotations are presented in Table 4 . Supplementary File 3 presents a narrative description and sample quotations for all themes across Theoretical Domains Framework domains.

Nine of the 18 reviews identified interventions that aim to improve ACP uptake at various phases and target either the patient, healthcare provider, or healthcare service levels (12, 28, 29, 31, 32, 38–40, 43). In Figure 3 , interventions have been mapped to the phases of ACP as presented by the Australian National Framework for advance care planning documents (45), with the addition of a preparatory phase, labelled Phase 1a. This figure also depicts the intervention target and interactions associated with delivering the intervention.

Table 5 compares the frequencies of Theoretical Domains Framework domains for barriers of ACP with the Theoretical Domains Framework domains for implied barriers targeted by ACP interventions across patient, healthcare provider, and healthcare systems levels. Across levels, there was a misalignment between barriers identified and implied barriers targeted by interventions. Interventions most frequently targeted the patient; however, more barriers for ACP were identified for healthcare providers. There were also implied barriers targeted by ACP interventions that were not identified as barriers to ACP in the included reviews. This occurred for interventions targeting the patient as well as the healthcare provider.

Based on this systematic overview of reviews, consistency is lacking in the literature in relation to defining ACP, its benefits, and its barriers and enablers in oncology settings. While the peer-reviewed literature lacks a consensus definition, there are key categories and sub-categories that align with the benefits of ACP and overarching values associated with optimal patient care that should be consistently used in its definition. The most frequently used sub-categories to define the purpose of ACP are about making decisions to ensure that the patient receives care in-line with their preferences. Receiving care that is in-line with one’s preferences and values is the hallmark of patient-centered care (46) and known to improve care quality and patient satisfaction (47). It is also one of the empirically supported benefits of ACP (28, 41). We suggest that these content categories should be included in the standardized definition of ACP (presented in Figure 4 ), along with identifying who should participate in the conversation. Evidence suggests the involvement of family and healthcare providers in ACP conversations is an enabler for the patient and healthcare provider for ACP uptake (27, 41–43).

The lack of consensus around the timing of ACP should be addressed within oncology settings, as this is also associated with barriers for healthcare providers not knowing when to initiate the conversation (32, 41, 43). It is important to consider that, within this patient population, the timing of conversations does not necessarily have a negative impact on patients (40) but, rather, consideration of contextual factors is important, such as having the conversation in an appropriate and private setting important (27, 29, 34). Whilst there is agreement within the literature (12, 28, 30, 31, 35, 37, 41–43) and also in the Australian National Framework of ACP (45), that ACP should result in a legal document, emphasizing the importance of this step, we found no mention of barriers associated with creating this document or any process or person to facilitate this process. Nor did any interventions target this phase of ACP.

Interventions predominantly focused on a preparatory phase of ACP, which we identified as Phase 1a ( Figure 3 ): Preparation for the ACP conversation; currently beyond the scope of the Australian National Framework of ACP, which primarily focusses on three phases ACP; 1) having the conversation; 2) making an ACP document; and 3) accessing and enacting an ACP document (45). Interventions to enhance the uptake of ACP sometimes, but not always, addressed the known barriers and there appeared to be considerable variation in these interventions to improve ACP uptake. They also tended to target the patient rather than healthcare providers, even though the number of barriers associated with healthcare providers were a third greater than those for patients.

Further expanding the ‘importance criteria’ to a theme level enabled us to identify the mismatch of interventions in targeting empirically identified problems. Interventions that targeted patients did address patient barriers that were coded to important domains, and to some extent were effective in increasing ACP documentation. However, these interventions aimed to improve the knowledge of patients on end-of-life care decisions and gaining medical knowledge, yet the most important knowledge enabler was for patients to have an understanding of their prognosis. Interventions also focused on communication between patients and clinicians. While these interactions are important, the involvement of family members in the process of ACP was an enabler for both patients and healthcare providers. Yet, no interventions focused on educating and actively engaging family members in ACP. This is despite empirically supported psychological benefits and satisfaction with care being linked to the involvement of family members (28, 41).

Few interventions targeted empirically identified problems for healthcare providers, and these were mostly ineffective in increasing ACP documentation. These interventions targeted barriers coded to only two of the seven domains identified as important in influencing ACP uptake for healthcare providers (i.e., skills and knowledge); and were placed in phase 1 of the Australian National Framework of ACP (45). Interventions have failed to address the most frequently reported barriers for healthcare providers, specifically, beliefs that ACP conversations would have a negative impact on patients. This is in spite of patient accounts that this assumption is incorrect and contrary to empirically identified benefits for patients (40).

The pathways from having the ACP conversation to phase 2 of the Australian National Framework of ACP, making an ACP document, were not discussed in the literature reviewed in this overview. The barriers and enablers of making an ACP document have not been explored in the literature, nor addressed in any interventions. Yet, national frameworks identify this as a phase of successful ACP, consistent with many definitions that state ACP should result in some form of documentation. Interventions addressing phase 3 of the framework, accessing and enacting an ACP document, did not report effectiveness in improving ACP. System-level constraints was one of three themes coded to the domain of environmental context and resources and identified as important in influencing ACP uptake.

In summary of the findings discussed above, we recommend that future ACP interventions and research focus on:

The original contributions presented in the study are included in the article/ Supplementary Material . Further inquiries can be directed to the corresponding author.

LG conducted the search. Authors LG and SF screened reviews for inclusion and conducted the data extraction. LG, JF, AH and KG participated in the analysis of results. Writing of the original draft manuscript was prepared by LG. All authors contributed to the article and approved the submitted version.