Evaluating current quality indicators used in the care of adult patients with glioblastoma: A scoping review of the literature

Abstract

Background

Glioblastoma (GBM) is the most aggressive primary brain neoplasm in adults, characterized by high recurrence and poor post-recurrence survival. Validated quality indicators (QIs) have been used to assess the quality of care in many cancer populations, now providing clinicians, researchers, and healthcare policymakers with evidence-based metrics to enhance patient outcomes. In contrast, few glioblastoma-specific QIs have been described and their impact and meaningfulness are yet to be determined.

Methods

A scoping review was conducted of described QIs for adult patients with GBM. The literature was screened for relevance, and eligible QIs were evaluated and grouped into 5 domains: pre-intervention, surgical, postsurgical, supportive care, and recurrence/survival.

Results

A total of 80 articles were retrieved, with 12 of these studies meeting inclusion criteria. Twenty-six QIs were identified across the 5 care domains. Evidence linking these QIs directly to improved survival or quality of life is variable. Some QIs have solid evidence of impact (eg, accurate tissue diagnosis), while others are based on reasonably assumed benefits rather than robust evidence (eg, early palliative care referral). Frail or older patients and those with recurrent GBM are subsets with the least high-quality QIs.

Conclusions

Current QIs potentially provide valuable benchmarks to assess and optimize care in adults with glioblastoma, but many are yet to be supported by high-quality clinical evidence, with greater gaps in some patient populations. Further research is required to define and validate QIs that robustly assess quality of care, supporting urgent efforts to improve patient outcomes for this poor prognosis of cancer.

Key Points.

• There is a lack of robust, evidence-based quality indicators (QIs) for GBM care.

• Most QIs are based on expert consensus rather than strong clinical evidence.

• More research is needed to refine and validate QIs for improved patient outcomes.

Background

Glioblastoma (GBM) is the most common and aggressive form of brain cancer. Despite aggressive treatment, recurrence is inevitable, with a median time to recurrence of 6.7 months from diagnosis, and limited treatment options in this salvage setting,^1,2 resulting in poor overall survival (median ~ 14.6 months, 5-year survival <5%).^3–5 Beyond poor survival, the burden of glioblastoma on patients can include profound impacts on quality of life (QoL) due to the disease and/or treatment complications, which include pain, fatigue, neurocognitive decline, and psychosocial stress.⁶

The aggressive and complex trajectory of GBM warrants a multimodal, multidisciplinary, and patient-guided approach, all delivered in a timely and coordinated fashion. Gold-standard treatment involves maximal safe resection while preserving neurological function (informed by tumor location), then postsurgical chemoradiation and adjuvant temozolomide.^7–10 As there is currently no curative therapy available, malignant gliomas are approached with palliative intent and prioritizing quality of life. In some instances, treatment may be limited to supportive care aimed at managing disease-related and iatrogenic complications, including antiepileptics for seizures, steroids for cerebral edema, and venous thromboembolism prophylaxis.^11,12 The National Comprehensive Cancer Network recommends clinical trial enrollment for all eligible patients.¹³

Quality Indicators (QIs) are measurable elements of practice performance which can act as benchmarks to assess the quality of care at the hospital or population level. Robust QIs exist for many common cancer types, functioning as vital metrics for clinicians, researchers, and healthcare policymakers to evaluate whether current care aligns with best practice, and identify gaps that should be addressed.¹⁴ Unfortunately, due to a paucity of high-quality studies and significant disease heterogeneity, few evidence-based management metrics exist for GBM.¹⁵ Furthermore, while some sources give specific guidance (eg, optimal time in which surgery should be completed after diagnosis), it is often unclear if these are evidence-based versus expert opinion, and if adherence would drive meaningful improvement in patient outcomes. Thus, there is an urgent need to critically evaluate proposed indicators.

A preliminary search of MEDLINE (PubMed) and the Cochrane Database of Systematic Reviews found no current or underway systematic reviews or scoping reviews that evaluate current QIs in glioblastoma care. The scoping review methodology was selected because it allows broad and comprehensive identification and evaluation of recommendations in the published literature, including the “gray literature” (materials not searchable in standard databases) that might provide additional insights. While scoping reviews are limited by their focus on surveying the literature, rather than on systematically evaluating or synthesizing the evidence, the objective of this review was to find relevant QIs and identify those that are meaningful and founded in high-quality research. This review summarizes the current literature for adult patients with GBM, including the evidence behind proposed QIs and gaps that may require further research.

Methods

We conducted a scoping review in accordance with the PRISMA-ScR guidelines¹⁶ to identify studies that propose a set of QIs that should be used to benchmark GBM care. The aim of this review is to assess these research questions: (1) Are there any specific QIs for patients with glioblastoma? (2) Are these QIs measurable in the clinical environment? (3) Are these QIs meaningful in determining the quality of care received by patients? (4) Are there gaps that require further exploration?

Data Sources

We searched 3 online databases (Embase, PubMed, and MEDLINE) on September 20, 2024. As suitable articles were identified, a reference screen was also performed to identify missed articles or other supportive evidence to supplement the retrieved papers. Furthermore, a search of “gray literature” sources was performed through the Internet to locate any publicly accessible documentation that may provide more clinical recommendations (eg, Optimal Care Pathways, Cancer Australia, National Institute for Health and Care Excellence).

Search Strategy

The search was conducted using broad search terms such as keywords, titles, abstract, and MeSH, with appropriate truncations and wildcard syntax. The general search strategy was as described: (“glioma” OR “glioblastoma” OR “brain cancer” OR “brain tumor” OR “brain neoplasm”) AND (“quality indicator” OR “quality care” OR “quality improvement”). The search was limited to full-text, English-language articles describing adult patients with GBM. There were no limitations on the year of publication.

Eligibility Criteria

Studies were considered eligible if they focused on quality metrics relevant to adult patients (18 years or older) with glioblastoma. All article types were considered appropriate for inclusion, including (but not limited to) randomized and non-randomized trials, analytical and descriptive observational studies, and pure qualitative studies. We also included articles that designed QIs (eg, based on a Delphi survey or expert consensus).

Selection of Sources

The selection process involved title and abstract screening, followed by full-text review and data extraction; reasons for exclusion were recorded (Figure 1).

Figure 1.

PRISMA flowchart showing databases search and number of studies included for review.

Data Extraction

Data were extracted by reviewers (JS and LG) and discussed jointly during analysis. Data extracted included: author(s), year of publication, country of origin, the number of QIs, and methodology used to develop QIs. Data were also extracted to identify the QIs and any impact on patient outcomes. All QIs were written in the format “proportion of patients with…” followed by the prescribed action. The reviewers evaluated the extracted data based on their measurability and meaningfulness, as above. Any QI not meeting both criteria was excluded during the consolidation, and any disagreements were resolved through discussion.

Results

Study Characteristics

The search strategy yielded 80 articles, of which 24 duplicates were removed. After screening the remaining 56 articles by titles and abstracts, 50 were excluded. The most common reasons for exclusion were studies focusing on pediatric patients (n = 10), wrong cancer or not relevant to neuro-oncology (n = 14), and wrong study type or no explicit mention of QIs (n = 26). Six articles were sought for retrieval, and reference screening found six additional sources with explicit reference to QIs. Thus, a total of twelve studies underwent full-text review and were included in our analysis (Table 1).

Table 1.

Characteristics of Studies Found Via Literature Search and Reference Screen

First author (year)	Location	Number of QIs	Method(s) to develop quality indicators
Vanhauwaert (2022)17	Belgium	32	A systematic review of available QIs and guidelines, followed by a 2-round expert Delphi survey (major sources included SCT, AAN-SNO, and DNOR papers)
Matsuyama (2022)18	Australia	37	Database and an internet search of guidelines, 2-round modified Delphi survey, and refined by the multidisciplinary working group
Menke et al (2022)19	Germany	13	Synthesis from literature and guidelines by a multidisciplinary team, and then applied to case and control groups to identify if improvements were observed
SCT (2024)20	Scotland	14	Systematic search of selected websites and 2 databases to find national and global guidelines that meet criteria for “overall importance,” “evidence based” and “measurability,” then refined by input from clinicians, patients, and the general public
AAN-SNO (2018)21	U.S.	5	A literature search by a medical librarian, a multidisciplinary team review, and a modified Delphi process to develop QIs, followed by a 21-day public commenting period
DNOR (2016)22	Denmark	8	Findings from the Danish Neuro-Oncology Registry generated a discussion within a multidisciplinary team who proposed QIs
Riblet (2014)23	Lebanon	10	Independent literature review by a team of physicians across several disciplines, nursing staff, schedulers, and social workers, with QIs based on “scant evidence and brainstorming”
Achari (2022)24	India	14	Prioritized QIs were chosen from the PRIME Quality Improvement study Zada (2018) were selected to “reflect key content areas… and the feasibility of data collection”
Zada (2018)25	U.S.	16	Synthesis of a set of “quality-based…NCCN (National Comprehensive Cancer Network) guideline-directed” indicators from key areas
ECC (2023)26	Europe	19	Indicators compiled by a “working group of European experts representing disciplines involved in cancer care” and neuro-oncology
Back (2018)27	Australia	5	Outcome and process indicators selected by the authors based on “reflecting high quality of subspecialized neuro-oncology care”
CAQ (2023)28	Australia	16	Derived by a committee of neuro-oncology doctors through the use of a Queensland oncology repository with information about 1 million cancer patients from 1982 to 2020

AAN-SNO, American Academy of Neurology-Society for Neuro-Oncology; CAQ, Cancer Alliance Queensland; DNOR, Danish Neuro-Oncology Registry; ECC, European Cancer Concord; SCT, Scottish Cancer Taskforce.

Six studies conducted a comprehensive literature review and generated a candidate list of QIs from consensus-building approaches such as a modified Delphi technique. Four studies^20–22,28 presented QIs adapted independently from large neuro-oncology databases; 2^19,23 used the institutional experience to inform their QIs (eg, for the purpose of prospectively testing on a small cohort of patients); and the remaining 6^{17,18,24–27} aggregated existing QIs, optionally suggesting additional QIs based on “gray” sources and consensus opinion. All studies were published in the last 10 years from a variety of countries. Most studies^{17–20,23–26,28} identified at least 10 QIs, with the largest identifying 37 QIs¹⁸; 3^21,22,27 identified fewer than 10 QIs.

Appraisal of Sources

There was significant heterogeneity in the quality of QIs in each article. Only 4 of the 12 articles directly referred to evidence from the literature in support of each proposed QI that would validate their use in clinical practice.^17,18,20,21 Furthermore, few articles defined their QIs using quantitative measures (where applicable), such as specific timeframes within which clinical actions should be completed (eg, “early” postoperative MRI²¹ versus postoperative MRI within 72 hours of surgery²⁰). Nonetheless, overlaps between QIs on similar topics allowed evidence-poor QIs to be superseded by more robust indicators. Finally, while many of the articles consulted non-peer-reviewed sources, all 12 articles mentioned discussion or debate within a multidisciplinary team to refine and assess the clinical utility of their suggested QIs.

Consolidation of QIs

A raw number of 189 QIs relevant to GBM were extracted across all the articles, with many QIs in common. The QIs were consolidated and short-listed on the basis of the following criteria: (1) if multiple QIs address the same topic, they were amalgamated into a single generalized QI; (2) if a QI is considered trivial or an expected element of care it was excluded; and (3) if the QI cannot be practically, consistently or objectively measured, it was not considered a viable QI (examples of non-viable QIs are presented in Table 2).

Table 2.

Sample List of Non-viable QIs and Associated Reason for Exclusion

Reason for exclusion	Examples of non-viable QIs (paraphrased)
Expected element of care	Proportion of patients whose treating team includes: neurosurgeon; neurologist; oncologist; radiologist… Proportion of patients managed in a tertiary center with neuro-surgical and/or -oncological experience Proportion of patients having timely communication between the treating team and general physician Proportion of patients in whom an MRI scan is done prior to craniotomy and surgical tumor resection Proportion of patients who were given chemotherapy education and informed consent for their treatment Proportion of patients given “standard postoperative orders” (e.g., mobilization, thrombosis prophylaxis)
Cannot be objectively or consistently measured	Proportion of patients spending less time in hospital and more time at home from diagnosis until death Proportion of patients in whom their emotional and spiritual well-being is monitored throughout therapy Proportion of patients where the patient and/or their families are actively involved in the decision-making Proportion of patients who had the following (given these measures only apply to a subset of patients): ● appropriate use of corticosteroids; ● appropriate use of AEDs; ● an ophthalmological appointment; ● referral to a psychiatrist; ● consultation by a social worker, etc

Ultimately, 26 unique and viable QIs were identified and their corresponding source(s) in the literature are presented in Table 3. The QIs were grouped into 5 overarching domains: pre-intervention (QI 1–3), surgical (QI 4–6), postsurgical (QI 7–13), supportive care (QI 14–18), and recurrence/survival (QI 19a-d, 20a-c).

Table 3.

Compiled List of Established QIs Adapted From the Literature

Quality indicator	Source(s)*	Supporting evidence
Pre-intervention
QI 1: Proportion of patients discussed in a multidisciplinary team (MDT) meeting prior to definitive management	SCT, AAN-SNO	MDTs lead to higher rates of postoperative imaging and adjuvant therapies offered to patients, but no significant increase in median survival.29 MDTs improve patients’ care experience through better coordination, earlier input from specialties, and lower risk of effort duplication, resulting in higher satisfaction and QoL.30
QI 2: Proportion of patients with documented performance status (eg, KPS) before and after definitive management	SCT, Matsuyama	Higher baseline performance status (PS) is associated with improved survival irrespective of age31–33; lower PS is associated with only marginal therapy benefit.34,35 Unchanged or improved PS post-therapy correlates with greater progression-free and overall survival rates.36
QI 3: Proportion of patients with tumors reported based on the latest WHO classification, including molecular analysis	SCT, Matsuyama	Standardized classification allowed accurate prognostic estimation and decisions for specific agents (eg, MGMT promoter methylation status in TMZ chemotherapy).37–40
QI 4: Proportion of patients who are managed in a high-volume tertiary center after diagnosis	Matsuyama	Treatment in a high-volume tertiary center and academic or teaching hospital is shown to correlate with improved survival outcomes and reduced all-cause mortality.41,42
Surgical
QI 5: Proportion of patients treated through maximal safe surgical resection (extent based on functional boundaries)	SCT, AAN-SNO	Improved prognosis and time to recurrence irrespective of patient age and tumor characteristics when at least 98% of tumor resected.43–46
QI 6: Proportion of patients in whom ≥2 surgical techniques (eg, intraoperative MRI, 5-ALA) are used to guide resection	SCT	Use of multiple concurrent surgical techniques leads to more complete resection of the tumor and therefore better patient survival outcomes.47
QI 7: Proportion of patients who undergo resection within 14–30 days of diagnosis and/or MDT	SCT, CAQ	Earlier surgical resection is associated with improved patient functional status and better survival outcomes.48,49
Postsurgical
QI 8: Proportion of patients in whom contrast-enhanced MRI is performed before and ≤72 hours after the surgery	SCT, AAN-SNO	Delays in conducting early postoperative MRI lead to unreliable residual tumor interpretation, thus delaying postsurgical decisions50–52
QI 9: Proportion of patients who have follow-up exam and contrast-enhanced MRI scan within 6 weeks of the surgery	Vanhauwaert, Matsuyama	Early postsurgical clinical assessment might identify early disease recurrence, which is associated with poor survival outcomes.53
QI 10: Proportion of patients who have follow-up MRI scans and volumetric assessment every 2–4 months after surgery	Vanhauwaert	Regular monitoring and follow-up protocol improves overall survival, although the optimal strategy is unclear.54
QI 11: Proportion of patients where radiation therapy and/or chemotherapy is started ≤6 weeks after surgical resection	SCT	Use of postsurgical therapy improves survival outcomes compared to surgical resection alone,55,56 and delays beyond 6 weeks are associated with reduced survival.57,58
QI 12: Proportion of patients <70 years receiving radiation with concurrent and then adjuvant temozolomide (TMZ)	Vanhauwaert, Matsuyama	Concomitant radiation and chemotherapy results in an improvement in survival in patients <70 years with good performance status.8
QI 13: Proportion of patients ≥65–70 years in whom therapy is guided by the performance status and MGMTp methylation	Vanhauwaert, Matsuyama	Poor evidence—see Table 4 for suggested QIs for older patients and associated evidence in the literature.
QI 14: Proportion of patients enrolled in clinical trials and/or biobank research	SCT, Matsuyama	No evidence—theoretical benefit since enrollment into trials is the only rigorous way to improve treatment options.
Supportive care
QI 15: Proportion of patients with a clinical care coordinator	SCT, Matsuyama	Clinical care coordinators are associated with reduced healthcare visits,59 improved quality of life and reduced stress for patients and families.60
QI 16: Proportion of patients receiving an early referral to palliative care, regardless of the initial choice of treatment	Matsuyama, Menke	No evidence—trial currently registered, pending results.61
QI 17: Proportion of patients with access to neuropsychology assessment during their care	SCT	Neuropsychology input has been shown to help predict and reduce any impacts of resection on postprocedural cognitive impairments.62,63
QI 18: Proportion of patients who receive early rehabilitation service referral after treatment	Vanhauwaert	Rehabilitation services such as physiotherapy have been shown to improve functional outcomes in patients seen 2 weeks after surgery64; similar results are seen in patients treated by chemoradiation.65
QI 19: Proportion of patients with seizures evaluated by neurologist and/or proportion of patients prescribed antiepileptic in the absence of epileptic insult	SCT, Vanhauwaert	No evidence—prophylactic antiepileptics and neurology review are not associated with improved survival, but well-controlled seizures may improve quality of life.
Recurrence/survival
QI 20a-d: Recurrence a. Proportion of patients seen at MDT before new treatment b. Proportion of patients treated with re-resection, re-irradiation, and/or systemic therapies c. Proportion of patients that are considered for a clinical trial d. Proportion of patients given palliative care in the last months of their disease progression	Vanhauwaert, Matsuyama	No evidence—these are mainly theoretical benefits, since retaining indicators similar to patients with a new diagnosis of GBM may ensure patients with recurrence are not being prematurely taken down the supportive care pathway when they may benefit from more targeted therapies.
QI 21a-c: Survival metrics a. Proportion of patients who died within 30 days of treatment b. Proportion of patients who are alive at 1 year after surgery c. Proportion of patients who are alive at 2 years after surgery	SCT, DNOR	No evidence is required, as these are good markers for treatment efficacy, given the expected survival with and without treatment at these timepoints is documented in the literature.

AAN-SNO, American Academy of Neurology-Society for Neuro-Oncology; CAQ, Cancer Alliance Queensland; DNOR, Danish Neuro-Oncology Registry; SCT, Scottish Cancer Taskforce. (*) For brevity, a maximum of 2 sources are listed per QI, preferencing sources that are more specific. QIs with no or poor evidence are highlighted in red.

Supportive Evidence

Of the 26 short-listed QIs, the majority (n = 18) had good quality evidence supporting their impact on patient outcomes, either for survival, QoL, or both. Interventions established to be effective in other cancer types—MDT discussion, maximal safe resection, treatment in a high-volume center, and chemoradiation—are also well-evidenced in GBM. Most of the QIs based on quantitative criteria, including optimal time to surgery, postoperative follow-up, and chemoradiation therapy, were also supported, reinforcing the importance of early and timely treatment. Furthermore, supportive care measures, including the involvement of care coordinators, neuropsychologists, and rehabilitation services, are assumed to reduce psychosocial stress and increase functional and cognitive outcomes.

However, the remaining 8 QIs did not have sufficiently adequate, high-quality evidence to justify their inclusion. For example, while early referral to palliative care might be reasonably assumed to carry merit based on data from other cancer types, there is no robust evidence to show any meaningful impact on patient outcomes in GBM; this is particularly because the survival times for GBM are lower than the timeframe for “early referral” shown to be effective in other cancers.⁶⁶ Similarly, enrollment in clinical trials or research, and seizure review by a neurologist, are not substantiated by the available literature. While it may still be reasonable to measure these QIs on the basis of their theoretical benefits, further prospective studies are required to validate their utility.

Literature Gaps

While there are QIs spanning the entire disease course in GBM, there is a lack of robust indicators for several key aspects of care, especially compared to other cancers with similar treatment modalities (eg, lung and breast). For instance, while there are QIs for the timely initiation of surgery and adjuvant therapies, there are no clear benchmarks for diagnostic efficiency, such as the timeliness of preoperative imaging or time elapsed from first symptom presentation to treatment. Moreover, recent advances in molecular testing and nuances in diagnostic paradigms are not well captured with existing QIs and would be fertile ground for future work.

Furthermore, there is a lack of tailored QIs for specific subgroups, chiefly older and/or frail patients. While older patients with breast or colorectal cancer benefit from QIs to inform optimal age- and performance status-adapted treatments, similar evidence-based benchmarks for GBM were not identified. Table 4 attempts to list potential QIs based on studies in older patients and gray literature sources to illustrate this gap. Moreover, QIs for patients with recurrent disease or those directly entering the supportive care pathway at diagnosis are limited and lack measurable frameworks. Similarly, no QI metrics were identified in the literature pertinent to end-of-life care, which is an important component in the care of these patients. Unlike other cancers, where advanced molecular testing and access to novel agents are validated, GBM studies provide insufficient clarity regarding their implementation or impact, likely due to the still evolving body of evidence in this area.

Table 4.

Suggested QIs for Older Patients (≥65–70 Years) With GBM

Quality indicator	Evidence
Q13a: Proportion of patients ≥65–70 years and a KPS ≥ 70 receiving hypofractionated radiotherapy (eg, 40 Gy in 2.67 Gy fractions over 3 weeks)	Hypofractionated radiotherapy has similar survival outcomes with fewer side effects in older patients.67
Q13b: Proportion of patients ≥65–70 years with KPS ≥ 70 and MGMTp methylation treated with chemoradiation and adjuvant temozolomide (TMZ)	While TMZ in older patients is associated with hematological and other toxicities, MGMTp is a strong predictor of response to TMZ, and is a recommended test for most patients.68
Q13c: Proportion of patients ≥65–70 years with KPS < 60 and MGMTp methylation treated with temozolomide (TMZ) monotherapy only
Q13d: Proportion of patients ≥65–70 years and a KPS < 60 or negative MGMTp methylation treated either with radiotherapy or supportive care only	In this subgroup, TMZ is more likely to cause harm than benefit; thus shorter fractionated radiotherapy can be used—however, the evidence for this is unclear, and supportive care may be the only option available.69

Discussion

This scoping review synthesized 12 diverse studies in evaluating QIs across multidisciplinary care for adult patients with GBM and presents 3 major findings. Firstly, there is a paucity of QIs in the primary literature, representing a significant gap in our knowledge regarding standardized metrics to assess the quality of care in GBM. Secondly, most studies lacked an evidence base having formulated QIs based on a review of the literature, national or global guidelines, and consortium opinion, often by experts via Delphi survey (or similar), and only occasionally with input from patients or carers. Finally, this review underscores the need for research to refine these indicators, ensuring they are rooted in robust evidence and effectively address the many facets of GBM care. Ultimately, establishing a comprehensive set of well-defined and evidence-based QIs is crucial for ensuring high-quality care for any cancer type, facilitating a virtuous cycle of ongoing quality improvement, and improving clinical care outcomes.

Strengths and Limitations

The strength of the study is that it reviews the array of QIs previously suggested by expert review and considers the evidence that underpins them. It also identifies areas for further QI-based research. However, this review has some important limitations. Firstly, the inherent nature of scoping reviews means that the findings are limited to mapping the existing literature, rather than systematically synthesizing or evaluating the quality of evidence. Described QIs may be limited by a lack of robust validation, making it difficult to ascertain their direct impact on important outcomes like survival and QoL. Secondly, only a small number of studies met the inclusion criteria, with these studies showing significant heterogeneity in methodology and quality. Finally, this review does not adequately cover frail and older patients, or patients in the recurrent disease or supportive care phases, due to a lack of evidence in the literature. While this review may not directly incite change in current clinical practice, we believe it illuminates deficiencies in GBM care and guides future quality improvement efforts.

Conclusion

Our evaluation of QIs in the care of patients with GBM reaffirms the importance of multidisciplinary efforts, from pretreatment assessment to end-of-life care, and timeliness of care delivery. While many QIs show potential in helping to meaningfully measure quality and to inform efforts to optimize patient outcomes, robust evidence linking these indicators to survival and/or quality of life outcomes remains limited. Some QIs rely more on assumed benefits or are extrapolating the experience from other cancer types, rather than being evidence-based for GBM, especially in the supportive care sub-category, and many would benefit from higher-order empirical evidence.

Furthermore, the limited components of standard of care, including imaging and molecular markers, and the limited range of surgical, medical, and radiation oncology options result in less treatment options and aspects of care to be assessed. However, progress is being made in each of these areas. The few high-quality studies limit the breadth of QIs available for GBM compared to other, more well-researched cancers, where biomarker-driven care is delivered across multiple lines of therapy. Nonetheless, this scoping review is to our knowledge a novel exercise and a good starting point that gives a broad account of most currently used QIs, underscoring the need for more rigorous research to improve them, and thereby establish more meaningful metrics for best practice in patients with GBM.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Conflict of interest statement

All authors declare that they have no conflicts of interest.

Authorship statement

Literature search, original draft, review & editing, and conceptualization (J.S.). Review & editing (C.D.). Review & editing (J.K.). Review & editing (P.D.). Review & editing, supervision, and conceptualization (L.G.).

Data availability

All data supporting the findings of this study are available within the paper.