Patient-reported outcome (PRO) instruments used in patients undergoing adoptive cell therapy (ACT) for the treatment of cancer: a systematic review

Introduction Adoptive cell therapy (ACT) is a rapidly evolving field. Patient-reported outcomes (PROs) allow patients to report the impact of treatment on their quality of life during and after treatment. The systematic review aims to characterise the breadth of PROs utilised in ACT cancer care and provide guidance for the use of PROs in this patient population in the future. Methods A systematic search was conducted (MEDLINE, PsycINFO, Embase and CINAHL) in August 2021 by two reviewers. Search terms covered the following: “adoptive cell therapy”, “patient-reported outcomes” and “cancer”. Studies were included if they used a PRO measure to report the impact of ACT. The methodological quality of PROs was assessed. Forward and backward reference searching was conducted of any relevant papers. A quality grading scale was applied based on Cochrane and Revenson criteria for classification of high-quality studies. Key data from the studies and the included PROs was extracted by two researchers and tabulated. Results One-hundred nine papers were identified; 11 papers were included. The majority of studies were single-arm trials or observational studies. Twenty-two different PROs were identified; none was ACT specific. The PROMIS-29 and EQ-5D were most commonly used. Few studies collected PRO data in the first 1–2 weeks. Four studies followed patients up for over a year, and a further four studies followed patients for approximately 3 months. Discussion None of the PROs identified have been designed specifically for ACT. Appropriateness of existing instruments should be considered. It should be considered whether it is appropriate to collect data more frequently in the acute stage and then less frequently during follow-up. It should be considered if one tool is suitable at all time points or if the tool should be adapted depending on time since treatment. More research is needed to identify the exact timings of PRO assessments, and qualitative work with patients is needed to determine the most important issues for them throughout the treatment and follow-up.


Background
Surgery, chemotherapy and radiotherapy have been the main treatments for cancer for many years.More recently, however, new treatments such as targeted therapies and immunotherapies have started to be developed and have shown promising results in terms of survival [1].Adoptive cell therapy or adoptive cell transfer (ACT) is a form of immunotherapy which harnesses the natural ability of immune cells to specifically recognise and eliminate target cells; thus, tumour-specific T cells can be infused to patients with the aim of the host immune system recognising and attacking cancer cells [2].ACT has quickly become one of the fastest-growing areas of immune-oncology (IO) clinical research in the world [3].ACT could be an additional treatment option for patients where other targeted and immunotherapy approaches have failed [4].
There are many types of ACT [5], but chimeric antigen receptors cell therapy (CAR T-cell) has made the most progress in terms of both clinical development and regulatory approval [6].CAR T-cell treatments which target CD19 have demonstrated significant clinical benefit in clinical trials of patients with CD19 positive B-cell malignancies.A systematic review and meta-analysis of CAR-T trials found that CAR-T had better survival outcomes for large B-cell lymphoma patients compared to high-dose chemotherapy or autologous stem cell transplant [7].It has been reported that children with aggressive lymphomas had very few treatment options available to them before CAR-T developments [1].
In 2017, the first two CD19-directed CAR-T therapies, tisagenlecleucel and axicabtagene ciloleucel, were approved by the Food and Drug Administration (FDA) and subsequently the European Medicines Agency (EMA) to treat patients with diffuse large B-cell lymphoma (DLBCL) and B-cell acute lymphoblastic leukaemia (B-ALL).Both of these licenced treatments are now being widely used in the commercial setting [8].Since 2017, the haematological indications for approved CD19-directed CAR T-cell therapies have broadened to include conditions such as mantle cell lymphoma and certain types of follicular lymphoma, and in 2021, the first B-cell maturation antigen (BCMA)-directed CAR-T, idecabtagene vicleucel, was approved by the FDA for use in multiple myeloma.Tisagenlecleucel is another form of ACT which is also licensed for use.Since ACT is an emerging and expanding field, many treatments are still only available within the context of early phase clinical trials.Therefore, detailed knowledge of specific toxicities and in particular long-term effects may still be unknown.There is no consensus on what constitutes short-and long-term effects in this context; in a review of late effects, Chakraborty et al. [9] define toxicities that occur beyond 1-3 months post infusion as long-term effects, suggesting that short-term effects would occur in the first 3 months.
Due to the unique way ACT therapies work, many of the toxicities experienced by patients differ from those linked to traditional cytotoxic drugs and immunotherapies.CAR T-cell toxicities or the so-called ontarget effects are variable, and the spectrum of toxicities depends on the specificity of the precise antibody target and T-cell activation [10].Not all ACT treatments will have the same severity or range of toxicities.As safety data continues to emerge and mature, the toxicity profiles for these novel therapies will develop allowing more tailored patient management depending on the particular type of ACT therapy received.The toxicity profile for CD19 CAR T-cell is the most mature with over 1000 patients treated on CD19 CAR T-cell clinical trials in the USA alone, and increasing numbers of patients now treated both on and off trials globally [10].Although even this group where toxicity data is more established, information on long-term events remains limited [11].
Acute toxicities are more well documented, and in fact, both cytokine release syndrome (CRS) and neurotoxicity, both of which have proved to have serious and/or life-threatening consequences, have received significant attention [12].CRS is a spectrum of clinical and laboratory findings of fevers, hypotension, hypoxia and neurologic changes associated with substantial elevations of serum cytokine levels.The time of onset of CRS can be variable, ranging from a few hours to over a week after CAR T-cell infusion [13].Neurologic toxicity is the second major side effect which has been seen in a substantial number of patients treated with CD19-targeted CAR T-cells.This toxicity is now widely referred to as immune effector cell-associated neurotoxicity syndrome (ICANS) [14] as it has also been observed following other types of cellular therapies.The clinical presentation of ICANS can be varied and includes tremor, headache, encephalopathy (confusion or delirium), expressive aphasia, motor weakness, seizures, depressed level of consciousness and, rarely, diffuse cerebral oedema.The onset of ICANS is also variable and can occur as early as 1 day post treatment, although presentation tends to be later than CRS and can occur up to the third or fourth week after infusion [13].
Patients can report toxicities they are experiencing using patient-reported outcomes (PROs).PROs are increasingly being used to ensure that patients have the opportunity to accurately report their own experience during and after treatment and provide a greater understanding of the impact of a disease and/or its treatments including any toxicities experienced [15,16].In clinical practice, PRO data can be used to inform and guide patient-centred care and clinical decision-making.In clinical trials, PROs can be used to assess the efficacy, safety and tolerability of treatments from the patient perspective, providing valuable insights into patients' symptoms and health-related quality of life (HRQOL) [17,18] and can be used to inform regulatory decision-making, clinical guidelines and health policy [19][20][21][22].Evaluating PRO data alongside other trial outcomes can provide important information to aid in the understanding of the risks and benefits of treatment from the patients' perspective.A Medicare Evidence Development and Coverage Advisory Committee (MEDCAC) meeting included a discussion with key stakeholders and experts in the field on the use of PROs in CAR-T trials.The panel emphasised the additional valuable data PROs provide but voiced concerns about their use due to lack of standardisation in scoring and patient and clinician understanding of the measures.These concerns need to be addressed to fully embrace the use of PROs in CAR T-cell trials.
It is important to consider the timing of PRO assessments within advanced cell therapy trials.Lasiter et al. (2020) recommend both short-and long-term follow-up.Regular PRO assessment should occur during the active treatment stage but given the curative expectations of these therapies, long-term follow-up (potentially up to 15 years for some trials) is recommended to identify any long-term side effects.Despite these treatments being in their infancy and the changing profile of toxicity overtime, it is necessary to further understand the short-and long-term effects of ACT.It is the aim of the potential lack of studies exploring long-term effects of ACT; it is still the aim within this review to include studies focusing on both short-and long-term effects.
Recent reviews have explored the collection of HRQOL data [23] or the use of PROs in CAR T-cell trials specifically [24].Messina et al. [25] reported that the use of PROs in CAR T-cell trials is considerably less than the industry average (6.17% compared with 27%), despite the growing importance of HRQOL and its impact on valuebased care [26][27][28].The authors concluded that despite the increase in interest in ACT trials, there continues to be a deficiency of including and reporting of PROs in the trial design of this new therapeutic area.Similarly, Raymakers et al. [23] identified 424 CAR-T trials, and only 29 (6.8%) included HRQOL as a primary or secondary outcome.
Qualitative studies exploring the experience of patients receiving ACT treatment are limited.The three recent studies in this area have all focused on CAR-T rather than ACT more broadly [29][30][31].Cheng et al. [29] reviewed a number of PROs that had been used in CAR-T trials and explored whether their study participants endorsed the items covered in these questionnaires.They reported that physical, emotional, social, role functioning and fatigue were all highly endorsed by patients, and cognitive function, pain, sleep, and general symptoms were moderately endorsed.They concluded that the EORTC-QLQ-C30 had the best coverage of items, but a CAR-Tspecific questionnaire may be required to cover some of the key symptoms.Whisenant et al. [31] created a list of the commonly reported CAR-T treatment side effects, the most common being fatigue.Similar to Cheng et al. [29], Whisenet et al. [31] found that existing questionnaires did not cover all areas of importance of this patient group, and as a result, suggested adding additional items to the MDSAI to create the MDSAI-CT, a tool specific for patients receiving cellular therapy.In Jenei et al. 's qualitative study [30], they reviewed an online social media forum, and their findings focused on patient experienced more broadly such as accessing and navigating treatment and overcoming uncertainties.
Since ACT is a rapidly evolving field in cancer care with the potential to offer some patients durable response, it is important to understand what the short-and longterm effects of these novel treatments are for patients living with and beyond cancer.PRO data could inform the effective management of both short-and long-term physical and psychosocial morbidities.
The aim of this systematic review was to characterise the breadth of PROs utilised in ACT cancer care and provide guidance for the use of PROs in this patient population in the future.Specific objectives were as follows:

Search strategy
A systematic search was conducted on four databases (MEDLINE, PsycINFO, Embase and CINAHL) in August 2021.An information specialist helped to develop the search strategy.We used similar keywords across the databases, adapting the Boolean operators and MeSH vocabulary.The search terms used were related to the following: "adoptive cell therapy", "patient-reported outcomes" and "cancer".As the majority of ACT treatment is given in the context of clinical trials, it is anticipated that many of the studies identified will be clinical trials.We did however want to include as many relevant papers as possible; therefore, the search was not limited to clinical trials.Any studies including ACT patients in a clinical trial or clinical practice context were included.An example of the full research strategy can be found in Table 1.
Results were not restricted by date or language.Articles identified were stored and managed in EndNote and duplicates removed.

Selection and screening
Identified articles were imported into the Rayyan systematic review reference system [32], and all were independently screened by two reviewers (S.T. and J. C. M.) against the inclusion and exclusion criteria.Studies were included if they used a PRO measure to report the impact of ACT treatment.There were no restrictions based on comparisons, outcomes assessed or study design.Initially, the titles and abstracts were screened.The full text was retrieved for any paper which potentially met the inclusion criteria.The two reviewers would discuss any discrepancies, and a third reviewer (M.D.) would be consulted if required.Forward and backward reference searching was used to identify any additional papers for inclusion.

Data extraction
Two independent reviewers (S.T. and K. L.) used a structured Excel table to extract data from the selected full-text articles.Data collected included information regarding the publication (author(s), journal, year of publication), the study (type of study, setting), the intervention (ACT, treatment regimen), characteristics of the population (cancer type, stage, type of therapy) and outcomes.Data extraction also captured information related to the identified PRO measure(s) and aspects of clinical utility including name of the PRO, the concept it measured, mode and timing of administration, recruitment and completion rates and methodology used for the analysis (statistical or clinical significance, thresholds, type of measure and the method used for the analysis).Once the list of included papers had been generated, a list was created of the issues covered in the identified PROs these issues were cross-referenced against the symptoms and functional issues identified in available qualitative studies [29,31] to explore if any of the PROs fully address the needs of this patient group.

Methodological assessment of PRO use
The consensus-based standards for the selection of health status measurement instruments (COSMIN) checklist is a tool designed to assess key psychometric qualities (validity, reliability and responsiveness to Patient Reported Outcome Measures/ 9141 7 (("Patient Reported" or "Patient-Reported") adj2 ("Outcome*" or "Measure*" or "Recovery" or "experience*")).ab,ti24,352 8 (("patient reported treatment" or "patient-reported treatment") adj2 ("Outcome*" or "Measure*" or "Recovery" or "experience*")).ab,ti24 9 (("self reported" or "self-reported") adj2 ("Outcome*" or "Measure*" or "Recovery" or "experience*")).ab,ti11,101 10 (("self Reported Treatment" or "self-reported treatment") adj2 ("Outcome*" or "Measure*" or "Recovery" or "experience*")).ab,ti27 change) of PROs [33].Given the anticipated dearth of PROs developed specifically for the ACT population, it was decided that the modified version of the COSMIN checklist as recommended by the FDA [21] would be applied to any PROs not specific to ACT, and the full COSMIN tool would be applied if any ACTspecific tools were identified.The key psychometric qualities assessed in the modified version include conceptual framework, reliability and content validity, construct validity and clinical relevance of score changes (Table 2).It was felt that this would be sufficient for any non-ACT-specific PROs.Original validation papers for the included PROs were examined to collect relevant information of psychometric properties.An additional search was carried out for each questionnaire to identify any additional studies where the questionnaires had been used in the ACT population.Given that no RCTs were identified in the review, it was not felt appropriate to use the Cochrane risk-ofbias criteria.A description of the quality grading scale applied is presented in Table 3.This classification system was devised using Cochrane [34] and Revenson [35] criteria for classification of high-quality studies and has been used.

Results
The search retrieved 103 papers, seven duplicates were removed and the titles and abstracts of the remaining 96 were reviewed.A PRISMA flow diagram is presented in Fig. 1.Sixteen papers were selected for full-text review, and a further six were identified following forward and backward reference searching.Of the 22 papers where full text was reviewed, 11 were excluded.Reasons for exclusion are as follows: no PRO reported (n = 1), review paper (n = 5), commentary paper (n = 2), abstract only (n = 1), protocol only (n = 1) and qualitative study (n = 1).References in the five review papers were searched to ensure all relevant papers had been included.Some of the included papers were published as abstracts only, but they included sufficient detail for data extraction.Searches were conducted to ensure full-text papers were not available.Given the limited number of eligible papers, it was decided that these papers would be included.

Patient-reported outcomes
A total of 23 different PROs were used across the studies (Table 5).The most commonly used PRO were the PROMIS-29 [48] which was used in four of the identified studies [36,[40][41][42] and the EQ5D [49] which was used in three studies [38,42,43].Ten of the PROs were generic measures not focusing on any particular disease group.Seven of the generic PROs were measures assessing a broad range of different functional aspects such as mobility, activities of daily living and impact on social and emotional function.One of these generic tools was developed specifically for paediatric patients.Four of the generic questionnaires focused on a specific symptom (pain, anxiety and depression, sleep, cognition).A further one that could not be located appeared to focus on fatigue.Four PROs were cancer specific and measured a wide range of symptoms or functional issues.Three PROs were disease specific and focused on neurological diseases, myeloma and lymphoma.Five studies either use PROs specific to the included patient population or state that the questionnaires had been validated in the stated patient population.None of the questionnaires used had been developed specifically to collect PRO data for patients receiving ACT.Given that none of the identified PROs had been developed specifically for ACT patients, we felt it was important to examine whether the PROs covered the experiences of this patient group.Two qualitative studies [29,65] were identified which explored the QOL experiences of a total of 39 ACT patients.The issues identified in these studies were tabulated and then cross-referenced with the items covered in all the PROs included in this review.None of the included PROs covered all items identified in the two qualitative research studies (Table 6).The PRO-CTCAE had the best coverage of items, but there were still some areas that were not addressed.The majority of studies used multiple PROs in a single study.The quality of the included PROs was mixed, some were well validated whereas others had been developed specifically for the study and had not been subjected to any psychometric testing.All but one study [45] used at least one validated PRO.The timing of PRO administration varied across the studies, some were completed at a single time point only (n = 3) [40][41][42] whereas other studies included multiple time points.There was no consistency in the time points used, only one study collected PRO data at 7 days [38] and three collected it at 14 days [36,37,39].
Four studies followed patients up for over a year [43][44][45]47], with the longest follow-up period being 5 years [43]; a further four studies followed patients for approximately 3 months [36][37][38][39].The completion rates for most studies were above 70%; three studies however had very low response rates (44%; 38%; 18%).The majority of studies do not provide details as to how the PRO was administered.The three studies where details were provided were administered online; one of these studies also had a paper option if required.
Although only two studies included a comparison arm [45], the majority of studies reported on whether there was a significant difference in their outcome measures.Only one study [39] reported a statistically significant difference in PRO responses.Sidana et al. reported that the CAR T-cell group experienced significantly less worsening in quality of life as measured by FACT-G than both autoSCT and alloSCT groups from baseline to each time point (week 2, months 1, 2 and 3) [39].Five studies reported minimal clinically important differences in some elements of the PRO data [38,40,43,44,47].

Discussion
Eleven studies were identified in this review, the majority of which were conducted in the USA.A relatively low number of ACT studies were identified that collected PRO data.In comparison to the number of studies, a large number of PRO instruments were identified which highlights the need for further research to standardise assessment in this area.Measuring patient experience and patient-reported outcomes is crucial in the development of new treatments.PRO toxicity data has been reported to be more accurate than clinician-reported data [66,67].As expected given the focus of ACT clinical trials [68], the majority of studies only included patients with haematological cancer.Only one study [39] reported a statistically significant difference in PRO responses; the CAR T-cell group experienced significantly less worsening in QoL as measured by FACT-G than both stem cell transplant groups.
The studies included in this review have highlighted many methodological challenges to the use of PRO data in the ACT population.The wide range of PROs used make it difficult for any comparisons to be made across the data collected.As highlighted in other research, the majority of studies do not use the PRO as their primary outcome [69].The majority of ACT trials are early phase with safety as a priority; therefore, investigators may be reluctant to include QoL as an outcome [23].The study designs were also not methodologically robust, no RCTs were included and only two included a comparison arm.This is a problem unique to ACT as traditionally ACT studies would generally be tested in early phase trials only.RCTs are the gold standard in clinical trials, and RCT data would be needed to fully explore the impact of ACT on toxicities and quality of life.The type of patients included is also a concern as some of the studies only report results on the more well patients or have a significant dropout rate; therefore, the results may not be generalisable.Furthermore, the needs of underserved populations may not have been considered [70].
Choosing an appropriate PRO instrument is a crucial step when developing a trial.Ideally, a PRO should be valid, reliable, sensitive to change and be generalisable to the target patient population [71].PROs can be generic or disease specific.Many of the cancer PROs aim to assess quality of life and key symptoms or toxicities.None of the studies identified in this review uses PROs designed specifically for the ACT population.Further research is required to understand the concepts that matter to patients undergoing ACT.In their qualitative study, Whisenant et al. [65] explored the symptom burden of CAR T-cell therapy.Participants reported experiencing 34 symptoms related to the disease and treatment; they also described how their symptoms interfered with their functioning in many different areas.In this review, we cross-referenced qualitative findings with the issues covered in the identified PROs and found that none of the PROs covered all the issues pertinent to this patient group.This is perhaps why many of the included studies used multiple questionnaires.There is a danger however of overburdening patients if they are expected to   The timing of PRO assessments is an important issue that needs to be considered [69].Lasiter et al. suggest there are three distinct phases in PRO data collection: acute, sub-acute and long term; they suggest that timing of PRO assessments should vary within these phases, and different PROs may also be used in order to address the most pertinent issues at each time point [72].The acute phase when patients are likely to experience toxicities is considered to be weeks 1-4, and it is recommended that PRO data should be collected at least once a week during this phase [73].Some of the key toxicities such as CRS and ICANS are likely to occur 1-2 weeks after treatment.Only one of the included studies collected PRO data at 7 days, and three collected it at 14 days.The majority of studies therefore may not have collected data on the key toxicities patients may experience.It is important to monitor toxicities in new therapeutic areas as these toxicities could be predictors of worse complications in the future.One qualitative study [29] suggested that the majority of patient side effects had improved after 6 months.After this time point, the emphasis of collecting data may shift to more general QoL rather than PROs that collect information on symptoms.
The follow-up period varied across the included studies.Four studies followed patients up for over a year, with the longest follow-up period being 5 years; a further four studies followed patients for approximately 3 months.Long-term follow-up is important with a relatively new drug as data needs to be collected on long-term toxicities.Existing research has not explored the role of collecting of PRO data overtime [69].There are practicality issues with following patients up for a long time however as their care may be transferred to other centres, and therefore, keeping track of patients and getting clinical teams to manage and take ownership of follow-up may be difficult [73].Electronic patient-reported outcomes (ePROs) are becoming more common place and may make longer-term follow-up more feasible [46]; however, issues of digital inclusion must be considered [70].There is also the issue of patient compliance.In some studies included in this review, compliance rates were very low.Whatever time points are selected, it is important to ensure that baseline data is collected as the patients in this population may have received several lines of treatment before their ACT, and as a result, their baseline data may be significantly lower than some patient populations.
Attempts have been made to make recommendations for the most suitable questionnaires to be used in the ACT population.In this review, the most commonly used PROs were the PROMIS-29 which was used in four of the identified studies and the EQ5D which was used in three studies; however, frequency of use should not be the main driver for future practice.Rather this should be informed by addressing concepts that matter to patients and other key stakeholders.PROMIS, FACT-G and PRO-CTCAE were recommended in one review as possible PROs to use in this patient population [73] PROMIS was recommended due to its high correlation with SF36, ease of comparison with general population and free availability.FACT-G was recommended due to the availability of historical data in different cancer subtypes and PROCTCAE was recommended as a suitable measure of toxicity [73].The Centers for Medicare & Medicaid Services (CMS) panel have also made their own recommendations about the most appropriate tools to use (PROCTCAE [51], MD Anderson Symptom Inventory [60], EORTC-QLQ-C30 [62] and PROMIS [48]), all of which are flexible questionnaire systems that use item banks or a modular approach.It is important to consider the purpose of the PRO tool as PROs are designed to measure different things.Some PROs focus on HRQOL, whereas others focus on toxicities; therefore, different PROs may be required at different points of the disease trajectory.

Limitations
There are many methodological concerns with the studies identified in this review such as a lack of robust study designs and concerns about the patient population included; additionally, a wide range of PROs have been used across the studies.These issues make it difficult for any recommendations to be made about the appropriate PRO to be used in the ACT patient population.It was a concern that such a small number of papers were identified in the search.We did however work with information specialists to generate the search terms and also searched key authors and reference lists; therefore, we are confident that all relevant papers have been identified.

Conclusion
None of the PROs identified has been designed specifically for the ACT population, and none of them covered all the needs of this patient population.Appropriateness of existing instruments should be considered and if necessary a new tool developed.It should be considered whether it is appropriate to collect data more frequently in the acute stage and then less frequently for a considerable time during the follow-up in order to identify late effects and whether one tool is suitable at all time points or if the tool should be adapted depending on time since treatment.More research is needed to identify the exact timings of PRO assessments, and qualitative work with patients is needed to determine what are the most important issues for them throughout the treatment and follow-up trajectory.

Fig. 1
Fig. 1 Flow diagram of articles identified for use in the review

Table 1
Example of full search terms used in MEDLINE

Table 2
Modified version of COSMIN checklist

Table 3
Study quality grading criteria (grade 1 indicates the highest quality study)

Table 4 (continued) Author and year Country Cancer type Sample size (consented) Type of therapy Trial design PROs used
*The questionnaire was changed during the study so earlier participants completed SF-36 and later participants completed PROMIS-29

Table 5
Review of psychometric properties of identified questionnaires using modified version of COSMIN checklist