Mortality and functional outcome after surgical evacuation of traumatic acute subdural hematomas in octa- and nonagenarians

Extreme-aged patients (≥ 85 years) experience similar outcomes as younger geriatric patients following chronic subdural hematoma evacuation: a matched cohort study

Subdural hematoma (SDH) evacuation represents one of the most frequently performed neurosurgical procedures. Several reports cite a rise in both the age and number of patient's requiring treatment, due in part to an aging population and expanded anticoagulation use. However, limited data and conflicting conclusions exist on extreme-aged geriatric patients (≥ 85 years of age) after undergoing surgery. Patients undergoing SDH evacuation at a tertiary academic medical center between November 2013-December 2021 were retrospectively identified. The study group consisted of patients ≥ 85 years (Group 1) diagnosed with a chronic SDH surgically evacuated. A control group was created matching patients by 70-84 years of age, gender, and anticoagulation use (Group 2). Multiple metrics were evaluated between the two including length-of hospital-stay, tracheostomy/PEG placement, reoperation rate, complications, discharge location, neurological outcome at the time of discharge, and survival. A total of 130 patients were included; 65 in Group 1 and 65 in Group 2. Patient demographics, medical comorbidities, SDH characteristics, international normalized ratio, partial thromboplastin time, and use of blood thinning agents were similar between the two groups. Kaplan Meier survival analysis at one-year was 80% for Group 1 and 76% for Group 2. No significant difference was identified using the log-rank test for equality of survivor functions (p = 0.26). All measured outcomes including GCS at time of discharge, length of stay, rate of reoperations, and neurological outcome were statistically similar between the two groups. Backwards stepwise conditional logistic regression revealed no significant association between poor outcomes at the time of discharge and age. Alternatively, anticoagulation use was found to be associated with poor outcomes (OR 3.55, 95% CI 1.08-11.60; p = 0.036). Several outcome metrics and statistical analyses were used to compare patients ≥ 85 years of age to younger geriatric patients (70-84 years) in a matched cohort study. Adjusting for age group, gender, and anticoagulation use, no significant difference was found between the two groups including neurological outcome at discharge, reoperation rate, and survival.

The role of the craniotomy size in the surgical evacuation of acute subdural hematomas in elderly patients: a retrospective multicentric study

BACKGROUND

Elderly patients operated for an acute subdural hematoma (ASDH) frequently have a poor outcome, with a high frequency of death, vegetative status, or severe disability (Glasgow Outcome Score [GOS] 1-3). Minicraniotomy has been proposed as a minimally invasive surgical treatment to reduce the impact of surgery in the elderly population. The present study aimed to compare the influence of the size of the craniotomy on the functional outcome in patients undergoing surgical treatment for ASDH.

METHODS

We selected patients ≥70 years old admitted to 5 Italian tertiary referral neurosurgical for the treatment of a post-traumatic ASDH between January 1, 2016, and December 31, 2019. We collected demographic data, clinical data (GCS, GOS, Charlson Comorbidity Index [CCI], antiplatelet/anticoagulant therapy, neurological deficits, seizure, pupillary size, length of stay), surgical data (craniotomy size, dividing the patients into 3 groups based on the corresponding tertile, and surgery duration), radiological data (ASDH side and thickness, midline shift, other post-traumatic lesions, extent of ASDH evacuation) and we assessed the functional outcome at hospital discharge and 6-month follow-up considering GOS=1-3 as a poor outcome. ANOVA and χ2 Tests and logistic regression models were used to assess differences in and associations between clinical-radiological characteristics and functional outcomes.

RESULTS

We included 136 patients (76 males) with a mean age of 78±6 years. Forty-five patients underwent a small craniotomy, 47 a medium size, and 44 a large craniotomy. Among the different craniotomy size groups, there were no differences in gender, anticoagulant/antithrombotic therapy, CCI, side of ASDH, ASDH thickness, preoperative GCS, focal deficits, seizures, and presence of other post-traumatic lesions. Patients undergoing small craniotomies were older than patients undergoing medium-large craniotomies; ASDH treated with medium size craniotomy were thinner than the others; patients undergoing large craniotomies showed greater midline shift and a higher rate of anisocoria. The three groups did not differ for functional outcome and postoperative midline shift, but the length of surgery and the rate of >50% of ASDH evacuation were lower in the small craniotomy group.

CONCLUSIONS

A small craniotomy was not inferior to larger craniotomies in determining functional outcomes in the treatment of ASDH in the elderly.

Endoscopic Evacuation of Acute Subdural Hematomas: A New Selection Criterion

Introduction  Acute subdural hematomas (ASDHs) have a high mortality rate and unfavorable outcomes especially in the elderly population even after surgery is performed. The conventional recommended surgeries by the Brain Trauma Foundation in 2006 were craniotomies or craniectomies for ASDH. As the world population ages, and endoscopic techniques improve, endoscopic surgery should be utilized to improve the outcomes in elderly patients with ASDH. Materials and Methods  This was a single-center retrospective report on our series of six patients that underwent endoscopic ASDH evacuation (EASE). Demographic data, the contralateral global cortical atrophy (GCA) score, evacuation rates, and outcomes were analyzed. Results  All patients' symptoms and Glasgow Coma Scale improved or were similar after EASE with no complications. Good outcome was seen in 4 (66.7%) patients. Patients with poor outcome had initial low Glasgow Coma Scale scores on admission. The higher the contralateral GCA score, the higher the evacuation rate ( r  = 0.825, p ≤ 0.043). All the patients had a GCA score of ≥7. Conclusion  EASE is at least not inferior to craniotomy for the elderly population in terms of functional outcome for now. Using the contralateral GCA score may help identify suitable patients for this technique instead of just using a cut-off age as a criteria.

A proposed stratification system to address the heterogeneity of Subdural Hematoma Outcome reporting in the literature

A major challenge within the academic literature on SDHs has been inconsistent outcomes reported across studies. Historically, patients have been categorized by the blood-product age identified on imaging (i.e., acute, subacute, or chronic). However, this schematic has likely played a central role in producing the heterogeneity encountered in the literature. In this investigation, a total of 494 patients that underwent SDH evacuation at a tertiary medical center between November 2013-December 2021 were retrospectively identified. Mechanism of injury was reviewed by the authors and categorized as either positive or negative for a high-velocity impact (HVI) injury. Any head strike injury leading to the formation of a SDH while traveling at a velocity beyond that of normal locomotion or daily activities was categorized as an HVI. Patients were subsequently stratified by those with an acute SDHs after a high-velocity impact (aSDHHVI), those with an acute SDH without a high-velocity impact injury (aSDHWO), and those with any combination of subacute or chronic blood products (mixed-SDH [mSDH]). Nine percent (n = 44) of patients experienced an aSDHHVI, 23% (n = 113) aSDHWO, and 68% (n = 337) mSDH. Between these groups, highly distinct patient populations were identified using several metrics for comparison. Most notably, aSDHHVI had a significantly worse neurological status at discharge (50% vs. 23% aSDHWO vs. 8% mSDH; p < 0.001) and mortality (25% vs. 8% aSDHWO vs. 4% mSDH; p < 0.001). Controlling for gender, midline shift (mm), and anticoagulation use in the acute SDH population, multivariable logistic regression revealed a 6.85x odds ratio (p < 0.001) for poor outcomes in those with a positive history for a high-velocity impact injury. As such, the distribution of patients that suffer an HVI related acute SDH versus those that do not can significantly affect the outcomes reported. Adoption of this stratification system will help address the heterogeneity of SDH reporting in the literature while still closely aligning with conventional reporting.

Outcomes After the Surgical Evacuation of Traumatic Acute Subdural Hematomas: The tASDH Risk Score

BACKGROUND

Acute subdural hematoma (ASDH) is a common pathology following traumatic brain injury (TBI). There is sparse data on the prediction of clinical outcomes following traumatic ASDH (tASDH) evacuation. We investigated prognosticators of outcome following evacuation of tASDHs, with subset analysis in a cohort of octogenarians. We developed a scoring system for stratifying the risk of in-hospital mortality for patients undergoing tASDH evacuation.

METHODS

A retrospective chart review was performed to identify all patients who underwent tASDH evacuation. Baseline clinical and demographic data including age, traumatic brain injury mechanism, admission Glasgow Coma Scale (GCS), and Rotterdam computed tomography Scale (RCS) were collected. In-hospital outcomes such as mortality and discharge disposition were collected. A scoring system (tASDH Score) which incorporates RCS (1-2 points), admissions GCS (0-1 points), and age (0-1 point) was created to predict the risk of in-hospital mortality following tASDH evacuation.

RESULTS

Being an octogenarian (OR = 6.91 [2.20-21.71], P = 0.0009), having a GCS of 9-12 (OR = 1.58 [1.32-4.12], P = 0.027) or 3-8 (OR = 2.07 [1.41-10.38], P = 0.018), and having an RCS of 4-6 (OR = 3.49 [1.45-8.44], P = 0.0055) were independently predictive of in-hospital mortality. The in-hospital mortality rate was lower for those with a tASDH score of 1 (10%), compared to those with a score of 2 (12%), 3 (42%), and 4 (100%).

CONCLUSIONS

Octogenarians with an RCS of 4-6 and an admission GCS <13 have a high risk of mortality following tASDH evacuation. Knowledge of which patients are unlikely to survive ASDH evacuation may help guide neurosurgeons in prognostication and goals of care discussions.

Prognostic Factors of Mortality and Functional Outcome for Acute Subdural Hematoma: A Review Article

Acute subdural hematoma (ASDH) is the most frequent intracranial traumatic lesion requiring surgery in high-income countries. To date, uncertainty remains regarding the odds of mortality or functional outcome of patients with ASDH, regardless of whether they are operated on. This review aims to shed light on the clinical and radiologic factors associated with ASDH outcome. A scoping review was conducted on Medline database from inception to 2023. This review yielded 41 patient series. In the general population, specific clinical (admission Glasgow Coma Scale [GCS], abnormal pupil exam, time to surgery, decompressive craniectomy, raised postoperative intracranial pressure) and radiologic (ASDH thickness, midline shift, thickness/midline shift ratio, uncal herniation, and brain density difference) factors were associated with mortality (grade III). Other clinical (admission GCS, decompressive craniectomy) and radiologic (ASDH volume, thickness/midline shift ratio, uncal herniation, loss of basal cisterns, petechiae, and brain density difference) factors were associated with functional outcome (grade III). In the elderly, only postoperative GCS and midline shift on brain computed tomography were associated with mortality (grade III). Comorbidities, abnormal pupil examination, postoperative GCS, intensive care unit hospitalization, and midline shift were associated with functional outcome (grade III). Based on these factors, the SHE (Subdural Hematoma in the Elderly) and the RASH (Richmond Acute Subdural Hematoma) scores could be used in daily clinical practice. This review has underlined a few supplementary factors of prognostic interest in patients with ASDH, and highlighted two predictive scores that could be used in clinical practice to guide and assist clinicians in surgical indication.

Mortality of Surgically Treated Neurotrauma in Elderly Patients and the Development of a Prediction Score: Geriatric Neurotrauma Mortality Score

BACKGROUND

As the population worldwide is aging, the need for surgery in elderly patients with neurotrauma is increasing. The aim of this study was to compare the outcome of elderly patients undergoing surgery for neurotrauma with younger patients and to identify the risk factors for mortality.

METHODS

We retrospectively analyzed consecutive patients undergoing craniotomy or craniectomy for neurotrauma at our institution from 2012 to 2019. Patients were divided into two groups (≥70 years or <70 years) and compared. The primary outcome was the 30-day mortality rate. Potential risk factors for 30-day mortality were assessed in a uni- and multivariate regression model for both age groups, forming the basis of a 30-day mortality prediction score.

RESULTS

We included 163 consecutive patients (average age 57.98 ± 19.87 years); 54 patients were ≥70 years. Patients ≥70 years showed a significantly better median preoperative Glasgow Coma Scale (GCS) score compared with young patients (P < 0.001), and fewer pupil asymmetry (P = 0.001), despite having a higher Marshall score (P = 0.07) at admission. Multivariate regression analysis identified low pre- and postoperative GCS scores and the lack of prompt postoperative prophylactic low-molecular-weight heparin treatment as risk factors for 30-day mortality. Our score showed moderate accuracy in predicting 30-day mortality with an area under the curve of 0.76.

CONCLUSIONS

Elderly patients after neurotrauma present with a better GCS at admission despite having more severe radiographic injuries. Mortality and favorable outcome rates are comparable between the age groups.

Minimally invasive fibrinolytic treatment and drainage in patients with acute subdural hemorrhage and underlying comorbidities

The incidence of acute subdural hemorrhage (ASDH), which is often caused by head trauma, is steadily increasing due to an increase in the elderly population and the use of anticoagulants. Urgent surgical treatment is recommended if the patient has impaired consciousness, worsening neurological symptoms, or brain midline shift (MLS) due to large hematomas on brain computed tomography (CT). Although large craniotomy is traditionally recommended for ASDH removal, old age, comorbidities, and antiplatelet drugs are considered risk factors for surgical complications, many neurosurgeons hesitate to perform aggressive surgical procedures in these patients. In this study, we introduced a method that can quickly and effectively remove ASDH without general anesthesia. We retrospectively reviewed 11 cases of patients with ASDH who underwent hematoma drainage between June 2019 and December 2020. We measured the maximum subdural hematoma thickness and MLS on brain CT of patients and recorded the Glasgow Coma Scale scores before and after the surgical procedure. All patients had multiple comorbidities, and seven patients received anticoagulant or antiplatelet therapy. On initial brain CT, the median subdural hemorrhage thickness was 21.36 mm, median MLS was 10.09 mm, and mean volume of the subdural hematoma was 163.64 mL. The mean evacuation rate of the subdural hematoma after drainage was 83.57%. There was no rebleeding or operation-related infection during the aspiration procedure, and the median MLS correction after the procedure was 7.0 mm. Our treatment strategies can be a reliable, less invasive, and alternative treatment option for patients at high risk of complications due to general anesthesia or patients who are reluctant to undergo a large craniotomy due to a high bleeding tendency.

Does the Timing of the Surgery Have a Major Role in Influencing the Outcome in Elders with Acute Subdural Hematomas?

BACKGROUND

The incidence of traumatic acute subdural hematomas (ASDH) in the elderly is increasing. Despite surgical evacuation, these patients have poor survival and low rate of functional outcome, and surgical timing plays no clear role as a predictor. We investigated whether the timing of surgery had a major role in influencing the outcome in these patients.

METHODS

We retrospectively retrieved clinical and radiological data of all patients ≥70 years operated on for post-traumatic ASDH in a 3 year period in five Italian hospitals. Patients were divided into three surgical timing groups from hospital arrival: ultra-early (within 6 h); early (6-24 h); and delayed (after 24 h). Outcome was measured at discharge using two endpoints: survival (alive/dead) and functional outcome at the Glasgow Outcome Scale (GOS). Univariate and multivariate predictor models were constructed.

RESULTS

We included 136 patients. About 33% died as a result of the consequences of ASDH and among the survivors, only 24% were in good functional outcome at discharge. Surgical timing groups appeared different according to presenting the Glasgow Outcome Scale (GCS), which was on average lower in the ultra-early surgery group, and radiological findings, which appeared worse in the same group. Delayed surgery was more frequent in patients with subacute clinical deterioration. Surgical timing appeared to be neither associated with survival nor with functional outcome, also after stratification for preoperative GCS. Preoperative midline shift was the strongest outcome predictor.

CONCLUSIONS

An earlier surgery was offered to patients with worse clinical-radiological findings. Additionally, after stratification for GCS, it was not associated with better outcome. Among the radiological markers, preoperative midline shift was the strongest outcome predictor.

A Validation Study for SHE Score for Acute Subdural Hematoma in the Elderly

OBJECTIVE

The aim of this study was the verification of the Subdural Hematoma in the Elderly (SHE) score proposed by Alford et al. as a mortality predictor in patients older than 65 years with nontraumatic/minor trauma acute subdural hematoma (aSDH). Additionally, we evaluated further predictors associated with poor outcome.

METHODS

Patients were scored according to age (1 point is given if patients were older than 80 years), GCS by admission (1 point for GCS 5-12, 2 points for GCS 3-4), and SDH volume (1 point for volume 50 mL). The sum of points determines the SHE score. Multivariate logistic regression analysis was performed to identify additional independent risk factors associated with 30-day mortality.

RESULTS

We evaluated 131 patients with aSDH who were treated at our institution between 2008 and 2020. We observed the same 30-day mortality rates published by Alford et al.: SHE 0: 4.3% vs. 3.2%, p = 1.0; SHE 1: 12.2% vs. 13.1%, p = 1.0; SHE 2: 36.6% vs. 32.7%, p = 0.8; SHE 3: 97.1% vs. 95.7%, p = 1.0 and SHE 4: 100% vs. 100%, p = 1.0. Additionally, 18 patients who developed status epilepticus (SE) had a mortality of 100 percent regardless of the SHE score. The distribution of SE among the groups was: 1 for SHE 1, 6 for SHE 2, 9 for SHE 3, and 2 for SHE 4. The logistic regression showed the surgical evacuation to be the only significant risk factor for developing the seizure. All patients who developed SE underwent surgery (p = 0.0065). Furthermore, SHE 3 and 4 showed no difference regarding the outcome between surgical and conservative treatment.

CONCLUSIONS

SHE score is a reliable mortality predictor for minor trauma acute subdural hematoma in elderly patients. In addition, we identified status epilepticus as a strong life-expectancy-limiting factor in patients undergoing surgical evacuation.

Incidence of emergency neurosurgical TBI procedures: a population-based study

BACKGROUND

The rates of emergency neurosurgery in traumatic brain injury (TBI) patients vary between populations and trauma centers. In planning acute TBI treatment, knowledge about rates and incidence of emergency neurosurgery at the population level is of importance for organization and planning of specialized health care services. This study aimed to present incidence rates and patient characteristics for the most common TBI-related emergency neurosurgical procedures.

METHODS

Oslo University Hospital is the only trauma center with neurosurgical services in Southeast Norway, which has a population of 3 million. We extracted prospectively collected registry data from the Oslo TBI Registry - Neurosurgery over a five-year period (2015-2019). Incidence was calculated in person-pears (crude) and age-adjusted for standard population. We conducted multivariate multivariable logistic regression models to assess variables associated with emergency neurosurgical procedures.

RESULTS

A total of 2151 patients with pathological head CT scans were included. One or more emergency neurosurgical procedure was performed in 27% of patients. The crude incidence was 3.9/100,000 person-years. The age-adjusted incidences in the standard population for Europe and the world were 4.0/100,000 and 3.3/100,000, respectively. The most frequent emergency neurosurgical procedure was the insertion of an intracranial pressure monitor, followed by evacuation of the mass lesion. Male sex, road traffic accidents, severe injury (low Glasgow coma score) and CT characteristics such as midline shift and compressed/absent basal cisterns were significantly associated with an increased probability of emergency neurosurgery, while older age was associated with a decreased probability.

CONCLUSIONS

The incidence of emergency neurosurgery in the general population is low and reflects neurosurgery procedures performed in patients with severe injuries. Hence, emergency neurosurgery for TBIs should be centralized to major trauma centers.

Acute subdural haematoma in the elderly: to operate or not to operate? A systematic review and meta-analysis of outcomes following surgery

OBJECTIVES

Acute subdural haematoma (ASDH) is a devastating pathology commonly found on CT brain scans of patients with traumatic brain injury. The role of surgical intervention in the elderly has been increasingly questioned due to its associated morbidity and mortality. Therefore, a systematic review and meta-analysis of the literature to quantify the mortality and functional outcomes associated with surgical management of ASDH in the elderly was performed.

DESIGN/SETTING

A multidatabase literature search between January 1990 and May 2020, and meta-analysis of proportions was performed to quantify mortality and unfavourable outcome (Glasgow Outcome scale 1-3; death/ severe disability) rates.

PARTICIPANTS

Studies reporting patients aged 60 years or older.

INTERVENTIONS

Craniotomy, decompressive craniectomy, conservative management.

OUTCOME MEASURES

Mortality and functional outcomes (discharge, long-term follow-up (LTFU)).

RESULTS

2572 articles were screened, yielding 21 studies for final inclusion and 15 for meta-analysis. Pooled estimates of mortality were 39.83% (95% CI 32.73% to 47.14%; 10 studies, 308/739 patients, I²=73%) at discharge and 49.30% (95% CI 42.01% to 56.61%; 10 studies, 277/555 patients, I²=63%) at LTFU. Mean duration of follow-up was 7.1 months (range 2-12 months). Pooled estimate of percentage of poor outcomes was 81.18% (95% CI 75.61% to 86.21%; 6 studies, 363/451 patients, I²=45%) at discharge, and 79.25% (95% CI 72.42% to 85.37%; 8 studies, 402/511 patients, I²=66%) at LTFU. Mean duration of follow-up was 6.4 months (range 2-12 months). Potential risk factors for poor outcome included age, baseline functional status, preoperative neurological status and imaging parameters.

CONCLUSIONS

Outcomes following surgical evacuation of ASDH in patients aged 60 years and above are poor. This constitutes the best level of evidence in the current literature that surgical intervention for ASDH in the elderly carries significant risks, which must be weighed against benefits.

PROSPERO REGISTRATION NUMBER

CRD42020189508.

Association between Scene Time Interval and Survival in EMS-Treated Major Trauma Admitted to the Intensive Care Unit: A Multinational, Multicenter Observational Study

Objective: Major trauma is a major concern in public health and a leading cause of mortality worldwide. This study aimed to evaluate the association between the prehospital scene time interval (STI) and survival in emergency medical service (EMS)-assessed major trauma patients admitted to the intensive care unit (ICU). Methods: A retrospective observational study using the Pan-Asian Trauma Outcomes Study (PATOS) database was conducted. Adult trauma patients with injury severity scores (ISSs) greater than 15 who were admitted to the ICU were selected. EMS STIs were categorized into three groups: short (0-8 minutes), intermediate (9-16 minutes), and long (over 16 minutes). The primary outcome was survival to hospital discharge, and the secondary outcome was good neurological outcome at hospital discharge. Multivariable logistic regression analysis was conducted to calculate odds ratios and confidence intervals, adjusting for age, sex, mechanism of injury, prehospital alertness, prehospital shock index, response time interval, and EMS intervention (airway, oxygen supplementation, and intravenous fluid administration). Sensitivity analysis for patients who underwent surgery or nontraumatic brain injury cases and interaction analysis by EMS intervention were performed. Results: Data from a total of 1,874 eligible patients were analyzed. Intermediate and long STIs showed significant associations with outcomes, with adjusted ORs (95% CI) of 1.21 (1.07-1.38) in the intermediate STI group and 1.74 (1.55-1.96) in the long STI group for survival and 1.37 (1.32-1.40) in the intermediate STI group and 1.31 (1.22-1.41) in the long STI group for neurological outcome. In the sensitivity analysis, the highest ORs were found in the intermediate STI group, with adjusted ORs (95% CI) of 1.40 (1.37-1.42) for survival and 1.32 (1.26-1.38) for neurological outcome. In the interaction analysis, EMS intervention showed a positive interaction effect with an intermediate STI on survival. Conclusion: In EMS-assessed adult major trauma patients admitted to the ICU, we found significant associations between STIs longer than 8 minutes and outcomes. EMS intervention has a positive interaction effect with an intermediate STI on survival. More research is needed to understand the implications of practice for major trauma in the field.

Endoscope-assisted techniques for evacuation of acute subdural haematoma in the elderly: The lesser of two evils? A scoping review of the literature

INTRODUCTION

Surgical evacuation of acute subdural haematoma (ASDH) in the elderly remains a point of contention due to the significant associated mortality. Therefore, there is a dire need for alternative treatment options. Endoscope-assisted techniques (EAT) have been increasingly reported over the last decade with variable outcomes. In this scoping review, we identify studies reporting the use of EAT for ASDH evacuation in elderly patients. Outcomes and patient selection criteria are discussed to identify patients that may benefit from EAT.

METHODS

A multi-database literature search was performed between January 1990 and January 2021. Studies including patients aged 60 years or above who underwent EAT for ASDH evacuation with reported outcomes were included.

RESULTS

A total of 13 studies and 122 patients were eligible for inclusion. Patient age ranged from 65 to 101 years, and average age from 78.6 to 87.4 years. High comorbidity burden, advanced age, absence of adverse imaging features, and pre-operative neurological status were the most common eligibility criteria for EAT. 52% of all procedures were performed under local anaesthetic (LA). Mortality rates ranged between 0% and 40%, whilst favourable outcomes ranged between 26.7% and 96.4%. Re-bleed was the most commonly reported complication, ranging between 0% and 13%.

CONCLUSIONS

EAT pose a viable compromise for elderly patients with ASDH that may be unfit for GA. Heterogeneity of patient selection criteria prevents meaningful comparison between EAT and other approaches, and there is a clear impact of patient selection on outcome among studies reporting EAT. Further studies are required to identify the patient cohort that may benefit from this approach.