Original article
Validation of a frailty index in patients undergoing curative surgery for urologic malignancy and comparison with other risk stratification tools

https://doi.org/10.1016/j.urolonc.2015.06.002Get rights and content

Highlights

  • Compared and validated a frailty index to existing risk stratification tools for urologic surgery.

  • Examined whether our modified frailty index was predictive of death and complications.

  • Increasingly frailty patients with high frailty index scores have adverse outcomes.

  • Combining the ASA Risk Class and our modified frailty index was the best predictor of adverse events

  • A modified frailty index may help risk stratify patients who are not good surgical candidates.

Abstract

Objective

To retrospectively validate and compare a modified frailty index predicting adverse outcomes and other risk stratification tools among patients undergoing urologic oncological surgeries.

Materials and Methods

The American College of Surgeons National Surgical Quality Improvement Program was queried from 2005 to 2013 to identify patients undergoing cystectomy, prostatectomy, nephrectomy, and nephroureterectomy. Using the Canadian Study of Health and Aging Frailty Index, 11 variables were matched to the database; 4 were also added because of their relevance in oncology patients. The incidence of mortality, Clavien-Dindo IV complications, and adverse events were assessed with patients grouped according to their modified frailty index score.

Results

We identified 41,681 patients who were undergoing surgery for presumed urologic malignancy. Patients with a high frailty index score of >0.20 had a 3.70 odds of a Clavien-Dindo IV event (CI: 2.865–4.788, P<0.0005) and a 5.95 odds of 30-day mortality (CI: 3.72–9.51, P<0.0005) in comparison with nonfrail patients after adjusting for race, sex, age, smoking history, and procedure. Using C-statistics to compare the sensitivity and specificity of the predictive ability of different models per risk stratification tool and the Akaike information criteria to assess for the fit of the models with the data, the modified frailty index was comparable or superior to the Charlson comorbidity index but inferior to the American Society of Anesthesiologists Risk Class in predicting 30-day mortality or Clavien-Dindo IV events. When the modified frailty index was augmented with the American Society of Anesthesiologists Risk Class, the new index was superior in all aspects in comparison to other risk stratification tools.

Conclusion

Existing risk stratification tools may be improved by incorporating variables in our 15-point modified frailty index as well as other factors such as walking speed, exhaustion, and sarcopenia to fully assess frailty. This is relevant in diseases such as kidney and prostate cancer, where surveillance and other nonsurgical interventions exist as alternatives to a potentially complicated surgery. In these scenarios, our modified frailty index augmented by the American Society of Anesthesiologists Risk Class may help inform which patients have increased surgical complications that may outweigh the benefit of surgery although this index needs prospective validation.

Introduction

Frailty is a growing issue for surgeons, as frail patients have worse health outcomes with increased mortality rates, hospitalizations, and institutionalization rates [1]. Frailty is a medical syndrome with multiple contributors and is characterized by diminished strength, endurance, and reduced physiologic function, increasing an individual׳s vulnerability to dependency and death [2]. Frailty is associated with poor oncological outcomes such as disease progression and disease-specific mortality [3].

The Canadian Study of Health and Aging Frailty Index (CSHA-FI) is a clinically validated measure of frailty that includes the extent of comorbidities and quality-of-life variables in an accumulating deficit model of frailty [4]. Rockland et al. defined frailty as a function of the severity of a patient׳s comorbidities and declines in activities of daily living [4]. They validated their accumulating deficit model of frailty showing that it was equivalent to the phenotypic frailty model defined by the Fried frailty index, which takes into account factors such as walking speed and weight loss [5]. Abbreviated versions of the CSHA-FI have been validated as preoperative risk stratification tools in prospective and retrospective fashion in general surgery, gynecological oncology, and orthopedic surgery [6], [7], [8], [9], [10], [11]. An abbreviated version has been validated retrospectively using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) data set among patients undergoing vascular surgery, colectomy, and emergency and elective general surgery and cardiothoracic patients undergoing lobectomies [11], [12], [13], [14], [15]. In all cases, frailty measured by increasing score in the frailty index was associated with adverse outcomes.

We used the variables from the CSHA-FI mapped to the ACS-NSQIP data set to create a modified 15-point frailty index (mFI), with additional variables pertinent to our patient population in a model of frailty that measures accumulating deficits [4], [5], [16]. We validated our modified FI in patients undergoing genitourinary procedures to see how frailty and comorbidities affect patients across the most common oncological surgeries in urology: prostatectomy, cystectomy, nephrectomy, and nephroureterectomy (Neph-U).

Section snippets

Material and methods

Under the data use agreement of the ACS, we reviewed the NSQIP participant use files from 2005 to 2013. The NSQIP database is a national, validated, outcomes-based data set that is managed by the ACS. The hospitals participating in the consortium are the source of the data used herein; they have not verified, and are not responsible, for the statistical validity of the data analysis or the conclusions we have derived.

We collected 11 variables from the CSHA-FI matched to preoperative variables

Results

The ACS-NSQIP database was queried for 41,681 patients who met our selection criteria with the following clinical and demographic characteristics (Table 2). Patients undergoing cystectomy had the highest 30-day mortality rate (2.6%) and Clavien-Dindo IV complications (9.5%); those undergoing prostatectomy had the lowest 30-day mortality rate (0.2%) and Clavien-Dindo IV complications (1.1%).

For patients undergoing prostatectomy, increasing mFI was associated with increased rates of Clavien-Dindo

Discussion

When compared with healthy patients, frail patients who are exposed to stressors such as surgical intervention may have disproportionate decompensation because of a lack of physiologic reserve [22]. Therefore, the risk-benefit ratio of surgery should include frailty and severity of comorbidities to capture the full risk of a surgical candidate undergoing a surgical oncological intervention.

In this retrospective study, using the ACS-NSQIP data set, we validated a FI, modified it for patients

Conclusion

There has been a growing need for a structured, evidence-based preoperative evaluation for frail patients undergoing oncological genitourinary surgery [28], [29]. Our modified FI was associated with worse outcomes comparable to those of existing risk stratification tools when assessing 30-day mortality and Clavien-Dindo IV outcomes. When our mFI was combined with the ASA class risk stratification, it was superior to all existing risk stratification tools, indicating potential clinical

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  • Cited by (0)

    Funding for the lead author and primary investigator was awarded through the National Institute of Diabetes and Digestive and Kidney Diseases via a National Institute of Health, Bethesda, MD, USA T35 Grant 5 T35 DK 93430-3.

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