Does the Palliative Performance Scale Have Added Value Over the Karnofsky Performance Status in Ambulatory Cancer Patients Receiving Palliative Care?

Abstract

Dear Editor:

Since 1948 the Karnofsky Performance Status (KPS) scale has been widely utilized as an assessment tool to define performance status (PS) in oncology.¹ It has certain limitations that have motivated adaptations over time. In particular, the focus of the KPS on the need for hospitalization and medical intervention challenges the evaluation of advanced cancer patients that are being treated according to the palliative care (PC) philosophy.² The Palliative Performance Scale (PPS), which was developed in 1996, was adapted from the KPS as a novel tool to quantify the PS of patients receiving PC.³ The utility of the PPS outside the context of end-of-life care requires further clarification.

Seow and colleagues⁴ analyzed the PPS scores from a large cohort of ambulatory cancer patients (n=11,342); in this cohort, 78.5% of the patients presented with an initial PPS higher than 60%. The relative hazard of death increased by a factor of 1.69 for each 10-point decrease in the PPS score. We believe that this study is relevant because it provided new robust data regarding the utility of the PPS in determining the prognosis of ambulatory advanced cancer patients (ACPs), outside the context of end-of-life care.

The PPS and the KPS were prospectively calculated in 220 ACPs during their first consult in our PC outpatient clinic. Additionally, the patients answered the European Organization for Research and Treatment of Cancer Care Quality of Life Questionnaire (EORTC QLQ-C30) to enable the correlation between the PS scores and the physical functioning subscale. All the patients were followed until death or the time of analysis (planned for after 70% of the deaths had occurred). Univariate and multivariate analyses were performed using the Cox proportional hazards model.

The mean (standard deviation) values of the KPS and PPS were 75.5 (15.1) and 75.8 (14.5), respectively. There were 112 (50.7%) men, with a mean age of 60 years, and 116 (52.5%) patients were undergoing palliative chemotherapy. We observed a KPS/PPS concordance rate of 56.3%; when accepting an error of±10%, the concordance rate rose to 97.3%. The Spearman correlation coefficient between the KPS and the PPS was 0.876 (p<0.001). As expected, there were similarly strong correlations between physical functioning and the KPS (0.537, p<0.001) and the PPS (0.557, p<0.001). The univariate analysis of survival revealed a prognostic impact for both the KPS (HR: 0.968, 95% CI 0.957–0.978, p<0.001) and the PPS (HR: 0.974, 95% CI 0.964–0.985, p<0.001). When the KPS and the PPS were analyzed separately using multivariate Cox regression analysis, they both remained independent prognostic factors (models A and B, respectively; see Table 1). When both scores were included in the analysis, only the KPS remained in the final prognostic model (model C; see Table 1).

Table 1.

Multivariate Survival Analysis of Ambulatory Advanced Cancer Patients According to the Karnofsky Performance Status and Palliative Performance Scale

	Model 1 ^a			Model 2			Model 3
	HR	95% CI	p	HR	95% CI	p	HR	95% CI	p
KPS	0.963	0.941–0.984	0.001	–	–	–	0.965	0.953–0.977	<0.001
PPS	1.003	0.980–1.026	0.810	0.971	0.959–0.983	<0.001	–	–	–
Age	0.988	0.974–1.002	0.105	0.991	0.977–1.005	0.196	0.988	0.974–1.002	0.101
Antineoplastic active treatment
Yes	1	–		1	–		1	–
No	1.414	1.002–1.996	0.049	1.455	1.031–2.053	0.033	1.412	1.001–1.993	0.049
Primary tumor
Lung	1	–	0.492	1	–	0.271	1	–	0.451
Breast	0.618	0.333–1.147	0.127	0.561	0.301–1.043	0.068	0.616	0.332–1.142	0.124
Gynecological	0.994	0.507–1.949	0.987	0.907	0.462–1.779	0.776	0.996	0.508–1.952	0.990
UGI	1.176	0.653–2.118	0.590	1.183	0.657–2.131	0.576	1.180	0.655–2.123	0.582
LGI	1.365	0.727–2.561	0.333	1.449	0.770–2.726	0.250	1.382	0.742–2.572	0.308
Urological	0.861	0.468–1.587	0.632	0.958	0.522–1.758	0.889	0.871	0.476–1.593	0.653
Hematological	0.446	0.100–1.995	0.291	0.437	0.098–1.943	0.277	0.443	0.099–1.979	0.286
SST	1.251	0.545–2.872	0.597	1.303	0.568–2.898	0.532	1.260	0.550–2.887	0.585
Head and neck	0.943	0.448–1.985	0.878	0.851	0.406–1.781	0.668	0.939	0.447–1.974	0.868
Unknown	0.886	0.301–2.608	0.826	0.886	0.302–1.600	0.826	0.893	0.304–2.887	0.836
Number of metastatic sites
0	1	–	0.006	1	–	0.003	1	–	0.006
1	1.534	0.980–2.402	0.061	1.650	1.057–2.578	0.028	1.539	0.984–2.407	0.059
2	2.151	1.301–3.555	0.003	2.020	1.228–3.323	0.006	2.147	1.300–3.548	0.003
≥3	2.517	1.341–4.724	0.004	2.927	1.568–5.463	0.001	2.522	1.344–4.732	0.004

Model 1 includes both the KPS and the PPS, model 2 only includes the PPS, and model 3 only includes the KPS.

KPS, Karnofsky Performance Status; LGI, low gastrointestinal; PPS, Palliative Performance Scale; SST, skin and soft tissue; UGI, upper gastrointestinal.

We agree with Seow and colleagues⁴ that the PPS is a valid tool in ambulatory settings that provides valuable prognostic information. However, at least in outpatients with good clinical performance, the PPS has no added value over the KPS. Considering the simultaneous model of care, where patients are referred sooner to PC, these results may influence the logistics of certain cancer outpatient clinics.

References

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