The Association Between Performance Status and Health-Related Quality of Life

Background: Performance Status (PS) is often used to assess the functional status of cancer patients. One of the most commonly used scales is the Eastern Cooperative Oncology Group (ECOG) PS. Using the ECOG PS scale, the oncologist assigns a score ranging from 0 (Fully active, able to carry on all pre-disease performance without restriction) to 4 (completely disabled; cannot carry on any selfcare; totally confined to bed or chair). In multiple myeloma (MM), a PS > 2 has been associated with a 35% increased risk of death following autologous stem cell transplant (ASCT) (Turesson et al, Br J Haematol, 1999), and therefore a PS ≤ 2 is generally required for ASCT and for eligibility in clinical trials. 

PS is often seen as a surrogate for health-related quality of life (HRQOL), which are patient reported measure(s) of well-being; however, they are separate constructs. While poorer PS has been associated with a decrease in HRQOL, it is unclear how much of the variance in HRQOL is explained by PS.  

Objectives: 1) To determine the association between PS and HRQOL; 2) to determine how much variance in HRQOL is explained by PS.

Methods: Data was extracted from the open-access Multiple Myeloma Research Foundation (MMRF) Researcher Gateway corresponding with interim analysis 6 from the CoMMpass study. The CoMMpass study dataset included 562 patients who completed the EORTC QLQ-C30 and EORTC QLQ-MY20 at MM diagnosis. The range of scores for these HRQOL measures is 0-100, with higher scores indicating higher values. Data was analyzed using SPSS 21. The association between PS and HRQOL was assessed by one-way ANOVA tests; the amount of variance in HRQOL explained by PS was assessed by linear regression modeling.

Results: PS was associated with all 9 HRQOL scales analyzed (p<0.001). Poorer PS was associated with poorer global health, physical function, emotional functioning, cognitive functioning, social functioning, and role functioning; and greater disease symptoms, fatigue, and pain. However, PS explained only a portion of the variance seen with each scale. The most variance explained by PS was seen in the physical functioning scale (38%); the least was in the cognitive functioning scale (10%). Adding age and International Staging System (ISS) stage significantly improved 4 of the 9 models (physical functioning, emotional functioning, fatigue, and pain); however, improvements were modest (2-5%).    

Conclusions: PS was significantly associated with HRQOL but it was not considered a good explanatory model for any of the scales analyzed as it could not explain at least 50% of the variance, even after the addition of age and ISS stage. A broader examination of the patients' disease, functional, social, and socioeconomic context is needed to better understand HRQOL and to identify areas which may be improved by intervention.

Table 1: Association between Performance Status and Health-Related Quality of Life

	Performance Status 0 n= 202	Performance Status 1  n = 249	Performance Status 2 n = 47	Performance Status  3/4 n = 29	p
Global Health Scale	75	54	33	21	<0.001
Physical Functioning Scale	93	73	33	13	<0.001
Cognitive Functioning Scale	100	83	83	66	<0.001
Emotional Functioning Scale	83	75	66	41	<0.001
Social Functioning Scale	100	66	33	33	<0.001
Role Functioning Scale	100	66	0	0	<0.001
Disease Symptom Scale	16	27	50	53	<0.001
Fatigue Scale	22	33	66	77	<0.001
Pain Scale	16	33	83	100	<0.001

  Table 2: Amount of Variance in Health-Related Quality of Life Explained by Performance Status, Age, and Stage

	Model 1A			Model 2B
	R2	F	p	R2	F change	pC
Global Health Scale	0.233	35.7	<0.001	0.234	1.6	0.188
Physical Functioning Scale	0.381	72.0	<0.001	0.405	6.3	<0.001
Cognitive Functioning Scale	0.105	13.8	<0.001	0.121	1.3	0.259
Emotional Functioning Scale	0.102	13.3	<0.001	0.158	10.1	<0.001
Social Functioning Scale	0.215	32.1	<0.001	0.222	2.1	0.106
Role Functioning Scale	0.295	48.7	<0.001	0.297	0.7	0.563
Disease Symptom Scale	0.148	19.9	<0.001	0.164	1.9	0.132
Fatigue Scale	0.235	35.9	<0.001	0.259	5.9	0.001
Pain Scale	0.204	30.0	<0.001	0.218	2.7	0.048

A-    Performance status

B-    Performance status, age, and International Staging System stage

C-    Of F change