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Originally published as JCO Early Release 10.1200/JCO.2007.13.3439 on January 28 2008 © 2008 American Society of Clinical Oncology.
The Prognostic Significance of Patient-Reported Outcomes in Cancer Clinical Trials
From the Cancer Research Center of Hawaii, University of Hawaii, Honolulu, HI; Quality of Life Unit, European Organization for Research and Treatment of Cancer, Brussels, Belgium; and Health Outcome Research Unit, Italian Group for Adult Hematologic Diseases (GIMEMA) Data Center, Rome, Italy Corresponding author: Carolyn C. Gotay, PhD, Department of Health Care and Epidemiology, University of British Columbia, 5804 Fairview Ave, Vancouver, British Columbia, V6E 1R7 Canada; e-mail: carolyn.gotay{at}ubc.ca
Purpose: Patient-reported outcomes (PROs), routinely collected as a part of cancer clinical trials, have been linked with survival in numerous clinical studies, but a comprehensive critical review has not been reported. This study systematically assessed the impact of PROs on patient survival after a cancer diagnosis within the context of clinical trials. Design: Cancer clinical trials that assessed baseline PROs and mortality were identified through MEDLINE (through December 2006) supplemented by the Cochrane database, American Society of Clinical Oncology/European Society for Medical Oncology abstracts and hand searches. Inclusion criteria were publication in English language and use of multivariate analyses of PROs that controlled for one or more clinical factors. Two raters reviewed each study, abstracted data, and assessed study quality; two additional raters verified abstractions. Results: In 36 of 39 studies (N = 13,874), at least one PRO was significantly associated with survival (P < .05) in multivariate analysis, with varying effect sizes. Studies of lung (n = 12) and breast cancer (n = 8) were most prevalent. The most commonly assessed PRO was quality of life, measured by the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire C30 in 56% of studies. Clinical variables adjusted for included performance status (PS), treatment arm, stage, weight loss, and serum markers. Results indicated that PROs provide distinct prognostic information beyond standard clinical measures in cancer clinical trials. Conclusion: PROs might be considered for stratification purposes in future trials, as they were often better predictors of survival than PS. Studies are needed to determine whether interventions that improve PROs also increase survival and to identify explanatory mechanisms through which PROs relate to survival.
Patient perspectives are increasingly used as outcomes in cancer clinical trials, as well as in cancer surveillance and patient care.1 The United States Food and Drug Administration has recently drawn additional attention to these variables by defining patient-reported outcomes (PROs) as "measurement of any aspect of a patient's health status that comes directly from the patient (ie, without the interpretation of the patient's responses by a physician or anyone else)," including disease symptoms, patient functioning, and quality of life (QOL).2 PROs provide an assessment of patient well-being, but do they have other uses, such as predicting how long patients will survive? The predictive value of PROs, particularly QOL, for cancer survival has been noted in descriptive reviews.3-5 However, no systematic overviews have assessed the robustness of this observation and investigated whether PROs provide prognostic information that goes beyond standard biomedical predictors. This article provides a comprehensive critical review of cancer clinical trials that examined the relationship between PROs, biomedical predictors, and survival. The rationale for focusing this review on clinical trials was to control for effects of treatment: in other words, trials ensure that all patients are treated using a specified protocol, thus ensuring that baseline PROs (and other potential confounders, such as comorbidity) do not affect treatment and its effects on survival. Specifically, we wanted to determine the following: the relationship between PRO end points and cancer patient survival, the effect size of relationships reported, and implications for future research and clinical practice.
MEDLINE searches were conducted for English-language studies in cancer patients using the terms "quality of life" or "patient-reported outcome," "cancer," and "prognostic" or "survival." Searches were also conducted using words denoting specific PRO domains and scale acronyms often associated with PRO reporting. The following search terms were also used: depression, anxiety, fatigue, baseline pain, CES-D, BDI, QLQ-C30, STAI, RSCL, PAIS, HADS, BPI, MSAS, pain assessment, functional assessment, FACT questionnaire, FACT survey, FLIC, self-rated health. These searches were supplemented by reference list searches, the Cochrane database, American Society of Clinical Oncology and European Society for Medical Oncology abstracts, hand searches, and expert consultation. Studies that met the following criteria were selected:
A total of 39 published articles (1989 through 2006) met all inclusion criteria. Data were abstracted and independently reviewed by at least two raters. Summaries of key data can be seen in Tables 1 and 26-44; the majority of studies were in populations with primarily advanced or metastatic disease (Table 1). Several studies included multiple stages of disease in the same article or focused on nonmetastatic disease, but even many of these reports included large numbers of patients with advanced disease (Table 2). Study characteristics and findings were consistent across metastatic and nonmetastatic disease populations, and combined results are presented here. Studies on lung (n = 12) and breast cancer (n = 8) were most prevalent. Overall, 13,874 cancer patients provided PRO ratings, with a mean of 356 patients per study (range, 40 to 2,270 patients). Most studies (n = 29) were phase III trials.
PRO Assessment QOL was the most common PRO assessed. The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire C30 (EORTC QLQ-C30) or its modules were used in 56% of studies. Other measures included QOL questionnaires (eg, the Functional Living Index–Cancer and general and site-specific versions of the Functional Assessment of Cancer Treatment [FACT]) and measures of specific dimensions such as pain. Some studies assessed numerous PROs,7,37 such as Brown et al, 7 who used five linear analog scales of well-being: the FACT-Brain, the Symptom Distress Scale, and the Profile of Mood States short-form. See references1,45 for information on specific questionnaires.
Biomedical Variable Assessment
Analytic Methods
Follow-Up
Findings All three articles in which no PROs were significantly associated with survival in the multivariate analysis were in breast cancer.12,18,40 Coates et al12 presented further follow-up analyses of the subset of women who experienced recurrence and found that PROs collected near the time of recurrence were significant predictors of survival. Most associations between PROs and survival were in the expected direction, ie, better PROs predicted better survival, with a few exceptions: better emotional functioning,14 reduced fatigue,6 and better role functioning35 were associated with an increased risk of death.
Effect Size We characterized relative effect sizes for hazard ratios as moderate (either protective [.51 to 0.75] or contributory [1.35 to 1.99]) and large (less than 0.50 or in excess of 2), based on ratings used by the Institute of Medicine.46 It can be seen that, although statistically significant, the size of many reported effects was small. However, a number of articles reported moderate8,13,14,24,28,35,38,42 or large effects.9,23,29,33 The finding of Jerkeman et al23 that global QOL ratings were associated with nearly an eight-fold difference in survival rates was particularly striking.
This article reviewed data relating PROs measured at baseline to cancer patient survival, based on an analysis of published clinical trials. The use of clinical trials provides several advantages: well-characterized samples, use of consistent treatment protocols not based on PRO ratings, few patient comorbid conditions (owing to eligibility criteria), availability of mature data for adequately powered analyses, and rigorous quality control. In general, the quality of trials included here was high. At the same time, using clinical trials presents limitations: there were few trials in early-stage disease47 and trial participants were unrepresentative of the broader cancer patient population.48 In addition, we did not include unpublished analyses nor articles not published in English. The studies reflect considerable diversity—in patients, measures of PROs and correlates, and analytic strategies, complicating cross-study comparisons. Statistical models, particularly related to selection of PROs assessed and entered into analysis, were not theory-based. Although we do not have access to the original study protocols, analyses were described as ad hoc and exploratory, making it unlikely that examining relationships between PROs and survival was specified as an a priori primary or secondary hypothesis. PRO measures included single items and symptoms, multi-item batteries, broad constructs, and specific aspects of well-being. In most studies, relationships among closely related measures were not explored, nor were attempts made at item reduction, with the implication that considerable overlap, or multicollinearity, was likely across items; Efficace et al16 cited this factor as a possible explanation for why the PRO with the narrowest interpretation (appetite loss) emerged as the strongest factor in analysis, because the other PROs, in effect, may have canceled each other out. There were often multiple factors entered into analyses, with little attention to adjusting Type I error rates for multiple comparisons; consequently, it is likely that some findings are spurious and owing to chance. Not all articles included adequate information regarding follow-up time, and even some that did neglected to provide any reasoning behind the selection of those time periods. In addition, the clinical significance of PRO scores and effect sizes was rarely discussed. Dubois et al15 is an exemplary exception, with clinical significance of scores and effect sizes being specified a priori, building on contemporary advances in defining clinical significance.49 Although the studies here can be seen as forming a solid base for hypothesis generation, the next generation of research in this area should include focused hypotheses and measures. For example, specific measures that are believed to predict survival should be specified a priori, as opposed to using a broad range of nonspecific assessments, which often gives rise to inconsistent or conflicting findings. In addition, studies that go beyond documenting the phenomenon and test hypotheses about why PROs may be linked to survival are strongly indicated. Despite this heterogeneity, there is impressive agreement across studies supporting the link between PROs and survival. But what about the three studies that found no PROs predicted survival in multivariate analysis? It is noteworthy that all three were conducted with nonmetastatic breast cancer patients. In early-stage breast cancer, extended survival for many years is expected. It seems plausible that PROs assessed years before death may not predict survival length, as many subsequent events (eg, diagnosis of comorbidities) are more likely to affect life span. This hypothesis was supported by the study by Wisloff et al42 of multiple myeloma patients, where the relationship between baseline QOL and survival was strongest in the first 1 to 2 years of follow-up. In addition, for two of the three studies which found paradoxical relationships between PROs and survival, the authors further elaborated on their findings by adding interaction terms: Dancey et al14 found that emotional functioning was not associated with survival in patients with high global QOL, and that only in those with low global QOL did higher emotional functioning predict an increased risk of death. Roychowdhury et al35 reported that whereas their initial findings indicated that high role functioning was associated with a greater mortality risk, this depended on metastatic status; in patients without visceral metastasis, those with increased role functioning lived longer. The relationships between PROs and survival may be more complicated than main effects and again require causal models that are subjected to empirical testing. For studies that found a PRO-survival relationship, PROs retained predictive power after considerable variance in survival outcomes had been explained by well-established and powerful biomedical predictors, such as stage. Even given that there was a limited amount of variance to be explained, PROs were predictive, and many effect sizes were impressive. Even more remarkable, PROs generally remained significant predictors of survival even after accounting for PS ratings. In fact, in a number of studies, PS no longer held explanatory value once PROs had been entered into the analysis.9-11,15-17,20-26,29,30,33-35,40,43,44 PS is based on patient behaviors and functional ability, rather than disease characteristics, and is similar to some PROs (eg, ratings of physical and role functioning). Likewise, some toxicity indicators were linked to survival, but not as strongly as the associated patient symptom ratings. Both PS and toxicity ratings are based on clinician perspectives, rather than those of patients, and it seems that patient ratings are more sensitive in predicting how long they will live. Why should PROs be so consistently linked with survival? There are several possible explanations.
What are the implications of these findings?
The author(s) indicated no potential conflicts of interest.
Conception and design: Carolyn C. Gotay Administrative support: Crissy T. Kawamoto Provision of study materials or patients: Carolyn C. Gotay, Andrew Bottomley, Fabio Efficace Collection and assembly of data: Carolyn C. Gotay, Crissy T. Kawamoto, Andrew Bottomley, Fabio Efficace Data analysis and interpretation: Carolyn C. Gotay, Crissy T. Kawamoto, Andrew Bottomley, Fabio Efficace Manuscript writing: Carolyn C. Gotay, Crissy T. Kawamoto, Andrew Bottomley, Fabio Efficace Final approval of manuscript: Carolyn C. Gotay, Crissy T. Kawamoto, Andrew Bottomley, Fabio Efficace
We thank David Osoba, Madeleine King, Mirjam Sprangers, and Ian Pagano for guidance and support in the preparation of this article. Portions of this manuscript were prepared when Fabio Efficace worked at the Quality of Life Unit, European Organization for Research and Treatment of Cancer.
published online ahead of print at www.jco.org on January 28, 2008. Authors disclosures of potential conflicts of interest and author contributions are found at the end of this article.
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Copyright © 2008 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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