Dealing with heterogeneity of treatment effects: is the literature up to the challenge?

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Abstract

Background

Some patients will experience more or less benefit from treatment than the averages reported from clinical trials; such variation in therapeutic outcome is termed heterogeneity of treatment effects (HTE). Identifying HTE is necessary to individualize treatment. The degree to which heterogeneity is sought and analyzed correctly in the general medical literature is unknown. We undertook this literature sample to track the use of HTE analyses over time, examine the appropriateness of the statistical methods used, and explore the predictors of such analyses.

Methods

Articles were selected through a probability sample of randomized controlled trials (RCTs) published in Annals of Internal Medicine, BMJ, JAMA, The Lancet, and NEJM during odd numbered months of 1994, 1999, and 2004. RCTs were independently reviewed and coded by two abstractors, with adjudication by a third. Studies were classified as reporting: (1) HTE analysis, utilizing a formal test for heterogeneity or treatment-by-covariate interaction, (2) subgroup analysis only, involving no formal test for heterogeneity or interaction; or (3) neither. Chi-square tests and multiple logistic regression were used to identify variables associated with HTE reporting.

Results

319 studies were included. Ninety-two (29%) reported HTE analysis; another 88 (28%) reported subgroup analysis only, without examining HTE formally. Major covariates examined included individual risk factors associated with prognosis, responsiveness to treatment, or vulnerability to adverse effects of treatment (56%); gender (30%); age (29%); study site or center (29%); and race/ethnicity (7%). Journal of publication and sample size were significant independent predictors of HTE analysis (p < 0.05 and p < 0.001, respectively).

Conclusion

HTE is frequently ignored or incorrectly analyzed. An iterative process of exploratory analysis followed by confirmatory HTE analysis will generate the data needed to facilitate an individualized approach to evidence-based medicine.

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Most cited references 43

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Effect of intensive compared with moderate lipid-lowering therapy on progression of coronary atherosclerosis: a randomized controlled trial.

Steven E Nissen, E. Murat Tuzcu, Paul Schoenhagen … (2004)

Statin drugs reduce both atherogenic lipoproteins and cardiovascular morbidity and mortality. However, the optimal strategy and target level for lipid reduction remain uncertain. To compare the effect of regimens designed to produce intensive lipid lowering or moderate lipid lowering on coronary artery atheroma burden and progression. Double-blind, randomized active control multicenter trial (Reversal of Atherosclerosis with Aggressive Lipid Lowering [REVERSAL]) performed at 34 community and tertiary care centers in the United States comparing the effects of 2 different statins administered for 18 months. Intravascular ultrasound was used to measure progression of atherosclerosis. Between June 1999 and September 2001, 654 patients were randomized and received study drug; 502 had evaluable intravascular ultrasound examinations at baseline and after 18 months of treatment. Patients were randomly assigned to receive a moderate lipid-lowering regimen consisting of 40 mg of pravastatin or an intensive lipid-lowering regimen consisting of 80 mg of atorvastatin. The primary efficacy parameter was the percentage change in atheroma volume (follow-up minus baseline). Baseline low-density lipoprotein cholesterol level (mean, 150.2 mg/dL [3.89 mmol/L] in both treatment groups) was reduced to 110 mg/dL (2.85 mmol/L) in the pravastatin group and to 79 mg/dL (2.05 mmol/L) in the atorvastatin group (P<.001). C-reactive protein decreased 5.2% with pravastatin and 36.4% with atorvastatin (P<.001). The primary end point (percentage change in atheroma volume) showed a significantly lower progression rate in the atorvastatin (intensive) group (P =.02). Similar differences between groups were observed for secondary efficacy parameters, including change in total atheroma volume (P =.02), change in percentage atheroma volume (P<.001), and change in atheroma volume in the most severely diseased 10-mm vessel subsegment (P<.01). For the primary end point, progression of coronary atherosclerosis occurred in the pravastatin group (2.7%; 95% confidence interval [CI], 0.2% to 4.7%; P =.001) compared with baseline. Progression did not occur in the atorvastatin group (-0.4%; CI -2.4% to 1.5%; P =.98) compared with baseline. For patients with coronary heart disease, intensive lipid-lowering treatment with atorvastatin reduced progression of coronary atherosclerosis compared with pravastatin. Compared with baseline values, patients treated with atorvastatin had no change in atheroma burden, whereas patients treated with pravastatin showed progression of coronary atherosclerosis. These differences may be related to the greater reduction in atherogenic lipoproteins and C- reactive protein in patients treated with atorvastatin.

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Treating individuals 2. Subgroup analysis in randomised controlled trials: importance, indications, and interpretation.

Peter M. Rothwell (2005)

Large pragmatic trials provide the most reliable data about the effects of treatments, but should be designed, analysed, and reported to enable the most effective use of treatments in routine practice. Subgroup analyses are important if there are potentially large differences between groups in the risk of a poor outcome with or without treatment, if there is potential heterogeneity of treatment effect in relation to pathophysiology, if there are practical questions about when to treat, or if there are doubts about benefit in specific groups, such as elderly people, which are leading to potentially inappropriate undertreatment. Analyses must be predefined, carefully justified, and limited to a few clinically important questions, and post-hoc observations should be treated with scepticism irrespective of their statistical significance. If important subgroup effects are anticipated, trials should either be powered to detect them reliably or pooled analyses of several trials should be undertaken. Formal rules for the planning, analysis, and reporting of subgroup analyses are proposed.

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Renoprotective properties of ACE-inhibition in non-diabetic nephropathies with non-nephrotic proteinuria.

Piero Ruggenenti, Annalisa Perna, Giulia Gherardi … (1999)

Stratum 2 of the Ramipril Efficacy in Nephropathy (REIN) study has already shown that in patients with chronic nephropathies and proteinuria of 3 g or more per 24 h, angiotensin-converting enzyme (ACE) inhibition reduced the rate of decline in glomerular filtration and halved the combined risk of doubling of serum creatinine or end-stage renal failure (ESRF) found in controls on placebo plus conventional antihypertensives. In REIN stratum 1, reported here, 24 h proteinuria was 1 g or more but less than 3 g per 24 h. In stratum 1 of this double-blind trial 186 patients were randomised to a ramipril or a control (placebo plus conventional antihypertensive therapy) group targeted at achieving a diastolic blood pressure of less than 90 mm Hg. The primary endpoints were change in glomerular filtration rate (GFR) and time to ESRF or overt proteinuria (> or =53 g/24 h). Median follow-up was 31 months. The decline in GFR per month was not significantly different (ramipril 0.26 [SE 0.05] mL per min per 1.73m2, control 0.29 [0.06]). Progression to ESRF was significantly less common in the ramipril group (9/99 vs 18/87) for a relative risk (RR) of 2.72 (95% CI 1.22-6.08); so was progression to overt proteinuria (15/99 vs 27/87, RR 2.40 [1.27-4.52]). Patients with a baseline GFR of 45 mL/min/1.73 m2 or less and proteinuria of 1.5 g/24 h or more had more rapid progression and gained the most from ramipril treatment. Proteinuria decreased by 13% in the ramipril group and increased by 15% in the controls. Cardiovascular events were similar. As expected, the rate of decline in GFR and the frequency of ESRF were much lower in stratum 1 than they had been in stratum 2. In non-diabetic nephropathies, ACE inhibition confers renoprotection even to patients with non-nephrotic proteinuria.

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Author and article information

Journal

Journal ID (nlm-ta): Trials

Title: Trials

Publisher: BioMed Central

ISSN (Electronic): 1745-6215

Publication date Collection: 2009

Publication date (Electronic): 19 June 2009

Volume: 10

Page: 43

Affiliations

[1 ]Center for Healthcare Policy and Research, University of California, Davis, California, USA

[2 ]Columbia University, New York State Psychiatric Institute, New York, USA

[3 ]University of California, Los Angeles Neuropsychiatric Institute, California, USA

[4 ]University of Washington School of Medicine, Seattle, Washington, USA

[5 ]Department of Medicine, Harborview Medical Center, Seattle, Washington, USA

[6 ]Department of Family and Preventive Medicine, University of California, San Diego, California, USA

[7 ]Department of Internal Medicine, University of California, Davis, California, USA

Article

Publisher ID: 1745-6215-10-43

DOI: 10.1186/1745-6215-10-43

PMC ID: 2706823

PubMed ID: 19545379

SO-VID: 4cca0938-9f8c-4824-970b-1f3bfac797f3

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Dealing with heterogeneity of treatment effects: is the literature up to the challenge?

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Most cited references 43

Effect of intensive compared with moderate lipid-lowering therapy on progression of coronary atherosclerosis: a randomized controlled trial.

Treating individuals 2. Subgroup analysis in randomised controlled trials: importance, indications, and interpretation.

Renoprotective properties of ACE-inhibition in non-diabetic nephropathies with non-nephrotic proteinuria.

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