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XVIII Congreso Chileno de Cancerolog ía. Critical analysis of meta-analysis: Individual patient-level data or literature data?. Levels of clinical evidence.  Buyse, Bentzen, Tannock, Therasse EJC Suppl. 1(6), 2003. Meta-analysis: objectives.

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levels of clinical evidence
Levels of clinical evidence

 Buyse, Bentzen, Tannock, Therasse EJC Suppl.1(6), 2003

meta analysis objectives
Meta-analysis: objectives
  • to improve statistical resolution (sample size)
  • to provide a systematic review of the available evidence
  • to examine heterogeneity among/quality of studies

SAMPLE SIZE

slide6
Meta-analysis: Literature v individual patient dataAdvanced ovarian carcinoma: combination vs single agent chemotherapy

Stewart & Parmar Lancet 341: 418, 1993.

slide7
Publication status vs significance487 research projects approved by the Central Oxford Ethics Committee

Easterbrook et al. Lancet 337: 867, 1991

snp s and late toxicity after breast rt
SNP’s and late toxicity after breast RT
  • Substitution of an alternate base pair at a specific nucleotide location
  • Prevalence ~ 1:1000 nucleotides
  • Common SNPs in human genome
    • 7 million SNPs with MAF > 5%
    • 4 million SNPs with 5% > MAF > 1%
  • TGF-1 SNP -509C/T – candidate gene SNP for late RT toxicity

 Andreassen R&O (in press)

chemo locoregional therapy for hnscc
CHEMO LOCOREGIONAL THERAPY FOR HNSCC

 Pignon et al. Lancet 355: 949 (2000)

p 10 4
p<10-4

Postoperative radiotherapy in NSCLC

Weighted regression analysis

meta analysis of hypoxic modification
Meta-analysis of hypoxic modification

“…improved loco-regional control with no change in level of complications…”

meta analysis of hypoxic modification1
Meta-analysis of hypoxic modification

Importance of type of modification:

hyperbaric oxygen in ca cervix
Hyperbaric oxygen in ca. cervix
  • 327 cases with cancer of the uterine cervix stage IIb and III
  • 4-arm RCT, 10 or 28 F in air or in HBO
  • Treated at Groote Schur Hospital in Cape Town, SA
  • No advantage of HBO in terms of tumor control

 Dische et al.R&O53: 93, 1999

quality instruments
Quality instruments
  • A review for the U.S. Department of Health and Human Services found a total of 1602 publications relating to assessment of study quality or strength of evidence:
    • 121 systems were reviewed, including scales, checklists or other instruments or guidelines
    • 20 systems were developed for evaluation of systematic reviews
    • 49 systems for RCTs
    • 40 systems for grading the strength of a body of evidence.
  • West et al. AHRQ Publication No. 02-E016.

Rockville, MD, (2002)

the nice thing about standards is that there are so many of them to choose from andres s tannenbaum
The nice thing about standards is that there are so many of them to choose from.Andres S. Tannenbaum
quality scores
Quality scores
  • 25 quality scales applied to 17 trials of low molecular weight heparin (LMWH) vs standard heparin in the prevention of post-operative thrombosis.
  • For each scale, the possible relative advantage of LMWH was estimated separately in two strata: low-quality vs high-quality trials

HQ: Positive

LQ: No difference

Similar effect

estimates from

HQ and LQ trials

HQ: No difference

LQ: Positive

Juni et al. JAMA282: 1054 (1999)

large rcts versus meta analysis
Large RCTs versus meta-analysis
  • Material:
    • 12 large RCT's (1000+ pts)
    • 19 MA's on same question
  • Results:
    • Negative predictive value of MA: 67%
    • Positive predictive value of MA: 68%

LeLorier et al. NEJM337: 536, 1997

effect of rt in early breast cancer
Effect of RT in early breast cancer

EBCTCG,NEJM 333: 1444, 1995

slide26
Postoperative Radiotherapy inHigh-Risk Premenopausal Women with Breast Cancer Who Receive Adjuvant Chemotherapy

M. Overgaard et al. NEJM337: 949, 1997

slide27
Postoperative Radiotherapy in High-Risk Postmenopausal Women with Breast Cancer Who Receive Adjuvant Tamoxifen

M. Overgaard et al. Lancet 353: 1641, 1999.

the effect of radiotherapy in breast cancer trend with starting year of trial
The effect of radiotherapy in breast cancerTrend with starting year of trial

Van deStene et al. R&O 55: 263 (2001)

multiple meta analyses of same topic
Multiple meta-analyses of same topic
  • Acetylcysteine in the prevention of contrast associated nephropathy
  • 10 systematic reviews published August 2003 – March 2005
    • 9 pooled events despite heterogeneity
    • 5 recommended routine use of acetylcysteine and 5 recommended further research

Biondi-Zoccai et al. BMJ, e-pub, 2006

interpretations of ma
Interpretations of MA?

23 randomized controlled trials (RCT) and review articles on the efficacy of intravenous magnesium in the early post-myocardial infarction period organized chronologically and grouped in packages. Presented to 8 reviewers:

 Shrier et al. BMC Med Inform Decision Making8: 19, 2008

slide31

REQUIRES AN INFORMED AND CRITICAL READER

REQUIRES AN INFORMED AND CRITICAL READER

slide32

“To call in the statistician after the experiment is done may be no more than asking him to perform a postmortem examination: he may be able to say what the experiment died of.”Ronald A. Fisher (ca. 1938)

conclusions
Conclusions
  • A meta-analysis is never better than its constituent trials
  • Individual patient level data – updated where possible – is preferable to literature based analysis
  • Critical narrative reviews may rely in part on meta-analysis but will also involve assigning varying weights to various trials depending on quality