Meta-analysisindependent cross-checkabstract checked★ key study I-ODD-124 standard review

Pooled studies: pioglitazone linked to a small rise in bladder cancer

Pioglitazone and bladder cancer risk: a systematic review and meta-analysis.

Overview

Tang H et al.. Cancer Med 2018 · PMID 29476615 · DOI 10.1002/cam4.1354

Observational OR 1.13 (1.03-1.25), higher with longer and higher-dose use.

Does the study support the specific claim? Partly · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: Pool pioglitazone-bladder cancer studies.
How was the study done?: Meta-analysis.
How many people, animals or samples were studied?: About 4.8 million people.
What was actually found?: Small association with dose and time response.
How large was the observed effect?: OR 1.13.
What do the results mean in everyday life?: A small possible risk, mainly with long high-dose use.
What are the study's limitations?: Mostly observational.
What does it say about Elawady's specific claim?: Supports a risk, not its 63% size.
Do the results apply to Germany and Europe?: High.
What can explicitly not be concluded from this study?: Causation.

Authors: Tang H et al.
Journal: Cancer Med
Year: 2018
Identifier: PMID 29476615 DOI 10.1002/cam4.1354
Verification: verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: Not stated in abstract.

Is pioglitazone associated with bladder cancer?

Study design: Meta-analysis – Systematic review and meta-analysis of RCTs and observational studies with dose-response analysis
Population: Patients with diabetes
Country: International
Period: To 25 August 2016
Sample size: 2 RCTs (9,114 patients); 20 observational studies (4,846,088 individuals)
Inclusion and exclusion criteria: RCTs and observational studies of pioglitazone and bladder cancer

Exposure / intervention: Pioglitazone
Comparator: Placebo or never-use
Endpoints: Bladder cancer
Statistical methods: Conventional and cumulative meta-analysis; restricted spline dose-response

Results: RCTs OR 1.84 (0.99-3.42). Observational ever-use OR 1.13 (1.03-1.25), time-dependent (P=0.003) and dose-dependent (P=0.05); differences by region and funding source.
Absolute risks: Not reported in abstract.
Authors' conclusion: Pioglitazone may increase bladder cancer risk, possibly dose- and time-dependently; long-term high-dose users should be monitored.

CIs log-symmetric (stats/C-ODD-12.py). Pooled observational effect (13%) is much smaller than the 63% cited by the archive.

Supports a small association with dose-response, but its pooled size contradicts the 63% figure as a general estimate.

Lewis 2015 (I-ODD-123); Korhonen 2016 (I-ODD-125).

High.

Best summary: small, plausibly dose-dependent association.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	moderate
Directness	direct
Reproducibility	partly replicated
Consistency with the overall evidence	mixed
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Causality.