Metformin, Asian ethnicity and risk of prostate cancer in type 2 diabetes: a systematic review and meta-analysis
Bibliographic record
Abstract
Metformin is associated with a reduced risk of some cancers but its effect on prostate cancer is unclear. Some studies suggest only Asians derive this benefit. Therefore, we undertook a systematic review with particular attention to ethnicity. Medline, Embase, Scopus, Web of Science, and EBM Reviews were searched from inception to 2015. Two reviewers identified and abstracted articles. Studies were pooled using random effects model and stratified by Western- vs Asian-based populations. We identified 482 studies; 26 underwent full review. Of Western-based studies ( n = 23), two were randomized trials and 21 were observational studies. All Asian-based studies ( n = 3) were observational. There were 1,572,307 patients, 1,171,643 Western vs 400,664 Asian. Across all studies there was no association between metformin and prostate cancer (RR: 1.01, 95%CI: 0.86-1.18, I 2 : 97%), with similar findings in Western-based trials (RR: 1.38, 95%CI: 0.72-2.64 I 2 : 15%) and observational studies (RR: 1.03 95%CI: 0.94-1.13, I 2 : 88%). Asian-based studies suggested a non-significant reduction (RR: 0.75, 95%CI: 0.42-1.34, I 2 : 90%), although these results were highly influenced by one study of almost 400,000 patients (propensity-adjusted RR: 0.47 95%CI 0.45-0.49). Removing this influential study yielded an estimate more congruent with Western-based studies (RR: 0.98 95%CI:0.71-1.36, I 2 : 0%). There is likely no association between metformin and risk of prostate cancer, in either Western-based or Asian-based populations after removing a highly influential Asian-based study.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.010 | 0.021 |
| Meta-epidemiology (narrow) | 0.002 | 0.001 |
| Meta-epidemiology (broad) | 0.017 | 0.031 |
| Bibliometrics | 0.006 | 0.008 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".