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01.12.2018 | Research article | Ausgabe 1/2018 Open Access

BMC Cancer 1/2018

Metformin, Asian ethnicity and risk of prostate cancer in type 2 diabetes: a systematic review and meta-analysis

Zeitschrift:
BMC Cancer > Ausgabe 1/2018
Autoren:
Christopher B. Chen, Maxim Eskin, Dean T. Eurich, Sumit R. Majumdar, Jeffrey A. Johnson
Wichtige Hinweise

Electronic supplementary material

The online version of this article (https://​doi.​org/​10.​1186/​s12885-017-3934-9) contains supplementary material, which is available to authorized users.

Abstract

Background

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.

Methods

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.

Results

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, I2: 97%), with similar findings in Western-based trials (RR: 1.38, 95%CI: 0.72-2.64 I2: 15%) and observational studies (RR: 1.03 95%CI: 0.94-1.13, I2: 88%). Asian-based studies suggested a non-significant reduction (RR: 0.75, 95%CI: 0.42-1.34, I2: 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, I2: 0%).

Conclusion

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.
Zusatzmaterial
Additional file 1: Current Metformin Use Vs. No Current Metformin Use in Western- and Asian-Based Cohort Studies. Comparison of metformin use in western and asian-based cohort studies. (DOCX 26 kb)
12885_2017_3934_MOESM1_ESM.docx
Additional file 2: Current Metformin Use Vs. No Current Metformin Use in Western-Based Cohort Studies. Comparison of metformin use in western-based cohort studies. (DOCX 25 kb)
12885_2017_3934_MOESM2_ESM.docx
Additional file 3: Current Metformin Use Vs. No Current Metformin Use in Asian-Based Cohort Studies. Comparison of metformin use in Asian-based cohort studies. (DOCX 17 kb)
12885_2017_3934_MOESM3_ESM.docx
Additional file 4: Current Metformin Use Vs. No Current Metformin Use in Western- and Asian-Based Case-Control Studies. Comparison of metformin use in Western- and Asian-based case-control studies. (DOCX 22 kb)
12885_2017_3934_MOESM4_ESM.docx
Additional file 5: Current Metformin Use Vs. No Current Metformin Use in Western-Based Case-Control Studies. Comparison of metformin use in Western-based case-control studies (DOCX 22 kb)
12885_2017_3934_MOESM5_ESM.docx
Additional file 6: Current Metformin Use Vs. No Current Metformin Use in Asian-Based Case-Control Studies. Comparison of metformin use in Asian-based case-control studies (DOCX 16 kb)
12885_2017_3934_MOESM6_ESM.docx
Additional file 7: Risk of Bias ≤6; Current Metformin Use Vs. No Current Metformin Use in Western- and Asian-Based Cohort Studies. Comparison of metformin use in Western- and Asian-based cohort studies with a Newcastle-Ottawa score ≤ 6. (DOCX 21 kb)
12885_2017_3934_MOESM7_ESM.docx
Additional file 8: Risk of Bias ≤6; Current Metformin Use Vs. No Current Metformin Use in Western-Based Cohort Studies. Comparison of metformin use in Western-based cohort studies with a Newcastle-Ottawa score ≤ 6. (DOCX 20 kb)
12885_2017_3934_MOESM8_ESM.docx
Additional file 9: Risk of Bias ≤6; Current Metformin Use Vs. No Current Metformin Use in Asian-Based Cohort Studies. Comparison of metformin use in Asian-based cohort studies with a Newcastle-Ottawa score ≤ 6. (DOCX 18 kb)
12885_2017_3934_MOESM9_ESM.docx
Additional file 10: Risk of Bias ≤6; Current Metformin Use Vs. No Current Metformin Use in Western- and Asian-Based Case-Control Studies. Comparison of metformin use in Western- and Asian-based case-control studies with a Newcastle-Ottawa score ≤ 6. (DOCX 20 kb)
12885_2017_3934_MOESM10_ESM.docx
Additional file 11: Risk of Bias ≤6; Current Metformin Use Vs. No Current Metformin Use in Western-Based Case-Controls Studies. Comparison of metformin use in Western-based case-control studies with a Newcastle-Ottawa score ≤ 6. (DOCX 19 kb)
12885_2017_3934_MOESM11_ESM.docx
Additional file 12: Risk of Bias ≤6; Current Metformin Use Vs. No Current Metformin Use in Asian Based Case-Control Studies. Comparison of metformin use in Asian-based case-control studies with a Newcastle-Ottawa score ≤ 6. (DOCX 17 kb)
12885_2017_3934_MOESM12_ESM.docx
Additional file 13: Risk of Bias >6; Current Metformin Use Vs. No Current Metformin Use in Western-Based Cohort Studies. Comparison of metformin use in Western-based cohort studies with a Newcastle-Ottawa score > 6. (DOCX 21 kb)
12885_2017_3934_MOESM13_ESM.docx
Additional file 14: Risk of Bias >6; Current Metformin Use Vs. No Current Metformin Use in Western Based Case Control Studies. Comparison of metformin use in Western-based case-control studies with a Newcastle-Ottawa score > 6. (DOCX 18 kb)
12885_2017_3934_MOESM14_ESM.docx
Additional file 15: Current Metformin Use Vs. No Current Metformin Use in Western- and Asian-Based Observational Studies. Comparison of metformin use in Western- and Asian-based observational studies. (DOCX 26 kb)
12885_2017_3934_MOESM15_ESM.docx
Additional file 16: Current Metformin Use Vs. No Current Metformin Use in Western- Based Observational Studies. Comparison of metformin use in Western-based observational studies. (DOCX 18 kb)
12885_2017_3934_MOESM16_ESM.docx
Additional file 17: Current Metformin Use Vs. No Current Metformin Use in Asian-Based Observational Studies. Comparison of metformin use in Asian-based observational studies. (DOCX 14 kb)
12885_2017_3934_MOESM17_ESM.docx
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