Table 2.
Re-analysis of the meta-analyses by study design.
| Cancer Type | Overall | Randomized Controlled Studies | Observational Studies * | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of Studies | Random Effects (RR, 95%CI) |
p-Value | Evidence | No. of Studies | Random Effects (RR, 95%CI) |
p-Value | Evidence | No. of Studies | Random Effects (RR, 95%CI) |
p-Value | Evidence | |
| Bladder cancer | 13 | 1.07 (0.95–1.21) | 0.282 | Non-significant | 3 | 0.84 (0.64–1.09) | 0.180 | Non-significant | 10 | 1.11 (0.97–1.26) | 0.118 | Non-significant |
| Breast cancer | 62 | 0.91 (0.85–0.97) | 0.004 | Weak | 12 | 1.00 (0.80–1.25) | 0.661 | Non-significant | 50 | 0.90 (0.84–0.96) | 0.003 | Weak |
| Colorectal cancer | 59 | 0.92 (0.88–0.95) | <0.001 | Weak | 13 | 0.92 (0.81–1.05) | 0.214 | Non-significant | 46 | 0.92 (0.88–0.95) | <0.001 | Weak |
| Endometrial cancer | 15 | 0.94 (0.83–1.07) | 0.349 | Non-significant | 2 | 0.72 (0.19–2.67) | 0.621 | Non-significant | 13 | 0.94 (0.82–1.07) | 0.361 | Non-significant |
| Esophageal cancer | 27 | 0.70 (0.63–0.78) | <0.001 | Suggestive | 1 | 0.98 (0.69–1.40) | NR | Non-significant | 26 | 0.69 (0.62–0.76) | <0.001 | Suggestive |
| Gastric cancer | 16 | 0.74 (0.60–0.90) | 0.004 | Weak | 3 | 0.84 (0.61–1.14) | 0.259 | Non-significant | 13 | 0.71 (0.56–0.90) | 0.004 | Weak |
| Gynecological cancer | 23 | 0.89 (0.78–1.02) | 0.087 | Non-significant | 6 | 1.03 (0.65–1.63) | 0.902 | Non-significant | 17 | 0.88 (0.76–1.01) | 0.069 | Non-significant |
| Hematological cancer | 34 | 0.89 (0.82–0.96) | 0.005 | Suggestive | 8 | 0.96 (0.78–1.17) | 0.667 | Non-significant | 26 | 0.88 (0.81–0.97) | 0.006 | Suggestive |
| Kidney cancer | 11 | 0.91 (0.70–1.17) | 0.457 | Non-significant | 2 | 1.01 (0.57–1.78) | 0.985 | Non-significant | 9 | 0.90 (0.69–1.18) | 0.455 | Non-significant |
| Leukemia | 9 | 0.85 (0.74–0.98) | 0.031 | Suggestive | - | - | - | - | 9 | 0.85 (0.74–0.98) | 0.031 | Suggestive |
| Liver cancer | 27 | 0.58 (0.52–0.66) | <0.001 | Suggestive | 3 | 0.96 (0.62–1.49) | 0.867 | Non-significant | 24 | 0.57 (0.50–0.65) | <0.001 | Suggestive |
| Lung cancer | 33 | 0.89 (0.80–0.99) | 0.036 | Weak | 9 | 0.95 (0.85–1.05) | 0.324 | Non-significant | 24 | 0.87 (0.77–0.99) | 0.034 | Weak |
| Lymphoma | 16 | 0.85 (0.73–0.99) | 0.042 | Weak | - | - | - | - | 16 | 0.85 (0.73–0.99) | 0.042 | Weak |
| Melanoma | 24 | 0.94 (0.86–1.03) | 0.204 | Non-significant | 13 | 1.06 (0.90–1.25) | 0.474 | Non-significant | 11 | 0.92 (0.84–1.02) | 0.105 | Non-significant |
| Myeloma | 5 | 0.89 (0.53–1.51) | 0.674 | Non-significant | - | - | - | - | 5 | 0.89 (0.53–1.51) | 0.674 | Non-significant |
| Pancreatic cancer | 20 | 0.89 (0.75–1.06) | 0.207 | Non-significant | 3 | 0.99 (0.44–2.21) | 0.982 | Non-significant | 17 | 0.89 (0.74–1.07) | 0.202 | Non-significant |
| Prostate cancer | 64 | 0.94 (0.90–0.99) | 0.017 | Weak | 7 | 1.06 (0.93–1.20) | 0.386 | Non-significant | 57 | 0.93 (0.88–0.98) | 0.005 | Weak |
| Non-melanoma skin cancer | 17 | 1.07 (1.00–1.16) | 0.063 | Non-significant | 8 | 1.07 (0.86–1.33) | 0.519 | Non-significant | 9 | 1.08 (1.00–1.18) | 0.048 | Weak |
RR: Relative risk. * Observational studies include both cohort studies and case-control studies.