Table 3.
Ratios of the expected cases of invasive breast cancer under the Navarre, original Gail, and recalibrated Gail prediction models to the observed cases in the Navarre Breast Cancer Screening Program cohort by age interval and risk factor category, 1996–1998 to 2005
| Stratum | Observed cases of invasive breast cancer | Navarre model | Original Gail modela | Recalibrated Gail modela | |||
|---|---|---|---|---|---|---|---|
| Expected cases of invasive breast cancerb | Ratio of expected to observed cases (95 % CI)c | Expected cases of invasive breast cancerb | Ratio of expected to observed cases (95 % CI)c | Expected cases of invasive breast cancerb | Ratio of expected to observed cases (95 % CI)c | ||
| Age interval (years) | |||||||
| 45–49 | 49 | 48.87 | 1.00 (0.75–1.32) | 61.60 | 1.26 (0.95–1.66) | 50.81 | 1.04 (0.78–1.37) |
| 50–54 | 185 | 182.97 | 0.99 (0.86–1.14) | 208.61 | 1.13 (0.98–1.30) | 183.01 | 0.99 (0.86–1.14) |
| 55–59 | 202 | 198.90 | 0.98 (0.86–1.13) | 268.34 | 1.33 (1.16–1.52) | 201.40 | 1.00 (0.87–1.14) |
| 60–64 | 193 | 189.49 | 0.98 (0.85–1.13) | 281.55 | 1.46 (1.27–1.68) | 194.40 | 1.01 (0.87–1.16) |
| 65–69 | 166 | 161.72 | 0.97 (0.84–1.13) | 292.15 | 1.76 (1.51–2.05) | 167.14 | 1.01 (0.86–1.17) |
| 70–74 | 40 | 38.14 | 0.95 (0.70–1.30) | 103.24 | 2.58 (1.89–3.52) | 39.61 | 0.99 (0.73–1.35) |
| Age at menarche (years) | |||||||
| ≥14 | 335 | 339.14 | 1.01 (0.91–1.13) | 508.56 | 1.52 (1.36–1.69) | 341.86 | 1.02 (0.92–1.14) |
| 12–13 | 413 | 385.28 | 0.93 (0.85–1.03) | 567.08 | 1.37 (1.25–1.51) | 395.11 | 0.96 (0.87–1.05) |
| <12 | 87 | 95.68 | 1.10 (0.89–1.36) | 139.86 | 1.61 (1.30–1.98) | 99.41 | 1.14 (0.93–1.41) |
| Previous breast biopsy | |||||||
| Age <50 years | |||||||
| No | 42 | 41.84 | 1.00 (0.74–1.35) | 51.60 | 1.23 (0.91–1.66) | 42.56 | 1.01 (0.75–1.37) |
| Yes | 7 | 7.03 | 1.00 (0.48–2.11) | 10.00 | 1.43 (0.68–3.00) | 8.25 | 1.18 (0.56–2.47) |
| Age ≥50 years | |||||||
| No | 673 | 660.74 | 0.98 (0.91–1.06) | 1016.75 | 1.51 (1.40–1.63) | 691.11 | 1.03 (0.95–1.11) |
| Yes | 113 | 110.48 | 0.98 (0.81–1.18) | 137.14 | 1.21 (1.01–1.46) | 94.45 | 0.84 (0.70–1.01) |
| No. of affected first-degree relatives | |||||||
| Age at first live birth <20 years | |||||||
| 0 | 10 | 11.85 | 1.18 (0.64–2.20) | 13.60 | 1.36 (0.73–2.53) | 9.60 | 0.96 (0.52–1.78) |
| 1 | 1 | 0.54 | 0.54 (0.10–21.35) | 1.72 | 1.72 (0.31–67.95) | 1.25 | 1.25 (0.22–49.28) |
| ≥2 | 0 | 0.01 | – | 0.12 | – | 0.06 | – |
| Age at first live birth 20–24 years | |||||||
| 0 | 204 | 206.10 | 1.01 (0.88–1.16) | 259.50 | 1.27 (1.11–1.46) | 185.37 | 0.91 (0.79–1.04) |
| 1 | 12 | 13.47 | 1.12 (0.64–1.98) | 31.98 | 2.67 (1.51–4.69) | 22.84 | 1.90 (1.08–3.35) |
| ≥2 | 1 | 0.61 | 0.61 (0.11–23.98) | 2.60 | 2.60 (0.47–102.68) | 1.87 | 1.87 (0.34–73.89) |
| Age at first live birth 25–29 years or nulliparous | |||||||
| 0 | 434 | 409.97 | 0.94 (0.86–1.04) | 600.26 | 1.38 (1.26–1.52) | 411.27 | 0.95 (0.86–1.04) |
| 1 | 39 | 35.33 | 0.91 (0.66–1.24) | 66.61 | 1.71 (1.25–2.34) | 45.08 | 1.16 (0.84–1.58) |
| ≥2 | 2 | 3.11 | 1.55 (0.43–12.83) | 7.50 | 3.75 (0.94–14.99) | 5.03 | 2.52 (0.63–10.06) |
| Age at first live birth ≥30 years | |||||||
| 0 | 116 | 124.45 | 1.07 (0.89–1.29) | 210.19 | 1.81 (1.51–2.17) | 139.99 | 1.21 (1.01–1.45) |
| 1 | 16 | 13.77 | 0.86 (0.53–1.41) | 20.11 | 1.26 (0.77–2.05) | 13.23 | 0.83 (0.51–1.35) |
| ≥2 | 0 | 0.90 | – | 1.30 | – | 0.78 | – |
| Overall | 835 | 820.10 | 0.98 (0.92–1.05) | 1215.49 | 1.46 (1.36–1.56) | 836.37 | 1.00 (0.94–1.07) |
To correct for the optimistic bias induced by assessing calibration of the Navarre prediction model on the same data used to fit the model, a 10-fold cross-validation was used in which the absolute risk of invasive breast cancer for women in each 10 % random subcohort was calculated based on cause-specific hazards and hazard ratios estimated from the remaining 90 % of women in the Navarre Breast Cancer Screening Program cohort (see statistical appendix in Supplementary Material 1)
aThe Gail prediction model was tested for calibration in its original form, which combined the original relative risk estimates [1] with invasive breast cancer and mortality rates for white women in the United States [2], and after recalibration, which combined the original relative risk estimates [1] with cross-validated estimates of composite invasive breast cancer and mortality rates and risk factor prevalences among cases from the Navarre Breast Cancer Screening Program cohort (see statistical appendix in Supplementary Material 1)
bThe expected number of invasive breast cancer cases for a given age interval or risk factor category was calculated as the sum of the individual absolute risks of invasive breast cancer predicted by the models over that age interval or risk factor category
cRatios of expected to observed cases and 95 % confidence intervals (CIs) assuming a negligible variance for the expected number of cases and a Poisson variance for the observed number of cases. If the expected number of cases was below 5, exact 95 % CIs were calculated based on a Poisson distribution