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Table 1 Estimates of increase in 10-year mortality for different prognostic groups and for false-negative rates of 9.7%, 20% and 100% (all values are in percentages)

From: A mathematical model for the effect of a false-negative sentinel node biopsy on breast cancer mortality: a tool for everyday use

      ER-negative patientsa
      Age 40 years Age 60 years
      Grade 3 Grade 2 Grade 1 Grade 3 Grade 2 Grade 1
      <1 cm 1–2 cm <1 cm 1–2 cm <1 cm 1–2 cm <1 cm 1–2 cm <1 cm 1–2 cm <1 cm 1–2 cm
Row Risk/risk reduction FNR Explanation of calculations ENPb (15%) (35%) (12%) (30%) (10%) (25%) (15%) (35%) (12%) (30%) (10%) (25%)
1 10-year mortality risk in NN women     8 17 5 14 3 6 3 6 5 14 3 6
2 10-year mortality real risk in those with 1–3 positive nodes     33 33 30 30 13 13 33 33 30 30 13 13
3 Reduction in 10-year mortality with adjuvant therapy in NN women     3.8 7.6 2.4 6.3 1.3 2.8 0.8 1.6 1.4 3.8 0.8 1.6
4 Reduction in 10-year mortality with adjuvant therapy in NP women (as would apply to the false-negative patients)     14.2 14.2 13 13 6.1 6.1 8.1 8.1 7.5 7.5 3.4 3.4
5 Difference in absolute benefit between NN and NP women from chemotherapy (NP - NN)     10.4 6.6 10.6 6.7 4.8 3.3 7.3 6.5 6.1 3.7 2.6 1.8
6                 
7 Unsuspected harm in a SNB-negative woman = (overall risk for missing positive axilla [AFN = FNR × ENP] × difference between benefit for NP and NN women [NP - NN]) + (harm from axillary relapse [AFN × 0.1]) 9.7% Actual % of patients with missed positive axilla (AFN = ENP × FNR) 1.5 3.4 1.2 2.9 1.0 2.4 1.5 3.4 1.2 2.9 1.0 2.4
8    Mortality due to axillary recurrence (AFN × 0.1) 0.15 0.34 0.12 0.29 0.10 0.24 0.15 0.34 0.12 0.29 0.10 0.24
9    Mortality due to no chemotherapy (AFN × [NP - NN]) 0.15 0.22 0.12 0.19 0.05 0.08 0.11 0.22 0.07 0.11 0.03 0.04
10    Total 0.30 0.56 0.24 0.49 0.14 0.32 0.25 0.56 0.19 0.40 0.12 0.29
11 Unsuspected harm in a SNB-negative woman = (overall risk for missing positive axilla [AFN = FNR × ENP] × difference between benefit for NP and NN women [NP - NN]) + (harm from axillary relapse [AFN × 0.1]) 20.0% Actual % of patients with missed positive axilla (AFN = ENP × FNR) 3.0 7.0 2.4 6.0 2.0 5.0 3.0 7.0 2.4 6.0 2.0 5.0
12    Mortality due to axillary recurrence (AFN × 0.1) 0.30 0.70 0.24 0.60 0.20 0.50 0.30 0.70 0.24 0.60 0.20 0.50
13    Mortality due to no chemotherapy (AFN × [NP - NN]) 0.31 0.46 0.25 0.40 0.10 0.17 0.22 0.46 0.15 0.22 0.05 0.09
14    Total 0.61 1.16 0.49 1.00 0.30 0.67 0.52 1.16 0.39 0.82 0.25 0.59
15 Unsuspected harm in a SNB-negative woman = (overall risk for missing positive axilla [AFN = FNR × ENP] × difference between benefit for NP and NN women [NP - NN]) + (harm from axillary relapse [AFN × 0.1]) 100.0% Actual % of patients with missed positive axilla (AFN = ENP × FNR) 15 35 12 30 10 25 15 35 12 30 10 25
16    Mortality due to axillary recurrence (AFN × 0.1) 1.50 3.50 1.20 3.00 1.00 2.50 1.50 3.50 1.20 3.00 1.00 2.50
17    Mortality due to no chemotherapy (AFN × [NP - NN]) 1.56 2.31 1.27 2.01 0.48 0.83 1.10 2.28 0.73 1.11 0.26 0.45
18    Total 3.06 5.81 2.47 5.01 1.48 3.33 2.60 5.78 1.93 4.11 1.26 2.95
  1. The values for patients aged 40 years with a grade 2 or 3 tumour between 1 and 2 cm may be ignored because the benefit from chemotherapy is high (>5%) even if they are node negative. A 100% false-negative rate would be achieved if no axillary surgery was performed. aThe values given are for oestrogen receptor (ER)-negative patients and approximate those for additional benefit from chemotherapy in ER-positive patients on top of hormone therapy. bEstimated node positivity (ENP) is given in parentheses. AFN, estimated number of patients with a falsely negative axilla; FNR, false-negative rate; NN, node negative; NP, node positive.