Risk for Breast Cancer Probability Model for White Women

Description

Once a woman's relative risk for breast cancer has been calculated in the Gail model (previous section), it needs to be converted to the absolute risk for the individual patient. Absolute risks are calculated for the periods of 10, 20 and 30 years from the time that the woman is counseled.

Parameters:

(1) relative risk

(2) age of patient at the time of counseling in years

(3) number of biopsies taken

(4) presence or absence of known atypical hyperplasia

Benichout et al showed different figures for each set of parameters. The equations below were based on data extracted from the figures, with the line approximations derived using JMP.

If the age of the woman is > 50, then the figures in Benichou et al do not handle the absolute risk.

10 Year Absolute Risk	Figure	Age	Equation for Absolute Risk from Relative Risk
no biopsy	C2a	20	= (0.0671 * RR) - 0.067143
		30	= (0.42607 * RR) + 0.15393
		40	= (1.14786 * RR) + 0.345
		50	= (1.42929 * RR) + 0.4021
1 biopsy, no known atypical hyperplasia	C2b	20	= (0.0427 * RR) + 0.1706
		30	= (0.412 * RR) + 0.35867
		40	= (1.116786 * RR) + 0.4971
		50	= (1.4015 * RR) + 0.633
1 biopsy, atypical hyperplasia	C2c	20	= (0.064286 * RR) - 0.2619
		30	= (0.44045 * RR) + 0.21418
		40	= (-0.007456 * (RR^2)) + (1.2671 * RR) + 0.004
		50	= (-0.008342 * (RR^2)) + (1.50793 * RR) + 0.561157
>= 2 biopsies, no known atypical hyperplasia	C2d	20	= (0.05263 * RR) - 0.0526
		30	= (0.42615 * RR) + 0.1970303
		40	= (-0.008 * (RR^2)) + (1.2731 * RR) - 0.06935
		50	= (1.4465 * RR) + 0.423
>= 2 biopsies, atypical hyperplasia	C2e	20	= (0.05203 * RR) - 0.248448
		30	= (0.4045238 * RR) + 0.4007
		40	= (-0.005479 * (RR^2)) + (1.19746 * RR) + 0.195893
		50	= (-0.00829 * (RR^2)) + (1.49857 * RR) + 0.4

where:

• RR = relative risk

20 Year Absolute Risk	Figure	Age	Equation for Absolute Risk
no biopsy	C2f	20	= (0.51 * RR) - 0.03
		30	= (1.592857 * RR) + 0.157
		40	= (-0.04345 * (RR^2)) + (2.89345 * RR) - 0.125
		50	= (-0.0411 * (RR^2)) + (3.23839 * RR) + 0.02232
1 biopsy, no known atypical hyperplasia	C2g	20	= (0.5 * RR)
		30	= (1.499286 * RR) + 0.52857
		40	= (-0.014881 * (RR^2)) + (2.2345 * RR) + 0.4
		50	= (-0.0607 * (RR^2)) + (3.46857 * RR) - 0.66
1 biopsy, atypical hyperplasia	C2h	20	=(0.465909 * RR) + 0.2045455
		30	= (-0.00737 * (RR^2)) + (1.575857 * RR) + 0.3416
		40	= ( -0.017234* (RR^2)) + (2.24285 * RR) + 0.59307
		50	= (-0.040692 * (RR^2)) + (3.182526 * RR) + 0.16467
>= 2 biopsies, no known atypical hyperplasia	C2i	20	= (0.4639 * RR) + 0.2187879
		30	= (-0.010384 * (RR^2)) + (1.627 * RR) + 0.27744
		40	= (-0.01568 * (RR^2)) + (2.0325596 * RR) + 0.26261
		50	= (-0.04063 * (RR^2)) + (3.160179 * RR) + 0.31
>= 2 biopsies, atypical hyperplasia	C2j	20	= (0.4569 * RR) + 0.18214
		30	= (-0.010357 * (RR^2)) + (1.65107 * RR) - 0.308929
		40	= (-0.013167 * (RR^2)) + (1.917 * RR) + 1.1982
		50	= (-0.040286 * (RR^2)) + (3.16657 * RR) + 0.08

30 Year Absolute Risk	Figure	Age	Equation for Absolute Risk
no biopsy	C1a	20	= (1.77143 * RR) - 0.4714
		30	= (2.9357 * RR) + 0.18095
		40	= (-0.08024 * (RR^2)) + (4.40784 * RR) + 0.023287
		50	= (-0.08024 * (RR^2)) + (4.40784 * RR) + 0.023287
1 biopsy, no known atypical hyperplasia	C1b	20	= (1.5759 * RR) - 0.0357
		30	= (-0.02381 * (RR^2)) + (2.6667 * RR) + 0.2857143
		40	= (-0.046875 * (RR^2)) + (3.495536 * RR) + 0.25
		50	= (-0.089286 * (RR^2)) + (4.52143 * RR) - 0.7
1 biopsy, atypical hyperplasia	C1e	20	= (-0.01354 * (RR^2)) + (1.744365 * RR) - 0.08409
		30	= (-0.027697 * (RR^2)) + (2.6822 * RR) + 0.7905
		40	= (-0.04248 * (RR^2)) + (3.37689 * RR) + 1.05
		50	= (-0.039177 * (RR^2)) + (3.481 * RR) + 4.4797619
>= 2 biopsies, no known atypical hyperplasia	C1c	20	= (-0.017337* (RR^2)) + (1.8286 * RR) + 0.036
		30	= (-0.0319* (RR^2)) + (2.7047 * RR) - 1.1318
		40	= (-0.024 * (RR^2)) + (2.666 * RR) + 1.8
		50	= (-0.02823 * (RR^2)) + (3.364 * RR) + 3.94
>= 2 biopsies, atypical hyperplasia	C1f	20	= (-0.010405 * (RR^2)) + (1.6617857 * RR) + 0.1553571
		30	= (-0.01881 * (RR^2)) + (2.3069048 * RR) + 1.4357143
		40	= (-0.024186 * (RR^2)) + (2.6597381 * RR) + 2.0817857
		50	= (-0.063836* (RR^2)) + (4.1417669 * RR) + 0.6841035

The 95% confidence intervals for each risk prediction (10, 20 or 30 years) could be estimated, using different equations if atypical hyperplasia was known present or not.

95% Confidence Limits	Figure	Line	Equation for 95% CI
no atypical hyperplasia	C3	lower	= (-0.002054 * (AR^2)) + (0.76375 * AR) + 0.55
		upper	= (1.36 * AR) - 0.4
atypical hyperplasia	C3	lower	= (-0.00119 * (AR^2)) + (0.6467619 * AR) - 0.357143
		upper	= (-0.00566 * (AR^2)) + (1.651147 * AR) + 0.172727

where:

• AR = absolute risk from 10, 20 or 30 year risk equations

If age was not exactly at the decade (20, 30, 40 or 50), then a value between the absolute risk for the decade above and for the decade below were used.

absolute risk when between decades =

= (absolute risk for lower decade) + ((((age) - (lower decade)) / 10) * ((absolute risk for higher decade) - (absolute risk for lower decade)))

Limitations:

• The Gail model was found by Bondy et al to perform well at predicting the risk of breast cancer in women who adhered to the American Cancer Society screening guidelines, However, women who did not adhere to the screening guidelines, it tended to overpredict the risk.

• Bondy et al also noted that the model tended to overpredict the risk for women < 60 and to underpredict the risk for women >= 60 years of age.

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Description

Specialty

Objective

ICD-10

Probability of Developing Breast Cancer in White Women

Purpose: To convert a woman's relative risk for breast cancer to absolute risk in the Gail model.

Description

Specialty

Objective

ICD-10