In answering this question, we need to think about what we use models for. Models tell us the risk of mutation and the risk of breast cancer over time.
The risk of mutation helps to determine
- the need for genetic testing based on a locally agreed upon threshold( e.g., test if risk of mutation is 5% or greater)
The risk of breast cancer over time helps to determine
- The need for MRI (e.g., lifetime risk of breast cancer 20% or greater)
- The need for chemoprevention (e.g., 5-year risk of 1.66% or greater)
To answer the above question, we need to consider what parameters go into risk models and why a woman with ovarian cancer might or might not give spurious results.
At baseline all women with invasive ovarian cancer need genetic testing (NCCN) and all have had a bilateral oophorectomy. In addition, most women with ovarian cancer do not have a full life expectancy.
As genetic testing results have a huge impact on breast cancer risk if positive and an ameliorating effect if negative, it is important that any model used take testing results into account. This excludes all models except BRCAPRO and Tyrer Cuzick.
As oophorectomy produces a marked decrease in breast cancer risk (Even, it appears, in post-menopausal women) it is important that any model used take oophorectomy into account. This excludes Tyrer Cuzick and all other major models except BRCAPRO.
Hence, when dealing with a woman with ovarian cancer who has had genetic testing and an oophorectomy, only BRCAPRO will give useful results in terms of breast cancer risk.
At this point, a clinical estimation has to be made relative to the patient’s life expectancy. Lifetime risk should be calculated based on this age, not age 85.
Now clinical judgment comes into play. Is the woman’s risk sufficient to warrant prophylactic mastectomy, MRI screening or chemoprevention? The patient’s life expectancy (Based on the chance she has been cured of ovarian cancer) likely plays the major role in determining the approach. If the patient is not likely to have been cured of ovarian cancer, than management of the breast should be as non-intrusive as possible. If, on the other hand, the patient is likely to have been cured, her breasts should be managed based on the risk of breast cancer over time, best estimated by BRCAPRO.